andyb321

Hi all, can anyone shine a light on the flat spot problem I have with my 98 STI 4. Sometimes when I accelerate in 4th gear (it only happens in 4th gear) from around 3000 rpm the engine sounds flat and I get no boost what so ever. If I lift off for a few seconds and push the pedal again it takes off as normal. I have a full scooby sport exhaust and no cat (oops !!). The car has done 25k miles and is run on super unleaded all the time. The problem has been there since new and has been looked at by 2 highly respected service / tuning outfits but they haven't resolved it. Thanks for the help.

steve rally

Could be that you are getting "detonation" and the knock sensor is detecting it and the ECU then retards the ignition and also backs off the boost to about .5 Bar. I have a V LTD ver 3 and this "dets" on SUL between 3000rpm and 4000rpm.I know this cos I map ECU's for a living and have put my knock sensing gear on the car.The lack of CAT will also increase the chance of this.Only real solution is programmable ECU.

Steve

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by andyb321:
<B>Hi all, can anyone shine a light on the flat spot problem I have with my 98 STI 4. Sometimes when I accelerate in 4th gear (it only happens in 4th gear) from around 3000 rpm the engine sounds flat and I get no boost what so ever. If I lift off for a few seconds and push the pedal again it takes off as normal. I have a full scooby sport exhaust and no cat (oops !!). The car has done 25k miles and is run on super unleaded all the time. The problem has been there since new and has been looked at by 2 highly respected service / tuning outfits but they haven't resolved it. Thanks for the help.[/quote]

andyb321

Thanks for the info Steve. Could you recommend anyone (preferably local) who could check this out for me ? I have had my car hooked up to a Subaru diagnostic setup once before at ScoobySport and that didn't show up any problems (Pete did mention that there were no detonation problems). Would octane booster help do you think ? Are there any other benefits I would get from a programmable ECU (more power or torque ?). How much would your company charge ? Apologies for so many questions. Thanks.

steve rally

If you want to E-mail me your location I can have a quick look if I'm over your way doing some mapping - I often am! Worth a try with octane booster although in my experience I've only been able to get 1 or 2 degrees of additional advance with these additives - although that can sometimes be the difference between det and no det.

ECU would give more torque and would be mapped to give no det - but need to sort out problem first.First consultation is free!!!!
GEMS ECU is £1450 installed and mapped.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by andyb321:
<B>Thanks for the info Steve. Could you recommend anyone (preferably local) who could check this out for me ? I have had my car hooked up to a Subaru diagnostic setup once before at ScoobySport and that didn't show up any problems (Pete did mention that there were no detonation problems). Would octane booster help do you think ? Are there any other benefits I would get from a programmable ECU (more power or torque ?). How much would your company charge ? Apologies for so many questions. Thanks.[/quote]

andyb321

Ok mate I might just take you up on that. The car is due for a service and I am thinking of trying Power Engineering this time (any good do you reckon ?) as they reckon they can put in on the road and check the possible det problem. £1450 is a bit more than I want to pay really but do you reckon GEMS is the best. I read about a GEMS system being tried on an EVO6 with none too impressive results. Would it knacker it for the MOT ? I have the cat fitted back when its MOT time but would the new ECU make it tougher to pass ? Appreciate the advice.