87 vs 93 octane

[mr_minnis]

I am going to be taking my car to a friends dyno and tune it. What type of fuel should i tune it with? I normally run 87 or 89 octane. I have also thought about setting up a switch like the 80s Ford Turbo coupes had, "premium fuel" for a different timing table when I run 93. would I gain anything?

it is a stock 88 HO 302 it has about 9 to 1 compression

[SteveRST]

America must have different fuel octane ratings to the UK? We only have 95 to 99 octane here in the UK.

[mr_minnis]

America must have different fuel octane ratings to the UK? We only have 95 to 99 octane here in the UK.

Possibly, I do know that we are starting to use ethanol to "boost" the octane rating. IMO this changes the stoich ratio.

[billr]

I figure stoic for the common E10 is 14.2; but you only use that for calculating "required fuel", everywhere else you use the standard 14.7

[BigLou240sx]

America must have different fuel octane ratings to the UK? We only have 95 to 99 octane here in the UK.

Yes - see the difference between RON and AKI: http://en.wikipedia.org/wiki/Octane_rat ... ON_and_AKI

For choosing which octane you should use for the dyno... I would think that you would want to use whatever gas you would normally run. Without knowing your specific engine well, I think it's fair to say that you are likely leaving some power on the table by tuning ignition advance to knock threshold on 87 versus 93. Either way, I wouldn't want to tune ignition advance for 93 on the dyno, and use anything lower on the street.

[kaeman]

My engine builder, made me use the fuel I was going to run on the street when I dyno'd my engine, he said tuning it for something I wasn't going to use just creates fueling problems and broken engine parts... if you use 87 on the street then use 87 on the dyno.... otherwise you will be wasting your money and the dyno's time.