hapa

Today I went by to visit a client of mine that I deal with and he had a price list of his racing fuels. Out of curiousity I picked it up and he has 98, 110, 112 and 114 Octane available. What would be the highest octane you guys think could be run in our cars out of curiousity?

zeiss

Octane doesn't measure power of gasoline, but only its resistance to knocking. What possible benefit would derive from running more than a 91 octane rated gas through your S2000, unless you had modified it to have a higher compression ratio?

Fongu

I don't think you'll see a difference, but some people do claim the car runs smoother. But it seems that those guys are always in places that are stinking hot. So they actually might be getting some knock and getting their timing pulled.

If you do want to try it, make sure their unleaded fuel. A lot of racing fuel is leaded.

hapa

The fuels are all unleaded. I know they are meant for a higher compression ratio engines but I wonder what effect it would have in a high revving car like ours!

Fongu

It won't do anything. If your engine is not knocking, you're basically running the best you're going to run. The ECU by "default" runs the best performance that it is capable of until the knock sensor goes off causing it to retard ignition timing and probably dial back other stuff to run safer, less performance so the engine doesn't destroy itself.

The only real way of taking advantage of higher octane gas is to up the actual dynamic compression (by increasing compression, FI, I/H/E, cams, etc.), and/or upping the rev limit and fiddling with the engine management.

Here is the more you ever want to know about gas FAQ I've read on the subject.
http://www.faqs.org/faqs/autos/gasoline-faq/part1/

WornTiresAreBad

I believe higher octane fuel burns slower. It's only required for higher compression engines where if their is more compression I think perhaps a slower burning fuel is required to prevent detonation (ping).

If one uses more octane than required, more fuel is left unburnt and places a greater load on the catalytic converter. I used to use Sunoco 94, but after changing to 91, I actually get greater fuel economy, 8.3 l/100k with 94 and about 8 l/100k with 91. So you'll pay less for gas and use less of it.