Too high boost??

Imran21 · 03 July 2009, 08:54

Hi guys,
After reading various recent threads about over boosting & fuel cuts & restrictor pills etc etc i would like to ask a couple of questions.
I have a version 4 type R running a VF28. Car has a bell mouth 3" decat downpipe & stainless headers/up pipe. In 1st gear i can hit 1 bar of boost & all the following gears boost goes to 1.3 & creeps back to 1.1. Now i know this is referred to as boost creep & is probably due to the down pipe but the thing is that i have never hit a fuel cut in the 2 years i have owned the car.

Would anyone have an explanation for this as i thought that after 1.1 bar it would naturally hit a boost cut? I have still got the standard ecu, no chips (that i know of - never opened to check), boost controllers, bleed valves etc... So is there something wrong with this picture? The boost solenoid seems fine as i can hear it ticking even from inside the car when i blip the throttle.

I am now looking to get a VF34 - will this turbo behave the same? Am i headed for trouble? Any advise would be appreciated.

Thanks,
Imran

ReggieMY99 · 03 July 2009, 12:31

Those are boost spikes and they happen when decatting, spikes to 1.2 and falls back to 1.1 is not boost creep mate, boost creep is when it crawls slowly from 1.1 to say 1.2, so boost creep is when it creeps upwards, more boost in what it was set for and eventually hitting fuel cut

maybe you should give the boost solonoid a good clean with some brake cleaner

Imran21 · 03 July 2009, 14:02

Oh... my bad. I thought that it was known as boost creep since it "creeps" back from 1.3 to 1.1. Thanks for clearing that up mate.
However, shouldnt my car be hitting the fuel cut at 1.3??

ReggieMY99 · 03 July 2009, 14:26

Hmm it should hit fuel cut at 1.2

if its a standard ecu as you say

version 4 is a MY98 or is it a 97, you quite sure you dont have a superchip or a piggyback or something installed?

Imran21 · 03 July 2009, 17:11

Yes its a 97/98. I have never removed the ECU to check if its got a superchip or something or if its aftermkt..... i guess i should!!
But ya... it hits 1.3bar & creeps back to 1.1..... goes like stink as u can imagine. But is it safe???

Splitpin · 03 July 2009, 18:16

Quote:

Originally Posted by Imran21

Yes its a 97/98. I have never removed the ECU to check if its got a superchip or something or if its aftermkt..... i guess i should!!
But ya... it hits 1.3bar & creeps back to 1.1..... goes like stink as u can imagine. But is it safe???

Certainly worth checking around for any aftermarket stuff. However, think you'll find that the fuel cut value on the STi ECUs of this model year is 1.35 bar or so (the MY99 STi 5 ECU definitely is), so this could explain why you're not hitting it.

One question though - you say you've got a version 4, with a VF28? If this is true, then, theoretically at least, your car has a mismatch between the turbo and the ECU, as the ECU will be thinking it's controlling a VF24. This complicates the answer to your "is it safe?" question a bit, as if the turbo has been swapped, was it remapped to suit (and mapped for British fuel at the same time)?

Same applies to the future turbo swap. Provided it's mapped properly, all should be good. Simply unbolting one turbo and putting a different type on instead has the potential to be bad for the engine, and certainly, without remapping it, you're not taking maximum advantage of the new turbo.

Imran21 · 03 July 2009, 18:52

Thanks for that Splitpin - no i have not had a remap. I got the car like that from Japan. I'm in Kenya by the way - so nothing much in the way of mapping. ECU has been reset though.... although i know that wont do much. Fuel here (i use V-power) has lower RON rating than the UK V-power.
I hear there is a guy who can map an Impreza here in Nairobi- does his own rally car - so i might ask him to have a look.
Thank you for your advice!

Splitpin · 04 July 2009, 00:38

No problem at all Imran. Having a word with that gent is a really good plan given that he'll have a stack of local experience and will be able to see far easier than us exactly what's what with your car. The 97-98 cars aren't as easy to remap as the others but it can be done - let us know how you get on!