Okay,i've got an 88'Turbo.Recently the car will only boost up to 5lbs,the wastegate works and i'ved removed the turbo[stock] no issues.But here's the hting that puzzles me,if i disconnect the line that leads to the wastegate,it boosts like an reaped ape.ANYONE got suggestions?
THANKS.

 

Uhhh.. Normal operation? 5.7 PSI while the vacuum source is connected, and blown motor when its disconnected.

 

still doesn't help me.Boost controller helps ,but doesn't pull like it should.

 

You didnt mention anything about a boost controller in your first post. Is there a boost controller in the mix? IF so, what type?

WHAT EXACTLY IS THE ISSUE?

 

the boost controller was added after the fact[turbo XS] trying to raise the boost level to aleast 9PSI.controller is a screw-type for boost adjustment.

The issue is-------------the turbo screams[spool] but the results are the same,low boost pressure.My car is a 10th with a big street-port,walbro fuel-pump,550cc primary and 750cc secondaries.Full Racing Beat exhaust.I have no vaccum leaks,it's not pulling like it should,like before.
Thanks.

 

Okay, so whats the problem? The boost controller wont raise the boost?

 

it does ,about 2lbs,without the controller,it's back to about 5-ish.it's an s4 with s5 turbo and wastegate.It started doing this about 2 weeks ago,very strange.

 

Might want to start with the turbo. Check it for shaft play.

 

very little,non in and out ,slight side to side.i'll check it more closely tommorrow.
Thanks.

 

What about your BOV? Someone posted last week saying that his BOV was opening under throttle, but was still seeing around 9 psi peak.

 

perhaps a leak somewhere....do you hear air rushing under boost?
maybe just leave the wastegate disconnected!

 

Yes i can hear air rushing under boost,but CAN"T find it.I'ved checked every pipe connector,vaccum hoses,TBI,cold side of turbo and intercooler[top-mount].The only thing that i did notice was rubbing of the inter-cooler on the top of the alternator.My BOV is not opening prematurely[early]there are plenty of washers to keep it closed[turbo XS RFL BOV].The only mod to the turbo[s5]was a To4 upgrade to the cold side,before this happen this car was a ROCKET!I tried it with vaccum dissconnected from wastegate,HELLO-------can't keep the rear-end straight.

 

Seems like your wastegate is opening prematurely and dumping out all your boost? This seems to happen often enough with turbo FCs. Usually, you just need a new clamp or something to make sure the wastegate isn't slightly loose and leaking out air. But it's definitely something to look into.

 

You sure the BOV isnt leaking? I have a Turbo xs and it literally took 14 washers to adjust it till it didn't leak. Also dont go disconnecting the vacume to the waste gate and driving it it will have no way to control boost and you can rocket to 20+ psi (stock turbo would be hard to get there) and this WILL cause damage w/o supporting fuel mods. The waste gate theory is a possibility but if you put a boost controller in line I don't think that it should be the case. I would question your boost controller though maybe its not working correctly.

 

I'll add a few more washers to the BOV and see if that solves the problem.At idle this BOV doesn't leak,it is possible that under boost it might be leaking.
Thanks for the help[all you guys].

 

Of course it doesn't leak at idle! Why should it, there isn't positive pressure to push air out.

That's like saying that your plumbing doesn't leak when the water to the house is turned off.

--Alex

 

Thanks alex,i'm under alot of stress right now,not thinking straight.but i will add those washers and see if there is improvement.let you guys know if it fixes the problem.
It's FRIDAY![track-night] NO UP AND DOWN,just ROUND AND ROUND.

 

I'm not quite sure what you mean by no pressure to push it out. At idle w/o the throttle pushed the intake after the throttle body builds a vacume of 15-20psi before the throttle body the turbo isn't working but it is not drawing a vacume either (i had my boost gauge hooked up wrong to find this out lol) The pull of the vacume plus the pressure from the turbo side will easily push open a poorly adjust valve. The positive pressure built up by the turbo under boost is not all that opens the valve it is the huge instant vacume created by letting off the throttle. Just think about it if you have a lose spring and 15lbs of vacume pulling on it then whats to stop it from opening a little.

 

Because the vacuum will be pulling it closed.

 

added washers,it helped out.Was able to get 9lbs of boost with controller still connected,but it would jump from 7psi to 9psi vice-versa with hesitation.Was only able to put-down 8.80 on the 1/8 mile.My next step is to remove all components and inspect everything again.Tps is find and so to compreession.