What octane fuel you using?

[V452CB1100]

I've been using 91 from the git-go. The bike runs awesomely on it so I am loathe to go back to 87. I wonder if it does provide more power; I know many engines these days have knock sensors and can advance the ignition automagically to take advantage of the higher octane. My FJ Cruiser had this but no way would I pay a fortune for fuel in that thing. 17 mpg average. They said you got about 15 more horse with 91, though. Matter of fact I will try it in the FZ8 next couple tanks.

[Jim21680]

It's a relatively low-compression motor (9.5:1)...so I think regular 87 octane would be appropriate. With your FZ-8 being considerably higher at 12:1, I'd think 91-93 would be required. (When we're talking motorcycle gas tanks, the difference is rarely more than a few nickels total).

Anyway, a more direct answer to your question would be no - higher octane gas will not give you any more power. The reason modern engines have knock sensors is not necessarily to take advantage of higher octane, but to prevent damage in the event of lower octane being in the tank. Usually, the engine won't be able to run as designed, and that's where the power loss (or apparent "power gain") will come from.

[V452CB1100]

I read in the Aussie manual that 91 was required, so that is why I was using it. Then read in the US manual 86+ was OK.

Funny but the FZ8 also is fine on 87 according to the manual.

[Yoyodyne]

I think the most important goal when selecting fuel would be to find some ethanol-free gas, I think that would have more positive influence on how a CB1100 runs than 87 vs 91 octane.

[V452CB1100]

(07-07-2013 06:41 PM)Yoyodyne Wrote:  I think the most important goal when selecting fuel would be to find some ethanol-free gas, I think that would have more positive influence on how a CB1100 runs than 87 vs 91 octane.

I always use top-tier fuels.

[Jim21680]

I've read that ethanol-infused gasoline will make engines run hotter...true? If so, I can imagine it being a bad thing for any air-cooled motor.

[Yoyodyne]

FWIW, top-tier fuels are not necessarily ethanol-free.

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(07-07-2013 06:43 PM)Jim21680 Wrote:  I've read that ethanol-infused gasoline will make engines run hotter...true? If so, I can imagine it being a bad thing for any air-cooled motor.

Compared to pure 100% gasoline, ethanol-laced gas produces less power, yields worse mileage and promotes water accumulating in your gas tank, all Bad Things in my book.

[The ferret]

87 ...as recommended by Honda. I hate paying for premium in my ST.

[ChipBeck]

(07-07-2013 06:32 PM)Jim21680 Wrote:  .....The reason modern engines have knock sensors is not necessarily to take advantage of higher octane, but to prevent damage in the event of lower octane being in the tank. Usually, the engine won't be able to run as designed, and that's where the power loss (or apparent "power gain") will come from.

Jim,

There are several modern automobiles that are designed to and do produce more HP when using higher octain fuel. Their rated horsepower assumes 91 octain gas and their knock sensors work together with lightning fast spark advance/retard to give the engine maximum spark advance without detonation. They allow 87 octain to be used as the spark will be retarded automatically. The engine will run fine without any damage at all, it will just produce slightly less HP. The less sophisticated knock sensors in some other cars are set up to prevent damage by not allowing detonation but because the cars are rated using regular gas they will not allow enough spark advance to take advantage of premium gas so there is no benefit to using it.

I don't think the CB1100 has knock sensors at all but I'm not sure. I always use premium fuel in my bikes in any event. Cheers.

Chip

[Jim21680]

Yep, the Hyundai Genesis is a motor that comes to mind, but I'm sure there are others. I think they found a nice way of saying "we built this motor to run on high-octane gas...but you don't have to use it if you don't want to".