Porting - higher octane needed?

[Ron660]

Does a ported saw require a higher octane due to the increase in compression?

 

[nmurph]

89-91 is sufficient.

 

[cgraham1]

What does porting have to do with compression?

Most people recommend a richer fuel mix, like 32:1, on a ported saw.

 

[Ron660]

The question isn't about oil.....it's about fuel. Yes, he also recommended a 32:1 ratio which I already use. The individual porting my saw said to expect an increase in compression from 150 psi (my stock 660 may be a little more) to @200 psi. That would be a 33.3% increase in compression.

 

[redfin]

The bump in compression is from the change in size of the combustion chamber not the porting itself. read through the cut squish band vrs pop up thread. Lots of great info on octane for performance engines.

 

[cgraham1]

The question isn't about oil.....it's about fuel. Yes, he also recommended a 32:1 ratio which I already use. The individual porting my saw said to expect an increase in compression from 150 psi (my stock 660 may be a little more) to @200 psi. That would be a 33.3% increase in compression.

Like I said before, the porting has nothing to do with the compression bump.

Good luck with your newly ported saw!

 

[Ron660]

Sorry guys I was referring to a "porting job" which he stated would include all the extras that go with it....timing advance..MM..

 

[Mastermind]

I use 87 octane in all my saws......some are blowing 240psi.

 

[cgraham1]

If it's good enough for Mastermind...

Heck, I've always run 91 but I may start running 87 now!

 

[Mastermind]

87 makes more power.....

It's time consuming to explain way a short stroke engine don't need higher octane......and all I'll get is an argument.

I've quit trying.

 

[Ron660]

WOW 240psi....that's one strong Gorilla! The closest gas station that sells non-ethanol only has the 93 octane.
That's very interesting Randy on the octane....I believe you. My buddy and I always thought the higher octane stuff would perform better. But I'll look for the lower stuff now.

 

[Trx250r180]

87 makes more power.....

It's time consuming to explain way a short stroke engine don't need higher octane......and all I'll get is an argument.

I've quit trying.

Hi

 

[nmurph]

WOW 240psi....that's one strong Gorilla! The closest gas station that sells non-ethanol only has the 93 octane.
That's very interesting Randy on the octane....I believe you. My buddy and I always thought the higher octane stuff would perform better....like race car drivers use. But I'll look for the lower stuff now.

F1 cars only use 96 octane.

 

[Marshy]

opcorn:
Could I get a liter of 91 non E to go with this popcorn please?

 

[Mastermind]

87, 91, 93, are all fine. Whatever a guy can fine that is non-E.

Using avgas, racing gas......that's counterproductive in these engines. The fuel will be in the air before it burns completely.

 

[J rod]

Also higher octane will cause hotter head temps in non race type motors,

 

[KG441c]

87, 91, 93, are all fine. Whatever a guy can fine that is non-E.

Using avgas, racing gas......that's counterproductive in these engines. The fuel will be in the air before it burns completely.

So the 87 octane burns quicker than the higher octanes?

 

[Mastermind]

Exactly. Octane is fuel's resistance to burning.

That's what it helps with pre-ignition.

 

[blsnelling]

What Randy said And here I thought that I could burn Cam 2 in my Jonsereds and expect 20% more power. After all, they do have a turbo on them!

 

[KG441c]

Exactly. Octane is fuel's resistance to burning.

That's what it helps with pre-ignition.

You will hear no argument from me! Id love to hear what you have to say about the subject and and advantages of using 87 vs 93 in these engines? thanks