I was wondering what the pros and cons of 100 & 110 octane gas are. I know when I had my '88 hurricane, I put 100 octane in it and it ran so hot I could barely sit on it. So yes run it or no stick to 93 octane?

 

Makes me wonder what dictates the minimum octane rating. My 900 is content with 87, but my 1000 requires 93 (I think). Perhaps it's a fuel/air mixture ratio issue that contributes to overheating? I recall the dealer's mechanic warning me that if I put 87 in the 1000, it could over-heat. Makes me wonder exactly how this works.

Experts. . .your chance to impress those of us that do not know any better.

 

Octane = knock resistance. Run the lowest you can without pinging or knocking. Save some money and get better gas mileage.

 

If you run higher octane it will burn cleaner and faster, which may make it run hotter. If you run 100 or higher octane you should notice a small increase in the rpms.(meaning they should get up a little faster) When you do run a very high octane, you shouldnt do it all the time unless you bike is modded to accept the combustion the higher octane will make. You can also put octane boost in pump gas for the same results. If you want to run cam2 or something that you have to pump into a can at the gas station, I would mix it half and half with pump gas. All in all there isnt much of a difference if you are just going to use it for the street, except some of that really high octane stuff makes your bike smell like a 1/4 mile drag machine.....lol

 

You guys failed chemistry, didn't you?

The higher the octane, the more SLOWLY it burns. Why? Because the hydrocarbon burns more evenly and completely which also creates more energy per gram. Lower octane gases cause pinging & knocking because they have a habbit of "detonating" too quckly which also has the environmentally unsound habbit of leaving hydrocarbon chains that have not been bruned, in tact which are then expelled as exhaust gasses.

What I was looking for here, was why? Specifically, what is it about the air/feul mixture ratio that makes one bike use a 91/93 octane rating and other bikes work fine on 87? Why would a bike heat up with 110 octane fuel? If that bike's engine were modified to say - increase the amount of air - would it be ok?

 

Amzining enough, something else just occured to me. . .

The higher the compression ratio, the higher the octane rating needs to be. The reason for this is the similar to what I said above in that lower octane ratings will burn too quickly or auto-ignite (as in diesel engines) when subjected to high pressure levels. If I'm not mistaken, isooctane is the chief component of common gasolines an in pure form, has a rating of 100 (or something like that) and goes back to what "brewer" said about anti-knock. If the fuel has a low octane rating and is compressed to it's auto-ignition point, it will ignite even without a spark from your plug. So, if you can envision a cylinder in its compression phase moving upward that hasn't yet completed the stroke and met suddenly with a fuel detonation, it creates a lot of pressure resulting in power loss (that's converter to heat) and the familiar knocking that I'm sure everyone here has heard. The mystery to me remains to be why a fuel with 110+ octane rating would generate more heat Thus, we are back to my original question about air/fuel mixture ratios. I know an engineer who is an expert in combustion, but he's hard to reach. I'll try and get back to this thread.

 

example.. run 87 in a daily driver and you will eventually get pinging.why? because cheap gas leaves carbon build thus creating higher compresion that you will need to run higher octane to cure. now run 89 or 93 (not 100 octane) and the amount of miles before pinging starts if ever are way beyond the 87. also timing advance will like higher octane as well. i run and will always run 93 daily in my bike.

i put some BP 100 octane in my bike yesterday and went from just over 30mpg to 47.5. went 114 miles two times today riding to lake and back today, and the results were the same at both fill ups afterwards and i belive that 100 was 7.69 a gallon!!!!!!!!!!

most of my exp in this stuff comes from tuning my 5 liter mustang, even then my car had no cats or oxeygen sensors, i never put more then half tank.


so really i like 100+ octane like a fuel additive then just sraight fuel, not sure about bikes but in my stang if i kept plenty of gas in the tank you could smell it, notice/feel the difference for a good while. run cheap gas and you will get what pay for good gas is part of the cost of doig bussiness with performance motors

 

I've had 114 in mine the last few tanks(just because i siphoned the tank on the snowmobile for the summer didnt wanna waste it) Saw no difference in heat, seems a bit snappier, put the last of it in this morning, once i use it up its back to 91 for her.

 

Wow! A 3yr old octane thread???
No thanks... we have enough of them already.

 

Ya, I would give up but I just hate for peeps to waste cash because the forum experts think higher octane fuel leaves fewer carbon deposits or gives better performance.

In reality if your engine burns 87 efficiently with no predetonation then running 100 or 114 will leave MORE carbon deposits, not less. Why? Because higher octane means it is HARDER to ignite. Which is a good thing if you have super high compression or a blown motor or cast iron head (dissipates heat sloooooow) or advance the **** outta the ignition.

One small caveat, though. Generally the higher octane fuels contain more detergents than the lower octane grades. So you could run some higher stuff that does not burn as well but the detergents will keep the valves cleaner than a lower grade. I know QT adds the same detergents to all their grades so no benefit to premium unless your engine needs it.

And yes, the manufacturers share some of the blame. They will put a certain octane requirement in the manual that's only the RON ... in the U.S. most pumps are R+M/2 method.

I could post a list of the equivalent #'s but we've got a zillion octane threads floating around and I'm tired of the spoon feedings ...