I hope you may be able to provide a solution to the following problem :
I am having an overboost issue with a 1996 WRX as follows :

Car : 1996 (Mar) Impreza WRX (import)
Mods : Stainless steel exhaust
Dump valve
I dont know if it is chipped !! (how would I find out ?)

Problem :

On full throttle acceleration in 1st gear I get overboost that results in momentary fuel cut off. This problem is also happens in other gears but very intermittantly.
I have put a pressure gauge on car and found that in 1st it will hit 16 PSI + whle in other gears it (in general) runs at around 14 psi, except when the above fault occurs when it hits ~15 PSI. I have also heard "knock" when this happens.

I run the car on 95 octance with Millers Octane booster, so fuel should be around 97 octane with booster.

Also of note is that in 4th for instance when the throttle is floored at 3000 rpm, the boost rises to ~14 psi and then falls back to ~12/12.5 psi until 5000 rpm and then jumps to 14 psi

I have checked that main solenoid for clogging (none) and have also tried a different solenoid but this has no effect.

This is a pain as I now find that I am afraid to floor the throttle and actually get better acceleration by operating on part throttle (thought with knock at times).

I spoke to Graham Goode Racing and they said that I would need to change the restrictor as the freer flowing exhaust was the probable cause by allowing boost to rise much faster that ECU anticipates and is able to compensate for.

I seen from you web pages that you have done some work with the restrictors/boost and was wondering the following :

Where are these restrictors located, what size are they.
Should I be decreasing restrictor size
Where can I get restrictors (of varying sizes)

As it stands my boost solenoid has 3 hoses attached 1 at top of solenoid, 1 in middle and one at bottom. There is another small unit mounted just above the boost solenoid with 2 hoses, 1 I think is comming from turbo area (would need to remove air intake to see) and I cant remember where it is going ( possible to air box)

Any Ideas, sorry for the long winded message
What boost are they supposed to run ??
Regards,
Sean Dowd

 

hi Sean.
the restrictor is a very small brass tube located inside the rubber hose leading from
the manifold to the plastic T piece that goes to the waste gate and solenoid , you can feel it inside the hose by simply pressing the hose between your fingers .
try cleaning first if that doesn't help get the hole larger with a drill .

 

Hi
Thanks for the pointer, I will check this out
Regards,
Sean Dowd
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by light12:
<B>hi Sean.
the restrictor is a very small brass tube located inside the rubber hose leading from
the manifold to the plastic T piece that goes to the waste gate and solenoid , you can feel it inside the hose by simply pressing the hose between your fingers .
try cleaning first if that doesn't help get the hole larger with a drill .[/quote]

 

If yer feeling flush, an aftermarket boost controller such as HKS EVC or Apexi will fix the problem, allow you to control boost levels and give a smoother boost curve to boot.

A couple of people have done this with good results

James.