well, one by one I've handled the little issues of a new car and I'm pretty much down to the final one or two on my list. Since I finished the car it will not make over 9.5-10 psi of boost, in any gear up to 6200 rpm or so.

Here's what I have:

402 LS2 turbo-specific build, ET Performance 245cc heads, PMC sheetmetal intake, Nelson Racing headers, twin T67-76RE Precision ball-bearing turbos with twin 44mm Tial wastegates and single 50mm Tial blow-off valve. The 3.5" in/out intercooler was in the car when I bought it and the old motor could run 15+ psi of boost without issue. I have 3" mandrel bent downpipes and full 3" mandrel-bent exhaust out to the rear of the car.

The wastegates started with 13 pound springs and I run a manual boost controller on top of that. I swapped to 19# springs in the gates and tried with and without the boost controller, no change. I added a boost line to the top of the wastegates directly off the turbos, no change. I shimmed the blowoff so it cannot open, no change. I removed the air filters and then the inlet tubes (3" mandrel-bent) and no change. I pulled the inlet/outlet tubing out of the intercooler to see if there was a rag inside or something stupid, nothing. I swapped from the W2W turbo roller custom cam back to the stock LS2 Z06 camshaft; picked up idle vacuum, but no change in boost.

The turbos have .81 exhaust housings, but spool fine. Even if those were too big once it made boost it should go nuts. My laptop shows 160-165 kpa which matches my boost gauge at 9.5-10 psi, so I believe the boost reading is correct. The car runs great, but I'd really like to be able to make more boost. I am out of ideas at this point. I've spoken with Precision and Tial, no answers.

The boost comes up fine and then it's like it hits a wall and stops at 10 psi; that's why I thought the gates or blowoff were opening, but apparently not (I know the blowoff isn't as it's shimmed shut). The only other thing I can think to do is add a boost gauge off one of the turbos before the intercooler just to see what it shows. Does anyone have any other ideas?

Jody

 

Is there blockage in the intercooler? Also that is a bad *** set up I wet myself thank u. But there is a couple of things leaks can cause this check every sensor in the intake, also do u run a filter if so anychange with or with out a filter. Do the turbos spin free when warm? has vacume change alot since the issue.

 

thanks. I pulled the inlets and outlets of the intercooler and with a telescoping mirror you could see real well, nothing wrong I could find. I did try without the filters, no change. Turbos spin for 20-30 seconds when the engine is idling and then shut off (ball-bearing liquid cooled). Vacuum is un-changed other than the cam swap.

Jody

 

Are you doing pulls on the street if so does the seat of pants feel change? Also check the v band clamps. I dont think the dp pipes would cause you an issue. Are you shure the bov is not bleeding boost? Man you coverd everything I could think of this is beyond me. What type of boost controller are you using and are the lines to it the same size?

 

Well if you don't run any lines to the gates as a quick test that will rule out some stuff.
Also if you can get access to a automotive smoke machine hook that up and check for leaks. Chances are you have massive boost leak somewhere. Talon guys sometimes make a boost leak tester and hook air compressor and pressurize the engine. This can work but the smoke machine works better.

If you turbos are working then there should be no way you are not going to get tons of boost.

 

it runs good, feels like maybe 700 hp or so. No change seat of the pants with all the things I've tried. I'm sure the bov isn't opening, I removed the spring and shimmed it shut, cannot open.

 

I tried early on with no lines to the wastegates, at 13 psi spring and 19 psi spring, no difference or change. Seems like if it's a leak it'd be big and easy to spot, but maybe not. every clamp and fitting has been triple-checked.

I'm going to shim the wastegates closed tomorrow and "carefully" go for a drive. If it's still the same it has to be leaking or a major restriction in the inlet somewhere.

Jody

 

I run tial 44 on my 97 talon and tial 50 blow off.Tial is good stuff. I have had cars that wouldn't boost up before. Some were fubared turbos. Cracks in exhaust housing ,in exhaust manifold .some were boost leaks. A pretty small leak can be magnified a lot at high boost. I would also posisbly drop exhaust or maybe you did that already and just run open downpipes ot make sure no exhaust restriction. An sts car I was in had clogged cats and it ran and boosted terrible till we firgure that one out.

As said an automotive smoke machine could tell in minutes if you have leaks. Yeah they can be intercooler connectors.I use quality silicone couplers not rubber and t bolt clamps.worm clamps come off and can cut thru the hose.

It can leak at intake manifold as well. It could leak at tb to intake. You could have hole in intercooler. crack or whatever. smoke will tell you fast. If its not smoke and not something in the intercooler tubing then what else can it be. if you try no lines to the gates they will go to max boost. Of course the springs in there affect max boost but you have 19s in there you should be able to hit 25 maybe 30 psi so that should not be an issue.the blow off could be leaking at the pipe?
I say smoke test it if you can. If not you can got ot home depot and make a boost tester up from maybe fernco rubber stuff and a bicicyle valve. Use compressor to pump air in and check for leaks with soapy water and your ears.
Huge boost leak would be obvious if car is draw thru but on blow thru not as obvious. On draw thru the car just stalls if the leak is bad. On blow thru the car still runs but of course less boost.

Good hunting but if the turbos are good boost leak is likely all it could be.

 

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.).

 

Is there some way you can check it on the car? Maby a smoke machine,

 

that picture gave me a chubster. u need some other eye candy
(a hottie with a bawdy, half nekkid) bent over that fender in hot shorts and make a poster, thats it one sickinstall. great work!
i dont even feel bad it doesnt run...it's still badassjust sitting there. i dont sukk the stem off many apples..but i've neverseen anything quite like that...im buggin,...that made my night. i do hope u solve the issue soon...enjoy ur weekend.


here are a few of my girl and my R1...when i get my turbo in the "V" i'll
make her take a few more.

 

wow. badass chevelle and setup. Oh btw nice girl too!

 

grab some PVC pipe ends that fit inside the throttle body inlet coupler and the turbo outlet couplers. put a valve stem on the thorttle body PVC cap, and a pressure gauge as well. make sure the couplers are TIGHT!! they will blow off if not!!!

then pressurize the intake tract to around 30psi and watch the gauge to see how fast it falls. most systems have very small leaks from time to time and these can be found and corrected with a brush and some soapy water to find bubbles. my guess though is your intake manifold is either lifting underboost creating a nasty leak or your intercooler has seperated somewhere from info you provided in the previous test you ran.

you can also no switch the PVC cap and put it on the throttle body and pressurize the motor side to see if there are any leaks present there. I like this method so you can best find the leaks in the tract without all the variables of ring seal and what have you on the motor side.

Good luck, sounds like a puzzler though!

Chris

 

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.

 

Sweet I have the same T body I cap it off. Dam in the pics i never noticed it LOL. Now more pics are in order Oh by the way to ctsv NICE BIKE COUGH COUGH! And what o rings are u talkin bout?

 

test for leaks in your charge pipes

 

You are really over the design of the original intercooler, it might be adding to your problem.

Car looks great.

Kurt

 

that was a thought Kurt, thanks for the response. Might have to learn to live with it. So it isn't made to flow enough for this combo it sounds like. Do I need a larger intercooler to support my combo, or could I have the core replaced with a different type/config of the same size so it bolts right in?

I've often wondered about eliminating it completely and just running a water/alky setup. I know it isn't ideal, but it's worked for me in the past. Thing is I can't go larger, car is done and there's no room.

Jody

 

Very nice setup on the car....only topped by the other guys bike ornament..nice!!

 

Mark would probably have the best memory on that car, but I think the core was a 650-700hp piece when we first built it. It will cool extremely well because its a little small, but you will need to learn to live with it or change to air-water someday if you need to upgrade.


Kurt