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some help please,boost cut and low boost :)

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Hi guys! so i have just aquired a wrx sti my95 going by the chassis number and some online recourse


you will have to forgive me as im used to working on toyotas and nissans ive never worked on a subarus untill today. . . . 


ok so i picked it up and drove it home 1.5hrs and on that drive ive noticed a few Dodgy findings


the cars only running 0.6 bar 


the car will rev quite high in 1st and 2nd but in 3rd,4th, it will only rev upto 5000/5500 untill what i can only describe as boost cut 


the car has alot of upgraded parts but the ecu looks standard, he mention that it is an upgraded ecu i suspect a lie and the loom behind it is butchered 


he mentioned it had yellow injectors a bigger turbo , 3" turbo back apexi FMIC and "loads of other bits done to it mate" he showed me an old map of 300 bhp witch i think id be lucky if it was 100 bhp haha


it has an apexi boost controller but its either missing some bits or turned off and its not doing anything bit work as in lights up and has a menu. . . . . . . . . . . 


my question is how i can get it running to its standard 240bhp ish performance and to find out why its not revving correctly 


any ideas would be appreciated im reading up on alot of threads/post here aswell 


i guess i always have the option of breaking it for parts but its my 1st ever subaru and would prefer not to leave with a bad taste in my mouth


i can take photos of anything you guys request and try give any more info you require 


cheers guys :)


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Hi mate welcome &sorry to hear about your troubles, easiest thing would be to get it on a dyno, that will give the best indication of what's happening or not as the case may be,

If ecu is upgraded it's either a standalone apexi or has an els board or one has been put in from a later model, how many plugs does it have ? The boost issue could be anything from a split hose to more serious problems, best off taking loads of pics and posting it all up, we're all friendly here and will try to help out as much as we can

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haha cheers dude im quite mechanically minded so but im in no way trained but the boost maybe that just that its running on actuator pressure?


what exactly would you like pics of ?


ill get a picture of the inside of the ecu but it did have pink writing on but no way can what it says be made out 


ill get pics of the engine bay i did notice that some think dont look standard  for example the maf has a logo on or maybe just a sticker lol 

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Yeah actuator pressure is around .5 bar, could the wast gate be sticking and working intermittently?

It will go into limp mode too if somethings wrong but will only rev to 2.5k. Just post up anything you have issues with & wiring vac lines etc that don't look right, easiest.

Don't suppose you've plugged the green and black connectors in beneath the steering wheel to see if you get any historic faults come up ?

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Hi n welcome to soc moxxie .

The standard ecu for pre 98 imprezas can't be mapped without having a esl daughter board fitted so I'd start by popping the cover off to see if it has one .As with those mods and the boost controller not working right I doubt the ecu knows what's going on .

Here's a pic of a esl boarded ecu


Do you know what "version" it is via the model code ?

As this will help with identifying what type of fuel set up/inlet phase you have [emoji6]

A self code check and a few pics of the bay , vac lines would help as well, bud

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Think that's a avcr when plumbed in they're a good bit of kit to monitor the engine parameters .

It's a v2 which has a phase 1 inlet and fuel rail set up .

So if you search for or buy anything engine related make sure they'll fit a v2 phase 1 .

Did you get any codes from the ecu or whip the cover off to check for a esl ?

I wouldn't have thought that's the original ecu for a v2 sti as I think the early sti ecus had pink labels , my v1sti had a pink sa sticker on it

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Doesn't the acvr only work with the power fc ?

If so methinks somone whipped out the ecu and repalced it with one from a breakers, hence the gc8 written in pink on the cover ?

Just a thought

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Ok so I've had a very quick look before I go out and I've found my boost problem it's all plumbed into the apexi boost controller, so with this not working because the apexi ecu has gone it's just running off waste gate pressure 0.6 bar? Seems plausible

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Somewhere on here there's a list of boost solenoid vac line positions for all models that I've posted which would be handy if your intending on putting the boost control back to standard .

I think yours will have a 3 port boost solenoid

bottom port to intake pipe ,somwhere between turbo intake and air filter (mine vta in the pic)

Middle port to actuator

Top port to turbo outlet

Not the best pic to illustrate as mine isn't running the standard vac set up post-1399-143254455195_thumb.jpg

Can't help much today as I was "allowed" to play with the car yesterday so have to do some gardening today [emoji53]

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Ok so I've had a play today and found a few things

I can not do the diagnostics as the CEL does not active like it's not there

The ECU is a standard unit

The apexi avcr reads a few things such as:

Boost (correctly)

Rpm (not correctly)

Kmph (not correctly)

Injector cycle (unsure)

Today doing a few runs it reved fine in 1st and 2nd again but at any other gear @ 5500 it cut again but seemed to go past it if I'm not nailing it

When watching the Kmph on the avcr it spike when I was steady on the throttle is the speed sensor going?

Tomorrow I will do the spark plugs and clean the maf as it hesitates abit in 1st on WOT

Here are some pics from today



I'm also in mega need of some head lights and rear light if anyone's got some going or know we're I can get some



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I'm in Southampton fella but can travel . . . . . Well depending on how it gets on lol bu

I've just looked and I infact have grey injectors wich is good I suppose as it's on standard management

I have some more pics for you guys to look at :)

I'll post them in a sec

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Split in the hose but seems to seal ok


Standard injectors?

Wtf is this? It's missing 2 cables out if it I think and has lots if earth straps lol



It ends here



General engine bay pic for you eagle eye dudes/gals

Cheers guys :)

Can i getter a quite DV as it's horid and quite annoying

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The pic with the skull ?? In it is a sender unit for oil pressure at a guess, could be oil temp though,

Is that an oil catch can located at the top of the bay with the yellow sticker?

Injectors look like 380cc ones although don't hold me to it

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Ahhhh makes sence as I've found in the glove box the necessary guage and a few other guages including 3 other boost guages ?! Wtf haha

Yes it is a catch can

And I've have confirmed them as stick injectors :)

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The bit near the skull will be a sender unit for a aftermarket oil pressure gauge (or maybe the avcr)

On the drivers suspension turret there's a boost solenoid with 3 vac lines coming off it where does each one go to ?

Also on the same turret bracket there's the map sensor with a black plug and one vac line attached where does the vac line go to ?

I think your ecu should be a 6k or a z4 I think the v5 is out of a auto wrx wagon running lower boost and 220 hp .

If so your probably hitting boost cut in higher gears as the pressure in the inlet rises when In higher gears or under more load (going uphill)

I can't help with electrics much I'm afraid but imo with the fmic in place and the cutting issues I'd look into getting the right ecu and if it improves get it on a dyno before giving up on it just yet

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Cheers savage I'll answer all your questions tomorrow but it all look ok from a generic turbo setup

I think the ecu is the problem tbh I personally think it's been taken out before I bought it and replaced with that one

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