Need some help, twincharging...

[boosthard05]

Originally Posted by Doward

Ah, yes - I should have pointed that out - STD atmospheric pressure.

Something to keep in mind, is that 'potential' pressure won't be the same as 'actual' pressure - exhaust backpressure will play a large role. As of tonight with my new exhaust, I'm only making about 13.5-14psi from a 2.9" pulley - my system is more efficient at moving air through it, so I see less pressure in the system.

In your case, I would run a 3.8" pulley + 6psi wastegate spring for the turbocharger as a good, solid starting point.

Something to keep in mind, is size the exhaust housing on the 'big' side for your plans - no need to build up more exhaust pressure in the manifold than need be

Increasing pressure from the turbocharger is a very simple matter - start small, and work your way up.

Sweet...

the turbo i have now is a 60-1 .60 a/r compressor side and a TO4E .54 trim exhaust side.

[RandD]

Just want to clear up some misconceptions... If done correctly AITs are actually lower with compound charging than turbo alone. some of you guys may remember me I was the 1st to twincharge the redline and also developed the twincharger kit for Helix for the mini cooper S. currently I am the R&D guys for Helix predominantly working on the new direct injection BMW turbos. now onto the math.


if you start with 100 degree ambient temps and use turbo alone at 20 psi and 70% compressor efficiency you come out with 322 degree fahrenheit outlet temps.

if you start with the same 100 degree ambients and from turbo and compress it to 1.55 bar (8 psi) at 70%(in a properly setup system your efficiency should be far better than 70%) then compress it again at 1.55 bar and 70% efficiency in the supercharger your outlet temps are 290 degrees fahrenheit at 20 psi pressure in the intake manifold.

These mathematical figures are done on a calculator but they match what i have found in my testing "in real life"

you guys have to realize the inter-relation both compressors have on each other.
-the blower helps spool the turbo at low rpm and the turbo helps spin the blower at higher rpm. typically a blower has to work against a vacuum and as rpms climb this vacuum increases leading to an eaton blowers efficiency disadvantage as compared to a proper turbo.
-the turbo has to work against the pressure its creating on the compressor side and the needed restictionon the turbine side to get the turbo to spool, this turbine restriction ultimately limits the amount of power you can put down.

now when you combine them properly heres what you get---keep an open mind!

you hit the gas and the supercharger starts compressing>the more air it moves the more fuel is consumed leading to higher exhaust gas volume(at .55 bar your 2.0l is now effectively a 3.0l), this volume spools the turbo very quickly and allows you to run a bigger turbine(lessening restriction and allowing more potential power at higher efficiencies) at this point the turbo is now feeding the supercharger(so now the SC doesnt have to pull against a vacuum instead its being force fed leading to better efficiency...what your left with is an almost perfect situation where the compressors are complimenting each other if sized and pulleyed correctly. Its a mistake to bleed any of the air charge off you've already wasted energy to get the air into the system so use it. BUT i will repeat one last time you need to design the system correctly in regards to turbo and pulley selection!

[GMredline]

Great post. Thanks for chiming in.

Are you talking about this car?

Looky Looky

04 Saturn Ion Redline Twincharged M62 Blower Garre - Car Videos on StreetFire

[Doward]

RanD - very good information, but I have to point out - max compressor efficiency of a turbocharger is generally 76-78%, and the M62s maximum is 68% (over a very small island)

I'm not saying you're wrong - you CAN have better efficiency from a twincharged setup vs turbo only - but that all depends on the system.

[RandD]

Originally Posted by Doward

RanD - very good information, but I have to point out - max compressor efficiency of a turbocharger is generally 76-78%, and the M62s maximum is 68% (over a very small island)

I'm not saying you're wrong - you CAN have better efficiency from a twincharged setup vs turbo only - but that all depends on the system.

very true on the turbo compressor efficiencies BUT thats only if the turbo is sized correctly. what turbos are 75%+ efficient at .55 bar and 35-40lb min?(a little quiz) a factor noone talks about is turbine efficiency and that is a factor that can be greatly enhanced with twincharging because you can run a larger more efficient turbine,(with the ultimate goal of crossover*a pretty cool phenomenon, if you dont know what it is look it up*) when designing a turbo only system a good developer will combine the compressor and turbine efficiencies as they interrelate.
on the eaton side of the equation you can basically throw the dismal efficiencies out the window because most of the blowers inneficiency is garnered thru the fact it has to pull against an ever increasing vacuum as the rpms climb. add a turbo into the mix and now you are feeding the supercharger so it doesnt waste some of its energy "trying" to draw air in.