Rikki23

I'll say whats been happening then I have some questions...


My car has been cutting, like hitting a wall, under hard accelration in 1st and sometimes 2nd gear. My boost peaks at 0.9 bar, and drops to 0.8. The car is a 95 WRX.
I checked the oil a while back snd found that it was over filled at that time but has dropped now.

I took it to Lavender Hill Garage today. They cleaned the solenoid and the pipes going to it. It was better but still cut out a bit. So they put a restrictor in one of the pipes - the guy said it was the 'fuel something' pipe going to the solenoid, so shouldn't affect boost. I took the car out and boost had dropped to 0.7 bar. The problem seems to have gone but I have lost power, which I did not want to happen.

So, here are my questions:

1) What level of boost should a 95 WRX running? (only mod is a scoobysport back box?)

2) Is the solenoid different from the sensor?

3) What are the 2 pipes going to the solenoid? Has anyone got a diagram?

4) Does more boost = more power/speed always?

5) Is overboost when it cuts out from too much boost? If so, it sounds like this is not my problem because mine is cutting out early.

6) Can I cure this problem with out using the restrictor or losing any boost? A new solenoid perhaps?

7) Is there any way boost can be increased without engine mods?

Thank you in advance for any help
Rikki

PS Does anybody know of any Impreza technical manuals (especially for WRX) and also some online resources/books about turbo engines etc, I want to learn more.




[This message has been edited by Rikki23 (edited 09 January 2001).]

Rikki23

Come on guys, please, somebody must be able to help me

JamesS

I will attempt to answer some of your question!!!.....

1) Not sure - dont have a WRX but around 12-13PSI would be about right (0.8 - 0.9bar)

2) There is a seperate MAP (manifold pressure sensor) and boost control solenoid - both on a metal bracket on the drivers side suspension turret.

3) Find the turbo compressor (front part of turbo as you look in engine bay). There is a pipe coming from the compressor side to a T-piece. From the T-piece one pipe goes to the wastgate actuator and the T-ed pipe goes to the boost control solenoid. There is a return from the solenoid back to the manifold. There is also a feed from the manifold to the MAP sensor. There is a brass restrictor in the pipe coming from the compressor out pipe to the T-piece.

4) More boost = more tq = more acceleration assuming your not running lean or at a high intake temp blah blah blah, basically as above!

5) The MAP sensor reads boost sends a signal to the ECU, when 15.5PSi is exceeded (on a 97MY) a fuel cut is enabled - net effect feels like hitting a brick wall!!

6) If your MAP sensor is reading correctly (is it?) and the solenoid is clean then this shouldn`t happen!!!!!

Basically the restrictor acts as a time delay in the pressure rise rate in the control circuit - a bigger hole lets more pressure through quicker therefore the wastegate is opened ealier and less overboost occurs; go to far however and you will run with about 7-8PSI boost max as the wastegate is open most of the time.

Conversely going to small restricts pressure rise, wastegate says shut and you get massive overboost.

So basically it is a `balancing` act between the restrictor and the control circuit.

I`m not sure why the boost would be cutting assuming everything is OK - anyone else????

7) To raise boost you either need to change the control circuit (bleed valve, boost controller etc) or turbo!!

Appologies for not helping directly!!!