Low Boost

[CJAllen]

I am having a low boost pressure problem that I cant seem to find to save my soul. Was hoping some of the experts on here might give me some insight on where to look next.

Current state -
Car has fresh stock turbo rebuild
Car runs and idles perfect.
Boost pressure is reading at 2psi on aftermarket gauge.

Things I have tried -
New intercooler hoses. (Minus the one directly off the turbo outlet - this is my next point of attack)
Vacuum lines have all been checked and no leaks have been found.
installed an MBC and tried to get the boost to go up with that - no change.

Things I know I need to check -

The BPV - Where is this located? I know I need to change the hose that comes off the outlet of the turbo, is it located there? (that is where it is on my MR2)

Heater controll valve - does this send any kind of signal to the ECU that might keep the car from running full boost before the car is running at full operational temp? My heater valve is cracked so I by-passed it.

Any help or insights you can give would be much appreciated, getting frustrated with this real fast.

Thanks,
CJ

 

[tubbie]

Boost leak......
It's from the one directly off the turbo. That is the most fail prone intercooler hose.

 

[GrimJack]

That or the coupler from the 3000 pipe to the throttle body. That's the second most prone to cracking.

The other thing to check is your wastegate - if the spring in it is broken, the wastegate will be constantly open, making it very difficult to build any boost at all. This is pretty simple to check - pull off the intercooler piping that crosses over the engine, pull the accordian hose intake off the front of the turbo, unbolt the wastegate actuator, and try to pull the entire actuator towards the front of the car. If there is significant resistance, your spring is fine.

FYI, the ECU has no control over boost levels - except if boost goes too high, in which case you'll hit fuel cut and your boost will drop accordingly.

 

[CJAllen]

I changed the turbo outlet hose and I am still only getting 2 psi

CJ

 

[GrimJack]

Build yourself a $5 boost leak tester and pressurize your intake to check for leaks.

 

[IHI-RHC7]

What are the modifications? What exhaust, downpipe, intake, etc...?

 

[chriso]

Build yourself a $5 boost leak tester and pressurize your intake to check for leaks.

Good idea, got any insight on how to do that or a pic or two???

 

[gixxer750]

go get 2 2 inch or 2.5 inch rubber pipe caps from home depot.... put one over the turbo inlet with the accordian pipe off... put the second over the TB end of the 3000 pipe. punch a hole in one and stick an air nozzle in it... Use 15-20 psi from an air compressor to pressurize it to check it(or higher if you have hardpipes... I used 55 psi on mine.) See if it bleeds down... The rubber pipe caps will hold 60+ psi of pressure.