spufus

iTrader: (2)

A plea for assistance to all you scooby gurus out there!
I have just fitted a full Scoobysport exhaust system to my MY99.
Now the car runs fine at low revs, but as soon as it hits the boost it misfires and looses power. The car is totally standard apart from the exhaust.
I noticed the de-cat downpipe is substantially larger diameter than the standard one - could the lower back pressure be causing this?

Thanks everyone.

JIM THEO

Boost creep - boost spikes, have you checked this?
JIM

spufus

iTrader: (2)

I haven't a clue what they are matey, never mind checked for 'em!
How would I do that?

Thanks

JIM THEO

It's abnormal boost behaviour (overboost like) due to free breathing of your engine, you can check it with a boost gauge or better with the DeltaDash software, Subaru select monitor device, SECS PSI etc etc etc
JIM

spufus

iTrader: (2)

Thanks for the info.
I think I need to see a man that can!

zhastaph

How severe is this misfiring, if the ECU detects the car over boosting (whereby the boost goes above a preset safety level) then the ECU will cut the fuel to protect the engine. If you are getting fuel cut you will know about it, it approximates to driving into an invisible wall. You will be thrown violently foward (quite a buzz, but at the same time scary ). Or is it a sorta very sick car feeling that really doesn't want to accelerate when throttle is applied?


If it is fuel cut, then it could be casued by any of the following;

Turbo overboosting created by an a down pipe that is breathing much easier. If this were the case then it wont happen all the time, only sometimes, and worst under circumsatances such as when the car is cruising at medium revs and then floored. Manual boost crontollers or a remap can sort this.

Wastegate or Acutator jammed open, this way the car will have no way to control boost, it will just build and build.

Hoses feeding the wastegate incorrectly fitted or missing, as above.


If it is the 'sick feeling car' then this is most likely caused by an air leak someplace when the intercooler was removed. Either a split or a hose not put back on. This would result in a very over fueled (and sick feeling) car when on boost.

spufus

iTrader: (2)

zhastaph,
Thanks for the reply.
It's more of the "sick feeling".
Up to around 3000 RPM it's fine, then it cries a little.
Over 3,500 it's major complaints and lots of poping and farting!
I have not dared to boot it yet so I can't tell you what happens over 5000.

thanks for your help.

Dean

spufus

iTrader: (2)

Another kwikkie,
I have a set of unused samco hoses from my STi V5.
Will these fit, and maybe aid my suffering?

zhastaph

Definately sounds like an air leak then. At these range your boost will be squirting out through the leak, but the ECU will be fueling based on the air that is being drawn in.

Probably not, the hose from the turbo to the IC on a UK MY99 is a solid plastic Y piece. I think on the STi the Y piece is solid metal with a short bit of hose connecting that to the turbo. Plus I think the mouth on the turbo on an STi 5 is bigger.

But don't take my word for it and rule it out, it is worth a look.

First check that all your hoses are on.

The one from the outlet of the turbo that then connects to a T piece, the T piece goes to the boost solenoid and the wastegate actuator.

Make sure you've refitted the thin vacuum hose that connects to the front of the dump valve and the bigger hose that the dump valve dumps to.

Anything else that you may have removed when you fitted the exhaust, check this.

After that then the most likely thing to look at is the hose from the turbo. Firstly ensure that you have pushed it on fully, it is a very very very tight fit. When fitted properly it buts up against a bit sticking out at the back of the turbo outlet (not a very good explanation I know). Next, remove the IC, as it's like that this hose may have split these are made of a solid plastic and can be quite brittle.

Best of luck.

spufus

iTrader: (2)

Thanks again,
Looks like I'm gonna be busy today!