cannot make over 10 psi of boost

[awr68]

Jody, sorry to hear that you are still having troubles....but we know you will figure it out.

And since you started this thread we all can learn from it!

[camcojb]

well, some progress made. I hooked a separate boost gauge to one of the turbo outlet housings and took a drive. That shows 15-16 psi at the turbo, before the intercooler, and the in-dash gauge and map sensor both show 10 psi at the intake plenum.

So there appears to be a big restriction in the intake system, or a huge boost leak. I think the intercooler is fine as it was on the car before without issue, but it's a definite possibility it's restricted or plugged somehow. Possibly the big 90 degree angle coming right off one of the turbos (required to clear) is affecting it, but I've had right angles on the pressure side before. Maybe the boost is pushing past the o-rings on the sheetmetal intake.

I need to get a longer piece of hose and hook the gauge to the other turbo and see if it's different. The intercooler will be a pain to remove, most of the front end stuff has to come off (grille, bumper, etc.).

[ohcbird]

Well that's a relief. PT usually doesn't get much wrong IRT turbo application.

Good luck on the rest of the troubleshooting...

[projectile]

Jody, I have some 90 degree bends on the pressure side of mine also! I don't remember what my pressure drop was from the turbo the the intake. I checked it about four years ago but just can't remember now. I've run boost as high as 18 psi and didn't see any high spikes in intake air temps or other issues. If you want, I can hook up a guage to the turbo tomorrow and take a reading. At least you can compare my results to yours before you go through the trouble of taking the front end off of your car. I know that your pressure drop is excessive, but maybe some real world numbers might help...

[camcojb]

Originally Posted by projectile

Jody, I have some 90 degree bends on the pressure side of mine also! I don't remember what my pressure drop was from the turbo the the intake. I checked it about four years ago but just can't remember now. I've run boost as high as 18 psi and didn't see any high spikes in intake air temps or other issues. If you want, I can hook up a guage to the turbo tomorrow and take a reading. At least you can compare my results to yours before you go through the trouble of taking the front end off of your car. I know that your pressure drop is excessive, but maybe some real world numbers might help...

I appreciate that Ray, but hate to have you go to the trouble. My next step is to make a 3.5" bypass for the intercooler and see what happens.

Jody

[J2SpeedandCustom]

Jody check your intercooler very carefully they crack and split quite often. If you can source a smoke machine and pipe it into the turbo outlet on the cold side you'll find the leak. That's how I check for leaks. I've run into that same problem quite a few times and 9 out of 10 times it's the intercooler(s).

I hope you get it fixed I want to see some VIDEO!!!!!!

Jeff

[camcojb]

well, I found 2 psi. The nice thing (for me) about getting older is that I can laugh at myself now. In my younger days I'd never post on a board about some stupid thing I'd done.

I built a plug and test fitting to pressurize the intake manifold. Hooked it up to 25 psi and found a big leak. In the throttle body there was (what I thought) a blind hole out the passenger side. I'd looked at it when I installed it, and it didn't go anywhere. Well, it does, goes out in front of the throttle blade. Not under vacuum, but a direct leak under boost. Thing is, you look straight at it and it looks like a blind hole; change the angle and you can just see a passage on the bottom side joining it. I tapped it for 1/8" NPT as you see here:



That now gets me to 12 psi at the intake. I can also hear some slight leakage at the intake o-rings. Very small amount, but who knows how much that may add up to total. Trying to find a stock LS2 intake to try. Don't want to spend a ton of money as I'll never use it permanently, but it will bolt right on and fit my 90mm throttle body. It's also what I had on this engine in the GTO, and had no boost leakage. If someone has one let me know.

Jody

[slownova]

i got a stock ls2 intake. PM me

[rich-allen]

I have one as well.

Let me know if you need it.... You can swing by my shop and pick it up, I'm in Richmond right off the San Rafael bridge.

[sacarguy]

Originally Posted by deuce_454

your headers look VERY blue, my guess, (which is only a guess) is that the turbos are on the small side, you could be at the surge limit at 10 pounds, have you done the math and checked the turbo maps?? it could be that the housings are the limiting factor.

you could be moving the same mass of air at 10 pounds thru the bigger heads as you weer at 15 pounds with the old ones.. and its the mass, not the pressure that matters, the ET 245 heads flow like a MoFo and on a 402 with your super optimal intake and hot side tubing, you could be outflowing the turbos

not even close those t-67 can support over 700 horsepower each no way they cant supply more then 10 psi to that motor he would be having to make 1000 rwhp at 10 psi to out flow those turbos.

did you change the cam shaft profile to much over lap can easily cause such a issue