COMPOUND TURBOS VS SINGLE TURBO-(WHO WINS?) SHOULD YOU RUN COMPOUND TURBOS ON YOUR JUNKYARD LS?

HOW TO RUN COMPOUND TURBOS ON YOUR LS. HOW WELL DO COMPOUND TURBOS WORK ON A CAMMED 4.8L LS? COMPOUND TURBOS LOOK AND SOUND AWESOME, BUT DO YOU NEED THEM ON YOUR STREET/STRIP OR EVEN FULL RACE LS? FULL DYNO RESULTS 11-20 PSI (10-16 ON THE SDINGLE TURBO). CHECK OUT THIS TEST RUN ON A CAMMED (BTR STAGE 2 TURBO) 4.8L LS. WE FIRST RAN THE MOTOR WITH A "SUPER RICHIE" COMPOUND (ATW INTERCOOLED) TURBO SYSTEM (T76 & S480), THEN WITH A SINGLE S475 TURBO. HOW EELL DID EACH SYSTEM PERFORM? IT'S ALL HERE.

[@hydrocarbon8272]

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.

[@BrockJaden]

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.

[@dzchey21]

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

[@1776FREE2]

THIS! 75mm way too big. Go 65mm - 69mm

[@azreeal1]

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.

[@kungfucommando1642]

Boost is good. Super fun experiment. Thanks Richard!

[@justin_does_it]

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.

[@zokusharuuku1091]

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.

[@PBWB2]

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.

[@aaronliddell4280]

Thank you as always Dr. Holdener 👍

[@orangetruckman]

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 🤩

[@richardholdener1727]

Maybe one day!

[@orangetruckman]

@@richardholdener1727 -I love the positive energy you continue to share as well! Sending you some positive vides sir.

[@StevenJohnson-gc2uo]

Awesome video,must have barely missed it when I subscribed to the channel,thanks for the input and the effort

[@braziliansheetbox2497]

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

[@1509archy]

Awesome as usual 👍

[@SethGrosss03]

28 seconds into the video I already like this guy.

[@davedunn7759]

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.

[@richardholdener1727]

it was a gee whiz exercise-it wasn't needed

[@jimbojimson]

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.

[@overbuiltautomotive1299]

sweet video Richard

[@0JThomps0]

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.

[@justRD1]

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

[@scrapmetal_sleepers]

Totally agree. I think this is almost the worst possible use case scenario for a compound setup.

[@alexwhite176]

I was wondering why I've hardly ever seen any thing gas i4 compounds and diesels . Thanks guys !

[@alexwhite176]

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 🤣😂

[@evil_me]

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.

[@BrockJaden]

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.

[@Staf00plz]

@@BrockJaden D/R should be used instead of P/R for more accurate/realistic calculations.

[@DirtyMoneyPullingVideos]

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

[@davidjpaddock]

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.

[@justRD1]

At that low of a total pressure ratio, it’s not possible to get both turbos up on their compressor maps.

[@scrapmetal_sleepers]

Couldn't agree more.

[@doomman700]

100 percent correct

[@marttirahi523]

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

[@robhudson6133]

Best intro Eva

[@lasthopelost9090]

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

[@benwhittaker8630]

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.

[@ChurchAutoTest]

If I'm feeling a little tired late in the afternoon, I just watch one of Holdener's videos on 1.5x speed. Spicy!!

[@richardholdener1727]

its better like that-after a few drinks

[@robertpatton7442]

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.

[@arcdestriumph586]

You want to be good at compounding interest .. Not compounding problems.

[@jackthayer904]

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

[@AndyFromm]

Heck yeah

[@deanbryan3034]

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.

[@bdugle1]

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.

[@dreamsofnails]

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

[@alexwhite176]

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.

[@nemanja162]

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.

[@Jim_Lawrence]

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!

[@jmaxx211]

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.

[@kellyheath8547]

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.

[@russelljackson7034]

Right on

[@trevorsnyder6627]

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?

[@rocketsurgeon11]

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.

[@danwedmaier9404]

Use the same size ‘large’ turbo and for the compound just add a smaller turbo into the system.

[@Smxsucks]

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

[@mattmusselman6499]

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.

[@Smxsucks]

62-68mm primary and a 80 up to a 88mm would be a lot better test. You want a small turbo to get it spinning up fast at lower Rpms and then the big one will keep it flowing up top. I bet it’ll pick up a lot at 2500-4k rpm going to a 62-68mm the it’ll level off to around the same as those graphs afterwords

[@kdsboosted4954]

I have a compound gt45 set up that I'll be snapping together once the block get back from the machine shop

[@RDC_Autosports]

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 👍

[@Metalwolf765]

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.

[@bill2178]

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

[@moparjohan]

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.

[@bladenrexroth2555]

Compounds are good for low rpm power gains. Sized correctly. HX27/GT45

[@bladenrexroth2555]

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....

[@bladenrexroth2555]

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.

[@boosted2813]

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.

[@doomman700]

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.

[@Dr_Xyzt]

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.

[@Kincentc]

Just do a 66mm backed by a promod 88 and run 60 psi xD easy 2k horsepowersss

[@TheProchargedmopar]

Compounds on my 6.7 diesel PLEASE! Single on my Magnum... 👍💪

[@azreeal1]

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.

[@rafaelfuentes6549]

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

[@joeyjojojr.shabadoo915]

The Diesel guys route basic compound setups as such. Start out with a single internally gated turbo/factory setup (let's call this our PRIMARY). They then take a 2nd Turbo (Secondary) and add it this way: The Secondary is fed it's exhaust signal from the output of the Primary exhaust and gate combined. The Primary's air intake is force fed from the Pressure side output from the Secondary. The Secondary (normally ungated) becomes the single exhaust output for the circuit. The Primary Turbo is essentially sealed up on front and back with the main air intake all from the Secondary and the final exhaust from the Secondary.

[@richardholdener1727]

that is how this was plumbed

[@doomman700]

First thing is , they are outrunning the small turbos efficiency. They add the big one to feed it boost, to get that back, because the window moved since it sees boost now not atmospheric pressure. I think the turbos here are too close together at this power level and will never get into their maps efficiency for very long together 🤷🏻‍♂️

[@schmitty_luv]

How are the exhaust turbine wheels sized for quickest spool up time? Would say that same layout and two 83mm/74mm turbine wheels with 1.01 exhaust housings work well for quickest spool up time since they would essentially spool up the exhaust sides at a 1:1 ratio?

[@BJL2142]

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

[@vech400]

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.

[@michaelblacktree]

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.

[@michaelrodgers6559]

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.

[@4077661466jp]

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 😉

[@Go4BrokeOffroad]

Maybe use 2 small svo/dsm turbos to feed the 475? Those should light off quickly.

[@kennethlocke4213]

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.

[@richardholdener1727]

it should tell you that you don't need a compound set up on an LS

[@totensiebush]

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.

[@RHYNOMAN12]

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

[@dennisrobinson8008]

Fuel tech has done a compound 2.0L 4 cyllinder and it's doing 3500HP with 120psi using compounds.

[@bladenrexroth2555]

Rich, You should put a compound set up on the Ameri-Barra 4.2. Sincerely, Cpt. Obvious

[@bladenrexroth2555]

He221/GT45

[@bladenrexroth2555]

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.

[@timbrwolf1121]

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.

[@hill_customs6807]

Maybe a smaller 66mm going into the s475 or a 78/75 .. ??

[@hallasnackbar1865]

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.

[@jdcabauwnl]

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.

[@richardholdener1727]

yes

[@forgottenknowledge8917]

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?

[@troublelessone7999]

Seems like a major point was missed; one turbo works harder than two turbos working together. The compound turbo system doesn't work as hard and possibly has lower EGTs as compared to the single turbo above 3K or so. It would have been interesting to see what you measured your EGTs at for both systems. I suspect that even if you were able to measure the speeds of the compressor wheels in both systems at that point, I suspect we would see slower wheel speeds for less work by two turbos. It would also make sense to learn that the compound system performs better at higher altitude or lack of atmospheric pressure than the single because of the induced pressure from the larger turbo into the primary. Good info.. and thank you for putting something like this together.

[@troublelessone7999]

I also forgot to mention wastegate pressure could have been modified to influence the curve or boost levels at certain rpms.. I believe the power curve is indicative of how effective the actual tune is. If you simply add a compound turbo system with limited tuning, it will produce ugly results. two turbos working together are always going to be more efficient than one.

[@dilsher12]

S362 and s488 would make for a nice setup on a 4.8

[@doomman700]

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

[@doomman700]

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.

[@joshmcelroy4927]

Thanks Richard! Let's see a small turbo with a t4 housing and a 60-70mm compressor that spools great at low rmp, paired with a large turbo that has a big t6, 1.2ar+, large tubine 90mm+ OD/inducer85mm+ exducer, and 85mm+ compressor inducer that doesn't start spooling until higher rpms. That little turbo should zip up the engine power to turn the big laggy bad boy snail and run some quadruple digits! :D

[@joshmcelroy4927]

Or maybe you could change it up to sequential tubos next???

[@richardholdener1727]

OR JUST PUT ON THE s480 OR s475 AND MAKE AND EASY 1000 HP

[@joshmcelroy4927]

So true, that's what I'm doing with my Tahoe right now! Honestly I just want to see the dyno graph of a small 500-700 hp rated single turbo and how it spools down low at 1500-2000 rpm. Especially with a torque and truck norris cam in an otherwise stock 4.8

[@lukeadkinson1582]

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

[@harris0ae86]

Need to feed the small turbo with the big turbo and use the t6 summit turbo

[@scrapmetal_sleepers]

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.

[@bobqzzi]

I think the obvious conclusion here is to rerun the test at the 2000HP level. I look forward to it.

[@richardholdener1727]

2000k HP STOCK BLOCK, CRANK AND RODS 4.8L-THAT WOULD BE A NEAT TRICK

[@bobqzzi]

@@richardholdener1727 Just needs a SuperRichie intake manifold.

[@PBWB2]

​@@bobqzziI found the infamous Audi/VW guy.

[@BoHorror]

Compound turbo vs twin scroll turbo (low key twin turbo solution) please

[@smithjohn3080]

@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?

[@richardholdener1727]

WE DO PLUMB TO BOTH SIDES OF THE GATE WITH THE CONTROLLER-JUST GOING TO THE TOP (ONLY) WAS A TURBO JOKE

[@boostedgringo5885]

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.

[@Bikemad24]

Torquestorm into a lsa would be cool

[@mightyfinejonboy]

👍🏼

[@timothybayliss6680]

This is just practice for the 2.2 1000hp setup.

[@richardholdener1727]

THAT ONE NEEDS LOTS OF BOOST

[@rocketsurgeon11]

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.

[@realtor-corrinemccaffery2161]

I would like to see the s480 over your PTE 62mm turbo.

[@bcbloc02]

Your high pressure turbo should be more like a 62 or 64 with that 80.

[@dzchey21]

Correct

[@SMOKEY-JAYS-DIESEL]

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 💯

[@richardholdener1727]

nope

[@SMOKEY-JAYS-DIESEL]

@@richardholdener1727 how do you figure because it doesn't show on your engine Dyno?

[@richardholdener1727]

1500 hp won't come with 14 psi of pressure in the intake unless your na motor made 750 hp

[@SMOKEY-JAYS-DIESEL]

@@richardholdener1727 yeah I guess it all depends on how much power you made before adding boost 👍🏻

[@SMOKEY-JAYS-DIESEL]

@@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 😧

[@053Honda]

Need a 65mm t4 turbine or smaller with a bypass gate

[@seancole7087]

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

[@pmd7771969]

Rich, these a better way to do this

[@A2J_Tim]

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]

LET ME KNOW WHAT HAPPENS WHEN YOU TEST THAT

[@A2J_Tim]

@@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.

[@dennisrobinson8008]

Pretty sure how that one is normally done, smaller one is used for multiplication.

[@A2J_Tim]

@@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.

[@dennisrobinson8008]

@@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.

[@jasmenter]

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.

[@dannytravis7118]

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]

you can but what motor needs 4 gt45s?

[@dannytravis7118]

@@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

[@allanmakkink8404]

do a twin turbo compound into huge turbo

[@donw4398]

I suppose for traction's sake on the street the compound setup would work better? Seems like the smaller turbo is just a major restriction....

[@doomman700]

Wrong , properly sized, compounds spool rapidly and then have the ability to hold bigger boost. They are only efficient in certain windows(based on atmospheric pressure inlet) you compound because the smaller turbo spools fast but runs out of its map, by then a good set up is now feeding the small one boosted air and moving that map on the smaller turbo back to efficiency, as it’s getting more air at its inlet. Good compounds will out achieve a single, but your end goal has to be air pressure that is much higher than the small turbo can supply efficiently

[@donw4398]

I wanted to change it to saying that setup.... he definitely should have tested with a much larger turbo.

[@Phil-rs5wl]

Why didn't the engine double the power at 14.7 pounds on the compound setup?

[@V8Lenny]

More turbos = more pumping losses.

[@armchairmechanicsnetwork9839]

I use a t3/t4 and a gt45

[@krakhedd]

I think of compounds like a 4th order bandpass bass enclosure - amazing solution for a very specific (read: small/limited) application. Diesels love them cuz they have a limited RPM range Needs an intercooler between boost stages for max efficiency, probably losing some power there You're also losing a bunch by using "slapped together" turbos rather than (as you admitted) calculating the correct turbos More boost + equal/less power = too much heat, not enough airflow

[@smithjohn3080]

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.

[@jeffclark2126]

Two things. We're going to need to see this test on a diesel engine. Based on comments, we need to see this test again with bigger power/boost goals. Also, I've been curious how this works on a diesel. It seems like there isn't enough rpm window for this to work.

[@andrewmontgomery1763]

He doesn't test diesels on the dyno. And besides, diesels are gross lol

[@sabero5668]

If you have a compound setup on a diesel you are probably trying to make stupid power in which case you are also probably spinning the thing about as high as this 4.8 was spinning under boost

[@Jim_Lawrence]

@@sabero5668 diesel compounds can be for big power or towing. Mainly it's for big pressure ratio. Diesel needs big air flow to run cool. Most big power dyno or drag diesels are big single. Rich air fuel diesel is smokey and high egts, lean a/f gas engine runs hot. That's the short version anyway

[@doomman700]

It’s pretty easy to out run the efficiency of a small turbo on a diesel. Then you throw on the bigger one to get the efficiency back. It’s not rocket science, you just have to have a goal much bigger than the small turbo can support alone. I don’t think that’s the case here.

[@daviddroescher]

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