I don't see what all the arguing is about, twin scroll is obviously better suited for circuit duty. It will lose top end, there is no doubt about that. If your car is all top end, it will only be good in a straight line. To properly conquer a race track, you need power and torque ALL over the RPM range (to properly accelerate into, around, and out of turns with minimal shifting). This is why the twin scroll has an advantage. However the twin scroll is not the end all solution for better midrange power. More displacement, playing games with the intake/exhaust manifolds, mivec, cam timing, porting the cylinder head, and the turbine housing all are huge factors. A good example is the AMS time attack Evo, which doesn't use a twin scroll setup, and yet it manages to scorch down lap times comparable to that of an open wheel formula 1 race car.

 

3" is fine. There are turbo'd V8's that don't have 4" exh.

 

I agree with your whole statement about setting up the motor but am curious how many decade old F1 are you talking about?...either that or how bad was the driver?!!

I'd go 3" and if have issues, go out to 3.5"...
what I would personally do is step off the turbo from 3 out to 4" then taper back down to 3.5" then to 3" out....
the larger downpipes have shown decrease in spool up. We've done a test of 3" vs. 3" flaring to 4" and the results were pretty suprising.

 

Not sure, but according to the latest issue of modified magazine, the AMS time attack Evo set a new course record on some track in Canada during the redline time attack competition. The previous record was set by some kind of open wheel race car (maybe it wasn't a formula 1 car). The AMS time attack machine is just plain ridiculous and it murders the competition wherever it goes.

 

Might wanna drop the "1" after formula.

l8r)

 

Hey, who knows, maybe the AMS car would whoop up on a formula 1 car! In the rain...

 

so true...the old Formula SAE car I use to race topped 6th at 120
but it pulled 1.65 g's when turning

 

if the twinscroll is setup incorrectly, it will lose top end.

If you do it right, it will gain top end.

that is the honest truth

 

Quote:
Originally Posted by ill-luzion
Hey, would you need to run a 4inch Turbo back if you went with a built 2.4 93oct/meth on the GT4094R? or is a 3inch fine?

3" is fine. There are turbo'd V8's that don't have 4" exh.

Thanks

 

I am not ao sure about that. What I am going to have to ask you is to send me a GT35R Twin Scroll kit to decide wether or not that is true. PM me and I'll send you my mailing info and we can go from there. Please included some injectors and a nice FMIC to cool the intake charges.

 

i love this thread

 

Eh... probably not Hard to compete with 900hp, 1500lbs, and something like 3k lbs of downforce. They can pull over 4gs in the corners for a reason!

 

eh, I dunno geoff...thinking about a twinscroll with the same a/r as a single entry...
the twin has more surface area = lower velocity fromt surface friction and more heat loss...wonder how that would affect the top end as normally the top end issue is choking and thus causing reversion...
I think his statement might have some truth to it and dyno graphs that I've seen agree...

now if done right, I don't think the top end loss will be much at all or outweigh area under the curve gains.

 

Ill post this again:
To quote a Garrett engineer - "Twin scrolls often flow a hair less at equivalent a/r as boundary layer effects come into play.

Efficiency-wise, twin scrolls take a small hit due to increased 'wetted' surface area imposed by the divider wall. However, this is way more than offset by the vastly superior pulse conversion you get.

Edit: I should probably clarify that last bit. Twin scroll turbines, as mapped on a gas stand (steady state conditions) will exhibit a slight drop in efficiency compared to an otherwise equivalent non-divided housing. On-engine, however, is much different. The flow conditions are highly unsteady. The ability of a twin scroll to utilize the pulsing, unsteady flow of the exhaust exiting the engine gives it a huge bump in "apparent" efficiency, and ultimately spools up the turbine that much sooner.

Twinscrolls also isolate the cylinders' blowdown events much better than a non-divided housing, preventing the exhausting cylinder's very high PEAK exhaust manifold pressures from finding their way into the other cylinder on its overlap period. "

 

yeah, so you are agreeing with what I said...haha...different words and I used less engineering specific words as it is a public forum...generally try to put in common terms.