Ok guys I'm hoping you can help me out here. I've been having a problem with my car for a while now. After I got my custom tune I got the standard 3 tunes on the SCT Flash 1 box. Economy, High Performance and Valet. After I got it done I would drive around with the High Performance tune loaded and for the first couple of weeks it was fine. After that I started to notice that under full throttle acceleration it would have a weird surge feeling, it felt like traction control was cutting in but it also happens when T/C is off. I thought it could have been low fuel but it has happened with all sorts of fuel loads from 100% full to very low. So ruling out fuel load and T/C I thought it was the stock fuel pump. I have since fitted the Walbro GSS 340 in tank pump but once again it is happening.

So I have been trying to figure out what it could be. It only happens on the 15psi High Performance tune, on Economy Tune (which I reckon would be around 8-10psi from a seat of the pants feel as my tuner never told me) the car runs perfectly fine. I can give it full throttle all day long and it never happens. However once the 15psi tune is loaded up it starts happening again.

So what could it be? It doesn't really happen until she really comes on boost around 3000rpm and will happen anytime after that under full throttle. Could it be fuel surge? Could it be valve springs? Could it be the stock cat not flowing enough?

I have stock valve springs and it is a BF mk 1. It also has a stock exhaust and is a 6 spd auto. For all my mods see sig.

Thanks for any help guys. For now I am stuck driving around on economy tune until I can get it worked out. Lucky it is still a weapon to drive with this tune in haha!

sounds like something isnt flowing with the extra power (possibly cat), talk to your tuner and chuck it back on the dyno to check everything is ok

Yeah I am starting to think exhaust also but not exactly sure. I don't like the idea of running the 15psi tune anyway as the bottom end is stock. I think when I took it in, the tuners thought 'Hey this guy is young, lets give him a number that he will be stoked with' and admittedley I was impressed when I was told "Yeah your car made 300rwkw" but I dont like the idea of 15psi. I think I'm going to save for an exhaust so that way I can have the same power at less psi...

Do you think the valve springs could cause the sort of issue I am describing also?

yeah definately back on the dyno to check the tune.

stupid question though: are you running 98 octane in it?

dont risk full throttle till its sorted out, if its leaning out due to wrong afr's, youll pop something.

Yeah I always run 98 now since it has been tuned.

I'm hoping the afr's are ok. Didn't get a printout of those either when I got my dyno sheet, just a power graph..

what wrong with 15psi, mines running 17psi on stock ba mkll bottom end

I don't like the idea of running the 15psi tune

dont worry about that so much. im running 16psi settling back to 15psi with a stock ba bottom end!

its all in the tune.

got a boost gauge? watch for overboosting too.

if you are suss that the tuner is not giving you his best, go to a different one. one of the site sponsers should be fine....

Haha yeah its probably ok but just want to be safe not sorry! It spikes to 15psi then tapers back to 10, but yeah would not like to blow an engine that's for sure.

on stock ba mkll bottom end

hey tv, was the mk 11 bottom end diff to the mk 1?

15 and back to 10? it sounds like that tune might suck. I would expect boost to not fluctuate so much. 15- 12 or 13 would give a better feel and pull.