willizm

iTrader: (10)

So i wanted to start this thread to hear from some of you guys like Martin, Denmah, and Lil John. My setup consists of the following:

Forged 346 LS1 9.5:1 CR
317 heads
LS6 intake
TU1 Cam Lift is .581/.581, Duration @.050 is 225/225, and is on a 113LSA
dual spring kit
PT7675 CEA
3" DP
4l80e
s60 3.54
28" tire

Anyway, my question is, is my cam holding the car back at higher boost levels? I'm pushing 20-22psi and it seems as though I'm only gaining 5-6mph over 10psi in the 1/4. My logs look a-ok, KR is flat, timing is good (18-19*) and I hold boost throughout the run. It seems the more boost i'm trying to push the more I'm experiencing diminishing returns. Is it that my cam is creating a restriction? Should I be looking elsewhere? Best runs in cool weather were 9.8@139mph and 9.7@140mph. The setup as it sits spools quickly. Fun on the street.

WheelsUp84z

iTrader: (14)

have you measured back pressure as well?

JoeNova

There are people running a whole lot faster than that on a smaller cam.

What is your 60 foot like?
And your weight?

I'd say your downpipe is holding you back more than your cam. If anything is off with the cam, its the timing.

RatCityRex

iTrader: (3)

I'm gonna say not a big enough downpipe. That much boost...... that thing needs to breath. Open that ***** up with a 4". But first I would make a home made back pressure tester, they are pretty easy to make.

Forcefed86

iTrader: (4)

Did you degree the cam in? Is the down pipe an open 3" dump?

I'd think you'd out run the turbo hotside before that cam. How high are you revving? What AR housing on your 76/75? 18-19* of timing seems on the high side for 22lbs to me.

Ryans99ls1

iTrader: (16)

I think I remember you saying there isnt much weight taken out of your car so with the 4l80 I'd guess you were right around 3800lbs. With the heavy drivetrain you have, your numbers arent too far from the power you are probably making.

Calculator puts you around 750whp and id say thats accurate. Especially since im running a near identical setup but through a 6speed. I saw diminishing returns after 16psi. The numbers i made at 18 psi werent much less than what i made 20psi.

BTW Im a 346 with 317s and 230/230 .613/.592 111+2 cam with a cast wheel precision 76mm. 3" downpipe, T56 Magnum, 9" (3.50 gear) and 28in DR's. Also on E85 and running 19* up top.. VERY close setups.

willizm

iTrader: (10)

My 60' has been 1.3's and my race weight is about 3800lbs. Here are some slips. Left Lane

Attachment 724240

93camaro_zzz

iTrader: (13)

I agree on enlarging the downpipe, but you are doin pretty good with it in the first place.

willizm

iTrader: (10)

I did not degree the cam per speed incs recommendation. The DP is indeed 3" and I've often wondered if that is holding me back. The AR is .96. The timing has helped me to get a few mph out of the car. It's on e85 so no issues with KR.

Yeah that's been my experience as well. It seems i'm hitting deminishing returns past 16psi. I don't doubt it's related to the DP.

So if it is DP related, would I just taper up the 3" vband connection to 4" as close as I can to the turbine or am I still hitting a restriction on the turbine itself? Also need to figure out my kmember situation as I doubt I'll be able to route a 4" pipe through there to hook up to a cutout/exhaust.

roastin240

iTrader: (13)

Your DP is killing it. Build a little dump pipe and run it again. I bet you pick up quite a bit. Your EGT's will also go down and you will have a higher detonation threshold...and you will spool faster. Basically, put a larger downpipe on it. Are you bone stock 317's?

Slowhawk

iTrader: (12)

As said, downpipe needs to be 4"

NicD

iTrader: (7)

You say it's a 3" downpipe, but how long is it and how many bends? Do you have full exhaust? What does the rest of the exhaust setup look like?

Do you have a dyno chart showing your 22 psi run vs 15 psi? That could show power falling off early in the rpm at the higher boost levels which might indicate valve float. I don't think your cam is holding you back though.

Just for reference I have a stock cube LS1 at a low 8.5:1 compression with an old 76GTS with a 3" downpipe with several bends and then it flares to 3.5" and dumps out near the rear tire and it's trapping 152-153 at 20 psi. Anything higher than 20 psi for me just doesn't pick up anymore power as the turbo is tapped. I wish I could fit a bigger downpipe but I just can't.

DEFYANT

I don't think your fully tapped on the turbine quite yet, I'd say you're close though.

You live close to Straightline correct? I would take it to Joe and at least have him build you a 3 1/2" downpipe.

Forcefed86

iTrader: (4)

I also don't agree that a 4" pipe is necessary with that turbo.

As a general rule 120% of the exducer when sizing a down pipe is more than adequate. (As said, that's assuming a dump of sorts, no muffler or complex bends etc) So 3.5" would be optimal, 4" would be a little excessive.

High'ish back pressure and that cam won't get along well together IMO. I don't think changing the cam is your best bet though. I'd guess at your cubes that turbine & housing are out of steam. Knowing the systems current back pressure would tell you a lot. larger Turbine/housing would allow the combo as a whole to work better.

ZGLASS

iTrader: (11)

4 in downpipe FTW! Same turbo pt7675 .96 BB. Well over 900whp at 21lbs. Trying for over 1000whp with the new head/cam and a small shot.

RonSSNova

iTrader: (3)

What do you have for a torque converter?

Forcefed86

iTrader: (4)

While extremely cool, your car seems to do the impossible! Ever had it to a track?

Assuming 100% turbo efficiency the most you can do is double stock NA HP at 1 bar. (and that’s at the crank) I don't get how "stockish" L33 is putting out over 900whp at 1.4 bar of boost. If we assume crank HP, an impossible 100% efficient turbo system, and zero drive train losses... you would have to be making 375hp NA with your L33 to net 900 at the crank. By the time you added in a 10-15% drive train loss and 70ish% efficient turbo system... you'd need to make well over 400hp at the crank to hit 900 at the wheels. Seems impossible to me.

Either way... Unless both cars are tested on the same dyno, dyno numbers are a very poor comparison.

ZGLASS

iTrader: (11)

Its not a stock l33 anymore. Forged iron 5.3 with afr 210s and a 227-231 tick turbo cam.. My stock l33 with ls6 cam and ls6 intake did make over 800whp on two different dynos on 20lbs though. Figure the motor with no boost before was over 300whp. Now id have to guess closer to 400whp with the head cam setup. about 10:1 compression.

RedRocketZ28

iTrader: (19)

Start taking weight out of the car. My car was in the 3400 range with me in it and trapped 140-141 on 14-15 lbs with the Turbonetics 7875. On 10 lbs through my full exhaust it trapped 136. My downpipe was also "clearanced" to fit through the turbo k-member after it was installed as well. A nice dent about 4-5 inches long, lol. I could definitely feel power drop off when I turned it up to 18-19 lbs. Never got a clean pass with it on kill though. I ran the TU1 cam with the 7875 btw.

Ryans99ls1

iTrader: (16)

This was something i didnt mention either. My downpipe is short. Its got 2 90* bends (1 off the turbo and 1 to go through the kmember), the whole thing in itself is less than 2 ft long. It dumps juuuuust past the kemember, behind the starter.

All im saying is, i dont think switching, to say a 4 in dp out the front bumper, will gain THAT much. I dont think it would be worth the hassle because if im going to go through the effort of making a new DP, you better believe im going to take advantage of it and throw an S476R in there. The turbine is getting to close to being done, but thats just my opinion.