my car is a 2003 sti,and fitted a prodrive downpipe just before mapping to go with the decat centre and backbox already on.also has an uprated fuel pump

while it was being mapped, it could boost to 1.4 bar but couldnt hold it at over 4k ish revs. the mapper and the garage it was being done at tried many things and decided it could be the turbo on its way out. so they sent the turbo to be looked at, and it was refurbed due to the shaft being faulty apparently. im just going on what i was told so i cant give any further details on this. the turbo went back on and was mapped again, but STILL couldnt hold boost. the people who fixed the turbo said it should be fine. could it be a back pressure issue? i know that the prodrive downpipe should be fine for the 330 bhp i should get off my VF35, so does anyone know why it wouldn't hold boost???

air intake is standard box with a simota panel filter, turbo should be fine now,could it be the downpipe is blocked?it came off a wr1 that had done 8k miles.they also say its not electrical,so not plugs etc

it puzzles me that it'll do 1.4 bar to a point then cant.

pleeeeease help,i need to throw some ideas at them to help them to figure out what could be wrong with my car.

thanks in advance

 

Might be the fuel pump?..is it a walbro 255?.... just had mine mapped to 1.3 and was doing the same...put fuel pump on and FSE fuel pressure reg and turned up fuel pressure and it would pull to 6k..might be something else though?

 

who is doing the mapping and what is his thoughts! Surely he would know.

 

You could normally expect your turbo to run to 1.4 bar and hold that for a bit before tapering off down to perhaps 1.2 bar. Generally it would hold 1.4 bar from under 4K rpm until 5.5 or whatever and then taper off. Your mapper can look at the waste gate duty cycle and determine what may be happening.
The fuel pump has no influence on the ability of the turbo to maintain boost.

 

you may have a week actuator for the wastegate valve,or may be the restrictor pill needs downsizing? i have read when upping boost levels the pill hole size needs to be changed.to control boost levels correctly.might be an idea worth a look though.

 

i wouldn't let them go anywhere near my car. who are they? ask a quality mapper and they will tell you the problem striaght away. you have to tell them what's causing the issue? get in touch with JGM or Andy Forest.

 

I was being polite. It sounds like your mapper and garage have little Subaru experience or specific knowledge and it also sounds as if you have had a turbo overhaul which was not required because you still have the same issues now as you had before the alleged turbo shaft issue.
Get someone who knows what they are doing and cut your losses.
JGM/Simon Roe may not be too far from you and he is prepared to travel.

 

i dont wish to say who's doing it as i fully trust them and believe me they have PLENTY of experience in mapping and working on subarus,its just a puzzler at the min, would a split hose somewhere still allow it to reach 1.4 bar boost or would it not get there? could it be the standard dump valve leaking?

 

anyone think a 3 port boost solenoid would help?or is it a turbo issue

 

i think it 2 port solenoid is problem as there poo.

 

Ah - that explains it then


So what does the boost profile do after 4k rpm - does it creep down slowly or suddenly collapse, with power dropping off quickly?
Is a silicon inlet pipe fitted?

Nick

 

i think they creep down an every1 recommends a 3 port. i got mine mapped an they didnt even know why they put a crap 2 pot on them. that wud be my next thing to replace. shud get 1 cheap mate. only thing to do is change the piping an the connectors as they are different

 

Bollocks. If the company carrying out the work are so good why have they not diagnosed the problem and put it right instead of having your trousers down spending money on a turbo overhaul with nothing to show for it and why is it necessary for you to come on here instead of the people you have given money to sorting it for you.
THe problem could be one of several things but I am sure any experienced Subaru tuner that was competent could get to the bottom of it very quickly.
The answer is not a 3 port boost solenoid valve.

 

I am also having this same problem with my impreza sti vers5. Mine was mapped Andy F but problem didnt occur till a few weeks later so nothing to do with his mapping. I'm thinking turbo actuator, what you guys think?