Higher compression. When do u start using higher octane?

[ReeperLT500]

I have a cool head with the stock dome size 62cc on my zilla. I have a 59cc dome I want to put in. I wondering at what point would I need to use higher octane gas. I really don't feel like getting race gas everytime I go riding. Hell, in my area it's 2.11$ a gallon for 93. I can't imagine what 104 will cost. Thanks for any advice. -Mark

[PA_Banshee]

You just need to run 93 in it and see what happens. If you hear some knocking I'd step up to something around 104 or 105. Don't go right ahead and get 115 or 120, that's just overkill. My friend has a banshee with 18cc domes, stock is 23 or 22 (I can't remember, but there's a thread somewhere on here that has it). He ran 93 and he could tell it just wasn't right. He's running 104 or 105 VP race fuel in it now. I think he just bought a 5 gallon drum for $35.99, but I think that was a ripoff. It should be about $5/gallon right now.

Let everyone know how you make out with it and how it goes once you're done.

[mamhbfun2]

need to use race fuel comes with all mods. remember higher octane not only controls the point of ignition but also it runs cooler. 2 dollers more a gallon will be cheaper then blowing top ends. i have a 500 with 55cc dome with major port work and run vp c12. all 500 like higher octune ever if completely stock. ive pump before but i can instantly feel the increased heat on my legs. all in all its better to be safe then sorry.

[ReeperLT500]

Well I use 93 and it's doesn't dentonate. But I always thought if a engine doesn't have a high compression you don't want to use a higher octane gas cause some of the fuel will not get burned. With stock/low compression you want to use the lowest octane possible to achieve combustion. Case in point, my mustang has stock compression. If I put 112 or 116 in it I lose power and the car runs like a$$. It may run cooler with higher octane because it's not getting a good combustion due to not all the fuel is being burned. Less fuel burned= cooler cylinder. -Mark

[PA_Banshee]

Yeah, that's the way it is. High octane doesn't equal high power. Anyone that tells you that if full of it. High compression equals higher power (to a point), but needs a higher octane gasoline that won't predetonate due to a higher compression along with the heat. Higher octane needs a higher heat to combust so the comment about it running cooler is crap. The reason for knocking with a lower octane is the lower than needed octane gas detonating while the piston is still traveling upward.

Like Mark said,
"It may run cooler with higher octane because it's not getting a good combustion due to not all the fuel is being burned. Less fuel burned= cooler cylinder."