Reset ECU after putting 95 Octane??

[Guest]

Hi all,

LOL just went for a horse ride and swimming ard Goat Island and since there were NO PETROL STATIONS that sold 98 octane, I decided to fill half tank of 95.. Obviously the car knew and decided to keep my boost under 6psi (goes up to 14~15 then drops and holds at 6PSI). I've used up 95 (or nearly) and filled full tank of 98.

Just wondering whether I should reset my ECU cause I think I've heard from somewhere if the car detonates and retards the cam timing, even if you put higher quality fuel it won't make a difference?

Cheers

[Joker]

no it will learn the new lower octane

reset is advised once you get back onto pure 98 (give it 2 tanks then if you remember might be a good idea

[Guest]

 JoKer said:

no it will learn the new lower octane

reset is advised once you get back onto pure 98 (give it 2 tanks then if you remember might be a good idea

Yeah thought so.. so even if I keep putting 98 the ECU will keep using parameters obtained from using 95 octane and not re-adjust itself to 98, right?

[ReubenH]

I think they re-adjust back, part of a learning ECU is that it's always learning right?

Whenever i have no option but 95, i will always stick it on low boost, and try keep off boost. Boost, and loading will be the killers, since that's when the car is likely to detonate.

[Joker]

I believe (have heard/read) the ECU will err on the side of caution and keep the 95 setting regardles of how many 98 fills you put in

retard timing and stuff to stop detonation....

[ReubenH]

Hmm. Oh well, ECU reset after 95 then, just to be sure. :

[Durty-Sanchez]

Depends how old your car is.. I believe from 1998~2000 onwards the ECU's started trying to advance the timing again after a while. This was about the same time as the 'remove the ECU/battery to wipe the memory' stopped working as it stored most values in non-volatile memory. I had no idea 95 was thought of as such a scummy gas..

[Joker]

I end up with a sooty residue around rear orifice from 95.... (poorly burnt fuel)

[Andrew NR]

So to reset the ECU you just disconnect the battery for a minute or 2?

[Joker]

you can try pumping the brake pedal at same time - APPARENTLY helps drain residual power from circuitry (not proven method)

24hrs un plug/overnight has always been the best bet - and/or try ECU reset procedure (green and black diagnostic plugs snd gor for a drive over 11 kph till CEL flashes continuously)

[Andrew NR]

 JoKer said:

you can try pumping the brake pedal at same time - APPARENTLY helps drain residual power from circuitry (not proven method)

LOL ;D

[Joker]

Its what they recommend on NASIOC I kid you not

I can also understand the theory but like I say un-proven, maybe a test for Mythbusters?

[Guest]

Mythbusters +1

[ReubenH]

 Durty-Sanchez said:

I had no idea 95 was thought of as such a scummy gas..

I view 98 as scummy, our cars are tuned to run on 100 ron remember.

[Durty-Sanchez]

Mines tuned to run on 95 and even then I could push it past factory for the timing, not even close to detonating at low-mid load points. Sure 95 isn't the ideal fuel, but I still think it gets a bad wrap IMO.

Pumping your brake pedal will do SFA. The capacitor that stores the power to keep the volatile memory alive lives past the voltage regulator circuit, which is a bit of a one way street for electrons. Either short the capacitor or leave the ECU without power overnight, maybe longer, that'll do the trick!

[ReubenH]

Well you've messed with your ECU haven't you

You bring up a good point with 95 being demonized though, i'm guilty as sin for doing that, but what do we actually know on the subject?

The extent of my knowledge (and I may be wrong - idiot/n00b disclaimer there), is that the lower octane is more volatile, and thus more prone to detonation. Detonation happening when you have a high heat/compression going on, i.e. on boost, or loading a high compression N/A.

Is that 3 octane gap actually a big difference, or not so much? We know that running 91 for example, will kill a new STi engine - i remember a thread on the old forum about a guy with a brand new 08 sti who went to the track on 91, and brought the car home on a trailer. Subaru did not cover it under their warranty

[Guest]

I take back on what i said before.. sorry lol i filled my car with 98 octane from gull today and notice after 5minutes of driving my car was boosting a lot better than before.. before i had filled 95 octane from Caltex and it was boosting .5 bar.. and now its back to normal boosting 1 bar. F

From reading this forum/subject it is great to know that our Subaru ecu can read what type of fuel we are putting onto our cars and than learning to adjust.

For all you Subaru drivers Gull 98 Octane is the safest bet for gas!

[kamineko]

 palwow said:

For all you Subaru drivers Gull 98 Octane is the safest bet for gas!

i know your trying to be helpful but be carefull with broad, unqualified statements like this.

[misfit]

is 95 bad for ur adverage stock standard subaru turbo with no mods ?or is it fine and not doing any harm if the ecu ajusts to suit? is it just the modifyed subarus running more boost etc that suffer from this fuel?

[pl0x]

 misfit said:

is 95 bad for ur adverage stock standard subaru turbo with no mods ?or is it fine and not doing any harm if the ecu ajusts to suit? is it just the modifyed subarus running more boost etc that suffer from this fuel?

I would try put 98 whenever you can

I would say it is bad, it detonates in some cars under high load &/or boost

then again if your car doesn't detonate at any point with lower octane gas, under high boost &/or load. Then i dont see why not to run lower octane gas

[kamineko]

 misfit said:

is 95 bad for ur adverage stock standard subaru turbo with no mods ?or is it fine and not doing any harm if the ecu ajusts to suit? is it just the modifyed subarus running more boost etc that suffer from this fuel?

it'd be safer putting it into a NZDM car, they are detuned for our fuel. it works in JDM sti's etc but it will generally ping if you thrash it. these cars are designed to run on Japanese premium fuel which is something like 100octane.

usually theres a note on the back of the fuel flap. if its in japanese just post a pic, will translate

[Guest]

i was under the impression that GULL was bad for subaru's

I even read on the subaru website a while ago they reccomend that cars older than xxxx dont use it...?

There an ethanol part that feks the engine?

And i was actually just wondering the gas thing myself..

im only boosing 8 PSI now and i was hitting 16 and boostcutting previously

This is running Shell V power. (never noticed a problem till now)

[Too Broke]

I always use 95 in my GTB, never had issues with a lack of boost.

While I know there are alot of people on here that would notice the difference between 95 and 98 octane in their cars, I am not one of them. The power might be down slightly on 95, but there is no difference in fuel economy in mine.

[misfit]

yea unfortunatly they dont sell 98 where i am but when i do go out of town and use 98 it makes a huge difference but i havent had any problems with 95 yet apart from having a slower car haha

[Guest]

Hm, for me it makes huuuuge diff... the boost decreases to about 6PSI and if I put my foot down (maybe 80%) on the accelerator for about 6~7 seconds, I get full boost back then soon goes down to 6PSI again... the cycle keeps repeating...it happens rarely with 98 but happens very very often with 95... (subaru B4 btw... temp = hot hot hot!)