Benji554

iTrader: (18)

Hi. I've just noticed my V3 sti is suffering from hesitation/surging on hard acceleration. For everyday driving its not noticeable. Its definitely not the MAF becasue I run a Simtek and it occurs on both my map settings although much more violent on the high boost. What is likely to be causing this? I'm guessing coil packs, leads, plugs, boost solenoid??? Any advice would be helpful. I did a search but most of the ones i found are MAF problems. Thanks

Benji554

iTrader: (18)

My boost gauge doesn't change when the surging happens so I guess it's not a boost issue?

harvey

iTrader: (48)

Has the car been mapped recently.
Surging usually occurs when the wastegate duty cycle is too much and boost is pulled in too quickly. If you have not just been mapped and it was not present before the cold weather it may well not be apparent when it gets warmer.

Benji554

iTrader: (18)

Thanks Harvey. The car was mapped by Bob Rawle about 6 months ago so I can rule that out. Could just be the cold weather then, I'll keep an eye on it. Thanks.

harvey

iTrader: (48)

When the car is mapped the mapper likes to get the turbo to pull in as quickly as possible so he will only leave a little margin in duty cycles to keep it away from the surge point. There may have been a slight change in the inlet tract or even just the fact that temperatures are now 20C. or more below what they were when the car was mapped and that may just be enough to cause it to surge. No big problem and easily sorted by the mapper if it becomes a big issue for you.

Toffee

iTrader: (3)

Can this be caused by not having an uprated fuel pump (ie warlboro) does it mainly happen when you are below a quarter of a tank and coming out of a corner?

Lee.

davoid

I'm sure you're aware of this issue but, just in case, you haven't had oil changed recently have you? Overfilling will foul/block boost control solenoid and cause symptoms similar to yours

dave

harvey

iTrader: (48)

Benji : I don't know where you are located but Bob is here 29 and 30 December and we can look at your car and make a minor adjustment to the wastegate duty cycles which I am 90% certain will cure your problem which is probably only evident now because of the colder, denser air charge. 100% I know we will fix the problem regardless of whatever it is.
Lee: I think what Benji has described is a classic aggressive WG duty cycle problem and only brought on because of the much lower temperatures. Fuel cut tends to be a violent cut in the engine under heavy boost but not surging and Walbro pump issues or even standard pump issues tend to be that much more gentle, again without surging.

Toffee

iTrader: (3)

Benji554

iTrader: (18)

555EFC, the car has a walbro pump and a AFPR and I only notice it when gunning it on a straight!

Harvey, I'm in mid wales and unfortunately I'll be working on those dates but thanks very much for the offer. I think it is temperature thing. I did a couple of hundred miles on thurs when it was a bit milder and didn't notice it once.