I just got a S5 Tii JDM swap done into my 89 GTU, and I'm experiencing some boost problems. The engine is stock except FCD, 3" intake piping till the turbocharger, and 2.5" downpipe with hi-flow racing cat, sngle 2.5" straight exhaust and an Apex'i N1 muffler. I was expecting about 9-10psi of boost, and that's how much I boost sometimes... but after a bit the boost drops and holds to 7psi.

Example:
If I floor it in 4th at about 3000rpm, the boost eventually hits 9-10psi then just drops to 7psi and stays there.

Is this boost leak? Or could something else cause this?
Oil also seems to leak into the intake piping from one of the two hoses that go into it (coming from the turbo duty solenoid or the other...)

 

bump

 

Sounds like "spiking". Like your actuator is taking too long to fill up with compressed air.

 

I dont think it's a boost spike. I should be running ~9psi with my mods. Is it true that stock turbos dont have a steady boost, and it tends to fluctuate?

 

at what RPM does it drop to 7psi? what gear?

 

this isn't boost loss, this is a stock turbo.

 

my stock S4 turbo holds at 10psi all the way out...and that's with a ported wastegate...

 

Well I live in Cleveland, and for the past two F-ing weeks has been snowing. Not one dry day... so I really cant go arround flooring it. I will let you all know what gear and rpms, if the roads ever dry out. =(

 

btw, I am missing my idle adjusting screw compleatly (my idle is close to 2k most of the time)... from the BAC valve or by-pass air valve... could boost leak from that part of the manifold?