I got a leaking oil return line anyway lol, going to pull the motor and weld in a bung instead of a brass fitting when I get back and install a PCV system that is much required and not yet installed. but I wipe it down under there religiously

 

I agree.That 88 isn't even flexing till 15# and up.
Goood luck.

 

The horse is now dead, good luck, and post any updates in progress after the changes.

 

http://forums.corvetteforum.com/c5-f...mph-today.html

8s @ 158 with an 88 on the back.No way that turbo is too big.

 

update...okay While on R&R I got the car to the track, shortened the 3" DP to a 15" long piece, did a new plug wire setup (was burning LS1 wires left and right reguardless of insulation) Got the Trans went through did a bunch of maintnance things.. The car would not make any more than 11 psi with the boost signal hose disconnected from the turbo... Ran 10.82 @ 129.. HA at least Im faster !! lol ... The Two step made all the difference putting the car back into the 1.4s 60' wise.. Untill of course the 9" let go everywhere and caused a giant mess.

Intake temps were also horrifying, 160 is as cold as they would get with the puny A2W from PTK.....

Now that I have a good baseline of where to go, I will build a 4" DP for the setup, as well as a 3 1/2" Aluminum Cold side and install a PT3000 A2W I bought in the back seat. Hopefully reducing backpressure by NOT having a 3 pipe in a 4" outlet with no transition, and having a free-er flowing cold side, as well as an intercooler with 120 degree cooler air intake temps will liven her up and maybe alow me to run more than 11psi... Ill also be installing my 40"spline stuff I bought and new center section with 3.90 gears. After its all figured out completely... I have a PT101 sitting in waiting and modify the kit some more too install her. Plus my ignition timing curve is rediculously conservative. much more to gain there.. The car is going to be a rocket soon! 3 months left of Iraq and Ill be back to work :-D

 

160F is definately HOT...

what kinda timing did you run?

4" should be a big step in the right direction...I ran 7.99 with my little 4" downpipe...I'm upgrading to 5" now

 

Think I was in the neighborhood of 16 degrees by 5,000 at a slow ramp up my friend casey is doing the computer tuning, that was just my break-in tune. He knows what he's doing though, has what is most likely the worlds fastest rear mount turbo full weight street chevy truck, I would guess 5,500 lbs and running 9.40s with a similiar 408 motor and an S91 @ 22 PSI I think. I might be wrong on a few numbers except the 9.40 unless hes been faster in the past month!


Just an idea of what the future will soon hold! But not before finding the true potential of the T4 PT88 Im thinking Ill run 9.40s or so with her before swapping to the 101.

 

Get meth!!

 

If it's already been said i apologize, but what cam do you have in the car? Only being able to make 11psi with the wastegate completely closed sounds odd, are you sure there are no boost leaks?

 

The T76 will run 8's, so the T88's "true potential" would actually be mid to deep 8's.

 

1 5/8" headers are fine
2.5" crossover is fine
You need a 4" Exhaust at a mininum
Are the wastegates dumped to the atmosphere? If not move them, the backpressure after the turbo is what kills performance.

I've made WELL OVER 1500hp with 1 3/4" headers and a 2.5" crossover, **** I've been multiple trips in the 157-159mph to the 1/8 mile and one hit at 162 where the boost got up on us. The headers/crossover is not your problem. Any pics of the system?

 

You definetly have a problem somewhere. Either a boost leak, a major exhaust leak or a problem with that turbo. My bone stock LQ9 longblock (stock everything inside except pushrods) made 17 psi once I found my boost leak and had alot left in it. That was thru truck manifolds and 2 2.5" pipes feeding the T4 flange. I went 6.32@109.5 in the 1/8, lost a plug and coasted to a 10.03@124 with a 1.38 60' on mine. Put a rod out the side on the next pass but it CAN be done LOL.

I'm building a forged LQ9 (stock crank) right now. It will get a set of AFR225's and a meaty cam. Putting the PT88 kit right back on the way it was and am shooting for 8.90's @ 155+ MPH. Race weight is about 3700.

 

A 3" downpipe will support 150 in the quarter at 3800 lb, which is a far cry from his 129 mph.

 

I chased down a leak in my setup that had me so mad that I let the car sit for 2 weeks at one point. Turns out that my intake had a hair line split. Same thing, only about 10-11 psi of boost.

 

I had the same problem a couple years back. Put a 76 t4 on a 402 and made no power. I would only see 15psi with the waste gate hose off. The problem was the turbo. You didn't say what exhaust AR you have. I was running a 1.00 wich was too small. Also t4 is too small for the airflow a 402 needs. The charge side is also too small for your needs. I redesigned mine with 2.5" hot side piping, a t6 s88 from Forced Inductions, and a 5" down pipe to a 4" over the K-member. The difference was night and day! I am really surprised yours is running as well as it is now.

 

I realize a 3" DP and a PT88 people CAN run in the 8s with but don't they have much smaller cubic inch motors and lighter cars? Im 3800 lbs with a 402 cube motor. I should have built a 366 Im thinking what I got is way too restrictive FOR MY CUBIC INCHES... Ive got a .649/.651 224/230 117 or something of the sort, really dont think I have any boost leaks. Just guessing that the 160 of basically NOT Intercooled air and jacked up pressure ratios are doing all the damage here?

 

why dont you give us some pics of the setup? a picture is worth a thousand words, and whats going on could be something strange that you might not have thought of.

i really think you should try and fix what you have, see what works out. if it doesnt, then you know. try hooking up a pressure gauge and measuring back pressure. try actually fixing the problem instead of re working it.

for all you know, you'll do all this ******* work to find out you had a simple problem. wouldnt you be alittle pissed?

 

I had a 408 and the t4 pte 88...one time I was working on the car and forgot the wastegate reference and the car made 44 psi of boost. That turbo is not too small to provide the motor with more boost.

 

www.cardomain.com/id/z28boysteve Those are all the pics I have of the turbo setup which you can't really tell what's going where

 

Next time I go to dyno, I should put a balloon on the waste gate outlet and see if it blows up when I hit peak boost, with the signal hose off......
maybe I have a really high backpressure and its popping the wastegate early? is that possible? the 3" DP in a 4" outlet could that cause enormous backpressure? or what about the 2.5" cold side could that cause too much restriction on the compressor or something crazy? I can't seem to find a real problem other than a crappy setup. Going to re-vamp the cold side with the PT3000 and 3 1/2" aluminum charge pipe, and this time use t bolt clamps on all the silicone, hopefully I see some different results, I want the thing running right before I set my eyes on KILL with the 101