No Boost

[Studduck]

I have a 1990 supra turbo and have been having some problems with the boost. I normaly get more than 8 psi, now I get around 5 (at most). In first gear it wont go any higher than 0 psi. Also, when the car is not moving the turbo will not spin whatsoever. When I am at much higher speeds I can get way more boost than at lower speeds. I have checked all IC pipes, BOV, boost gauge, most of the vaccum lines, and the air intake. Any ideas on the problem?

 

[skim1040]

turbo making any funny noises when it spools?

Does it spin freely when the car is off? shaft play etc?

 

[oscolivar1]

inspect the turbo for shaft play.
check for boost leaks again, bend the rubber ic pipes if they crack replace.

 

[swaq]

So we took studduck's Supra out driving and we were boosting about 5-6 psi in each gear. The turbo sounds fine when it spools. We did notice the clutch was slipping however. The clutch slipping wouldn't affect boost though, right?

When revving in neutral the boost gauge doesn't register anything and we can't hear the turbo. Is this normal?

We haven't checked the turbo to see if it spins freely or if there is any shaft play yet.

The mods are a K&N filter in the stock airbox, downpipe, gutted cat, and exhaust.

 

[oscolivar1]

so its has a 3inch DP and exhaust??
if so u shud here it spool sum what or here the BOV( if its aftermarket).
u wont see the boost gauge move if your just revving it.

check the turbo for shaft play, or maybe its time for a rebuild or bigger turbo.
i still think it maybe a small boost leak somewherem but if u checked everywhere possible....its prolly the turbo.

 

[robeats91t]

I have a 1990 supra turbo and have been having some problems with the boost. I normaly get more than 8 psi, now I get around 5 (at most). In first gear it wont go any higher than 0 psi. Also, when the car is not moving the turbo will not spin whatsoever. When I am at much higher speeds I can get way more boost than at lower speeds. I have checked all IC pipes, BOV, boost gauge, most of the vaccum lines, and the air intake. Any ideas on the problem?

A slipping clutch will indeed limit your boost; I'd get that taken care of asap. I let my old clutch get so bad that I could essentially leave it in 1st...while stopped...and it'd slip so bad the engine would still barely be idling.

Initially it did what you said though; I'd feel it slip in 1st and 2nd (with lower boost than normal) but higher gears the slippage was almost undetectable, except for lower boost numbers than normal. Needless to say, I let it go much longer than I should've, and I couldn't put any power down.

And it's normal to not see boost in neutral when revving on these cars, unless you've got some fancy electronics that allow you to build boost (i.e. an aftermarket 2 step rev limiter)

If you know the clutch is slipping, fix that first. Much cheaper than a new turbo. By the way, how many miles are on the engine/turbo? And is it the original clutch?

 

[Studduck]

A slipping clutch will indeed limit your boost; I'd get that taken care of asap. I let my old clutch get so bad that I could essentially leave it in 1st...while stopped...and it'd slip so bad the engine would still barely be idling.

Initially it did what you said though; I'd feel it slip in 1st and 2nd (with lower boost than normal) but higher gears the slippage was almost undetectable, except for lower boost numbers than normal. Needless to say, I let it go much longer than I should've, and I couldn't put any power down.

And it's normal to not see boost in neutral when revving on these cars, unless you've got some fancy electronics that allow you to build boost (i.e. an aftermarket 2 step rev limiter)

If you know the clutch is slipping, fix that first. Much cheaper than a new turbo. By the way, how many miles are on the engine/turbo? And is it the original clutch?

The Supra has about 95,500 miles on it, the engine was rebuilt about 3000 miles ago. And yes it is the original clutch.

 

[starscream5000]

Replace the clutch and report back. That is most likely where your problem lies if IC hoses are fine and no boost leaks detected.

 

[Studduck]

I checked the turbo for shaft play, it was very minimal. The shaft moved 1/2 mm to 1 mm at most. The fins spun easily when we moved them. There was also some oil in the turbo and a pipe.

Is that normal?

 

[starscream5000]

The oil is normal, it's blow by.

 

[swaq]

How freely is the turbo supposed to spin? I spun it with my finger and it made about two revolutions. I could definitely feel resistance when rotating it.

 

[Studduck]

How freely is the turbo supposed to spin? I spun it with my finger and it made about two revolutions. I could definitely feel resistance when rotating it.

How much will this affect the boost, if at all?

 

[3p141592654]

I notice you have the stock BOV. Take it out and see if you can blow through it. I bet you can!

 

[swaq]

He's already checked the BOV...

 

[Studduck]

He's already checked the BOV...

yeah i tried to blow though it, no air whatsoever went through

 

[swaq]

How freely is the turbo supposed to spin? I spun it with my finger and it made about two revolutions. I could definitely feel resistance when rotating it.

Bump... Can someone answer this question? Mostly I'm just curious.

 

[Cya]

You should feel a little resistance, but that sould be from the initial force to rotate it. That force should be minimal. I'll check mine tomorrow, gotta alot of rounds to make for christmas. By the way Merry Christmas!!!