Hi
I've had my MY97 STi3 for a couple of months now and am on a very steep learning curve thanks to this forum. Soon after getting it I experienced a sharp cut off whilst accelerating. This has progressively worsened and has been characterised by a series of sharp cut-offs (quite dramatic loss of power, almost kangaroo like)accompanied by a fluttering sound.

It had an atmosphere dump valve, HKS induction kit and Magnex type rear box when bought. Tuesday I fitted a Gruppe-S header and up-pipe, H&S downpipe and Magnex resonated mid-section. The performance since then has felt phenomenal, unbelievably rapid acceleration, when not cutting that is.

Until today, when I thought I'd try to sort this cutting by cleaning the boost solenoid. This has cured the cutting and the fluttering sound, which also used to happen when 'feathering' the throttle. It will now accelerate smoothly BUT it seems to have lost power. The brute grunt has disappeared and it feels a little tame.

Could the cutting and fluttering have been caused by overboost?

 

Sounds very much like overboost caused by the solenoid sticking, probably venting to bleed off point. Do you have a boost gauge fitted as this would give you the answer? From your description you may also have a problem with your VTA dump valve not fully shutting under boost causing the bucking and whooshing.

[Edited by Delboy2 - 9/13/2003 10:18:19 PM]

 

Hi Delboy2
Thanks for replying

Unfortunately I don't have a boost, or any other gauges at present but am in on the group buy so will have one soon. The whoosh sound now only occurs on lift off (throttle pedal that is)so I think that all is now well. But what a difference the extra boost made.

I have a RR session booked for Weds. This is a 1st for me. Is there anything I should be aware of or what to watch for?

Thanks again,
Gerry.

 

Sounds like the VTA is working correctly The extra power you were gaining from the 'overboost' does feel great but also consider that the engine was probably detonating big time which is 'definitely not' so good and can cause serious damage. I take it this car is a Jap Import and with the level of modifications you are running you are using optimax and octane booster and would definitely recommend some type of knock detection. Has the car been remapped at all? The session on the rolling road should point you in the right direction as this should highlight the shortfalls if any.

Cheers

 

Hi and thanks for replying,

Yes this is a Jap import and I religiously fill up with Optimax and Millers. I also just managed to jump onto the Knocklink g/b so should have it this week (I hope).

Don't know about the ecu but I've been meaning to take a look at it. From what I can find, MY97 & 98 can't be re-mapped so may have to go for a Unichip when funds allow.

Thanks again for your advice
Gerry