The octane rating of the gasoline should not effect your idle speed in any way... At least not unless the engine is very, very hot or other extenuating circumstances come into play.
Recall that octane rating of today's fuels is a mathematical construct of an empirical set of tests that once determined fuel's ability to resist detonation.
If you want to read a bit about octane numbers and ratings try these pages:
http://en.wikipedia.org/wiki/Octane_rating
http://www.csgnetwork.com/octaneratecalc.html
http://www.ibmwr.org/otech/octane.html
http://www.sizes.com/units/octane_number.htm
For all intents and purposes you should really run the very
LOWEST octane numbered fuel your bike will run on without any symptoms of
detonation...
Not only will your bike make more power, but it will also run more efficiently and get better fuel mileage.
Why, you may ask?
Because you will get faster flame front propagation, and hence faster and more complete burning of the fuel in the combustion chamber. Faster burning of the fuel means more expansion in a shorter period of time and higher combustion pressures. More complete burning of the fuel means not just getting all you can out of the fuel and not spitting any unburned fuel out of the exhaust pipe, but fewer emissions as well. You may not believe it, but it's true...
Oddly enough, lower octane fuels should lead to improved idling and smoother running as long as detonation or pre-ignition isn't a factor. You need to experiment a bit with low fuel loads at various ambient temperatures and loads to determine if and when you might experience detonation, but it is certainly worth it, and not just to save money at the pump but also to get the most power to the ground.
I haven't had my Hypermotard long enough to do much experimenting with different fuel octane ratings, but I have run it on mid-grade 89 octane with no detonation or other ill effects. Granted, that was one tank where I was not stretching the throttle cable very hard nor were there heavy loads on the engine. However, I found I could regularly run regular 87 octane gas in my old BMW R-1150-R despite the manufacturer recommending only premium grade fuel. On the other hand my KLR-650 like at least mid-grade 89 octane, as on very hot days with spirited riding regular 87 octane gas will bring on slight detonation at certain throttle openings and high loads.
If you ride like a granny you could probably run regular gas all the time in your Hyper and never notice it. Your benefits would be better mileage and fewer combustion chamber deposits. However, if you ride as though you are trying to qualify for the front row at Phillip Island you might need premium fuel on a regular basis.
One other, perhaps more important, thing to consider is
where you buy fuel...
It is really a much better habit to buy fuel from a busy service station - one that has a lot of vehicles going through it each and every day. Why? Because the gas there doesn't stay in the ground very long. The longer fuel stays in the ground the worse it is. The fresher the fuel the better. Fuel station tanks are large vessels and over the years they can gather lots of trash, dirt, and other contaminants that you don't want going through your engine. Granted, the pumps have filters, as does your fuel system, but just how often does that station change its filters? If the in-ground tanks at the station are old enough they have probably gather quite a bit of water, too. Add to all this the fact that the gasoline starts flashing off its lighter volatiles literally from the moment it leaves the refinery and you begin to understand why fresh fuel is best. Again, the longer fuel sits in those in-ground tanks the more of these volatiles have evaporated away.
Anybody want to guess if gasoline's octane number goes up, or down, as it sits in the ground flashing off these volatiles -regardless of what octane rating it had when it was pumped into that underground tank?
Just FYI, and food for thought...
Dallara
Octane...
Nope...
Linear Mode
