The problem with gasoline compounds is when you run the small turbo at low boost, you actually restrict exhaust flow. The reason is exhaust under pressure needs less cross-section area to flow thru, so low boost means low drive pressure and exhaust that needs a large relative volume. The biggest mental hurdle for people is realizing a 400hp small turbo is flowing 800hp worth of air/exhaust compressed to a 400hp volume. If also hurts running them outsize their efficiency island. It's all made much worse when the turbos aren't sized right. You should size the large turbo to be bigger by the amount of the pressure ratio the small turbo runs. EG 16psi at the small turbo discharge would be ([14.5+16psi]/14.5psi=) 2.1:1, so you want a big turbo that's 2.1x larger. If the big turbo will make too big of numbers, you reduce the small turbo & recalculate. It's obviously much more complicated than any 2 turbos will make 4x power. You wouldn't slap a stage 4 cam & heads suited for a 427 onto a 4.8 and dyno it to 5500rpm to compare vs stock. Same with a compound - you can't build it wrong & run it wrong but expect it to work.
Screw compounds. The juice ain't worth the squeeze. -- My main beef with compounds is that we take hot boost air from one turbo, and put it into the impeller of another turbo that's not meant to flow such hot inlet air. The way around that is to run two intercoolers and a bunch of turbo piping. -- My second issue is you need at least two wastegates. -- My third issue is, compounds add a LOT of heat and plumbing under the hood. If you were to just get the right single turbo for the application, you'd be a lot happier.
I have a 67mm on my dart headed 355in gen 2 lt1. It's probably a bit small but it's a beast from 2500 to 6500. I wonder if the smaller turbo should closer to 60mm for quicker response would get the low speed back.
Your small turbo wasn't small enough for the amount of total power you wanted. In a ciompound setup, you want the small turbo to have just enough flow at a relatively high efficiency to provide the flow for the power you want at the p/r that the primary (larger) turbo is running at. It can become a little complex. Especially if you're wanting to run at variable boost levels, say like a street version and a strip version.
Yeah. I would agree with you. It would have been good to see him use a 66 or even a 64 or 62mm secondary for fast spool up. A turbo that small might have required two wastegates to control boost
You’re working with too big of an engine and/or too small of a power goal. You need a large difference between N/A airflow and target total airflow. If your engine flows 45lbs/min you’re never going to make a good compound setup only trying to move 80-90lbs/min. You need to be aiming for 3 to 4 times N/A airflow to make it worthwhile
Makes sense. From the data it appears by the power curve that the small compressor is creeping up into it's map and maybe made it on the 20psi run since it was partly multiplied by the big turbo . But the big one barely got tickled 🤣😂
Inlet pressure is probably the variable most responsible for the performance of a centrifugal compressor. If you cap the inlet the blower won’t blow. As you add more pressure (or reduce restriction) to the blower inlet (altitude, or another turbo blowing into the inlet) it can move more air more efficiently as a RATIO of inlet pressure to outlet pressure. Typically you’ll max out the smaller turbo, and essentially run it w/o a waste gate and dump everything from the small turbo’s exhaust side into the larger s turbo’s exhaust side. The larger turbo is there to pick up the slack to put the smaller compressor back into efficiency by providing enough inlet pressure to maintain the pressure ratio the smaller turbo is more efficient at. Mostly run on Diesel engines because the air movement can be fixed and independent of fuel supply. You could run a really small turbo with an oversized exhaust side, and a wastegate on the cold side pipe feeding the smaller turbo’s inlet to control inlet pressure at the smaller turbo, because the inlet pressure at the smaller turbo is really where the “boost control” needs to happen to keep the smaller turbo in its efficiency map. A compound isn’t going to work well if the smaller turbo isn’t maxed out or close to it. The larger turbo is really just there to cheer on the smaller turbo by way of force feeding it.
This was the explanation I needed to hear, I am interested in putting compound turbos on my sti because with a 4 cylinder you can only fit smallish sized turbos before you run out of a useable power band. Currently I have a pretty large blouch dom 5 which is essentially a gt35r turbo that spools at around 4200 rpm and I don’t want to have to rev higher than that before anything happens. My question is what size large turbo should I be looking for as I want to fit one that is as large as possible in order to make good turbo efficiency from both in order to make the most possible power. At 25psi currently I’m making 510whp but my engine is built to handle over 800 hp and if I just increase boost the turbo efficiency will eventually drop. It’s also not exactly easy to figure out how to plumb the waste gates, for maximum response I like your idea of only running one on the larger turbo and relying on the cold side to reduce boost pressure. Unless I miss understood what you said.
That 2nd paragraph is only true if you don't know what you're doing. Youre supposed to cap that turbo at a certain boost level (with a giant wastegate) so it stays in its efficiency zone and this will never over speed or become inefficient. What you're talking about is a traditional sequential setup and not a sequential compound setup.
The plumbing seems off - the larger turbo should feed into the inlet of the smaller turbo to multiply the pressure and I couldn't see that in the few pictures showing the compound setup. Either way the power goal and pressures are too low to benefit from a compound setup, you should be looking at over 50lbs to benefit from the compound. My diesel used to push over 70lbs accelerating under load with compounds. Not sure the stock LS block will reliably hold up to that much pressure.
I'd love to see my compound setup on that little LS... S400 75mm and a S500 94mm 😎 Normally the atmospheric compressor needs to be sized for the desired power, and the high pressure compressor is normally half the airflow of the atmospheric.
Close, but even that is too simplistic for the reality of making a good compound setup. You have to look at the desired total airflow first, which will be ENTIRELY supplied by the primary FI system, and this is the important part, AT the P/R that it will be running at BY itself... The secondary needs to be sized based on the flow needs when dividing the total P/R by the primary's P/R.
Sizing compounds? HP turbo shouldn't be capable of your power goal. Atmospheric should be rated over your power goal, like 1200 capable for 1000... must monitor inter-stage to get the setup correct, and enough gate flow to not restrict. I'm not sure compounds make sense at low boost though. Point is to compound for big boost!
the function of a turbine is to multiply the atmospheric pressure and send it to the engine, the compound advantage is that by sending atmospheric pressure + turbo pressure to the first turbine the first turbine multiplies both atmospheric and turbo pressure causing the two (in this case 3) multiply the atmospheric pressure much more easily at high multiplication ratios, in your case the multiplication rate of each turbine is so low that they are simply not made for it, try something above 40psi intake pressure
I'd love to see this again with a PTE 6266 and a PTE 7685 if that motor could handle close to 30lbs of boost. I'd love to see those back pressure readings too.
I'd be curious about how the exhaust back pressure curves looked with those combo's and also the air intake temperatures (ideally) before intercooling. Hopefully data logging had that data.
Point of interest; in a compound turbo setup delivering 100psig of boost, if the primary is supplying 25psig to the secondary and the secondary bumps that to 100psig, both turbos (pressure ratio wise) are sharing the load almost equally. IMHO, 99.9% of gas engines don’t approach the boost levels required to warrant compounds. Also, bringing in boost too early tends to break important things, especially on a mostly stock setup.
It's mostly seeing use in extremely high horsepower small displacement 4 cylinders for this reason, many of them above 100 psi of boost. But that isn't the only use, it is actually a really cool setup to use on something like a hill climb car with a turbocharged 4 cylinder. You can run a very small turbo for the high pressure turbo, something close to what you'd see in a stock application, and then a low pressure turbo that brings it up to the 800-1,000 horsepower range. It isn't being used in that case to achieve an extreme boost level, it's essentially being used as anti lag. The engine ends up acting like a single turbo on a 5.0L instead of a 2.0L. Most people would rather just start with a bigger engine and avoid the unnecessary complexity, but it is a cool application to use compounds.
Ok well from what i could tell from your compound turbo video the large turbos wastegate reference wasnt in the small turbos intake pipe. If you had the same springs in both turbos, with WG lines connected to the ic piping post small turbo then all you would get is lag as the large turbos gate would open with the small turbos. Turbos are also too close in size, at 76 and 80mm. Another thing to note is you had it running in a sequential setup, as without the big turbos boost added to the small turbos top wg port, the big turbo just takes over and no real "compounding" happens. Re run it on a small engine and test some big turbos like the GT45 and S480, that would be a cool test. LS engines are big enough that they dont need compounds. My compound setup on my 3L could spool my rearmount 74mm GT42 at about the same rpm that you are getting there and its on a 3" exhaust pipe.
for comparison what they use on the acert cat compounds small one is a garrett 4702 (102mm exducer)with a huge 5518 (118mm exducer) as the low pressure, the thing is the C15 acert uses 70psi to make 550hp but the first model single turbo (GTA4702) made 550hp at 32psi and you don’t have allllll the weight of the second charger, pre cooler and piping. but the same compound C15 in a off highway application it makes 998hp to where the single turbo C15 only makes 775hp.but diesel and gas it’s hard to compare 👍
I am very interested in compound Turbo set-ups. However, I am afraid to say that You made a total farce out of this test. When You ran compound, so i set-up, you said that You were afraid to let boost build-up. The boost was restricted to 7 or 8 lbs below 4,000 RPM. On a single turbo set-up You let the boost build as fast as it could with the electronic controller. There was almost 17lbs of boost at 3000 RPM with a single turbo. Is it surprising that a single turbo made so much power and torque at lower RPM while the compound made so little. You set it up that way!!! You limited the compound set-up on purpose! The real reason to run compound turbos is to make more boost then a single turbo can i.e. 70+ lbs of boost. (I use lbs of boost loosely, the proper term is psig, 75psig is 90psi absolute pressure in the manifold). This much boost will quickly destroy that 4.8L motor as it approaches 1,500hp! :) The other reason to have compound turbocharging is to build boost early. This implies a kind of sequential strategy. The easiest way is to work backwards from the top of RPM range down. Take the same S475. It made solid 17 lbs of boost from 3,000 RPM and up very well. Hence, from about 3,250 RPM, the small turbo needs to be completely bypassed, bot the turbine and the compressor! As one creates excessive back-pressure and the other just heats up the intake charge and creates intake restriction. Now, size the small turbo to deliver 17 lbs of boost from 1250 to 2750 RPM. Up to 2,750 RPM everything should run through the small turbo and the big turbo should be by-passed. Big turbine may not provide any back-pressure at low air flows but big compressor will heat up intake charge a lot, as it would operate outside of its "efficiency island". Between 2,750 and 3,250 RPM is the transition period where both turbos can work together, in a true compound fashion, while the big turbo comes on-line and takes-over by 3,250 RPM. Theoretically this should produce a flat boost curve off-idle to redline. Sizing the small turbo and waste-gates around it, managing the transition at different throttle openings is where the magic happens. Did You run 4" downpipe to the single big turbo? To equal 4" pipe cross-section (not real flow) with waste gates would take 2 x 70mm or 4 x 50mm. Practically, to account for flow restriction through a waste-gate and to provide headroom for control (100% open waste-gate = no control), 3 x 70mm or 6 x 50mm should be used and this is just to bypass the small turbo's turbine! It would be interesting to see, at what RPM level the small turbo can start building any boost. The limiting factor, here, will be the amount of available energy in the exhaust to spin even the small turbo. Will this extra boost at low RPM create a significant improvement in torque and drivability to justify all that extra expense and complexity? An efficient modern large turbo with split volute turbine, like an EFR9180 or similar may perform almost as well with a much simpler set-up. Do not forget that turbos are heavy! 50 lbs per unit with all the intake, exhaust, water and oil piping. Diesels like boost. It improves their efficiency, reduces emissions and smoke point and makes them feel even faster then gasoline motors. Big 18-wheel rigs have an air-to-air intercooler after each turbo. Some use more then 2 compound turbos. Some use turbos that have blades on both sides of the compressor wheel i.e. a compound turbo in one unit! A few people tried to set up a large turbo with a small positive displacement (Roots-type, etc.) supercharger in a compound arrangement. A positive displacement supercharger is much better at providing boost down low. At higher boost the boost from the turbo will actually spin the supercharger which puts a little power back into the crankshaft. The newest approach is to combine the turbo with an electric motor/generator like F1.
you missed the part where I said I ran two turbos I had laying around and was purposely not trying to make huge low-speed cylinder pressure-compound turbo is NOT necessary on a V8 LS
Just a thought exercise: maybe the 76 was a bit big for the "small" turbo. And with the 480 behind it, choking the exhaust, that was hurting it. The shape of the power curve reminds me of a 1JZ I had with a big turbo and stock exhaust (temporary for legal reasons), the exhaust restriction was great enough to stop the bigger turbo spooling for an extra thousand rpm or so.
Would make 7000rpm power @ 4500rpm. Inline motors seem to give the best architecture for compounds. A compounded 40-50 psi of boost might put you behind the blast window with a broom in hand. O ring the block and head, champher and widen the oil galleys on the mains and cam bearings, drill extra oil holes in the bearings, girdle and stud the block, mains and head. Leave everything else up to science and the dyno. 800hp between 4k-5k rpms is a win.
Well...I am kinda working on it. I have the bottom end together (forged crank, BC H-beam rods with 7/16 ARP bolts, 4-bolt main caps with ARP studs, MP billet end caps, JE pistons). I have a head that can do it (16V Masi, not 8V). I need some custom cams and solid buckets for it...then put it together and let 'er eat (well...needs intake and exhaust made, but I have those parts, too)! My original goal was 700hp, but I'd really like to crack that 4 digit number with a 2.2 just to prove it can be done. To add to the challenge, race gas only. I HATE E85 (I have reasons that are too long for this forum and some would argue they are petty). My original plan was to use compounds to pull it off, but newer turbos are so good it kinda doesn't make sense anymore. My biggest issue...no way to get the power to the ground! So, even if I DO get it all together, I dunno how I will ever be able to test it. :( As good as the stock FWD Dodge transmissions are, I don't think they will hold up to that much power. We know they will hold 600hp even being abused (talking A555/A568). Nobody has really gotten past that on a manual and maybe 2 people can really prove they made more though an automatic (VERY custom inside). What has held me back was safety...I didn't want to put all that power in something without a cage. Life got in the way and this all has taken a backseat for several years now. It's looking like the time is NOW to try for it.
I’m sure it’s been said over and over again but the goal with compounds is your small turbo (manifold turbo) should be able to efficiently make your desired air flow at low rpm. And then the large turbo steps in and completes the run when the small turbo is out of efficiency. Think about it like running two sets of fuel injectors. You have the small ones for low rpm. Good throttle response and idle and then say passed 4500 rpm they don’t flow enough fuel so that’s when the second set comes in and completes the required flow. A good cheap set up that I can think of would be say an hx35 out of a 12v Cummins under a s480. The hx35 (a 50~mm compressor) could easily hit your 10-15 psi requirement down at 2500 rpm and then at 4500-5000 when it’s at the risk of over speed the s480 is now taking all the load because it’s now at its ideal air flow. Also having such a large spread on the turbos allows for them to fill in the lag areas of the curve. The other issue with the comparison is that the s475 that you’re running is really a solid all purpose turbo that is small enough that it comes online nicely at low rpm but has plenty of air flow for the engine. Compounds really only show their strength against the BIG singles like a 90-100 mm turbo something where with a 4.8 you’d only see it really come online at 5500-6000 rpm
The science is in your exhaust housings. Also, small (secondary charger) dictates how fast it spools and primary (large charger) dictates power potential. For example on my 5.9 cummins I run a s476 over a s361. It spools as low as 1500 rpm and builds power upwards of 3200 rpm.
The issue was the small turbo was too big. The Summit turbo was of similar size to the small turbo. The big turbo was the big brother to the Summit turbo. Mismatched
As others have said, power goal was too low for this combo. Need to aim for something that would cause you to use a turbo that would take forever to reach boost threshold and then a smaller turbo (roughly 2/3 the size) to go along with it. The way the setup you had acted was basically there was a restriction for the exhaust to get to the big turbo (that restriction was the smaller turbo, even with the gates recirculating back to the larger one). From memory reading what others have had success with, it seems like you need a freer flowing exhaust side on the smaller turbo than you would normally run. When the system is right, it will come up on boost pretty quick (quicker than if it was just the single smaller turbo in the configuration for compounds) and then just keep pulling. There's a 4G63 guy that did a LOT of work with compounds a few years back and logged a LOT of information that was super informative. He tried all manner of control systems and I think some different turbo sizings as well. There was another 4G63 street car that also ran compounds with good results.
Curious as to what we're your exhaust backpressures. I tune a compound 2JZ and anything above 50psi, exhaust backpressures go thru the roof. 50and below we are less than 1:1
Yeah im not sure the reason for this setup unless pushing 20+ psi , as anything below can be done with single or twin turbos preferably single, but give credit to you for going threw the trouble too see results 😉
I think you'd have to be running at least 4 bar for this to work. Size the smaller turbo 2 bar (800hp) and the larger turbo 2 bar (1600hp) Treat the engine with the smaller turbo like an 800hp na motor and size the bigger turbo for that. A 76/75 small turbo and an 88/96 would be where I'd start. A 6.0l would probably help also. Just my opinion.
The turbos where vary similar, hence why it did not net the end result you were exactly looking for. You want to size the small turbo for how quick you want the spool up to be and that will get you that low end toque. I think something around a 66-68mm would pair well with that s480. If you want to use the 76mm as the smaller turbo, I would recommend jumping up to a t6 as the atmosphere and going with an 88mm
Should have used a gt35 with dual wastegates sprung to 10 psi. Then another gate for the s480 so it does the real work. The primary you used is too big to be really effective for this combo.
You have to be ready for big boost. You need to get both turbos working in the efficiency maps together. In this app, you don’t need it so you can’t get them working together. It’s not enough total boost at the end.
The right sized compounds on a LS should increase power from 1500-5500 rpms. Like having 600+ #/ft of TQ as early (or earlier than) 2400 rpms. Might be something to see this done on the 454 with peanut port heads....
Man that motor from 4500rpm climbed in power output by 100hp (basically a small 1.6l engines worth of power) in only 300 rpm, that's nothing to criticise to heavily
Good video Richard, If only you had unlimited budget for buying turbos to entertain and educate us all haha I wonder if the small turbo wasn't making much or any boost, as you said the expectation would be for the low speed power to come on real strong then the big turbo carries the team out through the revs.
Size small turbo to work from idle to 3500 and big turbo to take over from there so if your small turbo is producing 35 lbs of airflow that will spool a s480 with a massive hot side for efficiency and give you a broad power band and still make 1000plus without sacrificing soggy bottom of a big turbo
My mind has melted from how you don’t have over a million subscribers yet 🤯 you’re the man Richard and I truly appreciate all your hard work with providing this valuable information 🤩
What I think is going on and I am new. l to turbo compounding in general. So what I say is probably incorrect and read it with caution. What I think with this compound setup is that the secondary turbo should be smaller or the primary bigger. Because both the turbo are to simmilar they start to build up around the same level. If you would put an small tdo4 19t on it would have boost from 1750 rpm to around 3000 and then the big one take over.
just based off the diesel side of things (i own two cummins trucks with compound setups) it needs a smaller turbo on the manifold especially since you dont have the displacement. An s363 and a 480 work pretty well on the street and can still tow whatever you want with out waiting forever for it to spool a 72 and s480 dont really spool very well on a 5.9 but on a 6.7 its a lot easier and more streetable.
A complete diagram or description of the plumbing would help understand this series compound turbo application. From some of the posts it is clear you’d need to be shooting for LOTS more pressure for this to be useful, but it’s interesting as an exercise. The single S475 sounds good for the real world of gas engines, anyway.
Personally, I don't see any point in doing compounds on an LS V8, unless you want to run really high boost levels. But on smaller engines, compounds can be helpful.
This setup was done incorrectly. The small turbo was too large. If he'd sized it smaller and provided better wastegate flow into the larger turbo, he'd have boost from 2000 rpm all the way to red line. There's "boost everywhere" compounds, then there's just plain huge boost numbers compounds.
76mm =~ 110lbs/min single as the manifold in a compound =throwing a hot dog down a hallway, it's too big This motor making under 1k will never make this turbo sing ,not even as a single , now throw a compound on top of it and you have created the best in class" lagmaster 2k". Mani charger needs to be sized to be in the center of the 79%effecinty map at normal road speed. Aka 2500-3500rpm g25-550 - 35-700 size ,size it so that the small is used up by4k( wastegate 75_95% duitycycle). With your properly sized peek power charger(atmospheric) sized the way you have done for years.. industrial injection gave me advice of 40% difference in size of the wheels in other words you need a 106mm 20psi
This compound stuff needs to be tried on a VW 2.5L Built for boost. Needs to happen. You said the other night “I’ve tested everything”….. yet nothing on a straight 5. GT2860 and a GT3582
Why not compound turbo and nitrous? Big single turbo and boost controlled nitrous that activates at say 2000rpm and shuts off when you have enough boost from the turbo. Simple and effective. 😀
Try a 64mm at 15lb then try a 80mm at 15lbs then try the 80mm feeding the 64mm.. that’ll show you how much power each make at 15lbs and how responsive each are. Had a hx35 with a 84/88 feeding a 12valve and it was just as responsive as the hx35 alone was. Only issue was the boost creep was unreal. Tripled the hp and over doubled the torque. You need to have the waste gate from manifold to first turbo feeding into the big turbo. And you can have a second gate between the two. If you want 20lbs the first gate will be 20lb release the second would be basically your boost safety say 30lbs. My buddy had a single cam Honda d15b with sleeved block and all that jazz but with a tiny turbo being feed by a 62/66 it made crazy power for a single cam
Your description of the sequential turbo set up is off. It isn't a small to large set up. It is a 1 to 2 set up meaning to turbos the same size for the most part but one gets all the exhaust to give off instant power then the exhaust gets diverted to the turbo from the engine becoming a true twin turbo which is why at a certain point of the RPM most will see a power drop for a second then a huge surge of power.
@richardholdener1727 on which cars? I have an FD RX-7 and a Supra TT stock turbos in my possession, and the turbos on those cars are the same size. 2 completely different engine types, and both have the same sized turbos.
you are correct-my mistake (not sure why I have been under the impression of the different sizing size they were introduced), thnx for making me look up the data
I’m no expert but the way i understand it is size the small turbski for the response/spool you want and the large turbski for your power level you want. Obviously it’s more complicated than that but you get what I mean. The small one still has to be big enough to light the big one off. You’d have better results with something like 62mm/91mm turbos.
One important thing that almost no one seems to understand is that exhaust pressure and exhaust back pressure is two different things! If you just meassure the exhaust pressure you will just see the pressure and not the back pressure.
I think it’s not responsive because that’s a decent size compressor for the high pressure turbo . I’d drop down in compressor size & jump up in turbine & housing size
I think you need to redo this test till you find out why the people like using 2 turbos. Also try intercooler one turbo then intercooler it again into turbo and then intercooler that before manifold, AND have and then water cold intercooler manifold , ice water them ask someone to send you a turbo for testing. I could manage for ideas like talk on discord I would help for free unless my ideas help numbers. I know my #$&@
If you have the chance to run it I would love to see quad gt45 turbos. I think run two per side or a twin to the summit single. Just curious if that's even possible
@@richardholdener1727 I was thinking of driving one into the other to drop the intake air temperature and higher boost pressure at lower rpm for more response or less lag and drop backpressurre in the exhaust. Lower intake air, quick response, higher boost, less backpressurre sounds like a great idea
compound works great when you are trying to go a huge pressure ratio. like 4 or 5 or higher PR. high PSI in diesels or really thin air at high altitude. to get the small turbo to light off it needs to be small. restrictive small. so on a 4.8, something that is maxed out around 500hp. and have a boost controller for just the wastegates handling the small turbo set to less than the overall boost goal. 15psi on the small turbo gates and then 20 or more on the big turbo gates. you will need a lot of wastegate flow to get around the small turbo exhaust housing restrictiveness.
Also what are the intake air Temps feeding the 2nd turbo from the first? And the manifold intake Temps after compounding both turbos? Would be best to intercool the air charge between first and 2nd turbo and between the engine and the 2nd turbo... Hot air from the 1st turbo isn't going to be dense enough to benefit as a compound over atmospheric pressure .. it does opposite and makes a restriction on the intake side with a hot air charge feeding the 2nd turbo. Gotta cool the air charge alot because of the 2nd law of thermo dynamics. Please retry this test with a liquid to air for each turbocharger outlet.
My understanding was that the main reason for compound turbos is when you need a larger pressure ratio than you can reasonably get with one turbo, so I'm not surprised that at a reasonable boost level there's no reason to do it.
@@richardholdener1727 but the strange thing is I have a friend with a Honda Civic making over a thousand horsepower with a 100 mm thumper turbo That's on a 4 cylinder engine. Pretty crazy 😧
what happens when you put the Big turbo on the manifold then feed the smaller turbo second, on the exhaust side, wouldnt the small turbo spin up faster as it is unrestricted with nothing behind it but exhaust pipe? Then set up the charge side in the same manor as traditional compound with the large turbo feeding the smaller one. I think that would improve response. Also your turbo sizes in this test were not far enough apart in size to make a huge difference in spool time. Try 500 hp gt 35 with a 1200hp gt47
@@richardholdener1727 I have one half built for a dsm with smaller turbos that I might finish in the coming year, provided this crazy economy doesnt rob to much of my expendable income. I was hoping you would grab the idea and run with it. Thank you for all the testing that you have done though, I enjoy your videos.
@@A2J_Tim Thats what I've seen as well. It works when you do it right with huge boost numbers and a torque curve that stretches wider than single, parallel or sequential turbo systems.
I think you just need to size them for response and your power goal. The point of compounds is quicker response for a given amount of power. Of course at the same boost level you’ll have less power- turbos are restriction devices and adding a second one takes that extra energy to drive.
Sequential turbos do not need to switch between turbos, you can run them single/twin instead of small single to big single, for example the 2jzgte. Twin also implies the turbos are "twins" as in identical. I am running two s366's in my ram identical in operation to the 2jzgte and it works really well. As for compounds, it's always going to be worse unless you plan on trying to get huge airflow from a small/or low airflow engine. If sticking with the LS platform, try a stock 4.8 with springs ONLY, in fact, shim them to add seat pressure. Use the stock 4.8 cam. For turbos, s366 or gt35 HP turbo and an s488 gt55 lp secondary. Make sure you have alot of WG for bypassing the primary turbo, make sure you recirc into the secondary turbo inlet. 10-12 psi on the primary turbo and 28-30psi on the secondary, measuring pressure differential p1 vs. p2 and not MAP. The engine will see 40psi and on a 330ish HP engine, you should make around 1200hp.. on a stock engine, if it holds up to the torque. Both turbos are operating in their efficiency zone and that s488 thinks it's seeing a 550-600hp engine in terms of exhaust energy, thus spooling very nicely. Compounds certainly have their place, it just need to be done properly, no hate here, just trying to help. There's actually a guy running a compound turbo LS on a hill climb car and it's insanely fast and responsive.
I'm more interested in egts and such as well since placing two turbos in their most efficient range should severely reduce heat. Works on diesels extremely well.
My take on the purpose of the coumpound is to "try" to get true compressed air. Quality boost which idea should be increasing torque. All this told me is twin screw is a actual compressor and a turbo even coumpound is a shop fan.
Compounds are superb , run them on my ram. Turbo is only efficient at x range, based on the inlet of atmospheric pressure, spin a small one way to fast and overheat the air and smoke a turbo. Feed it some boost though and that window moves and you no longer over heat that air. Enjoy
You are correct. The reason you compound is to have the smaller faster spool , then you have the bigger one to feed the small one boost rather than atmospheric pressure. You need to because that makes the small one efficient again. Think about it this way, you run a small unit, it is efficient at 24# boost. You can spool it to 45-50#, that does not mean you are adding good air just boost. You are spinning that turbo twice as fast as it was designed to go. It’s heating the air, less good O2 it’s heating up and expanding. Now you throw a big unit on to get the bigger unit feeding it more air , that moves the efficiency window on that smaller unit. It’s getting boosted air not atmospheric pressure.
@richard holdener you mentioned plumbing to the top of the gate as a joke sarcastically. Are you not plumbing the tc1 to the top of the gates? Or are you trying to control by bleeding from the bottom ports of the gates and leaving the top ports open to atmosphere?
The problem with gasoline compounds is when you run the small turbo at low boost, you actually restrict exhaust flow. The reason is exhaust under pressure needs less cross-section area to flow thru, so low boost means low drive pressure and exhaust that needs a large relative volume. The biggest mental hurdle for people is realizing a 400hp small turbo is flowing 800hp worth of air/exhaust compressed to a 400hp volume.
If also hurts running them outsize their efficiency island.
It's all made much worse when the turbos aren't sized right. You should size the large turbo to be bigger by the amount of the pressure ratio the small turbo runs. EG 16psi at the small turbo discharge would be ([14.5+16psi]/14.5psi=) 2.1:1, so you want a big turbo that's 2.1x larger. If the big turbo will make too big of numbers, you reduce the small turbo & recalculate.
It's obviously much more complicated than any 2 turbos will make 4x power. You wouldn't slap a stage 4 cam & heads suited for a 427 onto a 4.8 and dyno it to 5500rpm to compare vs stock. Same with a compound - you can't build it wrong & run it wrong but expect it to work.
Screw compounds. The juice ain't worth the squeeze.
-- My main beef with compounds is that we take hot boost air from one turbo, and put it into the impeller of another turbo that's not meant to flow such hot inlet air. The way around that is to run two intercoolers and a bunch of turbo piping.
-- My second issue is you need at least two wastegates.
-- My third issue is, compounds add a LOT of heat and plumbing under the hood. If you were to just get the right single turbo for the application, you'd be a lot happier.
how about twin vs compound?
SAME RESULTS HERE
@@richardholdener1727 but how is the lag between the 2? how do that act differently or do they?
I have a 67mm on my dart headed 355in gen 2 lt1. It's probably a bit small but it's a beast from 2500 to 6500. I wonder if the smaller turbo should closer to 60mm for quicker response would get the low speed back.
Your small turbo wasn't small enough for the amount of total power you wanted. In a ciompound setup, you want the small turbo to have just enough flow at a relatively high efficiency to provide the flow for the power you want at the p/r that the primary (larger) turbo is running at. It can become a little complex. Especially if you're wanting to run at variable boost levels, say like a street version and a strip version.
Yeah. I would agree with you. It would have been good to see him use a 66 or even a 64 or 62mm secondary for fast spool up. A turbo that small might have required two wastegates to control boost
THIS! 75mm way too big. Go 65mm - 69mm
if a 75 spools without the big turbo it should spool with it added as long as the turbine on the larger turbo isnt a restriction.
You’re working with too big of an engine and/or too small of a power goal. You need a large difference between N/A airflow and target total airflow. If your engine flows 45lbs/min you’re never going to make a good compound setup only trying to move 80-90lbs/min. You need to be aiming for 3 to 4 times N/A airflow to make it worthwhile
Totally agree. I think this is almost the worst possible use case scenario for a compound setup.
I was wondering why I've hardly ever seen any thing gas i4 compounds and diesels . Thanks guys !
Makes sense. From the data it appears by the power curve that the small compressor is creeping up into it's map and maybe made it on the 20psi run since it was partly multiplied by the big turbo . But the big one barely got tickled 🤣😂
You want to be good at compounding interest .. Not compounding problems.
Inlet pressure is probably the variable most responsible for the performance of a centrifugal compressor. If you cap the inlet the blower won’t blow. As you add more pressure (or reduce restriction) to the blower inlet (altitude, or another turbo blowing into the inlet) it can move more air more efficiently as a RATIO of inlet pressure to outlet pressure.
Typically you’ll max out the smaller turbo, and essentially run it w/o a waste gate and dump everything from the small turbo’s exhaust side into the larger s turbo’s exhaust side. The larger turbo is there to pick up the slack to put the smaller compressor back into efficiency by providing enough inlet pressure to maintain the pressure ratio the smaller turbo is more efficient at.
Mostly run on Diesel engines because the air movement can be fixed and independent of fuel supply.
You could run a really small turbo with an oversized exhaust side, and a wastegate on the cold side pipe feeding the smaller turbo’s inlet to control inlet pressure at the smaller turbo, because the inlet pressure at the smaller turbo is really where the “boost control” needs to happen to keep the smaller turbo in its efficiency map. A compound isn’t going to work well if the smaller turbo isn’t maxed out or close to it. The larger turbo is really just there to cheer on the smaller turbo by way of force feeding it.
This was the explanation I needed to hear, I am interested in putting compound turbos on my sti because with a 4 cylinder you can only fit smallish sized turbos before you run out of a useable power band. Currently I have a pretty large blouch dom 5 which is essentially a gt35r turbo that spools at around 4200 rpm and I don’t want to have to rev higher than that before anything happens. My question is what size large turbo should I be looking for as I want to fit one that is as large as possible in order to make good turbo efficiency from both in order to make the most possible power. At 25psi currently I’m making 510whp but my engine is built to handle over 800 hp and if I just increase boost the turbo efficiency will eventually drop. It’s also not exactly easy to figure out how to plumb the waste gates, for maximum response I like your idea of only running one on the larger turbo and relying on the cold side to reduce boost pressure. Unless I miss understood what you said.
That 2nd paragraph is only true if you don't know what you're doing. Youre supposed to cap that turbo at a certain boost level (with a giant wastegate) so it stays in its efficiency zone and this will never over speed or become inefficient. What you're talking about is a traditional sequential setup and not a sequential compound setup.
At that low of a total pressure ratio, it’s not possible to get both turbos up on their compressor maps.
Couldn't agree more.
100 percent correct
The plumbing seems off - the larger turbo should feed into the inlet of the smaller turbo to multiply the pressure and I couldn't see that in the few pictures showing the compound setup. Either way the power goal and pressures are too low to benefit from a compound setup, you should be looking at over 50lbs to benefit from the compound. My diesel used to push over 70lbs accelerating under load with compounds. Not sure the stock LS block will reliably hold up to that much pressure.
I'd love to see my compound setup on that little LS... S400 75mm and a S500 94mm 😎
Normally the atmospheric compressor needs to be sized for the desired power, and the high pressure compressor is normally half the airflow of the atmospheric.
Close, but even that is too simplistic for the reality of making a good compound setup.
You have to look at the desired total airflow first, which will be ENTIRELY supplied by the primary FI system, and this is the important part, AT the P/R that it will be running at BY itself...
The secondary needs to be sized based on the flow needs when dividing the total P/R by the primary's P/R.
@@BrockJaden D/R should be used instead of P/R for more accurate/realistic calculations.
Just do a 66mm backed by a promod 88 and run 60 psi xD easy 2k horsepowersss
Sizing compounds? HP turbo shouldn't be capable of your power goal. Atmospheric should be rated over your power goal, like 1200 capable for 1000... must monitor inter-stage to get the setup correct, and enough gate flow to not restrict. I'm not sure compounds make sense at low boost though. Point is to compound for big boost!
the function of a turbine is to multiply the atmospheric pressure and send it to the engine, the compound advantage is that by sending atmospheric pressure + turbo pressure to the first turbine the first turbine multiplies both atmospheric and turbo pressure causing the two (in this case 3) multiply the atmospheric pressure much more easily at high multiplication ratios, in your case the multiplication rate of each turbine is so low that they are simply not made for it, try something above 40psi intake pressure
I'd love to see this again with a PTE 6266 and a PTE 7685 if that motor could handle close to 30lbs of boost. I'd love to see those back pressure readings too.
I'd be curious about how the exhaust back pressure curves looked with those combo's and also the air intake temperatures (ideally) before intercooling. Hopefully data logging had that data.
You needed a smaller manifold charger like s363 or s369 with .90a/r with the s480 with a 1. A/r or 1.10 a/r
So a compound setup is to drive a huge turbo and get the lag down and parallel set up is for low down power near to no lag at all
Point of interest; in a compound turbo setup delivering 100psig of boost, if the primary is supplying 25psig to the secondary and the secondary bumps that to 100psig, both turbos (pressure ratio wise) are sharing the load almost equally. IMHO, 99.9% of gas engines don’t approach the boost levels required to warrant compounds. Also, bringing in boost too early tends to break important things, especially on a mostly stock setup.
it was a gee whiz exercise-it wasn't needed
It's mostly seeing use in extremely high horsepower small displacement 4 cylinders for this reason, many of them above 100 psi of boost. But that isn't the only use, it is actually a really cool setup to use on something like a hill climb car with a turbocharged 4 cylinder. You can run a very small turbo for the high pressure turbo, something close to what you'd see in a stock application, and then a low pressure turbo that brings it up to the 800-1,000 horsepower range. It isn't being used in that case to achieve an extreme boost level, it's essentially being used as anti lag. The engine ends up acting like a single turbo on a 5.0L instead of a 2.0L. Most people would rather just start with a bigger engine and avoid the unnecessary complexity, but it is a cool application to use compounds.
Ok well from what i could tell from your compound turbo video the large turbos wastegate reference wasnt in the small turbos intake pipe. If you had the same springs in both turbos, with WG lines connected to the ic piping post small turbo then all you would get is lag as the large turbos gate would open with the small turbos. Turbos are also too close in size, at 76 and 80mm. Another thing to note is you had it running in a sequential setup, as without the big turbos boost added to the small turbos top wg port, the big turbo just takes over and no real "compounding" happens.
Re run it on a small engine and test some big turbos like the GT45 and S480, that would be a cool test. LS engines are big enough that they dont need compounds.
My compound setup on my 3L could spool my rearmount 74mm GT42 at about the same rpm that you are getting there and its on a 3" exhaust pipe.
for comparison what they use on the acert cat compounds small one is a garrett 4702 (102mm exducer)with a huge 5518 (118mm exducer) as the low pressure, the thing is the C15 acert uses 70psi to make 550hp but the first model single turbo (GTA4702) made 550hp at 32psi and you don’t have allllll the weight of the second charger, pre cooler and piping. but the same compound C15 in a off highway application it makes 998hp to where the single turbo C15 only makes 775hp.but diesel and gas it’s hard to compare 👍
I am very interested in compound Turbo set-ups. However, I am afraid to say that You made a total farce out of this test. When You ran compound, so i set-up, you said that You were afraid to let boost build-up. The boost was restricted to 7 or 8 lbs below 4,000 RPM. On a single turbo set-up You let the boost build as fast as it could with the electronic controller. There was almost 17lbs of boost at 3000 RPM with a single turbo. Is it surprising that a single turbo made so much power and torque at lower RPM while the compound made so little. You set it up that way!!! You limited the compound set-up on purpose! The real reason to run compound turbos is to make more boost then a single turbo can i.e. 70+ lbs of boost. (I use lbs of boost loosely, the proper term is psig, 75psig is 90psi absolute pressure in the manifold). This much boost will quickly destroy that 4.8L motor as it approaches 1,500hp! :) The other reason to have compound turbocharging is to build boost early. This implies a kind of sequential strategy. The easiest way is to work backwards from the top of RPM range down. Take the same S475. It made solid 17 lbs of boost from 3,000 RPM and up very well. Hence, from about 3,250 RPM, the small turbo needs to be completely bypassed, bot the turbine and the compressor! As one creates excessive back-pressure and the other just heats up the intake charge and creates intake restriction. Now, size the small turbo to deliver 17 lbs of boost from 1250 to 2750 RPM. Up to 2,750 RPM everything should run through the small turbo and the big turbo should be by-passed. Big turbine may not provide any back-pressure at low air flows but big compressor will heat up intake charge a lot, as it would operate outside of its "efficiency island". Between 2,750 and 3,250 RPM is the transition period where both turbos can work together, in a true compound fashion, while the big turbo comes on-line and takes-over by 3,250 RPM. Theoretically this should produce a flat boost curve off-idle to redline. Sizing the small turbo and waste-gates around it, managing the transition at different throttle openings is where the magic happens. Did You run 4" downpipe to the single big turbo? To equal 4" pipe cross-section (not real flow) with waste gates would take 2 x 70mm or 4 x 50mm. Practically, to account for flow restriction through a waste-gate and to provide headroom for control (100% open waste-gate = no control), 3 x 70mm or 6 x 50mm should be used and this is just to bypass the small turbo's turbine! It would be interesting to see, at what RPM level the small turbo can start building any boost. The limiting factor, here, will be the amount of available energy in the exhaust to spin even the small turbo. Will this extra boost at low RPM create a significant improvement in torque and drivability to justify all that extra expense and complexity? An efficient modern large turbo with split volute turbine, like an EFR9180 or similar may perform almost as well with a much simpler set-up. Do not forget that turbos are heavy! 50 lbs per unit with all the intake, exhaust, water and oil piping. Diesels like boost. It improves their efficiency, reduces emissions and smoke point and makes them feel even faster then gasoline motors. Big 18-wheel rigs have an air-to-air intercooler after each turbo. Some use more then 2 compound turbos. Some use turbos that have blades on both sides of the compressor wheel i.e. a compound turbo in one unit! A few people tried to set up a large turbo with a small positive displacement (Roots-type, etc.) supercharger in a compound arrangement.
A positive displacement supercharger is much better at providing boost down low. At higher boost the boost from the turbo will actually spin the supercharger which puts a little power back into the crankshaft. The newest approach is to combine the turbo with an electric motor/generator like F1.
you missed the part where I said I ran two turbos I had laying around and was purposely not trying to make huge low-speed cylinder pressure-compound turbo is NOT necessary on a V8 LS
Just a thought exercise: maybe the 76 was a bit big for the "small" turbo. And with the 480 behind it, choking the exhaust, that was hurting it. The shape of the power curve reminds me of a 1JZ I had with a big turbo and stock exhaust (temporary for legal reasons), the exhaust restriction was great enough to stop the bigger turbo spooling for an extra thousand rpm or so.
Your high pressure turbo should be more like a 62 or 64 with that 80.
Correct
Rich,
You should put a compound set up on the Ameri-Barra 4.2.
Sincerely,
Cpt. Obvious
He221/GT45
Would make 7000rpm power @ 4500rpm. Inline motors seem to give the best architecture for compounds. A compounded 40-50 psi of boost might put you behind the blast window with a broom in hand.
O ring the block and head, champher and widen the oil galleys on the mains and cam bearings, drill extra oil holes in the bearings, girdle and stud the block, mains and head. Leave everything else up to science and the dyno. 800hp between 4k-5k rpms is a win.
How many twin-turbo set ups can a twin-turbo set up, if a twin-turbo set up, twin-turbo set-up could twin-turbo set up set up set up set up set up ya?
This is just practice for the 2.2 1000hp setup.
THAT ONE NEEDS LOTS OF BOOST
Well...I am kinda working on it. I have the bottom end together (forged crank, BC H-beam rods with 7/16 ARP bolts, 4-bolt main caps with ARP studs, MP billet end caps, JE pistons). I have a head that can do it (16V Masi, not 8V). I need some custom cams and solid buckets for it...then put it together and let 'er eat (well...needs intake and exhaust made, but I have those parts, too)! My original goal was 700hp, but I'd really like to crack that 4 digit number with a 2.2 just to prove it can be done. To add to the challenge, race gas only. I HATE E85 (I have reasons that are too long for this forum and some would argue they are petty). My original plan was to use compounds to pull it off, but newer turbos are so good it kinda doesn't make sense anymore. My biggest issue...no way to get the power to the ground! So, even if I DO get it all together, I dunno how I will ever be able to test it. :( As good as the stock FWD Dodge transmissions are, I don't think they will hold up to that much power. We know they will hold 600hp even being abused (talking A555/A568). Nobody has really gotten past that on a manual and maybe 2 people can really prove they made more though an automatic (VERY custom inside). What has held me back was safety...I didn't want to put all that power in something without a cage. Life got in the way and this all has taken a backseat for several years now. It's looking like the time is NOW to try for it.
I’m sure it’s been said over and over again but the goal with compounds is your small turbo (manifold turbo) should be able to efficiently make your desired air flow at low rpm. And then the large turbo steps in and completes the run when the small turbo is out of efficiency. Think about it like running two sets of fuel injectors. You have the small ones for low rpm. Good throttle response and idle and then say passed 4500 rpm they don’t flow enough fuel so that’s when the second set comes in and completes the required flow.
A good cheap set up that I can think of would be say an hx35 out of a 12v Cummins under a s480.
The hx35 (a 50~mm compressor) could easily hit your 10-15 psi requirement down at 2500 rpm and then at 4500-5000 when it’s at the risk of over speed the s480 is now taking all the load because it’s now at its ideal air flow. Also having such a large spread on the turbos allows for them to fill in the lag areas of the curve.
The other issue with the comparison is that the s475 that you’re running is really a solid all purpose turbo that is small enough that it comes online nicely at low rpm but has plenty of air flow for the engine. Compounds really only show their strength against the BIG singles like a 90-100 mm turbo something where with a 4.8 you’d only see it really come online at 5500-6000 rpm
The science is in your exhaust housings. Also, small (secondary charger) dictates how fast it spools and primary (large charger) dictates power potential. For example on my 5.9 cummins I run a s476 over a s361. It spools as low as 1500 rpm and builds power upwards of 3200 rpm.
The issue was the small turbo was too big. The Summit turbo was of similar size to the small turbo. The big turbo was the big brother to the Summit turbo. Mismatched
No point when you can only use 20psi. Compounds are only good for something you can feed 60 pounds of boost to (diesels)
So the "loss" in the compound in a low boost situation was probably from extra heat and losses due to efficiency.
As others have said, power goal was too low for this combo. Need to aim for something that would cause you to use a turbo that would take forever to reach boost threshold and then a smaller turbo (roughly 2/3 the size) to go along with it. The way the setup you had acted was basically there was a restriction for the exhaust to get to the big turbo (that restriction was the smaller turbo, even with the gates recirculating back to the larger one). From memory reading what others have had success with, it seems like you need a freer flowing exhaust side on the smaller turbo than you would normally run. When the system is right, it will come up on boost pretty quick (quicker than if it was just the single smaller turbo in the configuration for compounds) and then just keep pulling. There's a 4G63 guy that did a LOT of work with compounds a few years back and logged a LOT of information that was super informative. He tried all manner of control systems and I think some different turbo sizings as well. There was another 4G63 street car that also ran compounds with good results.
Why w9nt rich listen to me and do a 4 turbo cadillac 500 36 psi boost forged internal build
Bloodviking
Curious as to what we're your exhaust backpressures. I tune a compound 2JZ and anything above 50psi, exhaust backpressures go thru the roof. 50and below we are less than 1:1
Yeah im not sure the reason for this setup unless pushing 20+ psi , as anything below can be done with single or twin turbos preferably single, but give credit to you for going threw the trouble too see results 😉
Nice Attempt, However the turbo's are not matching the application. Give it a shot with a smaller primary turbo, No need for huge turbine a.r's.
Turbos are to similar in size.
I think you'd have to be running at least 4 bar for this to work. Size the smaller turbo 2 bar (800hp) and the larger turbo 2 bar (1600hp) Treat the engine with the smaller turbo like an 800hp na motor and size the bigger turbo for that. A 76/75 small turbo and an 88/96 would be where I'd start. A 6.0l would probably help also. Just my opinion.
The turbos where vary similar, hence why it did not net the end result you were exactly looking for. You want to size the small turbo for how quick you want the spool up to be and that will get you that low end toque. I think something around a 66-68mm would pair well with that s480. If you want to use the 76mm as the smaller turbo, I would recommend jumping up to a t6 as the atmosphere and going with an 88mm
75mm way too big. Go 65mm - 69mm
Should have used a gt35 with dual wastegates sprung to 10 psi. Then another gate for the s480 so it does the real work. The primary you used is too big to be really effective for this combo.
Would love see it done with small turbo and big turbo so we can see the low rpm tq. Be cool to see the drive pressures of turbos too.
You have to be ready for big boost. You need to get both turbos working in the efficiency maps together. In this app, you don’t need it so you can’t get them working together. It’s not enough total boost at the end.
Use the same size ‘large’ turbo and for the compound just add a smaller turbo into the system.
Mmm not worth it it seems. I’ll just stick to the single, less complex turbo set up.
Compounds are good for low rpm power gains. Sized correctly. HX27/GT45
The right sized compounds on a LS should increase power from 1500-5500 rpms. Like having 600+ #/ft of TQ as early (or earlier than) 2400 rpms.
Might be something to see this done on the 454 with peanut port heads....
The 454 with a GT45/ S480 should (in theory) improve response between 1800-4500 rpm. Imagine diesel power specs out of a big block. 500hp/1200TQ.
Man that motor from 4500rpm climbed in power output by 100hp (basically a small 1.6l engines worth of power) in only 300 rpm, that's nothing to criticise to heavily
It would be interesting to see this at a 1300-1700 hp level to see if the larger turbo needed would give an advantage to the compound setup
Need to feed the small turbo with the big turbo and use the t6 summit turbo
Good video Richard, If only you had unlimited budget for buying turbos to entertain and educate us all haha I wonder if the small turbo wasn't making much or any boost, as you said the expectation would be for the low speed power to come on real strong then the big turbo carries the team out through the revs.
Size small turbo to work from idle to 3500 and big turbo to take over from there so if your small turbo is producing 35 lbs of airflow that will spool a s480 with a massive hot side for efficiency and give you a broad power band and still make 1000plus without sacrificing soggy bottom of a big turbo
Shooting 4 2000 hp, yes the block can take it
Hp turbo was too big, thats why you have had full boost at 4500
My mind has melted from how you don’t have over a million subscribers yet 🤯 you’re the man Richard and I truly appreciate all your hard work with providing this valuable information 🤩
Maybe one day!
@@richardholdener1727 -I love the positive energy you continue to share as well! Sending you some positive vides sir.
What I think is going on and I am new. l to turbo compounding in general. So what I say is probably incorrect and read it with caution. What I think with this compound setup is that the secondary turbo should be smaller or the primary bigger. Because both the turbo are to simmilar they start to build up around the same level. If you would put an small tdo4 19t on it would have boost from 1750 rpm to around 3000 and then the big one take over.
yes
just based off the diesel side of things (i own two cummins trucks with compound setups) it needs a smaller turbo on the manifold especially since you dont have the displacement. An s363 and a 480 work pretty well on the street and can still tow whatever you want with out waiting forever for it to spool a 72 and s480 dont really spool very well on a 5.9 but on a 6.7 its a lot easier and more streetable.
Compounds on my 6.7 diesel PLEASE! Single on my Magnum... 👍💪
Should have tested this on something hungrier. Both turbos maxed out is too much air for this much engine, and we didn't even get there.
A complete diagram or description of the plumbing would help understand this series compound turbo application. From some of the posts it is clear you’d need to be shooting for LOTS more pressure for this to be useful, but it’s interesting as an exercise. The single S475 sounds good for the real world of gas engines, anyway.
Personally, I don't see any point in doing compounds on an LS V8, unless you want to run really high boost levels. But on smaller engines, compounds can be helpful.
This setup was done incorrectly. The small turbo was too large. If he'd sized it smaller and provided better wastegate flow into the larger turbo, he'd have boost from 2000 rpm all the way to red line. There's "boost everywhere" compounds, then there's just plain huge boost numbers compounds.
Boost is good. Super fun experiment. Thanks Richard!
Rich, these a better way to do this
Torquestorm into a lsa would be cool
Heck yeah
Hey Richard! Can we get a twin turbo vs compound next? Maybe compare how boost and power curves a mirror setup has compared to compounding boost?
How big of a wastegate is controlling the boost level on these?
3 45mm gates
76mm =~ 110lbs/min single as the manifold in a compound =throwing a hot dog down a hallway, it's too big
This motor making under 1k will never make this turbo sing ,not even as a single , now throw a compound on top of it and you have created the best in class" lagmaster 2k". Mani charger needs to be sized to be in the center of the 79%effecinty map at normal road speed. Aka 2500-3500rpm g25-550 - 35-700 size ,size it so that the small is used up by4k( wastegate 75_95% duitycycle). With your properly sized peek power charger(atmospheric) sized the way you have done for years.. industrial injection gave me advice of 40% difference in size of the wheels in other words you need a 106mm
20psi
This compound stuff needs to be tried on a VW 2.5L Built for boost. Needs to happen. You said the other night “I’ve tested everything”….. yet nothing on a straight 5.
GT2860 and a GT3582
Fuel tech has done a compound 2.0L 4 cyllinder and it's doing 3500HP with 120psi using compounds.
Lol, he had to ask.......
Why not compound turbo and nitrous?
Big single turbo and boost controlled nitrous that activates at say 2000rpm and shuts off when you have enough boost from the turbo.
Simple and effective. 😀
Try a 64mm at 15lb then try a 80mm at 15lbs then try the 80mm feeding the 64mm.. that’ll show you how much power each make at 15lbs and how responsive each are. Had a hx35 with a 84/88 feeding a 12valve and it was just as responsive as the hx35 alone was. Only issue was the boost creep was unreal. Tripled the hp and over doubled the torque. You need to have the waste gate from manifold to first turbo feeding into the big turbo. And you can have a second gate between the two. If you want 20lbs the first gate will be 20lb release the second would be basically your boost safety say 30lbs. My buddy had a single cam Honda d15b with sleeved block and all that jazz but with a tiny turbo being feed by a 62/66 it made crazy power for a single cam
Your high pressure turbo (the smaller one) is too large.
USED WHAT WE HAD SITTING AROUND
Your description of the sequential turbo set up is off. It isn't a small to large set up. It is a 1 to 2 set up meaning to turbos the same size for the most part but one gets all the exhaust to give off instant power then the exhaust gets diverted to the turbo from the engine becoming a true twin turbo which is why at a certain point of the RPM most will see a power drop for a second then a huge surge of power.
factory sequential are different size turbos
@richardholdener1727 on which cars? I have an FD RX-7 and a Supra TT stock turbos in my possession, and the turbos on those cars are the same size.
2 completely different engine types, and both have the same sized turbos.
you are correct-my mistake (not sure why I have been under the impression of the different sizing size they were introduced), thnx for making me look up the data
I’m no expert but the way i understand it is size the small turbski for the response/spool you want and the large turbski for your power level you want. Obviously it’s more complicated than that but you get what I mean. The small one still has to be big enough to light the big one off.
You’d have better results with something like 62mm/91mm turbos.
One important thing that almost no one seems to understand is that exhaust pressure and exhaust back pressure is two different things!
If you just meassure the exhaust pressure you will just see the pressure and not the back pressure.
I think it’s not responsive because that’s a decent size compressor for the high pressure turbo . I’d drop down in compressor size & jump up in turbine & housing size
I think you need to redo this test till you find out why the people like using 2 turbos. Also try intercooler one turbo then intercooler it again into turbo and then intercooler that before manifold, AND have and then water cold intercooler manifold , ice water them ask someone to send you a turbo for testing.
I could manage for ideas like talk on discord I would help for free unless my ideas help numbers. I know my #$&@
I use a t3/t4 and a gt45
If you have the chance to run it I would love to see quad gt45 turbos. I think run two per side or a twin to the summit single. Just curious if that's even possible
you can but what motor needs 4 gt45s?
@@richardholdener1727 I was thinking of driving one into the other to drop the intake air temperature and higher boost pressure at lower rpm for more response or less lag and drop backpressurre in the exhaust. Lower intake air, quick response, higher boost, less backpressurre sounds like a great idea
compound works great when you are trying to go a huge pressure ratio. like 4 or 5 or higher PR. high PSI in diesels or really thin air at high altitude. to get the small turbo to light off it needs to be small. restrictive small. so on a 4.8, something that is maxed out around 500hp. and have a boost controller for just the wastegates handling the small turbo set to less than the overall boost goal. 15psi on the small turbo gates and then 20 or more on the big turbo gates. you will need a lot of wastegate flow to get around the small turbo exhaust housing restrictiveness.
Also what are the intake air Temps feeding the 2nd turbo from the first?
And the manifold intake Temps after compounding both turbos?
Would be best to intercool the air charge between first and 2nd turbo and between the engine and the 2nd turbo...
Hot air from the 1st turbo isn't going to be dense enough to benefit as a compound over atmospheric pressure .. it does opposite and makes a restriction on the intake side with a hot air charge feeding the 2nd turbo. Gotta cool the air charge alot because of the 2nd law of thermo dynamics.
Please retry this test with a liquid to air for each turbocharger outlet.
My understanding was that the main reason for compound turbos is when you need a larger pressure ratio than you can reasonably get with one turbo, so I'm not surprised that at a reasonable boost level there's no reason to do it.
Simple 60 mm small turbo external wastegated back into the 80 mm or 102mm big turbo guaranteed big horsepower numbers!!!! 1500 hp on 5.3l at 14 psi 💯
nope
@@richardholdener1727 how do you figure because it doesn't show on your engine Dyno?
1500 hp won't come with 14 psi of pressure in the intake unless your na motor made 750 hp
@@richardholdener1727 yeah I guess it all depends on how much power you made before adding boost 👍🏻
@@richardholdener1727 but the strange thing is I have a friend with a Honda Civic making over a thousand horsepower with a 100 mm thumper turbo That's on a 4 cylinder engine. Pretty crazy 😧
I think a HX35 flowing to a T76 would be a sweet setup to cover both halves of a rpm range.
Awesome video,must have barely missed it when I subscribed to the channel,thanks for the input and the effort
what happens when you put the Big turbo on the manifold then feed the smaller turbo second, on the exhaust side, wouldnt the small turbo spin up faster as it is unrestricted with nothing behind it but exhaust pipe? Then set up the charge side in the same manor as traditional compound with the large turbo feeding the smaller one. I think that would improve response. Also your turbo sizes in this test were not far enough apart in size to make a huge difference in spool time. Try 500 hp gt 35 with a 1200hp gt47
LET ME KNOW WHAT HAPPENS WHEN YOU TEST THAT
@@richardholdener1727 I have one half built for a dsm with smaller turbos that I might finish in the coming year, provided this crazy economy doesnt rob to much of my expendable income. I was hoping you would grab the idea and run with it. Thank you for all the testing that you have done though, I enjoy your videos.
Pretty sure how that one is normally done, smaller one is used for multiplication.
@@dennisrobinson8008 all the compound set up's I have seen put the small turbo on the manifold then put the larger turbo behind the small turbo.
@@A2J_Tim Thats what I've seen as well. It works when you do it right with huge boost numbers and a torque curve that stretches wider than single, parallel or sequential turbo systems.
Maybe a smaller 66mm going into the s475 or a 78/75 .. ??
I think you just need to size them for response and your power goal. The point of compounds is quicker response for a given amount of power. Of course at the same boost level you’ll have less power- turbos are restriction devices and adding a second one takes that extra energy to drive.
BWWWWAAAAAAAAAH
I think the obvious conclusion here is to rerun the test at the 2000HP level. I look forward to it.
2000k HP STOCK BLOCK, CRANK AND RODS 4.8L-THAT WOULD BE A NEAT TRICK
@@richardholdener1727 Just needs a SuperRichie intake manifold.
@@bobqzziI found the infamous Audi/VW guy.
Sequential turbos do not need to switch between turbos, you can run them single/twin instead of small single to big single, for example the 2jzgte. Twin also implies the turbos are "twins" as in identical. I am running two s366's in my ram identical in operation to the 2jzgte and it works really well.
As for compounds, it's always going to be worse unless you plan on trying to get huge airflow from a small/or low airflow engine. If sticking with the LS platform, try a stock 4.8 with springs ONLY, in fact, shim them to add seat pressure. Use the stock 4.8 cam. For turbos, s366 or gt35 HP turbo and an s488 gt55 lp secondary. Make sure you have alot of WG for bypassing the primary turbo, make sure you recirc into the secondary turbo inlet.
10-12 psi on the primary turbo and 28-30psi on the secondary, measuring pressure differential p1 vs. p2 and not MAP. The engine will see 40psi and on a 330ish HP engine, you should make around 1200hp.. on a stock engine, if it holds up to the torque. Both turbos are operating in their efficiency zone and that s488 thinks it's seeing a 550-600hp engine in terms of exhaust energy, thus spooling very nicely. Compounds certainly have their place, it just need to be done properly, no hate here, just trying to help. There's actually a guy running a compound turbo LS on a hill climb car and it's insanely fast and responsive.
I'm more interested in egts and such as well since placing two turbos in their most efficient range should severely reduce heat. Works on diesels extremely well.
I have a compound gt45 set up that I'll be snapping together once the block get back from the machine shop
My take on the purpose of the coumpound is to "try" to get true compressed air. Quality boost which idea should be increasing torque. All this told me is twin screw is a actual compressor and a turbo even coumpound is a shop fan.
it should tell you that you don't need a compound set up on an LS
Compound turbo vs twin scroll turbo (low key twin turbo solution) please
Compounds are superb , run them on my ram.
Turbo is only efficient at x range, based on the inlet of atmospheric pressure, spin a small one way to fast and overheat the air and smoke a turbo. Feed it some boost though and that window moves and you no longer over heat that air. Enjoy
You are correct. The reason you compound is to have the smaller faster spool , then you have the bigger one to feed the small one boost rather than atmospheric pressure. You need to because that makes the small one efficient again.
Think about it this way, you run a small unit, it is efficient at 24# boost. You can spool it to 45-50#, that does not mean you are adding good air just boost. You are spinning that turbo twice as fast as it was designed to go. It’s heating the air, less good O2 it’s heating up and expanding. Now you throw a big unit on to get the bigger unit feeding it more air , that moves the efficiency window on that smaller unit. It’s getting boosted air not atmospheric pressure.
I don’t think it’s technically a “twin turbo”
TWIN EQUALS 2
@@richardholdener1727 I love your work brother and you’re doing a fantastic job. I have to disagree with you. Twin = Identical.
@richard holdener you mentioned plumbing to the top of the gate as a joke sarcastically. Are you not plumbing the tc1 to the top of the gates? Or are you trying to control by bleeding from the bottom ports of the gates and leaving the top ports open to atmosphere?
WE DO PLUMB TO BOTH SIDES OF THE GATE WITH THE CONTROLLER-JUST GOING TO THE TOP (ONLY) WAS A TURBO JOKE
Need a 65mm t4 turbine or smaller with a bypass gate
Maybe use 2 small svo/dsm turbos to feed the 475? Those should light off quickly.
Needs a lot smaller small turbo.
The point is at the low boost level of the engine it’s pointless 🤷🏻♂️