It's not energy density in question here, it just takes more to ignite a high-octane air/fuel mix.

I did a bunch of reading on this last night. Gasoline turns out to be incredibly complex. Summary follows:

1. Higher octane gas isn't harder to ignite, it's more resistant to knocking. This isn't semantics, knocking isn't the same thing as igniting. Knocking is when the mixture explodes as a result of compression, which eats pistons.

2. Gas is really a soup of chemicals. The recipe varies according to the refiner, the season, the altitude and the octane rating.

3. Using a higher octane rating than an engine requires has no benefits at all and costs more money. BUT, on engines without knock sensors, using low enough octane to allow knocking to occur can grenade the motor. If knocking is going to occur, it will do so when the engine is under maximum load, which, on motorcycles, tends to coincide with lots of wind noise, which could obscure the knocking sound. Erring on the side of caution seems reasonable.

Unless an engine has been heavily modified, 91 or 92 octane premium seems certain to prevent knocking. I can't see any logical reason for using the 94 octane Chevron fuel unless you literally have money to burn. For bikes that were designed to run on regular 87 octane, even using premium is most likely overkill and has absolutely no benefit.

Here's a couple articles written by a guy who made his own motorcycle.

Fuel

Knock

When I ran nitrous it was important. ALso, I know someone who's got an RS6 with an aftermarket chip. He has to use 94 octane and he still adds octane boosters to his fuel.

WTF! Your little "quote" left out the beginning of my sentence - you know, the part that says "For bikes that were designed to run on regular 87 octane". Also, you left out the part that says "Unless an engine has been heavily modified, 91 or 92 octane premium seems certain to prevent knocking." Or maybe nitrous doesn't qualify as modified to you.

You can use 94 octane in your lawn mower for all I care, but watch how you quote people.

I got yer back Twinman

Sorry Nic, but that shit is funny! OK so we are straight now, right, octane prevents preignition, AKA KNOCKING. Everyone cool?

its not all about compression ratio either. fuel mapping, ignition and cam timing play a huge part in octane requirements.



running 94 in an engine desgined and tuned to run on 87 or 89 is pointless. our society has built an idea around misinformation that leads people to believe higher octane = more performance. i know a girl who runs 94 in her hyundai because she heard it made more power.

If I load some Euro maps into my Power Commander the bike will knock like a bastard!

I dunno I use midgrade in my bikes, always have. Daddy always told me that using anything higher than regular is a waste of money, but I also figured that motorcycles like better gas:) least most rider friends believe they do run better/cleaner with higher octane.

So, if a higher octane fuel is not more difficult it ignite, they why does it resist preignition better than a lower octane fuel?

It burns slower so it more completely burns the air / fuel mixture. More uniform flame front etc. etc. blah blah. Just wait until we get into discussions about squish and quench and somender singh grooves in the head and other crazy theoretical stuff.

Twinman I'm sorry, I didn't mean to misquote you, my bad! I don't know why you had to ridicule me using nitrous though.... Honestly it was the most fun I've ever had on four wheels. It's all just for fun, not competition. One more thing, I'm no poser. Trust me.

So, sorry again, didn't mean disrespect or anything like that.

It was all in good humour, no harm meant, I was actually making fun of sports car, especially "rice rockets", more than you. Once you get a bike and actually start riding you`ll learn 2 things: 1: you`ll realize how fast bikes actually are...even a "low performance bike" will roast the doors off of most cars.And god help Ricky Rice Racer if he takes on a fast bike. Any stock litre bike will make even the fastest cars look stupid. Bang for the buck they are king...short of a Top Fuel dragster you`ll never get a bigger rush than a big bore sportbike 2: Alway cover a brothers back...even if he rides a Suzuki

Now go see COLIN @ KELOWNA YAMAHA and get yourself a 2 wheeler.

hehe, I drive a 2005 Dodge sx 2.0 (Neon). Cheap on gas. When I get into my car after riding any motorcycle, I think the car is dying. Its so stupidly slow and heavy its really annoying.


Course the fastest thing I have ever driven is a 98 Vette. I heart fast cars, but I take bike over car anyday.