ok what causes a car to judder whens its coming on boost ? had my car mapped last friday all went fine, the saturday after as soon as it comes on boost it violently judders and wont accelerate. If feels like bad coilpacks, iv upgraded to newage coil packs and just tried another set today with no difference, plugs are brand new ngk racing 8's so i doubt its them. It does pop a lot on the overrun which i dont think it did before, il check afr as soon as i can get my lc-1 working with a usb convertor, car is a 95wrx with a 2.5 conversion, any ideas people ?

 

How much boost are you running?

 

1.5bar flat

 

hmmm id get a check on the map mate. dont sound to clever. im running 1.5bar too hmmm keep us informed how u get on

 

was only mapped on friday, by a very good mapper

 

Compressor surge?

 

will a 20g surge on a 2.5 ?

 

Can do yes

What boost, rpm, gear is the judder and is there noise to go with it?

 

Do you back off as it starts to judder? When I got surge on mine I just gave it WOT and it was okay after a bit of surging. It could be the plugs, try some 7s. 8s may be overkill.

 

boost is 1.5bar flat, the juddering happpens pretty much as soon as it comes on boost, flooring it from pretty much anywhere in the rev range in any gear tbh, it had sevens in before the 8's, tried the 8's as a fix. there was no hint of surge on the dyno or the road test the day it was mapped, it went very well 404bhp 430lb at enginetuner, just the day after it seems to have gone wrong, nothing had changed

 

Suggest you talk to ET

Simon

 

Sorted, problem only appeared after Ric installed the Launch and ALS codes so the appears to be a problem there.
Zeroing the codes has fixed it.

And now following a phone call the problem has been traced to an error in the wiring to the neutral position switch. All dealt with now.

 

lol you beat me to it ! massive thanks for helping again martyn especially on a sunday

 

lol, no sweat m8, we look after our own.

Martyn

 

i have the same problem but does it mainly in 4th gear at 5000rpm and i have launch control fitted on my53 wrx. but i shall open a new topic

 

Great service from the mapping crowd