Octane Options

[Bulldog9]

Lets talk Octane..... What is the consensus on grade of fuel? I'm running 96 x 71 bore & stroke with .060" deck height 58.8cc chambers in the heads, and flat top pistons with no valve reliefs, and figure my CR is around 8.6:1. I'm thinking I can run regular, but no idea.

I've been running Chevron 92 so far, but dont want to wast $ and leave unburnt fuel residue. The higher the octane, the more resistant the fuel is to combustion, so unnecessary use of 'hitest' is dirtier combustion wise than regular.

I haven't done any experimenting yet, but wanted to get some experience before I do. I plan to run the current tank down to close to empty, then put in 5 gallons of regular and see how that goes, but just wondering.

[914_teener]

Lets talk Octane..... What is the consensus on grade of fuel? I'm running 96 x 71 bore & stroke with .060" deck height 58.8cc chambers in the heads, and flat top pistons with no valve reliefs, and figure my CR is around 8.6:1. I'm thinking I can run regular, but no idea.

I've been running Chevron 92 so far, but dont want to wast $ and leave unburnt fuel residue. The higher the octane, the more resistant the fuel is to combustion, so unnecessary use of 'hitest' is dirtier combustion wise than regular.

I haven't done any experimenting yet, but wanted to get some experience before I do. I plan to run the current tank down to close to empty, then put in 5 gallons of regular and see how that goes, but just wondering.

Octane is a rating referring to the tendency to detonate. So the rating refers to a ratio of mix of octane and heptane. That is the standard. Octane and heptane are two different carbon chain molecules fuels. Buying a higher rated octane fuel doesn't mean it is a dirtier fuel.

I think when you posted combustion you meant detonation?

The propensity for detonation is caused by many factors but mostly by the combustion chamber and how the engine breathes and the fuel, so several things besides that octane rating.

Jake Raby has wrote untold threads on this.....he mostly says this in a few words as "its all in the combo" on how to create optimum power, not just in the CR ratio or the octane rating of the fuel.

[Bulldog9]

Lets talk Octane..... What is the consensus on grade of fuel? I'm running 96 x 71 bore & stroke with .060" deck height 58.8cc chambers in the heads, and flat top pistons with no valve reliefs, and figure my CR is around 8.6:1. I'm thinking I can run regular, but no idea.

I've been running Chevron 92 so far, but dont want to wast $ and leave unburnt fuel residue. The higher the octane, the more resistant the fuel is to combustion, so unnecessary use of 'hitest' is dirtier combustion wise than regular.

I haven't done any experimenting yet, but wanted to get some experience before I do. I plan to run the current tank down to close to empty, then put in 5 gallons of regular and see how that goes, but just wondering.

Octane is a rating referring to the tendency to detonate. So the rating refers to a ratio of mix of octane and heptane. That is the standard. Octane and heptane are two different carbon chain molecules fuels. Buying a higher rated octane fuel doesn't mean it is a dirtier fuel.

I think when you posted combustion you meant detonation?

The propensity for detonation is caused by many factors but mostly by the combustion chamber and how the engine breathes and the fuel, so several things besides that octane rating.

Jake Raby has wrote untold threads on this.....he mostly says this in a few words as "its all in the combo" on how to create optimum power, not just in the CR ratio or the octane rating of the fuel.

Yes, brain fart, detonation. Due to its 'resistance' to detonation, it burns slower and sometimes not as completely, hence 'dirtier'

Jake said something in a few words? (IMG:style_emoticons/default/chair.gif) (IMG:style_emoticons/default/poke.gif) Bur he is spot on with that comment, hence all the relevant data in my original post.