This has happened on 2 occasions now:

I have a MY03 WRX with about 20k on the clock. When accelerating full bore from a mid to tight left hander onto a straight, the car gets to about 4k revs and lets out an almighty bang, with an instantaneous but momentary loss of power. Very much like the feeling you get when traction control kicks in on normal cars (of course the scoob doesn't have traction control).

Predictably, Subaru cannot find a fault.

Has anyone experienced the same or know what it could be, the car is in warranty so I am keen to get it sorted.

thanks

 

Mmmmm, low on fuel when this happens per chance...???

 

Sounds like overboost - is the air temp particularly cold when this happens?

If so - overboost triggering a fuel cut - first time it happen is a bit of a shock!

 

Overboost wtf, please explain for my non-mechanic brain.

I have had the car remapped, would this have contributed?

thanks

 

sounds like she aint fueling rite and the bang could be a build up of fumes?

 

Over boost is where the limit might be set at say 15psi and for some reason you hit,for arguments sake,20psi,the ecu then cuts the fuel to stop the engine doing any damage to it's self.

In a simplified form.

 

Overboost pretty much self explanatory- the car exceeds it's peak boost value. Can happen on cold damp evenings when the dense air gives you a bigger bang for ya buck. If the overboost reaches a certain threshold, the ECU cuts fuel to the engine in order to protect it. It's not subtle, but I don't know that it makes a bang!

If you're low on fuel, and try and boot it out of a tight corner, you can get fuel surge meaning that you'll also temporarily loose power as you describe.....again, not heard of it being accompanied by a bang before though. Who mapped it. I'd have them look into it.

Ns04

 

seems like a valid explanation, but why would it occur accelerating out of a bend and not in a straight line? Could the fact that I am cornering and hence the revs aren't rising as quickly due to centripetal forces mean that boost is rising in a different manner when compared to straight line acceleration?

 

Eeeeerm, not wanting to worry you but don't the words "warranty" and "remapped" rarely go hand-in-hand????

 

Yep, I'd look to the map, and fuel cut due to overboost, although the circumstances under which it happens would suggest fuel starvation.

Who mapped it?

 

Sound like a fuel cut - relating to too high boost pressure.

Subaru cannot find a fault it, yet you've had it remapped - how can you expect them to?
Send back to people who messed with the boost ignition and fueling...the poeple who re-mappeed it.

A Subaru garage won't have the knowledge or equipment to see if that mapping on your car is ok or not - as they'll expect it to be stock or PPP.

 

Apparently it's due to the location of fuel pump in the tank, hence why it only occurs on left hand bends (and only with less than a quater tank full). When you take a corner the centripetal forces mean that the fuel is surging away from the pump.

NS04

 

mine dies a bit in second when i boot it
its an import wrx
is this a common problem

thx

 

And here was me thinking that as the fuel pump is located on the right side of the tank it is in fact right hand bends that cause fuel starvation not left hand ones...

...or could I be wrong?

I have certainly only experienced it the on right handers on track with hot slicks - from half a tank of fuel!!

 

LOL it's on one side, I don't recall which!! But the fuel surge problem is quite well documented, particularly for track use. I keep a quarter tank full in mine at all times so don't have a problem with it.

NS04

 

Mee too - after big roundabouts only, right hand bends.

 

Not had this fuel problem as yet but at least I now know about it!

Does sound as though the problem car is due to remapping....

 

did the car do the same before mapping ??
if you answer this question you have found your problem,

 

Aye, an overboost issue there me thinks. Had the same problem on my MY99 was hitting 1.4bar at 4k and doing exactly the same...
Yours may be asa result of the remap, mine was due to the car having a bleed valve that I didnt know to look for when I bought it and it was wound too much...
My subaru dealer tried to replace a "Wastegate Solenoid" at a £200 cost which naturally did nothing, so after some squabbling and a full refund I found a scoobynet member who sorted it for me (thank god and 'im)...
P

 

Someone had cranked up a dawes to 1.4 bar?!?!?! What a plonker. Lucky you found it when you did mate, wouldn't have thought you'd have been too far away from the engine letting go!!

NS04

 

It was an Ecutek II map which by all accounts is a 'one size fits all' map pretty much like a Prodrive chip, it wasn't a tailored map.

I wont reveal the company who did the map as they are a well respected member of this board.

And for you people 'blah blah how can you expect Subaru to pick it up blah blah' they did a road test on didn't do a diagnostic, they were looking for a mechanical failure due to the symptoms I reported. And if you don't tell them about the map, it ain't there! so my warranty is fine thanks very much

Will keep the tank with lots of fuel in it from now, though thanks