Blastomussa

hi there,

i recently swapped my 93 impreza ecu for a z4 ecu and was thinking that from the standard power figures at the time, would i be right in saying that using v-power would be slightly increasing the "standard" power figure for the car at the time, given the fuel being used in japan at that time was possibly a lower ron rating?

not quite sure if the z4 was before the change to 100 ron so shoot me down if i'm being stupid!

cheers

myblackwrx

iTrader: (1)

Hard to say really as i went from early 93 wrx ecu to Z4 and had sligthly less power but this can be put down to when i had it rolling roaded (ambient air temps etc etc) but the actual map on it is better (especially the fuelling).
I think when i swapped over i was using Optimax.
The only real way to find out is have it rolling roaded.
The Z4 was way before 100ron fuel was launched

sponners

iTrader: (4)

even if the fuel you are running is higher octane than what the ecu has been mapped for you will not make any more power.

Blastomussa

what about when you do the ecu reset trick?

will the z4 re-adjust perameters (ignition timing etc)for an increase in ron giving theoretically more power or does the z4 only run its optimal(max) power at 98ron i.e even running the higher ron it will only be producing 98ron power?or have i just answered my own question??

i know when i swapped over to the z4 it went from averaging 0.80 bar boost to averaging 0.95 bar, so that would have gave me an increase i know but from the fueling point im not sure.

Glowplug

iTrader: (8)

Am i right in saying that the use of V-Power offers better protection against knock?
Iam pretty sure that i can feel a difference when using something other than V-Power (Z4 with PP chip)

myblackwrx

iTrader: (1)

The increase in RON is from 98 (japan) to 99UK (Vpower /Tescos) so there is very little difference in the fuel the z4 was originally ,mapped for and what we use now.

i found with the z4 the smoothness of the drive was much improved

joz8968

iTrader: (13)

When Imprezas fitted with the Z4 were produced, as mbwrx says, there was no 100RON fuel available back then - I think the max available was 98RON in Japan at the time(?).

So it's fair to assume that Subaru made sure that the maximum ign. adv. that the ECU could use was when the motor was running on 98RON fuel. So, as has been said by sponners, theoretically, if you put anything higher than 98RON in, then the IAM feature of the ECU cannot go further on the ign. adv. than the max of '16' - as that is the level it was mapped for on 98RON (or whatever their max available RON was at the time).

That said, obviously if you put V-Power (or Tesco 99) in, then you should get that max ign. adv. of 16, thus allowing the motor to theoretically run at the full, quoted 260PS.

If you use 97, then the ign. timing will be retarded slightly for its lower octane content, thus reducing power a little.

Blastomussa

i see ,

and your right the car does seem to run smoother with the z4.

i also get much better fuel economy on long motorway runs as well (360miles to a tank), not that im really concerned about that to be honest.(dons fireproof jacket ready for the eco-warriors)
im usually hunting down twisties (no not 5 coilers, lol) which is where fuel economy goes out the window.

i get about 180ish miles normally i.e not driving economically!!

cheers

joz8968

iTrader: (13)

Sorry OP, I only skim read the 2nd paragraph in your post # 4 - yep, you've got it!

But, as you say, the max adv. is achieved when running the Z4's 0.95 bar of boost - hence why the motor produces 260PS - rather than the 240PS on only 0.8bar, of the pre-1995 WRX saloons.

Blastomussa

cheers mate, time for a rolling road session i think.
quite like to see the power figures with my minor mods.

joz8968

iTrader: (13)

With the Z4, your decat system and your new API-built engine , there's every reason to believe you'll be porducing at least 260PS (256bhp) at the fly. ... Dare I say it, maybe a little more? (Make sure you turn up with V-Power in the tank!... ).