"High Octane fuels in CBR's" and engines in general
We get a few members ask this question one way or the other, so with CovertOps permission I posted this up for him as a "How to"...
thanks mate ..

Posted by : CovertOps

I'm on my 63rd bike now, BMW Master Tech, Honda, Triumph, Ducati, Suzuki, H-D (yuk!) factory-trained. Gas burns in the cylinder at a certain rate. Once the plug fires, the flame front goes from the spark outward at a given rate based upon compression, combustion chamber shape, intake velocity, valve overlap, and fuel chemistry. Gas companies blab on about good, better, best when they talk about 87, 89, 91 octane, and the public thinks the higher number (and higher price) means what they are told: the higher that number, the better the gas.

BULL HOCKEY

Here's the thing: as compression increases, so too does the speed of the flame front on the ignition stroke, given the same fuel. If the flame front speeds up too much, then a burn of a specified duration (like watching an explosion in slo-mo) actually becomes a hazard to your engine. When the plug fires, the piston is still on its way UP! It's not at top-dead center, waiting to be kicked on over by the ignition stroke. Just how far the piston is ahead of the spark is called "advance"- you've heard of ignition advance I'm sure. Here's how it can be a bad thing to have a too-fast burn...

Say your piston is headed up toward the plug. The plug fires. The flame front starts blooming outward from the plug. The piston is still headed on a collision course with the flame front, but at this point the flame (and shock wave) won't hit the piston for a while yet. If your ignition is timed correctly, the flame front will compress and hit the piston only after it has fully developed into an efficient fireball AND the piston is at or just-after top dead center. The piston has momentum and inertia on its side, now, and the flame front will kick the piston on over, turning the crank.

IF, however, your timing is too early, the expanding flame front will slam into the piston while the piston is still on its way up. You know that can't be good. People call this many things, pinging, knocking, whatever, but whatever you all it will hammer your engine to death.
The most severe ignition / combustion problem would be pre-ignition, which is the case when compression is so high that the fuel/air mixture in your cylinder lights itself off before the spark plug even fires. In a simple way, that's why a diesel engine has no spark plugs- it's running such high compression that the fuel literally lights on its own.

The way all of this relates to octane is that higher octane slows down the rate that fuel burns. Generally speaking, octane requirements increase as compression increases. This is why Joe Blow putting race gas into his Taurus is a moron.
Octane in and of itself does not equal power, doesn't increase efficiency, clean your valves, give you better mileage, none of that.
It regulates the rate of combustion on a micro-second scale. You cannot convince Joe Blow that he can be perfectly fine using 87 octane in his car, or even many stock motorcycles.
If Honda puts a sticker on the gas cap saying you can use 89, then you can believe Honda.
They have to stand behind their engines, so why would they tell you to put the wrong fuel in? Race gas >>might<< make a particular bike respond better (marginally) or give it any number of perceived minor advantages, but it's super-expensive, it's usually leaded (that's all we need), and the benefits never outweighs the cost.
If you're not getting over 7,000rpm, one danger I see is the potential for lugging the engine. Just make sure you keep the RPMs up at a decent level. Running an engine at high RPMs doesn't wear it out faster (God I get tired of hearing that), so you can safely and easily bump your RPM cap up a bit. Once you get used to it you're probably going to be doing that on your own anyway.

What's more important to your engine's life is proper warm up. Start it, DO NOT BLIP THE THROTTLE, and let it idle for a couple of minutes from 1500 to 2000 RPM while you fasten your helmet strap and don your gloves.
You don't have to wait until the thing's at running temperature to ride off. Ease the choke in as close to idle speed as you can before you engage first to keep from over impacting your drive line, then just ride EASY until the thing warms up the rest of the way. Speeding up the warmup process by going WHABBA WHABBA WHAAAAABA on the gas hurts your engine and makes you look like a tool.

My fingers hurt, so I'm gonna shut up. The upshot here is: use the lowest octane gas possible while getting reliable performance with no knocking, pinging, or pre-ignition.

Please feel free to post up your thoughts on this subject...

 

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Yer a good one to point peeps too when the inevitable gets asked once again ...

Well om glad its for the CBR Mark .... that stuff would taste like chit !! ....LOL

 

I hear yu on that score Mark...these days I avoid the high octane personal lubricants ....
A few cans of 8% Jimmy Black and om doin just fine ..

The days of ripping into a bottle of rocket fuel and waking up with a truck parked inside my head are way gone ...... and btw , I do not miss those day at all....lol