how to tell what octane to use

[luisdeleon]

does it depend on compression?

thanks
luis

 

[ezmoney]

yes. Octane measures the resistance to ignite, so higher octane means the gas is more difficult to light. The more pressure gas is under the easier it lights. If your gas ignites too early, you get detination.

detination is when the gas in the cylinder explodes before it is at top dead center.

So. If you bump up the compression, bump up the octane. it is possible to get 104 or 110 octane leaded gas (great stuff) from oval tracks (like for cars). It's about $4 a gallon though.

 

[tor*p*do]

do a search- someone posted a chart of compression versus fuel requirements:smoker:
185+ = race gas:burnout:

 

[ToddW]

Napa has 110 5g for $39 too.

 

[Philip Clemmons]

There are other factors as well, such as ignition timing, RPM range, and type of riding (long full throttle runs vs quick on/off riding).

When in doubt, mix 50/50 race/pump to assure you have enough. Its much cheaper than engine repairs!