Ported 660: 93 Octane vs 110 Racing Fuel

[Ron660]

The test was a ported 660 with two different octanes (93 non-E and 110 Sunoco Racing Fuel). The wood was a Willow Oak (locally called a Pin Oak). The tree had been down for several months and was very dry. We couldn't split it with a hand maul. The 110 was an average of 10% faster.

 

[watsonr]

did you retune the saw?

 

[Ron660]

did you retune the saw?

No retune. I ran the 93 first and then the 110. After removing all the 93 and adding the 110, the saw idled fine with the 110. I could check it with a tach next time (idle and "H"). Next time I'll upload my videos from youtube as my friend suggested. Both fuels were mixed at a ratio of 32:1 using Motul 800 offroad oil. I was using a new Stihl square chisel full skip chain on a 28" bar.
I checked the times again with a stop watch. The average I got was a 9.3% faster cutting speed with the 110.

 

[CTYank]

No retune. I ran the 93 first and then the 110. After removing all the 93 and adding the 110, the saw idled fine with the 110. I could check it with a tach next time (idle and "H"). Next time I'll upload my videos from youtube as my friend suggested. Both fuels were mixed at a ratio of 32:1 using Motul 800 offroad oil. I was using a new Stihl square chisel full skip chain on a 28" bar.
I checked the times again with a stop watch. The average I got was a 9.3% faster cutting speed with the 110.

Any idea of how much compression? Even a gauge reading would be helpful. Only reason I ask is that higher octane becomes more useful as compression ratio goes up.

 

[zogger]

Were you getting more chainspeed, or just more torque/grunt so you could lean on it more?

also, cost diff per gallon

 

[blsnelling]

Race gas tunes ENTIRELY different that pump gas. There's no way that you can compare these fuels without properly tuning for each fuel. If it ran well on race gas, it was likely way lean on pump gas.

 

[KG441c]

Brad would it be just high speed adjustment or low and high?

 

[MustangMike]

So much for high octane slowing everything down! I'll bet the saw also runs cooler with the higher octane fuel, and that may be part of the reason it provides more power.

I always run high test (93).

 

[redfin]

Race gas tunes ENTIRELY different that pump gas. There's no way that you can compare these fuels without properly tuning for each fuel. If it ran well on race gas, it was likely way
lean on pump gas.

Is the viscocity different between these two?

 

[Deets066]

opcorn:

 

[blsnelling]

It has to do with the specific gravity and the way it flows. Without proper tuning, this test tells nothing. I'm not trying to be hateful, just stating the facts.

 

[super3]

There's no way that you can compare these fuels without properly tuning for each fuel.

That was my take when we tested the 4 different fuels at Jeeps yrs ago.

None of y'all agreed with me then.

 

[KG441c]

It's a molecular difference and the way it flows. Without proper tuning, this test tells nothing. I'm not trying to be hateful, just stating the facts.

Brad the saw in his video seemed higher rpm and leaner with the 110. Ive gotten confused with this octane thing! long stroke vs short stroke vs slow vs fast burn?????

 

[KG441c]

It's a molecular difference and the way it flows.W Without proper tuning, this test tells nothing. I'm not trying to be hateful, just stating the facts.

Brad if tuned to run 87 to 93 will running the 110 hurt the saw if not retuned?

 

[blsnelling]

Brad if tuned to run 87 to 93 will running the 110 hurt the saw if not retuned?

No. It would run richer with the race fuel.

 

[blsnelling]

Another example would be a Yamaha Banshee I had years ago. It was tuned for pump gas. I put Cam 2 in it and it was so rich it wouldn't even run right.

 

[KG441c]

But why did his saw run better with 110 and tuned for low octane if he didnt retune?

 

[066blaster]

I ran some 110 in my 290 and it ran so rich it soaked the air filter. I try to stay away from the stuff.

 

[MustangMike]

Keith, they may be different quality of fuels. People are assuming that higher octane burns more slowly. That is NOT what it means. It ignites at a higher temperature, and my burn faster, slower, or the same.

It is also possible (for whatever reason, like a hot day) that is saw was experiencing some minor pre ignition with the lower octane, although that is not likely.

This is why racers test everything. You use what works, even if you can't figure out why (although there usually is an answer).

 

[OnTheRoad]

Interesting stuff. I used to run a car that required 114 octane gas. The fuel that sat around too long would be used in lawn mowers and aside from the smell you would barely know the difference. Power was down very slightly on the 114.