I have developed a very strange problem with my 04 STi...

Whenever the turbo spools up (especially in the higher gears at lower speeds [More load]) I get a very strange chattering sound from the turbo/bov... and acceleration seems to get lumpy..

Specs:

HKS SSQV III (Possibly the problem? Sticking open?)
Japspeed 3" Turbo Back
RCM Air Intake


Everything else is standard STi Spec..

Its a sort of chattering noise as the Turbo spools (2500rpmish) and then again at 3500rpm...

Only seems to happen when the engine is under load (5th or 6th Gear pulling from 40mphish)

Anyone got any suggestions? My gut feeling is that its the BOV.. Opened the engine bay and I can hear a very high pitched, but very faint whistle coming from it. Could it be leaking boost? hmm

Cheers guys

 

My money's on the hks try putting the std one back on, I guess the cars mapped for the mods otherwise you'll be over boosting and probably leaning out on boost.

 

mine done this since getting a remap. Its only when in high gear under load , but if i look at my boost gauge its maxing out and the needle is bouncing . I assumed it was like a boost limit , so it would stay within powerband in normal instance but as it sees it , i'm in 5th/6th gear at low revs it is boosting as normal , but as its under un-necessary load , its reaching the limit and the ECU it holding it so it wont go higher and blow up !

I may be completly wrong of course ! I just imagine it to be like a car bouncing of the rev limiter , but in this case it a boost limiter and you are hearing the turbo chatter.

I just change gear now , and alway feel like i'm raggin the heck out off the car , but look down at the revs and its not .

 

Any of you guys running a VF35 turbo by any chance

 

Boost surge.....

 

Or 34 could be boost creep or turbo surge to much boost to early cutting boost

 

Yes.. lol

 

How would I go about fixing this issue?

 

Thought as much,i had the same problem on my last car fitted with a vf35 as they are prone to surging under high load,mine was that bad it would try and shake the engine out of the bay,simon JGM managed to map some of it out but its very hard to get rid of,talk to your mapper buddy.

 

Easiest fix is to tailor the boost curve to sit just under the surge limit you're hitting at those problem areas. Just needs some careful mapping. It has occurred because you've improved turbo spool up by freeing up the inlet and exhaust, so it is possible to run too much boost at too little air flow for the compressor. We found it on my vf34 during mapping, took andyf 5 mins to solve with some road mapping.