Compression ratios also figure prominently into the HP per CC thing.  Fuel burns with more explosive power when compressed.  A 500 cc engine with a high compression ratio could theoretically have more HP than a 600 cc engine with lower compression.  

You also have to take intake/exhaust dynamics in mind.

Good point Glenn. That is very true.
However, if you have a turboed engine, you want a lower compression ratio. I guess turbo's arnt as important in a motorcycle forum.

What is the GS500's compression ratio anyway?

Quote from: Rich500What is the GS500's compression ratio anyway?

9.0:1

By comparison, the Ninja 500's is 10.8:1

Most supersport street bikes are in the 12:1 range.

what happens if you raise the compression of the GS? like are there any adverse effects?

you would need to run higher octane fuel.

I know if you buy a GSXR 750 stock, they want 105 octane.  What a joke, you can't buy that kind of fuel anywhere.

Quote from: pizzleboyyou would need to run higher octane fuel.

I know if you buy a GSXR 750 stock, they want 105 octane.  What a joke, you can't buy that kind of fuel anywhere.

There are a few different octane ratings.  The one they are talking about is probably not referring to the one we use in the US printed on our gas pumps.

Higher than what? Higher than the premium (92 octane) I already run?

Wait a second, somehow I thought that the highest octane rating was 100.
100 as in no impurities?
and as it goes down more and more crap is added like lead

Octane rating has nothing to do with impurities or ingredients in the gas.  Octane is a way of measuring how fast gas burns.  The higher the octane rating, the slower the gas burns.  This is why higher octane is only needed in high compression engines or ones with advanced timing.  Octane rating has nothing to do with making more power in normal engines.  

They say to use high octane gas if you are experiencing "knocking or pinging".  This is caused by the gas burning too quickly for your engine and the explosion takes place too early in the piston's travel back up the cylinder.  High octane gas makes the explosion occur slightly slower and puts it back in it's proper place in the cumbustion sequence.

I'm on CRACK, I meant 95 octane.

The highest available stuff is 94 untra from Sunoco.  He was supposed to add octane boost with every fill up.

Just for reference you buy octane in levels over 100 octane.
At drag strips they usually offer levels in the 110's.
They due contain lead but if you are not using a cat and don't mind swapping out your o2 sensors often then you got some head room when tuning for maximum power.
Here in So Cal you can buy 100 octane unleaded at some of the local gas  pumps.
As it has been said here before, higher octane gas will allow you to make more power in an engine that has higher compression ratios and/or advanced ignition timing that requires higher octane fuel in order to operate at maximum efficiency. Mind you a stock 5.0 mustang only requires 87 octane and using any more will not gain you more top end on an otherwise stock motor.
When they "ask for 105 octane" they are most likely referring to the research octane number which is what they go by in Europe.
The gas that is sold in America is RON (Research Octane Number) + MON (Motor Octane Number) divided by two as is expressed on any gasoline pump that you use. These two numbers are derived by testing a gasoline's resistance to pre-ignition (knocking, pinging) in high load and low load situations.
Usually RON numbers are about 4-5 points higher than the (R=M)/2 method we use in the US which would give an effective required octane rating of 100 octane which as I stated before is available at certain local gas stations at the pump but costs around $3.50-4.00/gallon.  
Don't get me started on those octane boosters in a bottle.
You might as well buy some illuminated windshield washer nozzles to increase you 60ft times. :guns:

Evan

cc- cubic centimeters
hp-horse power