Ultimate 4 Race Fuel

I run a 13.5:1 Compression piston in my 400 should I be running race gas??? I usually run Amoco Ultimate. I was running Sunoco Ultra 94 but I get better performance out of the Amoco becuase there is Alcohol in the Sunoco. Should I run race gas though. My mechanic says no.

Gonzo at 13.5:1 you probably should run something a little better than pump gas. What lets these bikes get away with pump gas on 12.5:1 compression is the 3-d iginition timing map. When you wak the throttle open, the timing gets retarded back to avoid detonation at the lower RPMs. More torque is available at lower RPM if you can run a straight line style ignition map without detonating. To do that you gots ta have da good gas. I run 100 octane unleaded because it starts easier and runs a little cleaner. I dont notice any power gains, its just alot more consistent. I dont have the "it ran great last weekend, what the heck is wrong" syndrome.

Check out Eric Gorr's web site and look under the technical articles page for an in-depth discussion about fuel by Rich Rohrich.

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