Vettezilla05

My quest to make 1000rwhp has yet to be achieved. And im uncertain my current set up will allow me to make 1000rw.
My build is an 05 6 speed twin turbo c6.

-408 stroker * iron block * 9:1 cp
-Dart 250cc heads
-stock ls2 intake / TB
-1300+ fuel system
-Mcloed rxt
-UPP TT kit
-Twin 61/82 bb turbos
-2.5" hotside piping
-Dual Nozzle meth

So my issue i think im going to have is back pressure due to the 2.5 hotside piping. The downpipes are also 2.5" which will be dumped at bellhousing.

I recently dyno tuned the car on a dyno jet with my old set up which was an aluminum 408 with 57mm turbos, it pettered out at 800rwhp/ 805rwt. Although i am upgrading to slightly larger turbos do you guys think my piping will be a big restriction ?

Im still putting car back together after the engine swap so if i need to change some stuff now is the time to do so although my budget is about tapped out.

Tuomas FIN

Yes, too small, absolutely.

venomws7

I'd change the downpipes to 3" but I don't think the 2.5 hot side will be an issue.

Tuomas FIN

Have you measured back pressure?
What turbine wheel/ housing you have?
Lots of depends as well from the turbine side/ housing But the truth will be you definitely have there on that power level back pressure issue due to small(?) turbine wheel/housing and down pipes/ and exhaust is too small if 2,5".

slow ride

From the manifold to the turbo does not need to be 2.5". 2"-2.5" pre-turbo isn't going to be the restriction, the turbine housing will be. Although my setup is very short I used 2" ID piping to my v band housings and had no issue cracking 1000whp under 20psi intake pressure. A lot of the faster single turbo drag race guys might run a 2.5" crossover on a 1500-2000hp setup, but using that large of piping on a lower power setup will just add lag. Velocity is where it's at pre turbo, Yellowbullet has some good info on this topic if you wanted to read more.

C6 Curtis

2in is pretty small I'm guessing you have less then 400 cubes. Also not sure how much lag you're talking because I run 3in crossovers on my s480 and it makes boost way under 3k with a 1.58 housing. 2.5 is what I would recommend and as far as after the turbo 3 inch for twins.




-Curtis

slow ride

2" pipe flows way better than the smaller t3 turbine housing. With the length of his piping I'd run 2.25", but I know the kits are built with 2.5". Guys making light years more power than us are running 2.5" pre turbo. I don't feel displacement plays as much of a role as overall power output, but I have a 383 and 6265 t3 .82 housings.

http://www.yellowbullet.com/forum/sh...d.php?t=308464

Phil97SVT

I would build it with 2" pipes to the turbos and 3" pipes out of the turbos. 2.5" pre-turbo can support 2500hp. I went 168mph to the 1/8 with 2.5" hot side.

C6 Curtis

Wow that is moving, how much did the car weigh?

-Curtis

Vettezilla05

So you guys are saying it would be better to have an 2 inch manifold to turbo pipe? And a 3" downpipe?

slow ride

Right, Velocity over area in this case. The turbo is the main bottle neck.

Vert_Fan

What size inducer and exducer is the turbine?
What AR is the turbine scroll?

The 62mm exducer turbos should really have a 1.0 AR to Crack 1krwhp. Great example was the z06 aps kit, not the base c6 kits.

The 65mm can do this with 0.82 AR etc.

Dude_man

I would keep the 2.5" pre turbo since the outlet on the manifolds are 2.5" no point to neck down to a 2". You will have no lag or issues with the 2.5.

Post turbo I would put as big as you can fit.

0CK@UPPCOS

Keep the 2.5" Up-pipes, swap the down-pipes to 3". It's a proven setup and there's multiple people now that have cracked the 1K mark with that setup. 2.5" down-pipes would be a struggle, hence why we redesigned the kit to now have 3" standard and allow for the bigger turbos.


CK

sr20dime

What he said. The 2.5 up pipe is fine. The 2.5 downpipe is the issue.
I have 2.5 up pipes and 3" downpipes to make 1200whp at 20lbs of boost.

emoFTW

Any pics of the setups that you guys are running?

Tuomas FIN

I have 4" down pipes, 3.5" axle back and DKT turbine housing (same as APS) and PTE 6766 turbos, block mounted custom built setup. Till about 1200 hp@crank back pressure stays under or max same as boost. First setup down pipes were first 12 inch 3", then 4"/3.5" exhaust and I had serious back pressure problem started at 1000 hp level. Cut Outs helps little to exhaust pressure at higher boost but do not help to back pressure. Turbine side distress.
I'm measuring example both side back pressures and exhaust pressures, compressor side pressures, 8X egt's, 8X LSU 4.9's plus down pipes two more, Motec Level 2 1000hz logging.

slow ride

Most backpressure issues people talk about are completely turbine housing/wheel size driven. Exhaust after the turbo can add a tiny bit, but it's nothing to what is pre turbine.

Tuomas FIN

Correct, I think the biggest problem in Corvette is the space issue for turbo sizing, people looking for too high power levels with too small turbos (turbine side)= lots of issues, back pressure problem etc. Okay, works fine at 1/4 mile and street but make several full mile pulls after mile pulls on airfield is huge risk get failure, my opinion.

0CK@UPPCOS

Not completely true. Actually any pressure in the exhaust after the turbo equates out to 2x the pressure pre-turbo. Which is why the exhaust after the turbo is more important being larger than the exhaust pre turbo even though technically the same exhaust gasses flow through both. We've seen this many times when comparing smaller exhausts on our 3" downpipe vs a full 3" exhaust. Back pressures often become high enough that they generate enough pre-turbo pressure to blow the WG open. We see the WG's open and the power/boost taper on the high end. Simply swapping the exhaust after the turbo cures this, and the power difference is staggering.

But I also agree with the point that properly sized turbos for the application helps dramatically. From my experience most people aim too high. Twin 90mm T4 turbos to make 600whp.

CK