[GerryL]

With this engine's very high compression ratio, I'm sure it must have very sophisticated alogorithms in the ECU to compensate for octane and knock issues. Has anyone seen any information that would indicate how quickly it can compensate and readjust, particularly how quickly it can determine and adjust when 93 octane or better is available? I live in one of the areas where only 91 is generally available and I'm wondering if and when something better is available, how quickly it would take advantage of it. Some cars are very quick, and others can take several tankfuls to fully return timing and advance. I'm considering trying some unleaded track gas to see what those few octane points are worth, but it would help to know how long the adaptation process is or if there is some way to expeditie it.

 

[brianch]

The difference should be immediate but it might not be that noticeable. Cleaner pure gas will just run better but the ECU may not adjust to it right away but you should be able to feel it in the response and noise if you pay careful attention.

 

[Rockster]

I have 91 and 93 octane available here without ethanol and I can't tell the difference. I usually run 93 but if I need to buy gas elsewhere I go with 91.

I take pride in watching the car closely and as much as I'd like to say I can feel a difference, I can't.

 

[itwillboost]

It will only make a difference in the cylinder temps, and it will make a difference, but if your not beating on it I can't see it being a big issue. It's not a high comp. motor, but more along the lines of the usual now a days. If you look alot of newer boosted cars are even shying away from low compression motors as to avoid lag. I would not go below 91 though. Also when thing to remember is that number is not guaranteed, companies know this and they won't build a motor from factory with such little room.

 

[Zippy]

I found a place that sells Shell racing fuel in town! I'm so filling the next tank with it.

 

[brianch]

From 91 to 93 you likely won't be able to feel any difference but if Subaru truly did tune the car for 93 on the dyno with equal grade gas there should be a slight improvement with 93.

 

[dren]

The ignition tables likely change.

 

[devinglambin]

Rec fuel runs awesome anyone else run it