HELP > poorly Imprezza, boost problems
 

Hi,
I dont own the impreza in question, i own a mighty ST205 WRC. My mates subaru is bugging him that much hes thinking of selling and buying a GT4 aswell, which im trying to stop him from doing as he loves his car

He fitted a K&N cone filter to it, the impreza being a 99 JDM one, version 3 i think. Shortly after this his maf sensor became nacked and e replaced it with a new one. Thinking the new maf would solve his problems

the problem is : when flooring it, it pulls fine to 4.5 K then above there the boost drops down to 10 psi ish, it goes to 18PSI, Same every time you floor it, up to 4.5 > boost drops from 18psi down to 10psi.

Seems to be a massive flat spot, even if you push it it struggles to get up the rev range,

Please have you any suggestions of things to do , i have cleaned out the boost solonoid, and checked all the Actuator, actuator is opening as it should. Doesnt seem to be fuel cut, as its doesnt feel like my 4 when that used to hit fuel cut, > the impreza simplys back off boost > as the revs start being funny

He used to run on octane boost + VPOWER , he just uses VPOWER now, i would have thought that would be fine

PLEASE PLEASE any suggestions warmly accepted

induction kit has probably caused the boost to spool different and the ECU is struggling to control it.
You probably need to increase the size of the restrictor pill in the boost pipe from the turbo to actuator, near the small 'T' piece.
increase the size by 0.1mm and try again.

Or slacken the actuator off slightly if it has adjustment (some do some don't)

Cone filters are not recommended on Version 5/6 cars which if this is a 99 model it will be a v5 (also 5/6's suffered from maf failures)
A good panel filter is just as good :)
Also v power on its own isnt recommended on version 5/6 cars either due to the map having a lean spot in there, which isnt good as you see by how many P1 engines have failed (and the JDM cars dont have as much det retard built into them).

It also sounds as if the car has gone into a limp mode because its seeing problems, and tbh these can be quite fragile cars if you dont know what your doing with them :(

First thing first, you need the codes off the engine to see whats happening to it, a remap would also be nice for uk fuel as ive stated the JDM map isnt really that good for just v power (i use to see my MY03 Spec C retard on V power and octane booster and that has a far better ecu than that of a Version 5).

What other mods have been done to the car also?

Tony:)

Just S/S decatted zaust , SSQV dumpvalve > now back on standard air box and filter

When he first got it it used to be fine, i think when the maf sensor went tits up > there was another fault aswell, hiding in the maf sensor fault

Scoobytechnix did an ecu reset and found there to be no fault codes, once the maf code had been removed > due to the fault being fixed

i will get him to try running some octane boost though it. Thinking of doing fuel filter aswell , just trying a cheap inline jobbie from the local motorbike shop to start with
I did tell him to go down the panel filter route, as i have done. HKS all the way.

Dont think this is a rev 5, maybe i got my year wrong, might be a 1998

I noticed the little restrictor in the turbo to wastegate pipe work. Without this in place the car, still had the same flat spot, but wouldnt boost over 9/10 psi guess becuase the WG was seeing more pressure and opening

I have though about remving the pipe work all together for a try and see if it will pull to boost cut? to see if the whole boost thing is doing what it should do

any more suggestions on what to try

Bump anybody, gonna have a quick tinker with it tonight

hi there,

I know a WRX built in ~99 also with boost problems...
It is caused by the decat-downpipe, as we've found out
we got a boost controller fitted and that's it!
Go get an Apexi AVC-R, in my opinion a great tool!

cheers
Nico

in the world of my celica installing the a boost controller takes 5 mins, as you just disable the VSV for the boost control, and put the controller between the actuator and turbohouseing pipe work

i have a spare dawes device at home, if i were to put this on as a test, how would i plumb it in?