Back in the 80s I was lucky enough to work with some guys at Yamaha Japan and would pester them with questions on this subject and one gentleman who pretty much worked on this subject for 15 years would entertain me and I remember him telling me remember testing one port at a time is risky.... their is a lot going on.... it is kaos in there. I know the introduction of advanced computer modelling of air flow showed KTM a few things at the end of the 125 GP era. Awesome work making this video❤
Hi Ross, sounds like you had a really cool job back in the day. What were you doing? Was it in Japan? Noted about the one port. The instructions for the TorqSoft test do say to block other ports while testing the exhaust or the transfers... It would be good to use some 3d modeling to try to evolve the design. I'm sure it has come along a lot over the last few years with computing power increasing.
@AutoBeta2T in the 80s I was a mechanic for a couple of motocross riders and that lead me to working for Yamaha as their race team manager. Doing that here in Australia we would get involved in some preproduction testing. The late 80s andearly 90s was a time of innervation for Yamaha with lots of new technology being tried one of the guys I worked with built and rode the twin cylinder yz125 works bike and won the all Japan championship in the early 80s. A Japanese test rider wound up comming here for holiday and we let him say at my house and he rode and raced with us for a few months. The weather in Japan was very wet the next year with typhoons ruining their test and training schedule and for a time the came here for riders the riding and testing. It was at that time way cheaper than doing it in the USA with a favourable exchange rate and good weather they would get more done here in a short time. The Team YZ guys were great and fun people. I wish I had better translation skills because some of those engineers were there for the invention or implementation of Reed valves boost bottles centrifugal timed power valves and digital ignitions... some of the guys were driven and very smart people. I when on to be a race team manager for KTM in the 90s and Kawasaki in 2000s and finished off back with KTM at the end. At all of those companies their was core group of engineers and racers driving development and also a dedicated team of accountants and managers ensuring budgets were adhered to 😅. I was lucky enough to work with a few guys that would pass on some of their story's and experiences. Having experienced that and also run a tuning business bought several dynos and flow benchs I have found the subject fascinating. I have missed out on the recent digital era of computer modelling but have several old freinds still into that side of things. You never get to the end of a development project in that game you just wind up running out of time , money or get pulled away from it because they want you elsewhere.
Wow, thanks for the reply - it sounds like you had a very interesting and rewarding career! Really cool to have worked with the factory engineers too! Hopefully in a few years home computers will be able to solve the complex 3D flow models of a two stroke 😊
@AutoBeta2T there is a lot happening at once in even the simplest two stroke engine. One of the things I remember being told early on is to stop thinking you understand how it works in theory you man never know it all... it is Kaos in there.... 😀
@@AutoBeta2T What you need is an exhaust port floor that is spring loaded so that it follows the piston crown down as it uncovers the exhaust port, just knock something up that does that and you will be sorted! 🙂
@@AutoBeta2T port shapes all wrong.. perpendicular to the cylinder!.. look at your port roof vs the centre of flow of the gas stream flowing into the port.. you're ignoring the flow leaving the cylinder especially down the cyl wall & into the port.. a 30-45deg downdraft port angle.. impact is even more when you factor reverse flow packing & chamber tuning.. good study wrong conclusions
Nice! I would say the easy part is to get exhaust flowing enough, the hard part is to aim the transfers to keep the gas trapped. And having it trap a lot, the need for a good exhaust increases. By that i mean, that one should always start with the transfers when porting. And bear in mind, seldom in all simulation softwares, there isn´t any laws of physics holding you back, they predict everythings perfect. That 25.5hp worth of flow might not be the actual number. I noticed many are somewhat 'afraid' of rising up the transfers, for an example: the known 'roost' cylinder(100cc) for scooters are having 134 in transfer duration stock and it makes good power and a wide powerband that peaks around 12800-13500rpm And the transfers in my friends roost cylinders are rised from that, and still makes very good power(i´ll try dyno that one around upcoming christmas.) Rise up!! =)
Hi Patrick, Yes - I need to flow the transfers. Possibly they are restricting the engine. It will be interesting to see what the flow.time.area is!? I'm happy to raise the transfers and widen... There seems to be a lot of "rules" to two stroke engines and if you go outsiders the "rules" you are wrong... Hopefully in this process we may dispel a few "rules" and myths... I'm going to trust the Dyno and let it and the laws of physics dictate what is good in terms of making two strokes fast. I read some of what Roost does and he is really good at developing engines and cylinders with the restrictions that the initial layout dictate. In summary there are hard and fast rules but if something works and not within the "current" rules but it works then go with it😁
@@AutoBeta2T I´d say flow area is second to aim correctly and time it correctly, but yeah! When trying to squeeze all from a certain setup one needs to make ports huge. If i remember correctly the Aprilia RSA were in the neighbourhood of 140 in transfer duration. And an another example, i had a discussion with Frits about my old kawasaki 212cc build(kx250 engine). I dynoed that 70+ at the wheel(methanol) at 12600rpm, it pulled all the way to 13200rpm He said it was impossible to make that power at that rpm, well it did =) I had 142 in duration at B-transfers, and 203 in exhaust(203 at the aux ports also) Even if my 70+ was wrong, the rpm wasn´t, and the rpm was the big problem Frits said, it should be impossible to make power at those rpms he said ;) Bumblebees shouldn´t fly either was my answer to that =) Came to think of this thinking of 'rules' =)
My old boss use to say: rules are for fools and the guidance of the wise. That's me knackered as I'm certainly not wise. Back to transfers - i did epoxy mine to reduce them from 136/138 to where they are now so it should be simple to remove. Also I did a vinamold cast to make the transfer bungs and I haven't done as good of a job as I thought on the transfer duct roofs.
one old school trick of raising the transfers and therefore the peak overall power/rpm was to raise the whole barrel by adding extra lower barrel to crankcase gaskets and then removing the same amount off the top of the barrel to compensate for the loss in compression etc. obviously this also raised the exhaust port too which was no bad thing if you wanted to do that anyway.
I did a huge amount of this sort of flow testing on a home built rig in the 1980's on classic honda twins. One comment I would make is run the hoover for a good old while before starting to take measurements as to let the motor warm up and stabalise. Love what your doing, wish I'd had the software back then.
@@AutoBeta2T I learned a lot about reverse flow caused by turbulance at the wall boundaries and experimented with an aviation tuning technique called ratchet flow to try and counteract it. Check the vacuum drop for every 1/4 mil of port opening some flow everything in first few mil of opening, for me that meant rapid lift cams with shorter overlap. Others flowed through the whole of the valve lift meaning longer duration was better.
@mercedesvan-doors34 cool, so it helped then. I did a Google for ratchet flow tuning but it doesn't really come up with anything. Is it referred to another way? Are you able to explain a little about the technique? Cheers Dave
@@AutoBeta2T Even then it was almost unheard of, I have a book somewhere, if I can find it I'll get you the details. In essence it consisted of cutting small angled grooves in the inlet port to stop reverse flow at the boundary wall. Remember I was tuning 4 strokes. You have to forget about the charge acting like a slow moving fluid it is travelling at very high speed, friction against the inlet walls slows the charge down and this causes eddy currentls that restrict the effective diameter of the inlet, in some cases the layer next to the boundary can flow backwards. The small grooves were intended to kill off this behaviour.
Hi, the flowbench results itself are just half of the game. I would consider the shape of the port with constantly increasing cross section downstream the port window as important, because that helps the wave propagation of the pressure pulses. In mota 2 stroke software I obtained a power increase by raising the port floor of the exhaust window (just as Alex's PIP cylinder had). And mota doesn't even ask for flow coefficients, but does calculate the forward and returning waves from the shape (cross section) of the port. So the opening angle of that part of the exhaust port needs to be considered as well and should probably match the initial opening angle of the pipe.... Just my thoughts of what could be intersting here... Curios to know what you think about that :-)
Hi Stefan thanks for the comment. I've been about to reply several times now but I keep getting interrupted. Yes, in theory the exhaust duct should diverge at the same angle as the header pipe but I'm interested in the Wobbly duct design that restricts the outlet to about 90% of the window area. I intend to do some testing on this. I haven't played with raising the floor in the simulator yet but again something to try. I think getting the duct volume as small (optimal) as posible maybe key? Something to experiment with next year. I will try the shape.of duct you describe too. Cheers, Dave. PS - how much power did you gain in Mota with the raised exhaust duct floor? Did you notice any difference in the pressure wave when viewed in the wave viewer?
Hi thank you very much 😊 Next vid hopefully in a few weeks... I've had quite a lot on since before Christmas so nothing done... But l have lots of things I want to do this year.
Great job Dave!, you explain this stuff very well. I have two of those AR's that I'm going to begin to restore here soon because of your video's you produce. You get me motivated to get them in running shape 🙂
Hello from north-eastern USA, I’m a big fan of what you’re doing and the theories involved. I’ve also been watching David Visard’s videos. He and Ben Alameda believe the back flow of exhaust can be manipulated by essentially making it flow poorly backwards .
Hi - I'm pleased you are enjoying. Yes there is a lot of great stuff on David's channel. However two strokes are slightly different animal... Flow backwards in a two stroke exhaust can help with power as it stuffs fresh charge - over-scavenged from the cylinder back in. I believe 4 strokes rely on the intake flow quite a bit too?
3:39 The flow back in has a low volume and the natural shape of the port is quite good in the reverse direction so I don't see problems with that part. You can always flow test it in reverse to get an idea of how it is working. Restricting the volume in the port to reduce mixing is a good idea.
Hi Bill - a good idea to flow in reverse. I should be able to do that when I get around to making the transfer flow testing attachment. The restricting volume to reduce mixing isn't mine. I think i first heard about it from Neels Van Niekerk? It's definitely something I've read about somewhere...
Hi David, thanks for the complement and I'm pleased you are enjoying the vids. Note: I'm naturally quite dis-organised but I like process and procedure (it keeps me on track). I quickly realised how easy it is to forget what you have done so my big red book contains everything I do from now on. It is really helping keeping good notes. Happy Christmas to you too.
As someone's who's trying to fix up an AR50 that's been off the road for 30 years I'm chuffed to come across this series.. great work 👍 I've got a bdk ignition, bdk pipe, 21mm carb.. I thought I had it going but after sitting for a couple of months the cylinder was full of oil! :-(
Out of interest what sort of speed would you expect from the 93cc BDK setup? Also, I'm guessing you premix? Sorry for all the questions, not many of us with AR's nowadays and not much info about!@@AutoBeta2T
Sorry for the delay. I guess 80 mph maybe more if a full set-up. There have been claims of these going 100mph but I'm not to sure of the actual spec of the engine.
@@AutoBeta2T no problem.. I'd be happy with 80mph 🥴.. back when I was 16, I had a micron, 93 kit, 21mm carb and a supposedly derestricted cdi but it still struggled to get to 60mph.. but at 16 "tuning" involved trying to skim the head with a hand file and using cereal boxes for base gaskets! 😂😂
@user-ye8xx7gl3j haha - sounds a bit like mine... I think mine had the ar80 Ignition so would pull 65 and maybe 70 down hill. It had a micron pipe so probably not the best but it looked ace 👌
Keep in mind that the actual flow during blowdown is almost entirely choked flow , (Speed of sound) and bears almost no resemblance to low pressure cold flow as tested here. What seems to be an improvement in this testing may not have an effect at high pressure high temperature flow during blowdown. RULE OF THUMB if the exit pressure absolute is about 1/2(.5283) or less (or~ 2:1)of the stagnation pressure absolute(storage pressure) then the flow is choked (Mach 1) (in cold air anything above 13 psig gives Mach 1). Blowdown will start at ~100psi+ so will be choked for a good portion of blowdown time. This data is not in a format I expected so I have to think about it for a while to make sense of it. I want the actual areas, volumetric flow figures, flow velocity etc.
Its all good trying to improve the flow of exaust gasses but a two stroke also relys on resonance off the exaust gasses bouncing backwards and forwards in the expansion chamber. so changing the port size or shape also changes the resonance characteristics..... unlike a 4 stroke engine where you want the best flow in and out.
Interesting re the stall of air on the piston at half way, my thinking of flow from Gordon Murray on the t50 rear diffuser, anything more than "I think 17 deg" and it would stall.
Yes, it was. I'd like to do some more research into this at some point and certainly into flow inside the two-stroke engine. It's such a simple design, but so complex too. Yes, an angle of attack greater than about that, and the airofoil will start to stall. Maybe filling the lower exhaust duct is helping to keep the flow attached to the front face of the piston better?
Cool, I assumed he was born in the UK. There is a lot of interesting stuff on his channel. Although 4 stroke I feel some of it applies to 2 strokes too.
Me too. It's been fun to make but the time required to document everything is large. I've missed quite a bit of stuff I want to talk about as I'm limited by recording on my mobile phone. I could do with some better cameras as I use my phone to record and edit everything. I look forward to your thoughts on the testing Bill.
Great work buddy but if you have done this much effort on yamaha rx 115 engine you would had created a deadly hyper aggressive machine. Some how im convinced that yamaha rx platform is really invented for tuners like you. If you had done this much effort on yamaha rx...dramatically saying you would have reach 35 hp but great work dude your love and passion for 2 stroke is visible in your videos. love that..keep grinding 😉❤
Be curious if power could be found with this. In the 90's I filled this section using Belzona epoxy steel for the same reason, but I never noticed any obvious gains. It was seat of the pants tuning in those days!
I wonder what the difference would be if the exhaust port had a horizontal piece of metal inserted to basically split the top and bottom, obviously something quite thin.
Hi Pienari, I could do it that way but i would have to weld up the duct and i'm worried about distorting the cylinder. I'd like to bore out the duct and just use an insert but that will have it's problems too. I do want to try a smaller exhaust stub - currently it is 30 mm dia where is goes into the exhaust. 28 mm would be about 90% of the window area... Something to try. Cheers
years n years ago when performance bike mag first came out they did project (suzuki) GP100plus trying to get a little Gp to the ton . Air cooled 2 strokes are great for playing with good luck with the Ar i reckon you will get there .. Food for thought put a H100 honda engine in an mbx or mt5 see what it will do ..
My brother had ar50 in his teen years going back 30yrs ago or so, old man put ar80 head, carb and micron exhaust on and made it worth riding, I remember riding on the back with him as a 12yr old.... brakes were shite though😂. I never went down the bike route after that, though Bro did some scrambling as we called it back then and got a slighgly tuned big wheeled rm80. As a fairly small 14-15yr he struggled somewhat 😂... we shouldn't of sold that bike😢 but he bought an Rd125 instead. wished I taken it up more and got my bike license but never did and went into cars, into chainsaws and porting with my work now, so always had a love for 2 bangers. Would love a 2t dirt bike now, great series though❤👍
@AutoBeta2T Yeah, there's a guy in the States who has a channel. 'Dyno Joe', I'm curious about that flow testing... you put a hump on the floor of the port, not sure how that is increasing the hp. Is it like accelerating the flow out? Would you just weld that in and shape it with the foredom something🤷🏻♂️
@@AutoBeta2Tit is basically the same engine I think the crank is slightly upgraded but because it was 80cc from the factory it might would be interesting to see what the port arrangement and sizes look like. Not sure if the barrels where nickel plated or if they had liners I do know back when they were popular the small wheeled Kx80 was dangerous. Not sure how much power they made. Might give you some ideas if nothing else.
there's very little reverse flow. You have to think about whether or not return wave strength is lost due to any abrupt changes in diameter. Making the port floor higher benefits low RPM power at the expense of high RPM power. Adding a bottom ramp directs the movement of the reverse waves higher inside the cylinder, whereas the ideal direction is downward to the transfer ports. So the makers of that program obviously did no real life testing. I did which is why I know this. And its calculations for time-area for blowdown are incorrect.
Hi Cerberes, I'm not sure. But if they were too small the may act a a heat exchanger and heat up the fresh charge? I may however help? SOmthing to test when I get to the 3d printed insert stage.
Ciao ho sbirciato varie volte i tuoi video ed oggi mi sono iscritto. Vorrei sapere per cortesia dove hai acquistato il tubo venturi con le prese e i misuratori di pressione
Ciao, grazie per esserti iscritto. Ho aggiunto un elenco di articoli alla descrizione, ma vedi anche di seguito: TorqSoft equipment list: Venturi 20 mm is most suitable for cylinders with port diameters of less than 33 mm: www.shapeways.com/product/FTPHNUF3X/flow-venturi-20mm?li=shop-results&optionId=59345290 Venturi 27 mm is suitable for cylinders with exhaust port diameters between 30 and 44 mm, and is shown below.: www.shapeways.com/product/ZFQJ7UAL2/flow-venturi-27mm?li=shop-results&optionId=59381039 Manomenter: www.amazon.co.uk/dp/B07K87NQMD?ref=ppx_pop_mob_ap_share Brass nipple - 3mm: www.ebay.co.uk/itm/390948209350
Hi, pleased you are enjoying. I have 2 video worth's of footage to edit so hopefully another couple of vids soon. Dyno is one me and a mate bought years ago .
As an autistic bike nerd, this is like porn ! I think I said I was working on my simson, but these videos have given me a real boost. I am off to germany in the new year to make some friends. They have close ratio boxes, fully cnc cases etc. They make cylinders up to 110cc, but have recently been adapting the MTX125 cylinders to the Simson cases. They have a endurance race and festival every year, that I hope to attend. Just need to improve my school boy german! The book you asked about is the one by Graham Bell, which I am sure you have !
I'm pleased you are enjoying James 😊 More geekery to come! Enjoy Germany and the festival. I believe the Germans are fond of the two strokes? And yes I do have the Graham Bell book. I was flicking through it the other day.
2T engines are not comparable to 4T cylinder heads, and operate on the principle of unsteady flow, so flow testing is not likely to be of tremendous use. In the early days of 2T engines, the exhaust ducts were often overly large, and significant performance gains could be realised by welding up and reshaping the duct. Increased torque, is the most noticeable thing that is generally gained from a smaller exhaust port. Its a very good idea, to try and read up on 2T engine operation, and understand how the engines work. Not sure if its still available, but the best book I have seen on 2T engines is "The Two-Stroke Cycle Engine" by John B Heywood and Erin Sher. Scavenging is the most important part of the 2T cycle in terms of generating power, and if you have sealed off the transfer ports, any sort of flow testing is questionable, as it will not be even remotely related to the flow inside a running engine.
Hi - yes 2 strokes are massively different to 4 strokes and the unsteady gas flow inside is interesting. I'm no expert and I'm just documenting my experiences with this particular 2 stroke engine, really as a novice, but I did note Jan Thiel's words in his book and he did use flow testing to assess modifications to the engines he worked on. Jan Thiel developed the Aprillia RSA 125 which made 54 hp at the output sprocket. As with most of what I put up here it's just my meandering around the "what and ifs" of 2 Stroke engine technology. Something's may work and some not. Thanks for the comment - it's really appreciated.
@@AutoBeta2T I would guess Jan Thiel had a very good idea of exactly what he was wanting to achieve? It will have been something very subtle, and you may find you get better results from something other than flow testing? Welding up exhaust ports was carried out in the 60s on TSS Bultaco's. Increased torque, and made them come out of the corners much better. How many cylinders do you have? Its a good idea to have several, so you can try some different ideas. The idea that bigger is better still persists, and you might find that isnt the case, if you test several back to back with different configurations? I am trying to improve Yamaha trials motors, and have managed to collect up 5 or 6 cylinders, which wasn't that easy as they are very hard to find now, as the last one was made in 79!
Hi :) possibly but It's an area I wanted to explore. I think actual flow benches are very expensive but the set-up I am using is relatively cheap. Now cylinders are a problem - this is the only Autisa one that I have and they are like hen's teeth. I do have another but it's a copy of this and is all cast iron. I'd like to get some more and be able to do leap-frog testing but unless I can find another few that isn't going to happen. A standard AR80 cylinder would be good but these are difficult to find too. To make matters worse it's on it's last overbore...
@@AutoBeta2T If you cant get parts, then its going to be very difficult to make much forward progress. I would have thought something like a 50cc Minarelli might have been a better choice?
@@AutoBeta2T Obviously it's about 4T but have a look at Garage 4AGE, they've tested various fixed length velocity stacks/inlet runners as they call them as well as variable length ones, sort of ypvs on the intake on Toyota (Yamaha) engines
Ive a super flow machine ive been flow testing two stroke motor 14 years but ive been doing kart motor for 30years you doing stuff ive already done . You can do more work on inside the piston , run one ring . Bottom end pay big part in flow to . Flow test the carby the air box . Pipes Rule of thumb longer the pipe from the head of the motor to end of first cone give you more bottom end power that means the power band comes on early and goes out early so shorter the pipe more topend . Now you running a reed block same thing with that to thinner gasket thicker gasket . More testing. Good example my mate does outboard boat motors for racing 25hp because you can't change the pipe because the pipe is the leg of the motor you spaces the carbys out gives you more bottom end power . All so read your pug each run to . Remember this at work temperature thing change in shape too . For example nascar motor they hot hone their motor at working temperature something think about
Cheers for the info Storky. Where did your testing of the exhaust duct point you? From what I can see the flow favors the edges of the duct when the piston is in the blowdown phase and having a raised center section on the floor appeared to help the flow but it reduced the noise too.
Funny thing when I test my old motor kt100s we could not touch the ports I was looking for good barrel they were hard to find mostly we were looking at transfers port . Then years later I was speedway kart in open class did alot porting . One thing I found in running synthetic caster oil because it a dirt oil and carbon use to build up in exhaust port that were I use to grind what they call rabbit ears in exhaust port go wider not high in the port you go to high the power stroke is small you lose bottom power .your transfer port try flow them to front piston give you better torque . The head .8 to 1mm squish kept a sharp edge on squish to bowl better mix better responses down low and the position of spark pug as well point the opening towards the exhaust port more testing
Just throwing this out there but have you thought about making a cylinder head out of 2" thick lexan and then running the engine ? I have often thought about this for my Honda odyssey's so that I could video tape it and actually see exhaust flow and see what's going on inside the combustion chamber while the engine is actually running. The lexan head would be made with the same profile as the head you plan to run. I know that sounds crazy and you wouldn't be able to run the engine very long but you don't need to run the engine for long. CO
Hi, I've not thought of it in a running engine but it would be cool. I think the restriction would be getting a camera that can record high quality slow-mo...?
All the people that have done that only run the engine at idle and low throttle. Otherwise it will melt blow the head off very quickly. Seeing what it does at idle tells you virtually nothing about what it is doing under full power.
@@billshiff2060 Yes I agree. But you get everything ready and make a full power run on the dyno as fast as you can. With a camera rolling you will have the evidence you need within a few seconds of film. CO
I don't know what happened, I made a comment but it's not here. Anyway, great video Dave, I really enjoyed it and I think that I'll invest in the software and venturi myself. I have a damaged Bidalot 50 cylinder that you could borrow to study, if you think it would be useful!? It's the best 50cc cylinder that I have used so far. Just pm me if you're interested Dave. Keep up the good work and I look forward to the next video. Mark P
Hi Mark, I'm not sure? Comments seem to go missing from time to time.! Pleased you enjoyed it mate and I'll drop you a message in a bit as it would be good to have a gander at the Bidalot cylinder. Hope you are keeping well mate?
i use big pipe chamber on my kr150 its good for high rpm but give big drop powerband around 7 /8k rpm before power valve open, how to get rid that problem 😢
Hi - the latest post I have seen is here: facebook.com/groups/671081149638729/permalink/6915535795193202/?ref=share It looks like there are 100 English books still available. I also have this email: legacyjanthiel@gmail.com Cheers
Hi, details are here: Jan Thiel's book details are here: legacyjanthiel@gmail.com and: facebook.com/groups/671081149638729/permalink/6915535795193202/?ref=share
I don't know, I just put the readings into the programme. However, if the flow area power prediction goes up, then there will be an increase in mass-flow.
Hi! Could you advise how to calculate the exhaust for an engine with two pipes per cylinder? I have several old Soviet 175cc engines, they have 2 pipes, one cylinder and are very low in power. I don’t drive them all the time - it’s just small hobby.
Hi, I'm not too sure about these types of engines... I would imagine maybe two pipes that are 50 % of the area of a normal 175 cc engine? I think EngMod2T can model these types of engines? I'll have to have a look later if it can and if so if there is any guidance.
@@AutoBeta2T Thanks for the answer. It is a simple 175cc single cylinder engine, one of the Soviet copies of the old DKW - cylinder diameter and piston stroke 62x58 mm. There is no reed valve, their speed is low - about 6000 rpm at maximum power. About 14 horsepower. I have a program for calculating exhaust using the Blair formula, it’s quite simple, but it seems to work. The problem is that I don't understand if the single exhaust calculation will work with the dual exhaust. Some also advise me to take half the volume of the cylinder for the calculation, but I believe that this is the wrong way - after all, each exhaust has its own port.
Hi, I had a look on engmod2T and it does simulate this type of exhaust port. There wasn't a massive amount of info on there but it looks like the pipe configurations available are two separate exhausts or a two into one. I would think that a calculated two Stoke exhaust for the 175 engine would work but with the header split into two. Probably with the diameter of the header equating to half the area of the single exhaust header that was calculated.
@@AutoBeta2T Hello! Thank you for your time. Are you proposing to combine both pipes into one resonator? The calculation program uses the height and width of the exhaust port. It might be worth just designing two exhaust pipes, each with its own exhaust port. I have a more "advanced" version of the engine as well. This engine has a single exhaust, with the exhaust port being much larger than each of the two in the old version. And the pipe is also much larger. But I'm not sure the engineers planned to increase its power. Or rather, they tried to reduce the volume)))
Sir i have two stroke cylinder i want to increase its rpm, power please help me how i can increase the speed from its ports. Please help me tell me sir
Hi, what cylinder and what are the durations for the ports? I go through raising the exhaust port in this video ruclips.net/video/_4X0QWb8Wcs/видео.htmlsi=Fh-8-nIwXexxVCur Note: raising the exhaust port roof 0.5mm makes quite a bit of difference.
@@AutoBeta2T Sir give me your whatsapp number I will send you the picture of the cylinder and piston and also send you the video of its engine. Please sir help me in this task I am very confused that's why. I don't understand anything please sir help me tell me
@AutoBeta2T i mess about tuning mopeds on a hobbyist level and most ducts on cylinders taper out bigger. whereas according to wayne wobbly wright if they taper smaller they make the pipe work better. so for single exhaust ports the wobbly duct tapers to 90% of the diameter of ports effective area in the length equivalent of 1.5 x bore size. and then back to 100% bore size in 0.5x bore size. its a 2 part duct, total length 2 x bore diameter. so they narrow slowly and then open up again but a bit more sharply. heres my example. i did this to a 47mm 74cc gilardoni cylinder and ex port area was 490mmsq which using maths pi etc = a circle of 25mm diameter. first part of the duct is 1.5 x 47 = 70.5mm long, at that point i needed 90% of 490mm sq = 441 which is equal to diameter 23.6mm. the first 29mm of this part of the duct was my cylinder duct itself which needed altering. you can drill and insert the correct shaped piece or weld it up. so attached to my cylinder i needed a duct of 1.5 x bore MINUS the cylinders 29mm long duct 70.5 - 29 = 41.5mm. the start diameter of that duct i had to workout cos the first 29mm had already lost a mm or so. and then 2nd part of the duct is 0.5 x 47mm = 23.5mm long. and that goes back to 25mm diameter. bit hard to explain. but a diagram shows it much more clearly. ive done a simple cad drawing showing it with my sizes if you wanna see it. dunno how to get it to you?@@AutoBeta2T ?
@@aljaxon69 hi, that sounds like what I am trying to do with mine. The 1.5 x bore restriction works well in EngMod. And the Mach is around 0.8 too. It would be good to have a look at your design. My email is: autobeta2t @yahoo.com
Combustion don't work like that mate and expansion exhaust chamber works at pulse speed like a jet hot squeezed gas your better off trying different carbs
@@AutoBeta2T Interesting comment, from just looking at it the duct seems huge, optimum for a single port seems to have the duct end at around 90% of the full open window area. How does yours compare?
Hi Neels, a poor comment from me, I was thinking specifically about the area of the duct where is comes out of the port, it is fairly narrow (about 28mm Dia) but then it goes really big as the floor drops away. The outlet to the exhaust duct is 32.7 mm and the port window is equivalent to 30.4 mm diameter giving a passage to window area ratio of 115.5 %. However, the stub I am using has a entry of 32.7 mm but reducing to 30 mm dia (at approx 1.5 x bore) where the pipe starts (there is a fair radius on the entry but it feels smooth. This has a passage to window area ratio of 97.2% so still possibly too large. I did some testing in EngMod a while ago and I think 28.5 mm worked well. I have another observation but i'll reply in another comment as YT sometime dumps what I have written.
Neels, another thing i noted when doing some initial tests was the interface between the duct and the stub. It's this area that I tried to smooth for better flow (as it isn't a smooth transition) but it made no difference. I'm wondering now if I need to keep reducing that area until flow starts to drop off. Almost like trying to reduce the duct area until it just starts to hurt the flow. No increase in flow but no excessive volume in the duct to dissipate pulse energy?
@@AutoBeta2T As a first step I would reduce the duct area from window to duct end as recommended by Wobbly to 90% of window area at the duct end, and creating the ski-jump bottom floor as he recommends (which also improved the flow in your video) to the limit the fresh charge / burnt gas mixing as you clearly explain in your video, and do a dyno test with this to get a baseline.
Hi, the e haust port has already been raised to 203 degrees duration. I'll look to go higher if required. I do intend to look at squish tests, currently I believe it is too tight on my current setup.
@@AutoBeta2T All my porting has a flat floor, I’m old school going with formulas with MPA ( mean port area) and getting an effective rpm range. Tommy (Tom Turner) and I have different theories on 2 stroke porting, I don’t use his blow down theory, the formulas that I used I would get the exh and transfer port ERPM and there is so much just on shape of the exhaust port. As 2 stroke stuffing learned the hard way on going a 100% of the exh port width. If you want a decent ripping porting with reed’s 200 degrees of exh and 128-130 degrees of transfer porting. You’re kinda in the Blue printing stage of that cyl. I don’t think JB weld will hold up on the floor of your exhaust port. If you have a boost port, match the height and roof angle is key. Take the boost port and cut it like a slot and drill a hole into the piston and all the AFM under the piston at BDC will help get more AFM in the combustion chamber. Also, squish width, narrow for hi rpm, wide for bottom. Increase your primary compression ratio by stroking the crank, this will help your torque as you loose a good amount of by raising the ports. But 5-7mm stroke is far as I would go or you will blow out your crank seals. 2SS is destroying reeds cuz his “primary” Crank Case ratio is way too high. I can send ya formula’s if you want but Robert from Factory Pipe Products turned me on too a good 2 stoke theory, n I can get ya the ISBN number for it. I’m 61 years old n have ported a ton of cylinders and had the first EFI 2 stroke on the national tour and it make’s a huge bottom end HP which made it so I could over port it like a light switch and still have great power everywhere back in 1994. Remember always, it’s theory, so depending on the application, nothing is set in stone. That’s why there is no 100% internal combustion engine ever made. Your car or truck has a cat in it because it can’t be done.
@@radron14 Hi Radron, sorry for the late reply but your last comment was held for review for some reason? YT does weird and wonderful things sometimes. I'm currently at 202 exh and 130 transfers. I feel I need a little more transfer area but I don't want to go up and eat into the blowdown. There is epoxy (done badly) on the transfer roofs at the min - I want to redo it so I'll do a test of raising the transfers for more tx area but reducing the BD area. I think my SAR is a bit high at the min (48%) and I want to try some different squish dimensions. I've just cut two different heads, one with lower MSV than the current best and the same compression, and another with lower MSV and compression. I'm looking forward to testing them. I'd love to stroke this engine and get it a bit squarer but there is literally no meat on the crankcases to make them larder for the extra clearance required. Any ideas? I haven't measured the primary ratio on this engine. I should but not 100% sure on how to. Yes please with the ISBN for the book. I'm always after getting my hands on books on the subject Regards Dave
Don’t believe this, his “swirl” comment is a dead giveaway. Sorry mate, MPA and point of mean reflection will work. This is a Trials low end power n major drop off at RPM. It’s actually called scavenging. Total gimmick
![ARGENTINA vs. PERÚ [1-0] | RESUMEN | ELIMINATORIAS SUDAMERICANAS | FECHA 12](http://i.ytimg.com/vi/xtI25ENDDSY/mqdefault.jpg)
Great stuff!
Cheers Alex.
I did wonder if it would be a good test for your cylinder exhaust and transfers?
@@AutoBeta2T Definitely would be, especially for the exhaust duct.
Great to see team work here.
@@2STROKESTUFFING a compliment from you is a big deal lol
i feel a collaboration in the near future 😉
Back in the 80s I was lucky enough to work with some guys at Yamaha Japan and would pester them with questions on this subject and one gentleman who pretty much worked on this subject for 15 years would entertain me and I remember him telling me remember testing one port at a time is risky.... their is a lot going on.... it is kaos in there. I know the introduction of advanced computer modelling of air flow showed KTM a few things at the end of the 125 GP era. Awesome work making this video❤
Hi Ross, sounds like you had a really cool job back in the day. What were you doing? Was it in Japan?
Noted about the one port. The instructions for the TorqSoft test do say to block other ports while testing the exhaust or the transfers...
It would be good to use some 3d modeling to try to evolve the design. I'm sure it has come along a lot over the last few years with computing power increasing.
@AutoBeta2T in the 80s I was a mechanic for a couple of motocross riders and that lead me to working for Yamaha as their race team manager. Doing that here in Australia we would get involved in some preproduction testing. The late 80s andearly 90s was a time of innervation for Yamaha with lots of new technology being tried one of the guys I worked with built and rode the twin cylinder yz125 works bike and won the all Japan championship in the early 80s. A Japanese test rider wound up comming here for holiday and we let him say at my house and he rode and raced with us for a few months. The weather in Japan was very wet the next year with typhoons ruining their test and training schedule and for a time the came here for riders the riding and testing. It was at that time way cheaper than doing it in the USA with a favourable exchange rate and good weather they would get more done here in a short time. The Team YZ guys were great and fun people. I wish I had better translation skills because some of those engineers were there for the invention or implementation of Reed valves boost bottles centrifugal timed power valves and digital ignitions... some of the guys were driven and very smart people. I when on to be a race team manager for KTM in the 90s and Kawasaki in 2000s and finished off back with KTM at the end. At all of those companies their was core group of engineers and racers driving development and also a dedicated team of accountants and managers ensuring budgets were adhered to 😅. I was lucky enough to work with a few guys that would pass on some of their story's and experiences. Having experienced that and also run a tuning business bought several dynos and flow benchs I have found the subject fascinating. I have missed out on the recent digital era of computer modelling but have several old freinds still into that side of things. You never get to the end of a development project in that game you just wind up running out of time , money or get pulled away from it because they want you elsewhere.
Wow, thanks for the reply - it sounds like you had a very interesting and rewarding career!
Really cool to have worked with the factory engineers too!
Hopefully in a few years home computers will be able to solve the complex 3D flow models of a two stroke 😊
@AutoBeta2T there is a lot happening at once in even the simplest two stroke engine. One of the things I remember being told early on is to stop thinking you understand how it works in theory you man never know it all... it is Kaos in there.... 😀
Chaos
Great stuff! Your attention to detail and methods of experimentation are really interesting to watch.
Cheers mate. I love: process and procedure :)
@@AutoBeta2T What you need is an exhaust port floor that is spring loaded so that it follows the piston crown down as it uncovers the exhaust port, just knock something up that does that and you will be sorted! 🙂
Yes, that sounds simple! Haha!
If only... I'm hoping that there is a compromise somewhere in the duct shape.
@@AutoBeta2T port shapes all wrong.. perpendicular to the cylinder!.. look at your port roof vs the centre of flow of the gas stream flowing into the port.. you're ignoring the flow leaving the cylinder especially down the cyl wall & into the port.. a 30-45deg downdraft port angle.. impact is even more when you factor reverse flow packing & chamber tuning.. good study wrong conclusions
Nice!
I would say the easy part is to get exhaust flowing enough, the hard part is to aim the transfers to keep the gas trapped.
And having it trap a lot, the need for a good exhaust increases.
By that i mean, that one should always start with the transfers when porting.
And bear in mind, seldom in all simulation softwares, there isn´t any laws of physics holding you back, they predict everythings perfect.
That 25.5hp worth of flow might not be the actual number.
I noticed many are somewhat 'afraid' of rising up the transfers, for an example: the known 'roost' cylinder(100cc) for scooters are having 134 in transfer duration stock and it makes good power and a wide powerband that peaks around 12800-13500rpm
And the transfers in my friends roost cylinders are rised from that, and still makes very good power(i´ll try dyno that one around upcoming christmas.)
Rise up!! =)
Hi Patrick,
Yes - I need to flow the transfers. Possibly they are restricting the engine. It will be interesting to see what the flow.time.area is!?
I'm happy to raise the transfers and widen...
There seems to be a lot of "rules" to two stroke engines and if you go outsiders the "rules" you are wrong... Hopefully in this process we may dispel a few "rules" and myths... I'm going to trust the Dyno and let it and the laws of physics dictate what is good in terms of making two strokes fast.
I read some of what Roost does and he is really good at developing engines and cylinders with the restrictions that the initial layout dictate.
In summary there are hard and fast rules but if something works and not within the "current" rules but it works then go with it😁
@@AutoBeta2T I´d say flow area is second to aim correctly and time it correctly, but yeah!
When trying to squeeze all from a certain setup one needs to make ports huge.
If i remember correctly the Aprilia RSA were in the neighbourhood of 140 in transfer duration.
And an another example, i had a discussion with Frits about my old kawasaki 212cc build(kx250 engine).
I dynoed that 70+ at the wheel(methanol) at 12600rpm, it pulled all the way to 13200rpm
He said it was impossible to make that power at that rpm, well it did =)
I had 142 in duration at B-transfers, and 203 in exhaust(203 at the aux ports also)
Even if my 70+ was wrong, the rpm wasn´t, and the rpm was the big problem Frits said, it should be impossible to make power at those rpms he said ;)
Bumblebees shouldn´t fly either was my answer to that =)
Came to think of this thinking of 'rules' =)
My old boss use to say: rules are for fools and the guidance of the wise. That's me knackered as I'm certainly not wise.
Back to transfers - i did epoxy mine to reduce them from 136/138 to where they are now so it should be simple to remove. Also I did a vinamold cast to make the transfer bungs and I haven't done as good of a job as I thought on the transfer duct roofs.
one old school trick of raising the transfers and therefore the peak overall power/rpm was to raise the whole barrel by adding extra lower barrel to crankcase gaskets and then removing the same amount off the top of the barrel to compensate for the loss in compression etc. obviously this also raised the exhaust port too which was no bad thing if you wanted to do that anyway.
That’s why having the best point of mean reflection in your expansion chamber has to be on the money or your just wasting fuel
I did a huge amount of this sort of flow testing on a home built rig in the 1980's on classic honda twins. One comment I would make is run the hoover for a good old while before starting to take measurements as to let the motor warm up and stabalise. Love what your doing, wish I'd had the software back then.
Cheers for tip 👍
Did you learn much from the flow testing ?
@@AutoBeta2T I learned a lot about reverse flow caused by turbulance at the wall boundaries and experimented with an aviation tuning technique called ratchet flow to try and counteract it. Check the vacuum drop for every 1/4 mil of port opening some flow everything in first few mil of opening, for me that meant rapid lift cams with shorter overlap. Others flowed through the whole of the valve lift meaning longer duration was better.
@mercedesvan-doors34 cool, so it helped then.
I did a Google for ratchet flow tuning but it doesn't really come up with anything. Is it referred to another way? Are you able to explain a little about the technique?
Cheers
Dave
@@AutoBeta2T Even then it was almost unheard of, I have a book somewhere, if I can find it I'll get you the details. In essence it consisted of cutting small angled grooves in the inlet port to stop reverse flow at the boundary wall. Remember I was tuning 4 strokes. You have to forget about the charge acting like a slow moving fluid it is travelling at very high speed, friction against the inlet walls slows the charge down and this causes eddy currentls that restrict the effective diameter of the inlet, in some cases the layer next to the boundary can flow backwards. The small grooves were intended to kill off this behaviour.
It sounds a bit like vortex generators that are used on aeroplane aerofoil surfaces.
You have one of the most under rated channels on youtube.
CO
Thanks 👍 I'm sure it'll all work itself out... 😁
Hi, the flowbench results itself are just half of the game. I would consider the shape of the port with constantly increasing cross section downstream the port window as important, because that helps the wave propagation of the pressure pulses. In mota 2 stroke software I obtained a power increase by raising the port floor of the exhaust window (just as Alex's PIP cylinder had). And mota doesn't even ask for flow coefficients, but does calculate the forward and returning waves from the shape (cross section) of the port. So the opening angle of that part of the exhaust port needs to be considered as well and should probably match the initial opening angle of the pipe....
Just my thoughts of what could be intersting here...
Curios to know what you think about that :-)
Hi Stefan thanks for the comment. I've been about to reply several times now but I keep getting interrupted.
Yes, in theory the exhaust duct should diverge at the same angle as the header pipe but I'm interested in the Wobbly duct design that restricts the outlet to about 90% of the window area. I intend to do some testing on this.
I haven't played with raising the floor in the simulator yet but again something to try.
I think getting the duct volume as small (optimal) as posible maybe key?
Something to experiment with next year. I will try the shape.of duct you describe too.
Cheers,
Dave.
PS - how much power did you gain in Mota with the raised exhaust duct floor? Did you notice any difference in the pressure wave when viewed in the wave viewer?
That was FLIPPING AWESOME... cant wait for next vid... or to get out to the garage and play with exhaust mods
Hi thank you very much 😊
Next vid hopefully in a few weeks... I've had quite a lot on since before Christmas so nothing done... But l have lots of things I want to do this year.
lot ov work involved with this lad and albeit a lot off head scratchin keep at it lad great work
Cheers Mark. Yes, plenty of work but everyone seems to be liking it so all is good.
interesting design for flowing, great video 👍
Yeah, it's different to the usual but appears to work well. Thanks, Dave.
Great job Dave!, you explain this stuff very well. I have two of those AR's that I'm going to begin to restore here soon because of your video's you produce. You get me motivated to get them in running shape 🙂
Hi Andru, pleased the vids are giving you some inspiration 😀.
The world needs more ARs on the road!
Takes me back to the 80s. Have fun! Good luck, fella.
Cheers 😀
Hello from north-eastern USA, I’m a big fan of what you’re doing and the theories involved. I’ve also been watching David Visard’s videos. He and Ben Alameda believe the back flow of exhaust can be manipulated by essentially making it flow poorly backwards .
Hi - I'm pleased you are enjoying.
Yes there is a lot of great stuff on David's channel. However two strokes are slightly different animal... Flow backwards in a two stroke exhaust can help with power as it stuffs fresh charge - over-scavenged from the cylinder back in.
I believe 4 strokes rely on the intake flow quite a bit too?
3:39 The flow back in has a low volume and the natural shape of the port is quite good in the reverse direction so I don't see problems with that part. You can always flow test it in reverse to get an idea of how it is working.
Restricting the volume in the port to reduce mixing is a good idea.
Hi Bill - a good idea to flow in reverse. I should be able to do that when I get around to making the transfer flow testing attachment.
The restricting volume to reduce mixing isn't mine. I think i first heard about it from Neels Van Niekerk? It's definitely something I've read about somewhere...
@@AutoBeta2T Well it's nobodies idea, its just obvious and long standing principal.
You remind me of Walter Kaaden Mz / DKW meticulous step by step tuners you will surely get there Happy Christmas love your videos Amazing work Thanks
Hi David, thanks for the complement and I'm pleased you are enjoying the vids. Note: I'm naturally quite dis-organised but I like process and procedure (it keeps me on track). I quickly realised how easy it is to forget what you have done so my big red book contains everything I do from now on. It is really helping keeping good notes.
Happy Christmas to you too.
As someone's who's trying to fix up an AR50 that's been off the road for 30 years I'm chuffed to come across this series.. great work 👍 I've got a bdk ignition, bdk pipe, 21mm carb.. I thought I had it going but after sitting for a couple of months the cylinder was full of oil! :-(
Cool, I'm pleased it is of some help. I rode mine with the BDK set up and it was quick - front wheel went up very easily!
Out of interest what sort of speed would you expect from the 93cc BDK setup? Also, I'm guessing you premix? Sorry for all the questions, not many of us with AR's nowadays and not much info about!@@AutoBeta2T
Sorry for the delay. I guess 80 mph maybe more if a full set-up. There have been claims of these going 100mph but I'm not to sure of the actual spec of the engine.
@@AutoBeta2T no problem.. I'd be happy with 80mph 🥴.. back when I was 16, I had a micron, 93 kit, 21mm carb and a supposedly derestricted cdi but it still struggled to get to 60mph.. but at 16 "tuning" involved trying to skim the head with a hand file and using cereal boxes for base gaskets! 😂😂
@user-ye8xx7gl3j haha - sounds a bit like mine... I think mine had the ar80 Ignition so would pull 65 and maybe 70 down hill. It had a micron pipe so probably not the best but it looked ace 👌
Great video Dave👍
Cheers Marcus 😀
Keep in mind that the actual flow during blowdown is almost entirely choked flow , (Speed of sound) and bears almost no resemblance to low pressure cold flow as tested here. What seems to be an improvement in this testing may not have an effect at high pressure high temperature flow during blowdown.
RULE OF THUMB if the exit pressure absolute is about 1/2(.5283) or less (or~ 2:1)of the stagnation pressure absolute(storage pressure) then the flow is choked (Mach 1) (in cold air anything above 13 psig gives Mach 1). Blowdown will start at ~100psi+ so will be choked for a good portion of blowdown time.
This data is not in a format I expected so I have to think about it for a while to make sense of it. I want the actual areas, volumetric flow figures, flow velocity etc.
Hi Bill, all noted.
Hopefully further testing as described in the video may validate the results seen here 😊
Its all good trying to improve the flow of exaust gasses but a two stroke also relys on resonance off the exaust gasses bouncing backwards and forwards in the expansion chamber. so changing the port size or shape also changes the resonance characteristics..... unlike a 4 stroke engine where you want the best flow in and out.
Hi Dan, yes, you change one thing in a two stroke and it affects another 3 or more things!
I wonder if it's the same David Vizard that had the Mini tuning book in the 1970's , very popular at the time, made him enough to move to the USA eh??
I had that book on tuning the “A Series”. Very good read 👍
The very same. He talks about it in some of his videos
Interesting re the stall of air on the piston at half way, my thinking of flow from Gordon Murray on the t50 rear diffuser, anything more than "I think 17 deg" and it would stall.
Yes, it was. I'd like to do some more research into this at some point and certainly into flow inside the two-stroke engine.
It's such a simple design, but so complex too.
Yes, an angle of attack greater than about that, and the airofoil will start to stall. Maybe filling the lower exhaust duct is helping to keep the flow attached to the front face of the piston better?
Fantastic stuff !
Cheers Trevor 😀
DV was actually born in New Zealand, I mentioned it to him several years ago and he told me.
Cool, I assumed he was born in the UK. There is a lot of interesting stuff on his channel. Although 4 stroke I feel some of it applies to 2 strokes too.
not another 2stroke stuffing channel :)
Been waiting for this one.
Me too. It's been fun to make but the time required to document everything is large. I've missed quite a bit of stuff I want to talk about as I'm limited by recording on my mobile phone. I could do with some better cameras as I use my phone to record and edit everything.
I look forward to your thoughts on the testing Bill.
Nice work Dave looks like you’re going to be doing some cnc stuff.
Cheers Jonathan - the project for Christmas is getting that thing going!
Awesome!!!
Thank you.
Great work buddy but if you have done this much effort on yamaha rx 115 engine you would had created a deadly hyper aggressive machine. Some how im convinced that yamaha rx platform is really invented for tuners like you. If you had done this much effort on yamaha rx...dramatically saying you would have reach 35 hp but great work dude your love and passion for 2 stroke is visible in your videos. love that..keep grinding 😉❤
Many thanks buddy 😊
Love these vids
Thank you 🙏
Be curious if power could be found with this. In the 90's I filled this section using Belzona epoxy steel for the same reason, but I never noticed any obvious gains. It was seat of the pants tuning in those days!
Me too. I don't think there will be masses, but maybe 1/2 to 3/4 hp
I wonder what the difference would be if the exhaust port had a horizontal piece of metal inserted to basically split the top and bottom, obviously something quite thin.
Not sure... If it was thin there would be risk of it heating up and acting as a heat exchanger. It could help blowdown flow.
Looking good progress. 👍
Just make biggest hump and mill it down if it not make any difference.
Have you tested 2mm smaller arrister tube to ex port?
Hi Pienari, I could do it that way but i would have to weld up the duct and i'm worried about distorting the cylinder. I'd like to bore out the duct and just use an insert but that will have it's problems too.
I do want to try a smaller exhaust stub - currently it is 30 mm dia where is goes into the exhaust. 28 mm would be about 90% of the window area... Something to try. Cheers
years n years ago when performance bike mag first came out they did project (suzuki) GP100plus trying to get a little Gp to the ton .
Air cooled 2 strokes are great for playing with good luck with the Ar i reckon you will get there .. Food for thought put a H100 honda engine
in an mbx or mt5 see what it will do ..
Yes, a little before my time but I do have some of the GP100plus articles somewhere. John Robinson was great.
My brother had ar50 in his teen years going back 30yrs ago or so, old man put ar80 head, carb and micron exhaust on and made it worth riding, I remember riding on the back with him as a 12yr old.... brakes were shite though😂. I never went down the bike route after that, though Bro did some scrambling as we called it back then and got a slighgly tuned big wheeled rm80. As a fairly small 14-15yr he struggled somewhat 😂... we shouldn't of sold that bike😢 but he bought an Rd125 instead. wished I taken it up more and got my bike license but never did and went into cars, into chainsaws and porting with my work now, so always had a love for 2 bangers. Would love a 2t dirt bike now, great series though❤👍
Hi Rick - sounds like great fun strapped onto the back of your brother!
Are there any dynos for chainsaws?
Pleased you are enjoying 😀
@AutoBeta2T Yeah, there's a guy in the States who has a channel. 'Dyno Joe', I'm curious about that flow testing... you put a hump on the floor of the port, not sure how that is increasing the hp. Is it like accelerating the flow out? Would you just weld that in and shape it with the foredom something🤷🏻♂️
didnt they bolt an old air cooled KX80 engine in the AR50 years ago.. they go straight in on the original engine mounts.
Sorry, I missed this. Quite possibly, though. I'm keen to do it with the AR engine though.
@@AutoBeta2Tit is basically the same engine I think the crank is slightly upgraded but because it was 80cc from the factory it might would be interesting to see what the port arrangement and sizes look like. Not sure if the barrels where nickel plated or if they had liners I do know back when they were popular the small wheeled Kx80 was dangerous. Not sure how much power they made. Might give you some ideas if nothing else.
there's very little reverse flow. You have to think about whether or not return wave strength is lost due to any abrupt changes in diameter. Making the port floor higher benefits low RPM power at the expense of high RPM power. Adding a bottom ramp directs the movement of the reverse waves higher inside the cylinder, whereas the ideal direction is downward to the transfer ports. So the makers of that program obviously did no real life testing. I did which is why I know this. And its calculations for time-area for blowdown are incorrect.
Neat stuff. What would happen if there were vanes in the exhaust duct?
Hi Cerberes, I'm not sure. But if they were too small the may act a a heat exchanger and heat up the fresh charge? I may however help? SOmthing to test when I get to the 3d printed insert stage.
Ciao ho sbirciato varie volte i tuoi video ed oggi mi sono iscritto. Vorrei sapere per cortesia dove hai acquistato il tubo venturi con le prese e i misuratori di pressione
Ciao, grazie per esserti iscritto. Ho aggiunto un elenco di articoli alla descrizione, ma vedi anche di seguito:
TorqSoft equipment list:
Venturi 20 mm is most suitable for cylinders with port diameters of less than 33 mm: www.shapeways.com/product/FTPHNUF3X/flow-venturi-20mm?li=shop-results&optionId=59345290
Venturi 27 mm is suitable for cylinders with exhaust port diameters between 30 and 44 mm, and is shown below.: www.shapeways.com/product/ZFQJ7UAL2/flow-venturi-27mm?li=shop-results&optionId=59381039
Manomenter: www.amazon.co.uk/dp/B07K87NQMD?ref=ppx_pop_mob_ap_share
Brass nipple - 3mm: www.ebay.co.uk/itm/390948209350
I'm enjoying the channel and I'm interested in your journey. It's nice to see the progression. Where do you go to dyno it?
Hi, pleased you are enjoying. I have 2 video worth's of footage to edit so hopefully another couple of vids soon.
Dyno is one me and a mate bought years ago .
@@AutoBeta2T That's great to have you're own dyno!
@@pierrefpv yep - it's a great asset.
As an autistic bike nerd, this is like porn ! I think I said I was working on my simson, but these videos have given me a real boost. I am off to germany in the new year to make some friends. They have close ratio boxes, fully cnc cases etc. They make cylinders up to 110cc, but have recently been adapting the MTX125 cylinders to the Simson cases. They have a endurance race and festival every year, that I hope to attend. Just need to improve my school boy german! The book you asked about is the one by Graham Bell, which I am sure you have !
I'm pleased you are enjoying James 😊
More geekery to come!
Enjoy Germany and the festival. I believe the Germans are fond of the two strokes?
And yes I do have the Graham Bell book. I was flicking through it the other day.
2T engines are not comparable to 4T cylinder heads, and operate on the principle of unsteady flow, so flow testing is not likely to be of tremendous use. In the early days of 2T engines, the exhaust ducts were often overly large, and significant performance gains could be realised by welding up and reshaping the duct. Increased torque, is the most noticeable thing that is generally gained from a smaller exhaust port. Its a very good idea, to try and read up on 2T engine operation, and understand how the engines work. Not sure if its still available, but the best book I have seen on 2T engines is "The Two-Stroke Cycle Engine" by John B Heywood and Erin Sher. Scavenging is the most important part of the 2T cycle in terms of generating power, and if you have sealed off the transfer ports, any sort of flow testing is questionable, as it will not be even remotely related to the flow inside a running engine.
I read Blair’s book, was impressed by the p/t sensors used and the data logging.
Hi - yes 2 strokes are massively different to 4 strokes and the unsteady gas flow inside is interesting. I'm no expert and I'm just documenting my experiences with this particular 2 stroke engine, really as a novice, but I did note Jan Thiel's words in his book and he did use flow testing to assess modifications to the engines he worked on. Jan Thiel developed the Aprillia RSA 125 which made 54 hp at the output sprocket.
As with most of what I put up here it's just my meandering around the "what and ifs" of 2 Stroke engine technology. Something's may work and some not.
Thanks for the comment - it's really appreciated.
@@AutoBeta2T I would guess Jan Thiel had a very good idea of exactly what he was wanting to achieve? It will have been something very subtle, and you may find you get better results from something other than flow testing?
Welding up exhaust ports was carried out in the 60s on TSS Bultaco's. Increased torque, and made them come out of the corners much better.
How many cylinders do you have? Its a good idea to have several, so you can try some different ideas. The idea that bigger is better still persists, and you might find that isnt the case, if you test several back to back with different configurations?
I am trying to improve Yamaha trials motors, and have managed to collect up 5 or 6 cylinders, which wasn't that easy as they are very hard to find now, as the last one was made in 79!
Hi :) possibly but It's an area I wanted to explore. I think actual flow benches are very expensive but the set-up I am using is relatively cheap.
Now cylinders are a problem - this is the only Autisa one that I have and they are like hen's teeth. I do have another but it's a copy of this and is all cast iron. I'd like to get some more and be able to do leap-frog testing but unless I can find another few that isn't going to happen.
A standard AR80 cylinder would be good but these are difficult to find too.
To make matters worse it's on it's last overbore...
@@AutoBeta2T If you cant get parts, then its going to be very difficult to make much forward progress. I would have thought something like a 50cc Minarelli might have been a better choice?
Hi Dave, how about trying a bell mouth on the carb?
Definitely, I have a 3D printer, so really want to explore how it affects power.
@@AutoBeta2T Obviously it's about 4T but have a look at
Garage 4AGE, they've tested various fixed length velocity stacks/inlet runners as they call them as well as variable length ones, sort of ypvs on the intake on Toyota (Yamaha) engines
soon I'm gonna try it on my bike haha nc work
Cool - and cheers :)
Ive a super flow machine ive been flow testing two stroke motor 14 years but ive been doing kart motor for 30years you doing stuff ive already done . You can do more work on inside the piston , run one ring . Bottom end pay big part in flow to . Flow test the carby the air box . Pipes Rule of thumb longer the pipe from the head of the motor to end of first cone give you more bottom end power that means the power band comes on early and goes out early so shorter the pipe more topend . Now you running a reed block same thing with that to thinner gasket thicker gasket . More testing. Good example my mate does outboard boat motors for racing 25hp because you can't change the pipe because the pipe is the leg of the motor you spaces the carbys out gives you more bottom end power . All so read your pug each run to . Remember this at work temperature thing change in shape too . For example nascar motor they hot hone their motor at working temperature something think about
Cheers for the info Storky. Where did your testing of the exhaust duct point you? From what I can see the flow favors the edges of the duct when the piston is in the blowdown phase and having a raised center section on the floor appeared to help the flow but it reduced the noise too.
Funny thing when I test my old motor kt100s we could not touch the ports I was looking for good barrel they were hard to find mostly we were looking at transfers port . Then years later I was speedway kart in open class did alot porting . One thing I found in running synthetic caster oil because it a dirt oil and carbon use to build up in exhaust port that were I use to grind what they call rabbit ears in exhaust port go wider not high in the port you go to high the power stroke is small you lose bottom power .your transfer port try flow them to front piston give you better torque . The head .8 to 1mm squish kept a sharp edge on squish to bowl better mix better responses down low and the position of spark pug as well point the opening towards the exhaust port more testing
Just throwing this out there but have you thought about making a cylinder head out of 2" thick lexan and then running the engine ?
I have often thought about this for my Honda odyssey's so that I could video tape it and actually see exhaust flow and see what's going on inside the combustion chamber while the engine is actually running.
The lexan head would be made with the same profile as the head you plan to run.
I know that sounds crazy and you wouldn't be able to run the engine very long but you don't need to run the engine for long.
CO
Hi, I've not thought of it in a running engine but it would be cool. I think the restriction would be getting a camera that can record high quality slow-mo...?
All the people that have done that only run the engine at idle and low throttle. Otherwise it will melt blow the head off very quickly. Seeing what it does at idle tells you virtually nothing about what it is doing under full power.
@@billshiff2060 Yes I agree. But you get everything ready and make a full power run on the dyno as fast as you can. With a camera rolling you will have the evidence you need within a few seconds of film.
CO
Search RUclips, it's been done a few times ( it usually ends with the plug threads giving in.
I don't know what happened, I made a comment but it's not here.
Anyway, great video Dave, I really enjoyed it and I think that I'll invest in the software and venturi myself.
I have a damaged Bidalot 50 cylinder that you could borrow to study, if you think it would be useful!? It's the best 50cc cylinder that I have used so far.
Just pm me if you're interested Dave.
Keep up the good work and I look forward to the next video.
Mark P
Hi Mark, I'm not sure? Comments seem to go missing from time to time.!
Pleased you enjoyed it mate and I'll drop you a message in a bit as it would be good to have a gander at the Bidalot cylinder.
Hope you are keeping well mate?
@@AutoBeta2T Yes, I'm keeping well thanks Dave.
I think warped perception did a see through cylinder if I remember right if anybody is curious to see what it looks like
Cheer Joe - I'll have a look. There have been a few see-through 2t cylinders. It would be good to view operation in super slow motion.
@@AutoBeta2T you videos are awesome too though-thank you sir
Cheers Joe :)
i use big pipe chamber on my kr150 its good for high rpm but give big drop powerband around 7 /8k rpm before power valve open, how to get rid that problem 😢
Unfortunately I think everything is a compromise...
Maybe a ATAC chamber?
just short question does your exhaust suck or blow i mean that your pressure are is not there where it should be ??
Hi, the vacuum sucks from the cylinder and out of the exhaust
Any ideas where to purchase the book "two stroke master" in English?
Hi - the latest post I have seen is here: facebook.com/groups/671081149638729/permalink/6915535795193202/?ref=share
It looks like there are 100 English books still available.
I also have this email: legacyjanthiel@gmail.com
Cheers
Where did you get that jan thiel book ?
Hi, details are here:
Jan Thiel's book details are here: legacyjanthiel@gmail.com
and: facebook.com/groups/671081149638729/permalink/6915535795193202/?ref=share
What about total volume of air per second? Was it more or less?
I don't know, I just put the readings into the programme. However, if the flow area power prediction goes up, then there will be an increase in mass-flow.
Hi! Could you advise how to calculate the exhaust for an engine with two pipes per cylinder? I have several old Soviet 175cc engines, they have 2 pipes, one cylinder and are very low in power. I don’t drive them all the time - it’s just small hobby.
Hi, I'm not too sure about these types of engines... I would imagine maybe two pipes that are 50 % of the area of a normal 175 cc engine?
I think EngMod2T can model these types of engines? I'll have to have a look later if it can and if so if there is any guidance.
@@AutoBeta2T Thanks for the answer. It is a simple 175cc single cylinder engine, one of the Soviet copies of the old DKW - cylinder diameter and piston stroke 62x58 mm. There is no reed valve, their speed is low - about 6000 rpm at maximum power. About 14 horsepower. I have a program for calculating exhaust using the Blair formula, it’s quite simple, but it seems to work. The problem is that I don't understand if the single exhaust calculation will work with the dual exhaust. Some also advise me to take half the volume of the cylinder for the calculation, but I believe that this is the wrong way - after all, each exhaust has its own port.
Hi, I had a look on engmod2T and it does simulate this type of exhaust port. There wasn't a massive amount of info on there but it looks like the pipe configurations available are two separate exhausts or a two into one. I would think that a calculated two Stoke exhaust for the 175 engine would work but with the header split into two. Probably with the diameter of the header equating to half the area of the single exhaust header that was calculated.
@@AutoBeta2T Hello! Thank you for your time. Are you proposing to combine both pipes into one resonator? The calculation program uses the height and width of the exhaust port. It might be worth just designing two exhaust pipes, each with its own exhaust port. I have a more "advanced" version of the engine as well. This engine has a single exhaust, with the exhaust port being much larger than each of the two in the old version. And the pipe is also much larger. But I'm not sure the engineers planned to increase its power. Or rather, they tried to reduce the volume)))
Hi, yes - both header pipes go into one resonator. A bit like some snowmobile pipes.
Sir i have two stroke cylinder i want to increase its rpm, power please help me how i can increase the speed from its ports. Please help me tell me sir
Hi, what cylinder and what are the durations for the ports?
I go through raising the exhaust port in this video ruclips.net/video/_4X0QWb8Wcs/видео.htmlsi=Fh-8-nIwXexxVCur
Note: raising the exhaust port roof 0.5mm makes quite a bit of difference.
@@AutoBeta2T Sir, please 🥺 give me your whatsapp number and I will send you the picture of the cylinder and also the picture of its crankshaft.
@@AutoBeta2T I'm so confused because of porting I've done a lot but I lost a lot help me please tell me
@@AutoBeta2T Sir give me your whatsapp number I will send you the picture of the cylinder and piston and also send you the video of its engine. Please sir help me in this task I am very confused that's why. I don't understand anything please sir help me tell me
@janeali1174 what engine do you have?
you might be experiencing part of what happens when you use a wobbly duct.
Yes. I was thinking that too. I want to do much more research in to the duct design and test it. Hopefully in the new year sometime.
@AutoBeta2T i mess about tuning mopeds on a hobbyist level and most ducts on cylinders taper out bigger. whereas according to wayne wobbly wright if they taper smaller they make the pipe work better. so for single exhaust ports the wobbly duct tapers to 90% of the diameter of ports effective area in the length equivalent of 1.5 x bore size. and then back to 100% bore size in 0.5x bore size. its a 2 part duct, total length 2 x bore diameter. so they narrow slowly and then open up again but a bit more sharply. heres my example. i did this to a 47mm 74cc gilardoni cylinder and ex port area was 490mmsq which using maths pi etc = a circle of 25mm diameter. first part of the duct is 1.5 x 47 = 70.5mm long, at that point i needed 90% of 490mm sq = 441 which is equal to diameter 23.6mm. the first 29mm of this part of the duct was my cylinder duct itself which needed altering. you can drill and insert the correct shaped piece or weld it up. so attached to my cylinder i needed a duct of 1.5 x bore MINUS the cylinders 29mm long duct 70.5 - 29 = 41.5mm. the start diameter of that duct i had to workout cos the first 29mm had already lost a mm or so. and then 2nd part of the duct is 0.5 x 47mm = 23.5mm long. and that goes back to 25mm diameter. bit hard to explain. but a diagram shows it much more clearly. ive done a simple cad drawing showing it with my sizes if you wanna see it. dunno how to get it to you?@@AutoBeta2T ?
@@aljaxon69 hi, that sounds like what I am trying to do with mine. The 1.5 x bore restriction works well in EngMod. And the Mach is around 0.8 too.
It would be good to have a look at your design. My email is: autobeta2t @yahoo.com
Combustion don't work like that mate and expansion exhaust chamber works at pulse speed like a jet hot squeezed gas your better off trying different carbs
Have you tested this type of exhaust duct? What did you find happend when the duct was raised from your testing?
Also, what carb do you recommend?
hello , how many horses powers you hope?
Hi Oliver - I need about 20 - 21 hp on my dyno, that's 23 - 24 hp on a DynoJet.
It seems to me not so much the shape but the diameter. The higher the air speed, the better the flow.
Hi Jaap, possibly... Or maybe the correct airflow?
The current duct is quite small still. I do wonder if the power will.pick up with a larger duct?
@@AutoBeta2T Interesting comment, from just looking at it the duct seems huge, optimum for a single port seems to have the duct end at around 90% of the full open window area. How does yours compare?
Hi Neels, a poor comment from me, I was thinking specifically about the area of the duct where is comes out of the port, it is fairly narrow (about 28mm Dia) but then it goes really big as the floor drops away. The outlet to the exhaust duct is 32.7 mm and the port window is equivalent to 30.4 mm diameter giving a passage to window area ratio of 115.5 %.
However, the stub I am using has a entry of 32.7 mm but reducing to 30 mm dia (at approx 1.5 x bore) where the pipe starts (there is a fair radius on the entry but it feels smooth. This has a passage to window area ratio of 97.2% so still possibly too large. I did some testing in EngMod a while ago and I think 28.5 mm worked well.
I have another observation but i'll reply in another comment as YT sometime dumps what I have written.
Neels, another thing i noted when doing some initial tests was the interface between the duct and the stub. It's this area that I tried to smooth for better flow (as it isn't a smooth transition) but it made no difference. I'm wondering now if I need to keep reducing that area until flow starts to drop off. Almost like trying to reduce the duct area until it just starts to hurt the flow. No increase in flow but no excessive volume in the duct to dissipate pulse energy?
@@AutoBeta2T As a first step I would reduce the duct area from window to duct end as recommended by Wobbly to 90% of window area at the duct end, and creating the ski-jump bottom floor as he recommends (which also improved the flow in your video) to the limit the fresh charge / burnt gas mixing as you clearly explain in your video, and do a dyno test with this to get a baseline.
Raise the exh port, mill the head to 060” squish and 200 psi primary and you will do better than that gimmick
Hi, the e haust port has already been raised to 203 degrees duration. I'll look to go higher if required. I do intend to look at squish tests, currently I believe it is too tight on my current setup.
I assume you have tested raising the exhaust duct floor. How did it affect the power output in your tests?
@@AutoBeta2T
All my porting has a flat floor, I’m old school going with formulas with MPA ( mean port area) and getting an effective rpm range. Tommy (Tom Turner) and I have different theories on 2 stroke porting, I don’t use his blow down theory, the formulas that I used I would get the exh and transfer port ERPM and there is so much just on shape of the exhaust port. As 2 stroke stuffing learned the hard way on going a 100% of the exh port width.
If you want a decent ripping porting with reed’s
200 degrees of exh and 128-130 degrees of transfer porting.
You’re kinda in the Blue printing stage of that cyl.
I don’t think JB weld will hold up on the floor of your exhaust port. If you have a boost port, match the height and roof angle is key. Take the boost port and cut it like a slot and drill a hole into the piston and all the AFM under the piston at BDC will help get more AFM in the combustion chamber. Also, squish width, narrow for hi rpm, wide for bottom.
Increase your primary compression ratio by stroking the crank, this will help your torque as you loose a good amount of by raising the ports. But 5-7mm stroke is far as I would go or you will blow out your crank seals. 2SS is destroying reeds cuz his “primary” Crank Case ratio is way too high.
I can send ya formula’s if you want but Robert from Factory Pipe Products turned me on too a good 2 stoke theory, n I can get ya the ISBN number for it.
I’m 61 years old n have ported a ton of cylinders and had the first EFI 2 stroke on the national tour and it make’s a huge bottom end HP which made it so I could over port it like a light switch and still have great power everywhere back in 1994. Remember always, it’s theory, so depending on the application, nothing is set in stone. That’s why there is no 100% internal combustion engine ever made. Your car or truck has a cat in it because it can’t be done.
@@radron14 Hi Radron, sorry for the late reply but your last comment was held for review for some reason? YT does weird and wonderful things sometimes.
I'm currently at 202 exh and 130 transfers. I feel I need a little more transfer area but I don't want to go up and eat into the blowdown. There is epoxy (done badly) on the transfer roofs at the min - I want to redo it so I'll do a test of raising the transfers for more tx area but reducing the BD area.
I think my SAR is a bit high at the min (48%) and I want to try some different squish dimensions. I've just cut two different heads, one with lower MSV than the current best and the same compression, and another with lower MSV and compression. I'm looking forward to testing them.
I'd love to stroke this engine and get it a bit squarer but there is literally no meat on the crankcases to make them larder for the extra clearance required. Any ideas?
I haven't measured the primary ratio on this engine. I should but not 100% sure on how to.
Yes please with the ISBN for the book. I'm always after getting my hands on books on the subject
Regards
Dave
Don’t believe this, his “swirl” comment is a dead giveaway.
Sorry mate, MPA and point of mean reflection will work.
This is a Trials low end power n major drop off at RPM.
It’s actually called scavenging.
Total gimmick
Hi again, what's wrong about my swirl comment?
@@AutoBeta2T
Technically it’s called scavenging