Subaru Impreza GC8 & RS Forum & Community banner

1 - 20 of 27 Posts

·
Registered
98 GM6 EJ207 V7
Joined
·
704 Posts
Discussion Starter #1
I'll probably regret this, but entertain me.

Boxer Engine,,4/6 whatever..Supercharged; but it's feeding the exhaust side of a twin scroll turbocharger. Tell me why this is horrible idea and wouldn't produce near lag free boost

:corn:
 

·
Registered
98 GM6 EJ207 V7
Joined
·
704 Posts
Discussion Starter #3
ahhh....maybe? They just seem like they need to be combined, superchargers for that instant kick and turbos to take it all the way through the powerband; I've heard of various setups and I imagine I'm not the first to have the idea, just wonder where it turns into a bad idea since clearly everyone isn't doing it.
 

·
Registered
MY98 2.2 Swapped Foz L
Joined
·
281 Posts
If you're really good at designing/fabbing your own parts, it's a great idea.
 

·
Registered
2000 2.5RS/C BRP
Joined
·
2,321 Posts
This would make more sense with a non-twinscroll turbo. Twinscrolls are inherently lower lag.

But, it sounds like in your OP, you have the supercharger feeding INTO the exhaust of the turbo? That makes absolutely no sense. A proper twincharge setup is Turbo->Throttle->Supercharger->Engine->Turbo Exhaust housing.
 

·
Banned
Joined
·
4,438 Posts
the right turbo/cams/manifold(s - both sides) choice can lead to minimal lag.

that being said, what hydrochloric said above - how on earth do you propose feeding the exhaust side of a turbo? your order is completely backwards = spinning compressed air into a turbo serves no purpose
 

·
Registered
2001 D2 A8L
Joined
·
929 Posts
Forced Air Technologies used to have a kit you could buy. I think it made like 600whp and no lag. Of course they were not supercharging the exhaust side of the turbo :blol:
 

·
Registered
2000 2.5RS/C BRP
Joined
·
2,321 Posts
He's thinking of using the supercharger to spool the turbo instead of exhaust gasses.
Which makes no sense. We know from basic science that changing energy states expends some energy. So by using the SC to spool the turbo, not only does the engine have to power the SC, the SC has to power the turbo (which makes very little sense anyway, since turbos don't need pressure to spool, they need velocity).

So the conversion goes from the rotational energy of the engine to pressure & heat (SC), to rotational & heat (turbo exhaust side), to pressure & heat (turbo compressor side), to chemical & heat (final combustion). Additionally the pressure the SC can build is lost since it would just be ejected into the existing air after the turbo. It can't be pumped back into the intake of the turbo either, because then the SC has to spin the turbo that's trying to pressurize the SC's air... Which is basically infinite energy. I think the car would run, but at best you'd get less pressure from the turbo than you would from the SC by itself, and at worst the turbo would be a restriction and provide less air than an NA setup.
 

·
Registered
2000 2.5RS/C BRP
Joined
·
2,321 Posts
Forced Air Technologies used to have a kit you could buy. I think it made like 600whp and no lag. Of course they were not supercharging the exhaust side of the turbo :blol:
Xcceleration made a twinscrew setup with custom everything... I want the intake manifolds they made.
 

·
Registered
98 GM6 EJ207 V7
Joined
·
704 Posts
Discussion Starter #12
ahh I knew there would be some experts on here. I remember looking at some stuff from Xcceleration, I actually got my vented fenders from them. Looks like good, expensive stuff. I guess my mental image of how everything worked was a little off center. I was thinking the turbo lag was the time it took the exhaust to spool fast enough for the intake side to be able to compress the air, so I assumed the compressed air from the s/c side would spool the turbo faster and the turbo alone would feed the engine after the intercooler. I get how the traditional setup runs, I was having a half thought I guess. Thanks for the education.
 

·
Registered
2000 2.5RS/C BRP
Joined
·
2,321 Posts
I guess my mental image of how everything worked was a little off center. I was thinking the turbo lag was the time it took the exhaust to spool fast enough for the intake side to be able to compress the air, so I assumed the compressed air from the s/c side would spool the turbo faster and the turbo alone would feed the engine after the intercooler. I get how the traditional setup runs, I was having a half thought I guess. Thanks for the education.
You have correctly defined turbo lag. It is the time it takes the exhaust flow to get the exhaust turbine spinning fast enough to create net positive pressure on the intake side. That said, stealing power mechanically from the engine to spool it faster isn't the answer, as at best it is self-neutralizing and at worst it's self-defeating.

There are a few interesting production ideas on that, things like variable vane geometry turbos, twinscroll housings, etc. Then there's more traditional systems, anti-lag, NO2, etc., which just force the things to spin, dammit! After those you get into the really new tricks, like semi-electric turbos, compressed air spooling... The new turbo V6 F1 cars have some of the weirdest turbos yet- they have completely divorced housings! The exhaust and intake sides aren't mechanically connected at all, and in some cases both housings are eletro-mechanically linked to the crank, so at low RPM the crank spools the turbo and at high RPM the excess exhaust that would normally be vented through a wastegate is used to add additional CHP! Even some of the very new V6 and V8 Audis are playing games- the head's intake and exhaust is reversed, the intake is on the outside and the exhaust is inside the V, so that they can stick two turbos inside the V as well and reduce spool and such even further.

That said, while I know of these systems, and a little about how they work, I can't fully explain them. I can't even fully explain the twinscrolls' lower lag, and those have no more moving parts... We need a forum turbo engineer!
 

·
Registered
The subaru of many acronyms
Joined
·
1,919 Posts
i think more along the lines of what you were thinking was a compound charged setup with a turbo and SC, nissan march super turbo comes to mind.

i feel like in your original idea, a leaf blower powering the exhaust side of a turbo would push more boost then a supercharger propelling it lol.
 

·
Registered
2015 WRX
Joined
·
2,350 Posts
Turbo-compounding:

VanDyne SuperTurbo

Granted this is mostly for over highway (i.e. large diesel engines), but it can be applied to smaller gasoline engines. Engine torque is utilized where low exhaust energy is available to improve transient response of the turbine/compressor. At high engine loads where you'd typically bypass exhaust gas in excess of what is required to drive the compressor, it's dissipated mechanically back into the crankshaft.

:)
 
1 - 20 of 27 Posts
Top