High octane
Ultimate HDF Member
Joined: Sep 2005
Posts: 8,641
Likes: 26
From: Ozark Country
The octane rating of gasoline is a measure of how much you can compress the gasoline before it ignites, not how “good” it is.
This compression of fuel mixture into the cylinder is the 'compression ratio', which can be 8.0:1, 9.5:1, 10.25:1, or whatever.
Engines that require higher octane gas actually need that higher priced gas because the engines compress the fuel more before it is ignited. If you put regular gas in a engine that requires premium, the gas will prematurely ignite when it’s being compressed and the engine will give you a knocking sound.
Higher octane fuel will allow you to run a higher compression ratio, or 'hotter' spark advance without premature ignition, which will of course increase your horsepower.
But this horsepower increase isn't caused by the fuel itself, but by other modifications that have been made to the engine, ignition, etc..
If you have an engine running a 8.5:1 compression ratio, producing "X" amount of horsepower when using 91 octane gas, don't expect a noticeable horsepower increase from doing nothing more than filling the tank with higher octane fuel.
This compression of fuel mixture into the cylinder is the 'compression ratio', which can be 8.0:1, 9.5:1, 10.25:1, or whatever.
Engines that require higher octane gas actually need that higher priced gas because the engines compress the fuel more before it is ignited. If you put regular gas in a engine that requires premium, the gas will prematurely ignite when it’s being compressed and the engine will give you a knocking sound.
Higher octane fuel will allow you to run a higher compression ratio, or 'hotter' spark advance without premature ignition, which will of course increase your horsepower.
But this horsepower increase isn't caused by the fuel itself, but by other modifications that have been made to the engine, ignition, etc..
If you have an engine running a 8.5:1 compression ratio, producing "X" amount of horsepower when using 91 octane gas, don't expect a noticeable horsepower increase from doing nothing more than filling the tank with higher octane fuel.
Last edited by OldFenderGuy; Nov 14, 2009 at 11:59 PM.
Thread Starter
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Road Master
Joined: Nov 2007
Posts: 883
Likes: 2
From: Irving-Texas
Uh huh, y'all are just taking cheap shots cause I said I wouldn't say any more 
My mind is already made up from personal experience-but here is some interesting read
http://www.vpracingfuels.com/page469...ection15613263
Realize first that octane is a measurement of a fuels ability to resist detonationnothing more. The two types of machines used for testing octanea Motor Octane machine and a Research Octane machinewere designed in the 1930s. They were designed to test for octane numbers from the 0-100 range, therefore, any number above 100 is an extrapolation.
That should make some of you freaks happy
My mind is already made up from personal experience-but here is some interesting read
http://www.vpracingfuels.com/page469...ection15613263
Realize first that octane is a measurement of a fuels ability to resist detonationnothing more. The two types of machines used for testing octanea Motor Octane machine and a Research Octane machinewere designed in the 1930s. They were designed to test for octane numbers from the 0-100 range, therefore, any number above 100 is an extrapolation.
That should make some of you freaks happy
Advanced
Joined: Oct 2009
Posts: 91
Likes: 1
From: England
Road Warrior
Joined: Sep 2005
Posts: 1,511
Likes: 1
From: Michigan
Octane does NOT give you hp. It is in your head. You need to do a search on the net and read up. Look up burn rate, and what it does for and engine. This will keep you occupied for a few days.
BTW I build engines for a living. I also sponsor a few pro MX, and GNCC riders. The picture is some of my port work.
BTW I build engines for a living. I also sponsor a few pro MX, and GNCC riders. The picture is some of my port work.
Banned
Joined: Sep 2009
Posts: 7,580
Likes: 7
From: The Internet (& Dyer, Indiana)
I'm running 10.25:1 compression in my TC WideGlide and it runs just fine with BP 92 octane gas (the good stuff, not the blended crap)..
Friend of mine is running 10.5:1 compression in his Softail and his bike runs fine using the same 92 octane gas.
Guess if I was running at the track and needed every available ounce of power I would spend the extra money for additives or higher octane 'racing fuel', but for normal cruising down the road I don't see much point in it..
Friend of mine is running 10.5:1 compression in his Softail and his bike runs fine using the same 92 octane gas.
Guess if I was running at the track and needed every available ounce of power I would spend the extra money for additives or higher octane 'racing fuel', but for normal cruising down the road I don't see much point in it..
.
Road Master
Joined: Apr 2008
Posts: 992
Likes: 1
From: Mechanicsburg, PA
agreed on the octane discussion. I rank this among other discussions like the red spark plug wires and splitfire spark plugs, or whatever the latest craze may be. With that being said, if you expect a performance gain and you really really want it to be there, it will be there....in your HEAD. Now, as with any mod I believe most folks on here will tell you to "do what makes you happy" and this is no different. After all, one thing is for sure.....the smell of the exhaust is AWESOME. Makes me feel like I am at the races! I have pumped 100 octane gas many times purely for the smell, but there just ain't no performance to get......plain and simple.
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Banned
Joined: Sep 2009
Posts: 7,580
Likes: 7
From: The Internet (& Dyer, Indiana)
agreed on the octane discussion. I rank this among other discussions like the red spark plug wires and splitfire spark plugs, or whatever the latest craze may be. With that being said, if you expect a performance gain and you really really want it to be there, it will be there....in your HEAD. Now, as with any mod I believe most folks on here will tell you to "do what makes you happy" and this is no different. After all, one thing is for sure.....the smell of the exhaust is AWESOME. Makes me feel like I am at the races! I have pumped 100 octane gas many times purely for the smell, but there just ain't no performance to get......plain and simple.
But it seems that the OP's bike is tuned for higher octane, so he will indeed see real gains (not "in-your-head" gains).
He has a Fuelmoto package, not tuned on a local dyno. Likely has too much WOT advance.
If I were to advance my bike until it pings on regular fuel, I too would gain from higher octanes.
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