Power momentatcuts out???
 

I've just bought myself a freshly imported STI V2 which appears to be completely standard and origina, but I'm not sure if it has a problem...

If I pull away and get it moving in first gear normally and then just plant my foot to the floor, a couple of thousand revs build before the turbo spools and boosts really hard, then about 60% of the time momentarily the power violently cuts before coming back in.

Is this some kind of over-boost protection to prevent gearbox damage in first gear or could there be something awry?

If I put my foot 80% down instead of 100% it doesn't seem to happen. I have noticed something a bit similar in maybe third once when I began to accelerate and moved out to overtake, hesitated whilst I waited for the car in front of me to finish overtaking so I could see it was clear, then put my foot fully down. At that point it boosted, then cut momentarily before picking up again. Is this the 'ECU bug' I heard about manifesting itself?

John

sounds like fuel cut

It could be an overboost problem. You say the car is a fresh import, have you checked for a Japanese market ECU upgrade. I would recommend that you get it remapped for UK use, this will pick any potential problems with the ECU / boost level.

Yep sounds like fuel/boost cut!

Basically the ECU has a limit set for boost. If you go above the limit the ECU cuts and you headbut the windscreen!!
You usually notice it in long 3rd gear pulls from low revs where the boost over shoots target (what it is meant to run at). The over shoot is known as peak.
If the Peak it over the limit for more that a few seconds the ECU cuts.

Are you sure the Car is std?
Is there a cat in the downpipe from the turbo?
Are there any hoses or valves on the drivers side inner wing that don't look quite std?

I have no idea to check for a Japanese market ECU upgrade - any help?

It does have both cats, and all the wiring looks standard, no extra valves, hoses or wires - I looked at about 20 before buying this one.

What is fuel cut? Could it be that the fuel filter needs replacing?

Would getting it remapped for UK fuel mean lower performance (I always run Optimax)? How much would it cost? Any recommendations?

Many thanks,

John

Fuel cut is a safety measure that the ecu uses to stop overboost/running lean/det etc. (Bad for engine).

On a v2 sti, you would need a replacment ecu such as an Apexi Power FC. These cost in the region of £850 fitted and mapped.
Bit of a pointless mod without an exhaust upgrade at the same time. (£450-£700)
So for around £1400, you'll have a car that can run on UK fuel, and have around 310-330 bhp/torque.

:thumb:

I wouldn't really be interested in a full no-cat exhuast - it would have to pass the MOT without swapping pipes once a year. Also there is no way my girlfriend would stand a louder exhuast - the standard STI is more butch than the twin exit WRX system.

Will it pass the MOT if I remove the top cat?

Some do and some don't, more frequent they don't!

You could just scoobyecu your current ecu to run on uk fuel and give a power rise, this could then be custom mapped if you chenge the exhaust to give you a 300 bhp figure, and you will keep the factory safeguards that the apexi doesn't have.

Your problem may not be overboost, i say that because overboost normaly happens in higher gears due to engine load, full bost is not normally hit in 1st or 2nd, if it were overboost in 1st you would be getting it even worse in higher gears.

Does it behave like this https://www.scoobynet.com/1st-gear-boost-t534001.html

I have noticed since the original post that it does happen in other gears too, most notably with there is rapid rpm/boost rise... perhaps I should consider changing the fuel pump.

Overboost gives a complete fuel cut, 280bhp to nothing in a split second, feels like someone has slammed the brakes on and you normally get close to eating the wheel!! well almost!!

The problem I have on the other post is like a hesitation.

Do you have boost gauge fitted?

It feels more like the full power to nothing in a split second type thing. It does have a boost guage fitted actually, as part of din-sized three gauge plate. The pic isn't of my car, but it looks identical to these ones:

http://i23.photobucket.com/albums/b3...ictures027.jpg

Why do you ask?

I have seen a few pictures on the Internet of these gauges, does anyone know if they were a Subaru option or are they aftermarket?

John

The boost gauge will give you a visual indication that you are overboosting, I don't know the fuel cut figure for your car (someone on here will) lets say it's 14.5 psi then if your gauge goes above 1 bar then it's definitely fuel cut.

On the occasions when it does go smoothly, it tends to rise up to just above 1 bar and then settle down at just below. I haven't actually noticed what it's reading before the voilent cut outs.

Violent fuel cut was solved by adding NF octane booster to Optimax, However, with just on V-Power on it's own it doesn't seem to fuel cut.

Although I have heard it pinking under high load at lowish revs, e.g. 30 to 40 mph in 4th.

The seperate more hestiating problem seems to happen mid way through the rev range after flooring it up from about 2000rpm in any gear. The boost builds all the way past 1 bar and after a couple of seconds it hesitates. After about 4500 to 5000 rpm the boost levels out to about 1 bar and screams all the way to the red line.

I'm think I need to check all of the pipes around the turbo / dump valve (standard) for leaks.

Any other ideas?

I would advise gettig it checked out by a recomened specialist to at least have the boost lowered so you dont blow it up. I would also say get a knocklink, just to be on the safe side. Driving it like you stole it will destroy a scoob, you shouldnt need redline, as power drops off earlier than that ;) Good luck :thumb:

Thanks for the advice. I think I'm going to have to get it checked out properly.

Do you really think that driving to the red line will destroy an Impreza engine (assuming healthy of course) though? Surely the 'red line' is there for a reason - underneath is okay, but above bad. I followed that philosphy with my 205 GTI 1.9 for 7 years and caned it every day to no bad end. Sure the Pug isn't blown, but the my statement about the red line should stand.

Clean out your boost solenoid and piping before resorting to all these drastic measures. If it's full of oil, then there's the cause of your overboost problem.

Have cleaned out the the boost solenoid with brake cleaner and green clips under the dash connected. Also disconnected and sprayed through the three pipes that are connected to the solenoid. Hardly any gunk came out at all, and I used most of the 500ml can.

Still doing the mild boost-cut thing, maybe even a bit worse and I can't say it seems to going any better. Maybe the solenoid / wastegate a 'feel' like they are operating a bit smoother. Or maybe I'm imaging it.

John

why has no one mentioned the coil packs i had the exact same symptoms on also v2 sti , spoke to david at api he said coil packs , i did the job and problem solved , its the time of year for bustin coil packs

Someone did suggest to me that it could be the coil packs actually.

Any recommendations on where to get them for the right price?

api . set of four to your door for £235 . well worth it