Big props to Andrew@Dyno4mance. Next time the rad will have to come out [inside joke]

 

Essentially, octane refers to the speed in which the fuel burns. In our case, fuels that generally pack more energy per mass unit typically have a higher octane, which necessitates more spark advance to synchronize its slower burn time with the compression stroke. I suppose you can 'over octane' an application if so much spark lead is required that it interferes with the mechanical timing, but I don't think that's realistic.

 

i think there have been instances where an ignition system couldn't handle super high octane and lots of boost/air. you will get a really rich mix and lots of black smoke.

 

 

happened to my Z. and a few other Z cars. the stock ignition system couldnt' handle the slow burning high octane fuel so a lot of it went through the motor unburnt. of course, i didn't adjust my ignition timing....so that may very well have been the reason.

 

and FWIW it was 1 gal of 93 octane, and 6 gals of c16

 

In that case, it's likely that the fuel didn't complete the burn cycle until in was in your exhaust system, in which case you certainly aren't gettings the benefits of it at the very least.

 

yes, exactly. my stock ignition system didn't seem to be able to handle the octane

 

if you had better control of your ignition and fuel system and were running higher octane ... you should have been able lean out the mixture and advance the spark to get the power out of your engine. but what do I know ... I'm NOT a tuner, just a monkey. I should really leave this to the professional.

 

LOL. i didn't really have any way of controlling the ignition timing.

 

In that case, higher octane fuel wouldn't have benefited you much anyway. Typically, factory programming does not allow more spark advance than is advantageous to run anything much above pump premium.

 

What year EVO was this?

 

it allowed me to run A LOT more boost without any detonation. the octane was just too high in that particular case.

 

2003 with a little over 7000 miles.

 

But without proper fuel control you were injecting as much high octane as pump gas essentially drowning it