Some things like this it is better to demonstrate on an engine, but other things like the chamber i need to use diagrams etc so Ill try to mix more of this type into videos.
You ate definitely smart enough to install a stiyl m660 cylinder on an 80 cc China motor , others are trying to make videos showing how and failing miserably please take the time to build that motor I would greatly appreciate it thank you
Thank you for the comment. I would probably attempt that job however at this stage I don't have any useful purpose for the engine other than to use it in the videos to demonstrate various topic I'm covering.
Yeah Id use the word engineering loosely with this engine. At 154 Ex and 104 Transfer it's pretty poor and the piston is a world of wrong. Reed intake though but direct to case so no boost port I can see..
@@mordantly I'm sure they copied some engine and just did a real poor job of it. But for AUD 60 price it looks like i got what i paid for. Shame really because if they got the right cylinder and piston to use it might have been half decent.
Hi Dave, great video's, I've learnt a lot along the way. Even downloaded the calculator and built my first chamber. I have a question relating to port mapping. As you explained in another video, trace the port, work out the area then calculate the effective diameter which is then used in the calculations for the expansion chamber. However, like in this video at the 4 minute mark, my piston sits up into the port at BDC by about 3mm or the top ring just disappears. Should I therefore be reducing the measured area by the amount the piston is masking the exhaust port? By the looks of the engine in your video it looks like the piston is masking 15 to 20% of the exhaust window. I haven't re-measured mine yet but I'm guesstimating it's around 7 to 10%. I've recalculated the pipe and it makes a small but noticeable difference to the result.
the piston doesnt actually close the exhaust, though. the ring does. exhaust gas is escaping past the piston crown. so if you use the flashlight method to see when the actual light stop coming through the port you will get very different numbers.
Yes that is right however the reason we use the piston top is because although the ring is past the port, the gap between the piston crown and the bore provides only a very small gap in which gas flow is quite choked at that stage. And only when the crown finally arrives at the port creating a direct opening does a significant transfer of gas occur to the port suffice to have a speed near sonic which is what actually creates the compression wave that travels down the pipe and is reflected back, so that point is the beginning of the wave and what tuned length of the pipe is timed for. This is also why the exhaust power valve works to vary the port timing on the exhaust as well is increase the trapped compression ratio when the valve itself does not contact to seal directly to the rings or piston and is some distance away even more so than the piston to bore at the crown above the rings.
@@AuMechanic one problem is it is common on the engines I run to radius the ring land area if the piston to prevent seizures from heat expansion of lightened pistons. So that gap is substantial with the piston radius.
A trick that I've seen in the chainsaw world for mounting a degree wheel is using a keyless drill chuck mounted to the wheel then snug it on the crank end
Good idea, however you fit the degree wheel is good enough since its not that critical doing piston port timing where you are just reading one sweep on the crank Where doing cam timing its more critical since you have to set absolute TDC and any chance the wheel slips is not good.
You can mount the degree wheel with mounting putty like Prestik. If your wheel is light, it will stay in place if you don't bump it. To center it, just align the outside circle or perimeter with a fixed point. No bolts required.
Doesn't it matter to know the degrees from TDC to when the port begins to open? The effective power stroke. Then, from there were would calculate the 154 degrees in to that?
In a 2 stroke the port open is the same degrees as the closing from TDC (symmetrical). So if you want to know how far it is from TDC then just halve the open period,. Also, measuring half the open period from TDC halves the precision of the measurement where measuring the whole open period is more precise and is simpler too so less chance of a mistake. Setting TDC on the degree wheel is done for 4 strokes because cam timing periods are not equal degree from TDC (asymmetrical)
Same as single cylinder, just measure exhaust port timing of one cylinder. As mentioned in the vid, exhaust and transfer timings are symmetric, meaning they open and close at the same amount of degrees from top dead centre, so you only need to measure the total open period in degree's you don't need to measure how far from top dead centre they open or close at.
Hi Sir! Right now im fixing-rebuilding an old Fantic Lei moped from the 70s, with 49,6cc Minarelli engine, and i measured just 132 degrees on the exthaust port!!! its pretty far from the range you mentioned. Any idea why is the number this low... or suggestion what would a more experienced mechanic do in this case?
@@AuMechanic Thank You for your answer! You are right I watched a comparsion vid of three cylinders from Matt(the workshop) and there he measured an older OEM Piaggio with a similar difference between the Tr-port and the Ex-port(just 3.5mm).
Well spotted, 3 mm actually, Ill be doing a video on the other problems with this engine. So far I can see the cylinder they used does not match the stroke of the crank and the piston they used was a dirty fix to get the comp ratio high enough to run.
I've got one of these an I'm itching to port it but I've made the same observations as you guys. Would raising the barrel then skimming the head fix the problems do you think? It is possible to get a separate head for these engines...
Due to the fact degree in crank angle is dependent on rod length etc blow-down is expressed as piston travel. So knowing the exhaust open period in degree and transfer in degree giving you blow-down in degree, you can then calculate piston travel during that period. As a general rule anything less than about 4 mm of piston travel time between exhaust open and transfer open you risk excess back flow down the transfers when they open.
I have a question, is there any way to calculate the required octane rating on a 2 stroke? Please try to make it as simple as you can because I'm not as advanced so to speak as you
The octane rating will be based on the compression ratio so you would need to calculate that for the engine which you can do from the bore and stroke above the exhaust port which is called trapped cylinder volume and the combustion chamber volume which is with the piston at the very top that you measure with oil or some fluid to get the volume of it.
There is no formula to give compression ratio from cylinder pressure since the pressure you get on the gauge is subject to a number of variations which is why it is better to measure the actual CR and then calculate octane required from that.
Basically you raise the exhaust port to increase exhaust timing. Either by grinding the exhaust port itself OR to increase timing on exhaust and transfers you can raise the barrel and then remove some off the top of it to bring the head clearance back to what it was to begin with.
Dear Sir, I am Basil from India and I am looking for 2 stroke exhaust pipe design software. So if you can help me with it, will be great full. Please provide your contact details as well Sir. Thanks
Hi Basil See the most recent video I did, there is a link in the description section below it to 2 Stroke Exhaust Expansion Chamber software i wrote, it is freeware.
Here's the thing do you make money off of these videos, (that's your business) but if you do then I'm telling you if you advertise it and make a 4 or 5 part video YOU WILL GET 500,000 VIEWS, there is no other video on the whole world wide web you would be the first to do a video and do it right , please consider!! China motor 80 bucks , cylinder kit from AliExpress 25 dollars equals five hundred k views maybe a million views .
@@AuMechanic my friend you will find some imfo that is correct and some that is just false , I'm learning some , one thing is use 2 bushings on sides of 54 mm piston and use 10 mm wrist pin instsead of the 12 mm pin that comes with the cylinder kit. God I would just about send you a motor and cylinder if I could get it back when you are done for a decent price, PLEASE DO THIS PROJECT!!
You, 2STROKE STUFFING and Matt from the workshop are my favorite RUclipsrs. Merry Christmas btw!
Snap
Glad to hear it, you have a good Christmas too.
Me too, love all their vids 👍
Very nice video. Informative and fun to watch. I think I like this video format more, compared to the older, "screen view only" videos
Some things like this it is better to demonstrate on an engine, but other things like the chamber i need to use diagrams etc so Ill try to mix more of this type into videos.
You ate definitely smart enough to install a stiyl m660 cylinder on an 80 cc China motor , others are trying to make videos showing how and failing miserably please take the time to build that motor I would greatly appreciate it thank you
Thank you for the comment.
I would probably attempt that job however at this stage I don't have any useful purpose for the engine other than to use it in the videos to demonstrate various topic I'm covering.
Gotta love 5th grade ameteur engineering! Merry Christmas. Can't wait for other port vids.
Yeah Id use the word engineering loosely with this engine.
At 154 Ex and 104 Transfer it's pretty poor and the piston is a world of wrong.
Reed intake though but direct to case so no boost port I can see..
Very true. Either a piss-poor copy or scrap bin parts job.
@@mordantly
I'm sure they copied some engine and just did a real poor job of it.
But for AUD 60 price it looks like i got what i paid for.
Shame really because if they got the right cylinder and piston to use it might have been half decent.
Thanks again for all you do!
Love your work mate, thank you for these videos
Cheers Matt
Got another to upload later on that covers some more on this engine and another way to measure port timing.
Hi Dave, great video's, I've learnt a lot along the way. Even downloaded the calculator and built my first chamber.
I have a question relating to port mapping. As you explained in another video, trace the port, work out the area then calculate the effective diameter which is then used in the calculations for the expansion chamber. However, like in this video at the 4 minute mark, my piston sits up into the port at BDC by about 3mm or the top ring just disappears. Should I therefore be reducing the measured area by the amount the piston is masking the exhaust port? By the looks of the engine in your video it looks like the piston is masking 15 to 20% of the exhaust window. I haven't re-measured mine yet but I'm guesstimating it's around 7 to 10%. I've recalculated the pipe and it makes a small but noticeable difference to the result.
Yes, if the piston masks the port to any degree you would need to subtract that.
Very informative video. Thanks for uploading..
Thanks for the comment.
the piston doesnt actually close the exhaust, though. the ring does. exhaust gas is escaping past the piston crown. so if you use the flashlight method to see when the actual light stop coming through the port you will get very different numbers.
Yes that is right however the reason we use the piston top is because although the ring is past the port, the gap between the piston crown and the bore provides only a very small gap in which gas flow is quite choked at that stage. And only when the crown finally arrives at the port creating a direct opening does a significant transfer of gas occur to the port suffice to have a speed near sonic which is what actually creates the compression wave that travels down the pipe and is reflected back, so that point is the beginning of the wave and what tuned length of the pipe is timed for.
This is also why the exhaust power valve works to vary the port timing on the exhaust as well is increase the trapped compression ratio when the valve itself does not contact to seal directly to the rings or piston and is some distance away even more so than the piston to bore at the crown above the rings.
@@AuMechanic one problem is it is common on the engines I run to radius the ring land area if the piston to prevent seizures from heat expansion of lightened pistons. So that gap is substantial with the piston radius.
This is great info. Thanks
If you are installing a rocket key to advance timing, this needs to be done with it installed right?
You zero the timing wheel anyway to begin with irrespective of the ignition timing.
@@AuMechanic Ah silly question. However it helped me see the obvious. Many thanks again. You have a new subscriber. :)
I am looking for engines with the lowest Exhaust port duration.
What is this engine ?. What is its stock power band. ?
Best video ever!
Thank's for the comment.
A trick that I've seen in the chainsaw world for mounting a degree wheel is using a keyless drill chuck mounted to the wheel then snug it on the crank end
Wow, great idea.
Good idea, however you fit the degree wheel is good enough since its not that critical doing piston port timing where you are just reading one sweep on the crank
Where doing cam timing its more critical since you have to set absolute TDC and any chance the wheel slips is not good.
You can mount the degree wheel with mounting putty like Prestik. If your wheel is light, it will stay in place if you don't bump it. To center it, just align the outside circle or perimeter with a fixed point. No bolts required.
Thank you! :)
Merry Christmas
Thank's Sean, you have a good Christmas too
Doesn't it matter to know the degrees from TDC to when the port begins to open? The effective power stroke. Then, from there were would calculate the 154 degrees in to that?
In a 2 stroke the port open is the same degrees as the closing from TDC (symmetrical). So if you want to know how far it is from TDC then just halve the open period,.
Also, measuring half the open period from TDC halves the precision of the measurement where measuring the whole open period is more precise and is simpler too so less chance of a mistake.
Setting TDC on the degree wheel is done for 4 strokes because cam timing periods are not equal degree from TDC (asymmetrical)
Hi, I have a KX85 which I'm putting a 2mm stroker crank in, can I space the base of the cylinder to keep the port timing right. Thanks,
Did you ever figure out the answer to this
No
How do i mesure the timing on a two sylinder engine?
Same as single cylinder, just measure exhaust port timing of one cylinder.
As mentioned in the vid, exhaust and transfer timings are symmetric, meaning they open and close at the same amount of degrees from top dead centre, so you only need to measure the total open period in degree's you don't need to measure how far from top dead centre they open or close at.
@@AuMechanic thanks dude
Where can you buy those wheels
Do a search for metal timing degree wheels.
Hi Sir!
Right now im fixing-rebuilding an old Fantic Lei moped from the 70s, with 49,6cc Minarelli engine, and i measured just 132 degrees on the exthaust port!!!
its pretty far from the range you mentioned. Any idea why is the number this low... or suggestion what would a more experienced mechanic do in this case?
Being an older engine the fairly low timing number may just be the engine doesn't rev very high.
Is it out of a scooter ?
@@AuMechanic Thank You for your answer! You are right I watched a comparsion vid of three cylinders from Matt(the workshop) and there he measured an older OEM Piaggio with a similar difference between the Tr-port and the Ex-port(just 3.5mm).
Wow that is a mountain of piston not "clearing" the port at BDC. Anyways nice video and Merry Christmas!
Well spotted, 3 mm actually, Ill be doing a video on the other problems with this engine.
So far I can see the cylinder they used does not match the stroke of the crank and the piston they used was a dirty fix to get the comp ratio high enough to run.
I've got one of these an I'm itching to port it but I've made the same observations as you guys. Would raising the barrel then skimming the head fix the problems do you think? It is possible to get a separate head for these engines...
What is the best piston blowdown degrees and how to calculate it..
Due to the fact degree in crank angle is dependent on rod length etc blow-down is expressed as piston travel.
So knowing the exhaust open period in degree and transfer in degree giving you blow-down in degree, you can then calculate piston travel during that period.
As a general rule anything less than about 4 mm of piston travel time between exhaust open and transfer open you risk excess back flow down the transfers when they open.
thanks
Nice shirt love suzuki
I have a question, is there any way to calculate the required octane rating on a 2 stroke? Please try to make it as simple as you can because I'm not as advanced so to speak as you
The octane rating will be based on the compression ratio so you would need to calculate that for the engine which you can do from the bore and stroke above the exhaust port which is called trapped cylinder volume and the combustion chamber volume which is with the piston at the very top that you measure with oil or some fluid to get the volume of it.
@@AuMechanic I know what my compression is, it's
205psi. So any way to calculate off that?
There is no formula to give compression ratio from cylinder pressure since the pressure you get on the gauge is subject to a number of variations which is why it is better to measure the actual CR and then calculate octane required from that.
@@AuMechanic thanks
How can I increase the port timing my factory timing is 165° I want to make up to 175°
Basically you raise the exhaust port to increase exhaust timing.
Either by grinding the exhaust port itself OR to increase timing on exhaust and transfers you can raise the barrel and then remove some off the top of it to bring the head clearance back to what it was to begin with.
you tell about the opening time of the exhaust opening and show the intake opening really clearly
Im subscribe
Please subtitle Indonesia all vidio
🙏🙏🙏🙏🙏👍
Awesome video love watching them. Thanks for sharing. If you watch my RUclips you’ll see my chopper bike with a worked 66cc
Had a look, does that have one of those Zeda engines ?
Would u port and polish my 32 cc engine I will pay u for it. Please let me know message me
I don't do outside work anymore sorry but keep watching the videos and I will be covering more on porting..
Dear Sir,
I am Basil from India and I am looking for 2 stroke exhaust pipe design software. So if you can help me with it, will be great full. Please provide your contact details as well Sir. Thanks
Hi Basil
See the most recent video I did, there is a link in the description section below it to 2 Stroke Exhaust Expansion Chamber software i wrote, it is freeware.
Here's the thing do you make money off of these videos, (that's your business) but if you do then I'm telling you if you advertise it and make a 4 or 5 part video YOU WILL GET 500,000 VIEWS, there is no other video on the whole world wide web you would be the first to do a video and do it right , please consider!! China motor 80 bucks , cylinder kit from AliExpress 25 dollars equals five hundred k views maybe a million views .
I don't do the vids for money (I'd starve), however that said I never pass up a chance to earn a dollar.
Ill look at it and see what's involved.
@@AuMechanic my friend you will find some imfo that is correct and some that is just false , I'm learning some , one thing is use 2 bushings on sides of 54 mm piston and use 10 mm wrist pin instsead of the 12 mm pin that comes with the cylinder kit. God I would just about send you a motor and cylinder if I could get it back when you are done for a decent price, PLEASE DO THIS PROJECT!!