zafar51

Hi,
Does anyone know what ecu is better for fueling generally out of the U8,W6, and Z4, i dont tend to boost the car around much so which ecu will be more suited (saving fuel wise) for off boost driving. Thx zaf

myblackwrx

iTrader: (1)

z4 has a better fuelling map.
I've changed from U8 to Z4 and found the driveability of the car is a lot better but it won't save fuel it just use it more efficently.

zafar51

(myblackwrx), thx for ur reply, but doesnt it mean that if the ecu like the u8 and w6 boost less throughout the revs, therefor the amount of fuel going in will also be less compared to the z4?

myblackwrx

iTrader: (1)

Yes but i've found that I do get better fuel economy from the z4 when driving off boost but slightly worse when driving on boost.

zafar51

ok, thx, and would you say having a dump valve over the orginal recirc valve make any difference on the fueling and if so is it much?

myblackwrx

iTrader: (1)

leave the recirc on.
When i bought my car it had an old Blitz vta which worked fine but then after a year or so started to cause the car to stall at junctions,idle roughly (this was also to do with a sensor going but i don't think the VTA helped).
Took it off and the car is a lot smoother through the gears and doesn't stall at junctions.

zafar51

ive read alot of bad posts about vta dv on here,btw what sensor was faulty, my scoob seems to play up with the revs going slightly high and low when slowing down at junction etc then after a few times it settles,its doing it with a recirc and vta dv so its probably something else,any idea what it may be,can it be the maf?

zafar51

even after slowing down and stoppin at a juntion it will do it a few times, no fault code comes up, but if i drive around 80/90mph constantly then the check engine light comes up,ive tried to read the codes but nothing happens

myblackwrx

iTrader: (1)

MAF perhaps?

With mine the lambda sensor was changed.

zafar51

is there any difference between the u8 and w6?i know they give the same boost,so there must be some difference somewhere?

myblackwrx

iTrader: (1)

Nope

Boost Targets & Fuel-Cut Limits
WRX/STi Saloon ECU's 2C, U8, W6, W9 - As above, 11.47psi held to redline. Fuel-cut 14.57psi
WRX (1995/96) ECU Z4 - 12.71psi, dropping to 11.78psi @ 6600rpm. Fuel-cut 15.65psi

zafar51

what about ignition timing? is there any difference there?sorry 2be a pain!

zafar51

what about ignition timing? is there any difference there?sorry 2be a pain!

myblackwrx

iTrader: (1)

The 2c is a cross over between the U8/W6 ecu and the Z4 and iirc shares a few traits of each ecu but i'm not sure.
If you want some more knowledgeable advice speak to Scott T (PolarPerformance) as he has had alot of experience dealing with the earlier ecus.

zafar51

thx for all your help,much appreciated, by the way wer u from and ur name mate..

myblackwrx

iTrader: (1)

i'm in dorset and name is Paul

zafar51

thx alot paul for ur help,im going to try the u8 out and see how it works out, probably let u know in a few days but im sure your right about the fueling etc.