KenS55STI

I have a MY01 sti with 33k on the clock. It has a blue flame 3" decat exhaust with twin dump downpipe and a green panel filter. When driving on the motorway at a steady speed then accelerating it surges.

If I accelerate very gently it gradually increases speed and the surging isn't very noticeable. If I press the pedal further the needle on the boost gauge goes mad like the boost is fluctuating rapidly. If I accelerate harder then the needle settles but shows the boost going up and down and the surging is quite pronounced. It is as if I am pumping the accelerator pedal as I am driving along but occurs with a constant throttle opening.

I have cleaned the maf sensor and the boost solenoid with brake cleaner but it doesn't seem to have made any difference. If I pull the wire off the maf as the engine is running then the engine cuts out instantly. The idle seems fine.

When I got the car it had a vta dump valve on it. I had it removed straight away and the original recirculating one refitted. Could this have anything to do with it or can anyone advise as to what else it could be. I don't know if it was doing this before because I didn't get a chance to drive it on the motorway with the vta on.

I have heard of this problem with the MY00 classics but have done a search on here and it didn't reveal anything about the newage cars having the same problem.

Thanks

Ken

~DrEaM~

could it be the plugs?

KenS55STI

New plugs fitted last week so am ruling them out.

Andy.F

What boost level is it running at ?

gussy

iTrader: (2)

Andy it sounds like the problem which I had,which you cured I may add.

KenS55STI

Andy

When the surging is at it's most pronounced the boost is going up and down between around 5psi and 10psi. I don't have an exact figure for full boost but it is over 15psi. I will check at lunchtime and see if I can get an exact figure. The car is on the standard jdm map as far as I know, it has a green cotton panel filter and a 3" decat exhaust with twin dump downpipe. No other engine mods as far as I am aware.

Thanks

Ken

Andy.F

It sounds like the increased exhaust efficiency is causing the std boost control to over react, this causes the boost hunting you refer to.

Cheap option - Fit a slightly larger restrictor in the boost control line.

Not-so-cheap-but-proper-option - Remap the ECU to realise the potential gains from the exhaust system and also have it mapped for uk fuel while you're at it !!

Andy

KenS55STI

Thanks Andy

I checked the gauge at wot yesterday afternoon and the needle hits 20psi then drops back and holds at 17.5psi.

I think the cheap option is the way to go for now, then maybe the proper option when someone buys my old car.

What are the costs involved for a PowerFC or an ecutek remap ? I'm going to be doing 30000 miles this year so may have to change the car after a year. Would prefer to be able to transfer whatever I go for to the next car if that's possible and have it tweaked for that car. Current car is a MY01 and expect if I change it a year then it will be to a later MY.

Ken

Andy.F

Apexi don't produce an ECU for the new age cars, they do a 'piggyback' but there is no need for this when the original ECU is such an excellent unit and is fully remappable via Ecutek.
yhpm

Andy