# Compound turbocharging system



## boomerkk (Sep 5, 2008)

Some supra guys over in the US has developed this system for the 2JZ and its getting a lot of hype.

Seems it gives the best of both worlds, big peak hp but huge low down torque as there is big psi pressures at low rpms.

Boost Logic SupraTT Compound Turbo Kit :: Turbo Kit :: 93-98 MKIV Supra TT :: Toyota :: Boost Logic

I'm not very technically minded but the simple way of looking at it is to think of the engine + 1 small turbocharger as THE engine, and then turbocharge it with 1 bigger turbo.

I dunno but to my mind, the system would be great on GTRs as the low down torque can be properly put down by the 4wd, but might need to be a rb30 or a strongly built rb26 block to stand up to the big psis at low rpm.

Thoughts?


----------



## Moff (Sep 27, 2004)

Standard on the Supra Turbos was it not ?

Main problem is the boost drop during switch over, plus the variable cam timing on skylines. Would be an interesting experiment.


----------



## boomerkk (Sep 5, 2008)

Moff said:


> Standard on the Supra Turbos was it not ?
> 
> Main problem is the boost drop during switch over, plus the variable cam timing on skylines. Would be an interesting experiment.


Not at all.

Supras have a sequential system as standard. This means a smaller turbo spools first before a bigger one.

Compound system is a turbo compressing air that is further compressed by another turbo.


----------



## Howsie (Feb 25, 2002)

Wow - with that kit you could have four turbos on a GT-R.


----------



## rasonline (Mar 24, 2005)

so the outlet from the first turbo compressor wheel feeds into the second turbo?


----------



## Lambda One (Jul 3, 2007)

Check out any tractor pullers from the last 20 years and you'll find out all you need to know about Compound turbo charging.

Lyndon.


----------



## fabianGTR34 (Aug 6, 2006)

compound charging is also a name that is used for a turbocharged engine that has a turbine on it that is mechanically linked to the crank. 










But I don't think the supra guys did that 

It is either parallel or sequential..


----------



## GT-R Glenn (Nov 9, 2002)

Delta s4 ...
win / win


----------



## kismetcapitan (Nov 25, 2005)

this is somewhat difficult to make heads or tails of (it seems to me that the small turbo would somehow impede the larger one but clearly I know nothing about this kind of turbocharging, it could very well be that the larger turbo just pushes past the smaller one), but it doesn't appear overly complex and a similar system on an RB26 would be very interesting.


----------



## kismetcapitan (Nov 25, 2005)

GT-R Glenn said:


> Delta s4 ...
> win / win


the Lancia used a Roots supercharger with a turbo, this system seems to feed one turbo into another - never seen this setup before.


----------



## boomerkk (Sep 5, 2008)

The Lancia Delta is a 'twincharger' using both supercharger and turbo, like the Nissan March.

Boostlogic has 1 car running and several kits shipped - so it's very early in development.

The system is previously used in diesel applications esp. in tractor pull events where huge torque is needed - some used multiple turbos like 5-6 in series!

Apparently the smaller turbo closer to the engine is no restriction, it just compresses air that the larger turbo has already compressed.

Boostlogic's car makes 28psi at 2800rpm, but also goes to make something like 700whp at peak.

The torque curve is quite interesting.... I think it will be interesting to see a 4wd car with the setup.

Found some dyno plots of the car, compared it to a to4z rb30...
http://www.dyno-plot.co.uk/dyno/dynoplot/id=573_580&sort=pow&but_sea=qs/index.htm


----------



## R.I.P.S NZ (May 7, 2004)

Very interesting although possibly rather complicated, expensive and not so easy to fit, similar results can easily be had with a small shot of NOS early on but thats not to everyones taste I suppose.

Rob


----------



## kismetcapitan (Nov 25, 2005)

I suppose if the plumbing and setup were simple, it would have already been done...unless tuners are really a traditional lot?

Those dyno plots were a good comparison - both 3 liter engines. The compound system looks like it brings things in about 1000rpm earlier, but neither car will "pull like a V8" - you've still got nothing under 4000rpm and you've got to hammer the engine to spool the turbos.

Still, 2 bars of boost at 3000rpm is pretty enticing, and the plumbing for a lowmount/highmount setup would surely be pretty interesting and cool. If it's just pipes, people have done all kinds of custom pipework. What I suspect is the crux however, is matching and balancing the flows in the pipes, as well as carefully matching the turbos to said pipework.


----------



## Cris (Sep 17, 2007)

Just some thoughts which hopefully won't show my up enormous ignorance:

1) If the charge from one turbo is fed directly into the second turbo wouldn't the charge get VERY hot and thus hurt efficiency? I know that diesels burn cooler so perhaps this would be less of an issue on the (mentioned above) tractors

2) More pipework equals more pressure drop, again this would hurt efficiency

3) Turbo lag (ie time to spool up following say gear-change) would be twice as bad - turbo 1 needs to spool up, only after that can turbo 2 spool up. I imagine that this would be less of an issue with a drag car with nitrous etc but sounds like it could be a royal pain for a road/track car

Does that sound right?


----------



## kismetcapitan (Nov 25, 2005)

well, how much lag would there be if an RB26 was pushing a single N1 turbo? Not much! Take a stock-ish sized turbo and funnel all six cylinders into it, it'll spool up right quick, and then the big one can come online, especially if the flow from the little one helps to push start the big one (not sure if this actually happens).


----------



## boomerkk (Sep 5, 2008)

Cris said:


> Just some thoughts which hopefully won't show my up enormous ignorance:
> 
> 1) If the charge from one turbo is fed directly into the second turbo wouldn't the charge get VERY hot and thus hurt efficiency? I know that diesels burn cooler so perhaps this would be less of an issue on the (mentioned above) tractors
> 
> ...


I've got enormous ignorance as well and still trying to understand it but:

1)System can be intercooled as usual

2)Apparently, pressure drop is much less than compressed air compounded...
eg.. atmospheric air goes into 1st turbo = +14 psi, goes into 2nd turbo = +32 psi... (NOT +28psi). Compressing the already compressed.

3)Low lag...small turbo spools very early and keeps on spooling (dunno how they achieve this). Bigger turbo spools a bit later but huge amounts of air is compressed into engine (see point above).

There's a video somewhere of the car running... let me find it.


----------



## SmigzyGTR (Mar 20, 2006)

Compound Twin Turbocharging from Boost Logic - HybridZ


----------



## Cris (Sep 17, 2007)

SmigzyGTR said:


> Compound Twin Turbocharging from Boost Logic - HybridZ


If I read that correctly it seems to work like this:

Low rpm/boost - exhaust blows into the small turbo, small turbo blows into the big turbo (spent gas), big turbo to atmosphere (tail-pipe). Big turbo sucks in air, compressed air sent to small turbo to be compressed again, then into intercooler/plenum.

Switch-over point - when the small turbo reaches its boost limit the wastegate bleeds the excess pressure around the small turbo and into the small turbo (ie direct to the large turbo).

High rpm/boost - exhaust blows into the small turbo, small turbo blows into the big turbo (spent gas) and the small turbo's wastegate also blows into the big turbo, big turbo to atmosphere (tail-pipe). Big turbo sucks in air, compressed air sent to small turbo to be compressed again, then into intercooler/plenum.

Does that sounds right?

If so then on the intake side (at high rpm) wouldn't the big turbo "over-feed" the small. I'm assuming that the big turbo at high rpm will be flowing more air than the small one - does the small one not become the bottle-neck?

I think I must be missing something!


----------



## boomerkk (Sep 5, 2008)

Cris said:


> If I read that correctly it seems to work like this:
> 
> Low rpm/boost - exhaust blows into the small turbo, small turbo blows into the big turbo (spent gas), big turbo to atmosphere (tail-pipe). Big turbo sucks in air, compressed air sent to small turbo to be compressed again, then into intercooler/plenum.
> 
> ...


I've got zero knowledge on fluid dynamics but from the supra forums, apparently bottle-necks doesn't arise just being the nature of the flow system.

Those crazy tractor pullers run multiple turbos in series must have crazy flows by the time it reaches the final turbo but apparently doesn't experience bottle necks.

Just had another quick read - apparently the bottle neck doesn't arise as the smaller turbo would still flow well at high pressure... of course, you'd need to look at the compressor map to make sure.


----------



## boomerkk (Sep 5, 2008)

Picasa Web Albums - Sean - Dyno charts

Just having a quick look at these graphs , borrowed from this excellent site:
tyndago - Turbolag

Although *I know that they are not directly comparable ie. rb26 vs 2jz*, but that early development kit on the 2jz makes 266hp at 3500rpm and 400hp at 4000rpm and then going up to 700 plus.

So right from the lower revs, the curve will be way up compared to a normal twin turbo even with small turbos.

Now theyve got 4 cars under development.

I wonder whether anyone would like to start development on an rb30?


----------



## arnout (Oct 29, 2003)

I made a celica st205 (2 ltr engine 4 banger) with a GT40 turbo and a SLK230 charger:








the throttle response is unbelievable. The supercharger does all the work from 1800 rpm to 4500 rpm. the turbo does the rest up to 9000 RPM


----------



## Cris (Sep 17, 2007)

arnout said:


> I made a celica st205 (2 ltr engine 4 banger) with a GT40 turbo and a SLK230 charger:
> 
> 
> 
> ...


More about this please!


----------



## arnout (Oct 29, 2003)

what more?


----------



## daytona (Jun 28, 2005)

How did you solve the transition between Super and turbocharger Arnout? I know twin charging has been successfully done a few times but information on how a smooth transition is achieved is limited, Any info?


----------



## arnout (Oct 29, 2003)

transition is easy. The turbo spools by itself and when it has more boost than the supercharger I disable the supercharger. Here are two boost logs one with charger and one without.









Somehow, although it's more mechanically challenging and more mechanical stress I like the turbo+supercharger idea more than the turbo+turbo


----------



## daytona (Jun 28, 2005)

Thanks, much appreciated. Your way certainly sounds very straight forward compared with a few i've read about (mainly Australia), do you have any drawing's or photo's to help get me going in the right direction? Feel free to PM if you would rather.


----------



## boomerkk (Sep 5, 2008)

Interesting work arnout!

However, the thing with twincharging is that it is adding a whole other "system" or "dimension" altogether.

Whereas the compound system is just basically a 2-turbo system with 'different' piping.

Both achieve similar aims though, and I personally think the gtr is the ideal car for it considering it has the great 4wd system ie. to transfer all that low rpm power to the ground and huge tuning culture.


----------



## Cris (Sep 17, 2007)

arnout said:


> transition is easy. The turbo spools by itself and when it has more boost than the supercharger I disable the supercharger. Here are two boost logs one with charger and one without.
> 
> 
> 
> ...


How do you disable the supercharger? Is there a clutch in there somewhere perhaps?


----------



## arnout (Oct 29, 2003)

daytona said:


> do you have any drawing's


My cat did this drawing:


----------



## daytona (Jun 28, 2005)

All my cat does is destroy my furniture, time to enrol him in art class i think!:chuckle:
So it looks as though you do use a clutch to disengage the supercharger? How is this activated? Obviously at a given pressure point but do you use electronic's or the pressure itself?


----------



## arnout (Oct 29, 2003)

I enable the supercharger when the following is met:
coolant between 80 and 110 celcius
oil between 65 and 120 celcius
throttle at least 20%
manifold vacuum (boost) at least -0.3 psi
engine RPM between 1500 and 4500 RPM

I disable the supercharger when the boost is higher than the supercharger pressure, in my case that is 0.9 bar supercharger and 1.8 bar turbo charger so I disable the supercharger when the boost is higher than 1 bar.


----------



## Dynamix (Nov 1, 2007)

daytona said:


> All my cat does is destroy my furniture, time to enrol him in art class i think!:chuckle:
> So it looks as though you do use a clutch to disengage the supercharger? How is this activated? Obviously at a given pressure point but do you use electronic's or the pressure itself?


You could run the charger off the electric A/C clutch via the ECU NOS control (load rpm etc) depending what ECU is used, when the turbo boost exceeds the charger boost the ECU turns off the a/c clutch running the charger and the turbo takes over, the real tricky part is in the mapping trying to make the switch over as smooth as possible..


----------



## arnout (Oct 29, 2003)

I'm using the AEM v-tec function for controlling the supercharger on point. Also using the user switch #7 and the A/C delay for the oil temp switch.


----------



## Mookistar (Feb 5, 2004)

there are some pics of a compound charge RB26 on here somewhere.

looked awesome

mook


----------



## arnout (Oct 29, 2003)




----------



## GTRSTILL (Jul 27, 2006)

When I first joined the forum way back I was reading an old engineering book on Turbocharging. This featured a section on Tractor pull and especially a two and even three way compound turbocharging system. Being the helpful and responsive chap he was back then I fired over a question to Andy B to see what he thought and his views for the RB. Unfortunately he never responded.

In tractor pulling they relied heavily on water injection due to the extreme heat generated. I still have the book somewhere and will scan in the pics if I find em. 

Engineering wise I never fully understood a) how you can compress air twice?and b) wouldnt the second bigger turbo be very restrictive and "in the way"??


----------



## Pete G (Aug 18, 2008)

Interesting thread.
The MkV Golf GT had a 1.4 engine with a supercharger to give a power boost at low revs which also disengaged for a turbo to take over at higher revs for top end power. I don't know of any other car that had that setup as standard?


----------



## Boydie.NI (Aug 24, 2008)

Pete G said:


> Interesting thread.
> The MkV Golf GT had a 1.4 engine with a supercharger to give a power boost at low revs which also disengaged for a turbo to take over at higher revs for top end power. I don't know of any other car that had that setup as standard?


The old nissan micra super turbo.
Modified Nissan Micra Super Turbo 1990 Car Tuning Pictures & Spec Ref: #925 » ModifiedCars.com
Had a go in one when i was buying my starlet turbo, just bloody crazy, all that low down grunt in a front wheel drive car with 185 tyres :chuckle:
Similar setup in a GTR would be just the ticket :smokin:
arnout that pic will give me wet dreams mate.


----------



## mattysupra (Oct 31, 2008)

arnout said:


> My cat did this drawing:



My boat engines work very simular to this. Its old technology as it was built in 1992. The engines are also diesel. 



Basically each engine has a supercharger and a massive turbo. The superchargers are plummed straight into the turbos air intake. The superchargers start screaming/winding in (you need ear defenders. There that loud with the engine bay open) at 1600rpm and power the turbos. The superchargers disingage when the turbos are on boost at about 2500rpm. There is butterfly like the drawing above and a clutch on the supercharger that is electronically controlled that i can adjust to what ever Rpm i want the superchargers to come on line and back off. 


I may be way off here and what you lot are talking about, but it looks/sounds the same sort of set up! 

Plus its all mechanical, the ecu is very basic. Just a rpm controler for the superchargers i think. 


The engines produce massive torque tho. They manage to lift 13 ton of boat out of the water at about 2000rpm all the way upto 4800rpm!

I can grab the work shop manual next time im down the boat and put it on here if your intrested?


----------



## boomerkk (Sep 5, 2008)

Why are twin charging systems not more frequently used?They sound excellent...

Cost/space/complexity?

The Boost Logic kits are currently advertised as being complete kits, selling at around US$7000.

Maybe that is why theres so much interest by the supra boys, it sort of solves the issue of complexity and cost maybe?


----------



## NISFAN (Oct 11, 2003)

boomerkk said:


> Why are twin charging systems not more frequently used?They sound excellent...
> 
> Cost/space/complexity?


Probably because it is a compromised set up, and pointless really for the power junkie.


----------



## Cris (Sep 17, 2007)

arnout said:


>


If I'm reading your cat's drawing right then the above is different from your set-up in that the supercharger doesn't blow through the turbos. I assume that the above would need a pair of butterfly valves somewhere between either inlet on the intercooler and the supercharger and turbocharger.

Hmmmmmm

My dream R32 may no-longer have a VH41DETT in it. Skyline Superturbo has a nice ring to it!


----------



## boomerkk (Sep 5, 2008)

NISFAN said:


> Probably because it is a compromised set up, and pointless really for the power junkie.


What do you mean by compromised?

What about the compound system?


----------



## Boydie.NI (Aug 24, 2008)

Cris said:


> If I'm reading your cat's drawing right then the above is different from your set-up in that the supercharger doesn't blow through the turbos. I assume that the above would need a pair of butterfly valves somewhere between either inlet on the intercooler and the supercharger and turbocharger.
> 
> Hmmmmmm
> 
> My dream R32 may no-longer have a VH41DETT in it. Skyline Superturbo has a nice ring to it!


Yes the pic clearly shows the supercharger and turbos running in parallel, so the supercharger provides the low rpm boost pressure and the turbos start to spin up normally until they reach the max boost of the supercharger and then the charger disconnects. There must be some sort of valve to stop the supercharger boost stalling the turbos.


----------



## NISFAN (Oct 11, 2003)

boomerkk said:


> What do you mean by compromised?
> 
> What about the compound system?


Compound systems work well in applications where you want very high inlet pressures (as in Tractor pulling diesel engines that run at 10+ bar). 
In a petrol engine, a single compressor is more than capable of supplying the amount of boost pressure the engine can handle, therefore a compound system is not required (for the same reason tractor pullers use them). There is little merit in feeding a small turbo that does most of the work with a larger turbo running at a very low boost pressure, so I can't see how a compound turbo system will give any benefits. The other way round and the small turbo will just be a restrictor.

In the RB application shown in the pics, you would have to fit a number of flow control valves into the system, and as we all know these devices would rob the system of efficiency, therefore you end up with a compromised set up. Not to mention the complexity of the control of these valves/solenoids/clutches to ensure you get the best out of the overlap position of both technologies.

Let me run into a little scenario for arguments sake. The RB engine (pictured above) might have turbo's capable of let's say for example 800hp, that produce meanigful boost at say 5000rpm onwards. Cool!!!!
Now we add a complicated set of extra pipework, and one way valves, which add to flow resistance. But we also add a SC that will give us some boost between 2750rpm and our 5000rpm turbo kick in revs. All good?...............No not really, because of the pipework / valve restrictions our 800hp turbo's can only produce let's say a safe 700hp now. If we went for smaller turbo's capable of 700hp in the first place, we would be in meaningful boost by perhaps 4000rpm. 
But that is not all, our SC'd version has the additional drag on the engine of a good few hp (even if the SC is decoupled with an electric clutch, there is still a belt and pulley to turn), plus there is the weight of the SC that needs to be added to the car, = less power /weight ratio.
So between 2750 and 4000rpm you have a more responsive car, but other than at those revs, the non SC version with smaller turbo's is better. (For those that know the true meaning of lag, the SC has done nothing to help that)

Is all that really worth it for a bit of torque for 1250rpm, and at the rev range rarely entered unless you are just pootling along? 

Roll on KERS technology, where you could have the full 800hp, and a little extra help to get them spooling when needed.:chuckle:


----------



## boomerkk (Sep 5, 2008)

NISFAN said:


> Roll on KERS technology, where you could have the full 800hp, and a little extra help to get them spooling when needed.:chuckle:


Thanks for the explanation.

Could you elaborate on KERS? What is it?


----------



## NISFAN (Oct 11, 2003)

KERS = Kinetic Energy Recovery System ala F1


----------



## mattysupra (Oct 31, 2008)

im not sure if this is the same thing. This is one of the engines in my boat. Its a 1992 built engine so old technology. 

Its also diesel. Now so you can get an idea of size, the engine is about 5feet x 3 feet wide. The turbo is about the same size as a dinner plate. 

I will post up the service manual when i get my hands on it.


----------



## Cris (Sep 17, 2007)

NISFAN said:


> ..., the SC has done nothing to help that)
> 
> Is all that really worth it for a bit of torque for 1250rpm, and at the rev range rarely entered unless you are just pootling along?


I can see where you're going with this. The cost and complexity issue also seems like a good reason for OEMs not championing this cause.

However VW do now produce a 1.4 super/turbo which is apparently very good. Given that FIAT have gone down the pure turbo route for their 1.4 I assume that VW have found enough benefits to justify things. Does anyone know know why VW have gone down this route - have they solved some of the above issues perhaps?


----------



## fr0sty (Nov 28, 2007)

boomerkk said:


> Not at all.
> 
> Supras have a sequential system as standard. This means a smaller turbo spools first before a bigger one.
> 
> Compound system is a turbo compressing air that is further compressed by another turbo.




turbo diesel wont knock their engine since fuel is injected after the air has been compressed... not saying they wont know their engine... but its harder to due if you know what you are doing


gasoline engine have a spark plug to light the fuel... so compressing the air at 2 pressure ratio then adding more pressure to it.. heats it more so you would need lots of overfuelling + load of octane booster + proper water/air intercooling to even bother with compound turbo on a gasoline engine




kismetcapitan said:


> this is somewhat difficult to make heads or tails of (it seems to me that the small turbo would somehow impede the larger one but clearly I know nothing about this kind of turbocharging, it could very well be that the larger turbo just pushes past the smaller one), but it doesn't appear overly complex and a similar system on an RB26 would be very interesting.




the exhaust comming out of the manifold gets fed to the turbine on the smaller turbo.. then when sufficient pressure is reach it redirects the gas to the bigger turbine thus making the compressor on the big turbo work feeding the smaller compressor then intake plennum... but those turbo settup were never invented to be used outside of diesel land... for one reason... heat issue.... since diesel dont have the same method as gasoline engine to light the fuel they can accept these kind of setup.... but i would love to see someone do this to an overcooled rb30 


the solution to all those problem would be water/air intercooler with a permanent water chiller.... say -50c full load or even lower temps... kinda like ice water on steroid


----------



## tonigmr2 (Sep 12, 2002)

Bit of a revived post! Interesting as I am having a twincharge system built at the moment...should be finished in the new year (from an original HKS Twincharger kit for the 4agze - Toyota basically).

Works very similarly to what has been described above.


----------



## fr0sty (Nov 28, 2007)

Cris said:


> Just some thoughts which hopefully won't show my up enormous ignorance:
> 
> 1) If the charge from one turbo is fed directly into the second turbo wouldn't the charge get VERY hot and thus hurt efficiency? I know that diesels burn cooler so perhaps this would be less of an issue on the (mentioned above) tractors
> 
> ...




the smaller turbo can have VNT or even electric boost... all anti lag approach.. and since the smaller turbo is obviously smaller it cuts lag... but both turbo must be properly sized... and you dont size according to boost required but more on mass of air required.... say you need to make 900hp you would need the big turbo to push about 90lbs air per minute... so the small turbo only recompress the air more... 



btw sorry for reviving this thread.. but the subject is so great i had to bump it




boomerkk said:


> Interesting work arnout!
> 
> However, the thing with twincharging is that it is adding a whole other "system" or "dimension" altogether.
> 
> ...


twincharge is way different than compound.... 


compound turbo have complicated piping work indeed... but they have the possibility to boost upward of the 5 or even 10 in pressure ratio speak.... that's like 9 bar of boost... how much more would you want???? want to cut lag??? put a third turbo in there??? 


the limiting factor is the cooling of the air charge..... + octane ratio of the fuel 


+ why do diesel inject water instead of using an intercooler when using high boost pressure in tractor pulling??? maybe because they dont want pressure loss that at higher pressure might be even bigger than at average boost pressure.... so to cool those they inject more than a gallon per second great stuff indeed!!!


----------



## claude b (Dec 3, 2009)

greetings every1; first time here, keen on increasing the knowledge base.

as it relate to the twin charging, i see the benefits as not just having no lag but the linear and somewhat predictable power and torque from lower in the rpm band. for street, where u really punch it from 3rd gear onward, a slightly larger single turbine will always be more favourable and the debate has been going on fr b4 i was born. on the track, where i am very interested in running a 1.3 or 1.5 engine against a larger motor,taking advantage of the lower curb weight. to be able to draft and overtake wt the better acceleration at corner exits, the linear boost means i can just keep my foot at a steady position/rpm and that predictable boost is more usable thru tight corners. if 4 any reason u had to brake where normally u would fall out of the power band and get bogged down, u can get back up 2 speed rather earlier than ur opponent wt a single larger turbo and when he is hoping to get u on the straights, u will have that larger turbo that keeps going and going like the energizer ad. 

i will be using the SC12 supercharger from the 4A-GZE that comes wt the clutch and something in the range of a TD05 turbo, and the costs for those can be had on a shoe string budget. 

as for the control, the issues i have been hearing about is blowback, where once the supercharger is taken offline, air will flow back through it (could somebody confirm) unless u start using one way check valves which again adds restriction and complexity. i like the idea of the pipe and the wastegate to take the excess boost around the supercharger and reducing the bottleneck, i will be looking into that. it would be good to have the supercharger totally disengaged beyond the crossover period and say have it triggered by either a map sensor or AFM, this would reduce the parasitic effect it has up top.

as said b4, new to the game but eager to learn, bless.


----------

