Car won't boost above 0.5, loud whoosh noise...please help
 

Just had Alpha 28's, headers, injectors, rear intake piping, y-pipe, TB, and plenum on my 2001 996TT that already had 16G, exhaust, I/C and softronic tune.

Everything was initially pressure tested to 20 PSI.

When the EBC is turned off, the car will not boost above 0.6 and when it gets to 0.6 there is a loud whooooosh sound as you continue to accelerate. When the EBC is on, the car will boost up to 0.9 bar and then immediately drop to 0.6 and hold flat at 0.6 with the same whoooosh sound. The sound does not get louder the faster you go, its just a constant whooosh.

We thought the intake piping was collapsing in one area, so we had a custom hard piece made to go in that spot...nothing changes.

My mechanic that did all the install is unfortantely out of town for 2 weeks (:eek:), so the other guy is going to re-pressure test everything and check the diverter valves.

I really hope its not the intake piping in a different area that is not accessible without dropping the engine!

Anything else he can test?

Thanks in advance for any help/comments!

Plan is to put the car on the dyno and try to figure out where the leak is...any comments on things to look out for etc... are greatly appreciated!

you have a boost leak, that happens at .6 bar be it either your diverter valves giving up or hoses not sealing.

how do I know if the DV is bad? I was told that running pressure through it won't work since the spring is set to 0.2 bar. I was told the way to test it is to put my finger in the bottom of it to open the valve and then put my thumb to cover the top manifold, move my finger andthe valve should stay open until i move my thumb...sound right?

(I have Agency DVs)

If the DV is bad, would it cause that whoosh?

i dont know about that test method,

they generally dont go bad as aftermarket units, does this whoosh sound, sound jsut like when you chop the throttle under power as normal?

without being there its hard to know if the whoosh your talking about is the DV's openign and doing their job(maybe prematurely) or if you have a boost leak which is generally more of a hiss but if its big enough it could be a whoosh?

I would not waste time with a dyno. I would run a boost leak test. Its not the intake piping so dont worry about dropping the engine.

the whoosh sound is a very loud sound that happens as soon as the car hits 0.5 bar (and won't go any higher). It literally sounds like a heap of air is escaping out of the back.

I think the DVs are opening too early....how is this fixed?

pressurize from the turbo inlets (cap one & pressurize through a cap on the other), that will test the DVs

I was told by Matt @ Vivid that running a boost test on the DVs doesn't work since the spring is set at just 0.2 bar....which is why I should use my finger to test them (does this sound right??)

My mechanic thinks the DVs are opening to early

there should be pressurized air in the lines going to the top of the DVs, That+spring pressure, should keep them closed. DVs open upon reaching proper pressure differential (vacuum in the top lines when you close the throttle and positive pressure in your y-pipe trying to go somewhere), so "opening early" is a misnomer. If you're WOT, they shouldn't be open at all, regardless of time.

Couldn't I just take off the diverter valves and cap the f-hose? If it still has the problem i can take the DVs off the list?

yep, that's one way, though there's a small chance the DVs could still be contributing to the issue (if there's more than 1 leak). But since your hearing a whoosh, I would expect it to be a fairly large leak.

so if my DVs are opening while I am accelerating, there is a problem with the DVs?

What about if the hoses were not connected right to the DVs...could that cause a whoosh?

I would guess a hose has come loose and is dumping all the boost once the system gets to 0.5 bar. Simply pressure up the system at the turbo inlet and listen for leaks.

Have you serviced your DV's ? I recently took mine apart, cleaned and regreased (Mobil 1 red syn grease, or white lithium) . I've always tested mine by pushing in the diaphragm from the bottom while applying suction to the nipple. The diaphragm should stay in the upright position without any assistance until the suction is released, when the suction is released it should release all the way back down without sticking. Repeat a few times.

I would assume you would see about .8 all the way to redline if you were running off the wastegate spring (assumming 1 bar actuators), and no leaks.

Wish I could offer more, I went through this with Todd @ Protomotive recently. I also ran a pressure test at about 20 psi, and checked for leaks.

Good luck.

Do a pressure test from the turbos like I suggested via email... all your problems will show up.... forget doing the dvs test this and that.. the leak test as I suggested does all of that and much more.... trust me...

also, inspect the turbos... the compressor.. make sure they are not hitting the housing as they spin...

Thanks for the input Markski and the problem would most likely be mechanical in which would be found as you suggested.

Give me a call tomorrow and I will let my desk know.


Best Regards,
Scott

No problem,
thanks
mark

I agree. Check you hose connections carefully. I bet one is not securely fastened, especially since you are hearing a loud whoosh at higher boost.

Thanks everyone for your inputs! Inspector, MBailey, Earl, Markski (as always), Scott, TTDude, Neil @ Switzer, Jake @ Tial, and Mark @ Agency Power

MY mechanics will hopefully have this solved tomorrow.

Good luck!

If the intake is collapsing above the engine, wouldn't that cause the diverter valves to open up?

Do you mean the intake pipes are collapsing presumably from vacuum? This would kill the boost but I dont think it would cause the valves to open up and give a whooshing sound you describe.

Why are you asking this?

if you have a leak before the turbo that would not cause your problem.. that is the non pressure side...

shouldn't, but what intake piping do you have!? If you're at 0.6bar with the throttle open, the DVs should be shut.

The guys pressure tested everything..found a few small leaks and tightened everything up. Nothing changed.

The car is boosting up to .8 or .9 then immediately drops to 0.53 bar stable.

Mechanics think it is the intake piping above the engine.

Next step is to dyno the car with the turbos open to the air (i will make sure they brush and blow any crap out of the dyno way). If the car makes 1 bar of boost and holds it there we know the intake is in fact the problem.

Sound right?

where did you pressure test from? did you take out the stock N75 grey valve?
what is the greddy reading when car is at idle...
dyno will not solve or find the issue

Boost is actually a resistance. Are you going to take the hoses off the ouput of the compressor or the input? Either way is bad. Input will allow you to suck stuff in, and won't tell you much, with the output open, that will likely over spin the turbo to reach your target boost...which how are you going to measure if this is open?

Ok, so all leaks are fixed and still not boosting. How old are the spark plugs? I had old plugs once and it would not boost past 0.5 bar.

We were going to to take off the input, after cleaning out the area around the dyno etc...

I made my mechanic talk to Markski, who told him how to check for boost pressure from the turbo itself (before they were checking for boost leaks starting from right after the turbo) and then also look over the check valves on the turbo.

Its the check valves on top of the motor... but leak to lines to the catch cans and other few things....

Does the car go rich when this happens? if so boost leak after turbos. If its lean and the ECU is limping then it is pre turbos. Smoke it. one of my intercoolers split and the smoke was coming out the inlet air duct not in the engine bay or under the motor.. Just out the duct. who looks there?

Good luck!

Could this be an issue with the wastegates?

just got off the phone with the mechanic...the 3 hoses going from the plenum to the head were loose. Also, one of the check valves above the engine was leaking.

He has tightened everything up and is putting the car back together

Will update....

Ahh so finally someone listened to me lol

Any leak after the TB will make the car idle high, Don't remember you stating that. Those three lines wont loose enough air to keep you at .5 bar unless you have stock turbos and that's a maybe, even the check valve is iffy. I was running 3076R's and a dv let loose I was still making .9 bar like that.

After they fixed those things the car is boosting properly!

Couple issues

1) small hissing noise from the passenger side as the car spools up...not sure if its a leak or its the new turbos...will check my EBC to make sure its holding 1.3 steady when I leave work

2) car is not any faster even though i added $10k of parts...injectors, intake system, headers and alpha 28s lol....when i floor it, my brockway is saying 10.7!! Retune is needed ASAP!!!! Going to durametric over the weekend and send me results to Dan/Scott ASAP!!!

Thanks Markski for all your help!!!!!

Timeout... before you do any datalogging... find out whats that hissing noise..
that may throw the afrs.... what are the afrs at idle?

I will find out what it is. It might just be turbo noise...

I will check my EBC when i leave the office and see how steady its holding the 1.3 on pump.

I can't remember the AFRs...will find out as soon as i leave work.

Thanks again!