jrichardson

Im sure its a much disgust subject here. Just bought a 98 Turbo Wagon, immediatly changed air filter element for a pipercross as recomended by Carnosoir, (excuse spellin). Drives a lot nicer and far less lag with increased responsiveness. Well pleased, however the dump valve seems to have made little if any difference other than noise. Obviously it will prolong the life of the turbo, (no stop start). I read somewhere that performance and fuel economy could be reduced with this mod. Does anyone know if this is b****x, or is there some truth in this. Also do I need to reset the ECU and if so how is it done.

jrichardson

Thanks for your advise mate, nice one. It makes one hell of a woosh on lift off, and there is no popping of excess fuel in exhaust (STANDARD) though it does smell quite rich from exhaust. It hasnt slowed it down just seems the same as when I replaced the air filter (most improvement for only £30). Whereby it was far more driveble in traffic i.e. more responsive so could be in lower gears. Im gonna keep it on there anyway as Carnosoir stated this dump valve is intended for virtually standard Imprezas. Thanks again!

Fat Blerk

Hiya,

After much arsing about with my Forge dump valve I have found that you CAN seriously affect performance with your choice of dump valve...

If the spring in your valve is too soft, it takes too long to close and your boost takes longer to build......this is upsetting if you love being shoved back in your seat.

Also, a VTA (vent to atmosphere) valve causes a fuel overrun when you lift off to change gear - this is just the engine protecting itself as its confused by the air not being recirculated..... this is not a GREAT problem, but again, the softer the spring, the more pronounced this is. This leads to pops and bangs (much loved by some) from the exhaust as this unburned fuel goes through.... but as far as I am concerned, it's a symptom that my boost probably isn't building as fast it should when the valve shuts....

If on the other hand your spring is too stiff, the valve won't dump unless its under extreme boost pressure when you lift off. This means

1. No noise! Except some wastegate chatter.....
2. The valve isn't really protecting your turbo like it says on the tin.

Phew. Longwinded, but I think I've covered just about everyone's point of view there.......

Forgot to say..... really, the best you can hope for is that you don't detract from the performance of the car - there's no really pronounced gains to be had from a VTA valve.....

[Edited by Fat Blerk - 1/6/2003 5:20:24 PM]