Maintenance & Technical > KX500 Original
Race Fuel
Friar-Tuck:
Yea,
I got that,
I have been a part of the av gas debate as well, and was thinking I'd get more "hits"
fishing with the av gas statement...
The "average Bear" here seems to be well aware of my sophomoric ploy.... :-(.
and now, back to the regularly scheduled program... :-D
Tuck\o/
BDI:
We were at the dyno with my buddies turbo car, we had the boost cranked up as high as we could go with pump gas. We drained out the fuel and pored in some high octain race fuel. When we made the base line pass the car lost 40 horse. Now with the race gas we were able to turn the boost way up and make way more power then with the pump gas. the moral is you will make the most power with fuel whos octain is best matched to the compression of your engine. The reason a stock bike will run cooler with high octain fuel is you don't have the comp to burn it.
sandman540:
another thought on av gas is that 100 octane low lead or 100LL has more lead than regular gas of the 60's. theres so much lead that it will destroy an engine that is not at high altitude i.e. aircraft. gums em right up. more food for thought as a buddy is in the av gas business
Friar-Tuck:
So there's more to making your bike faster than just running synthetic oil and race fuel?
There is NO BENEFIT to using a higher octane than your engine needs.
I'll try to be brief.....
Octane rating is a measure of the auto ignition resistance of gasoline and other fuels used in spark-ignition internal combustion engines.
Octane is NOT a measure of power but of the fuels? resistance to ignition from heat.
A higher-octane fuel, under identical combustion chamber conditions, will burn slower than a lower number.
As the piston, quickly squeezing the fuel/air mixture into a small space, it can generate enough heat of compression to ignite the fuel well before the spark plug fires, with unpleasant results... Detonation....
If the fuel prematurely ignites while the piston is on its way up, the burning of the fuel, in conjunction with the rising piston, creates even more pressure, resulting in a violent explosion.
This explosion is equivalent to hitting the top of the piston with a very large hammer. If you want to be able to see through the top of your piston, ignore those sounds that are usually called: "pre-ignition", "ping" or "engine knock".
What we really want is a very rapid controlled burn of the fuel, not an explosion.
And we want the burning of the fuel to take place while the piston is in a better position to convert this pressure into productive work.
It might seem odd that fuels with higher octane ratings burn less easily, yet are popularly thought of as more powerful. The misunderstanding is caused by confusing the ability of the fuel to resist compression detonation (pre-ignition = engine knock) as opposed to the ability of the fuel to burn (combustion).
Premium grades of fuel often contain more energy per gal/ litre due to the composition of the fuel as well as increased octane.
This is why when BDI's dyno run with race fuel lost HP on the initial fuel swap.
The engine was tuned to run with the pump gas,
--- Quote ---we had the boost cranked up as high as we could go with pump gas
--- End quote ---
the race fuel would burn slower.
Tuning the engine to run with the race fuel produced more power as they could increase cyl. pressure/timing etc. (BMEP) without detonating the fuel prematurely.
The opposite will happen running the race fuel in your bike if it's not tuned/built to run with it. The slower burning fuel will cause your cyl. pressure to actually drop if nothing else has been changed.
Running the race fuel in a stock engine shouldn't do any damage.
I hope this makes some sense.
It's a pretty complicated subject worth spending some time on.
I am with you sandman, an aircraft engine is running in quite a different environment. :wink:
Tuck\o/
Larry Wiechman:
--- Quote from: Friar-Tuck on December 16, 2009, 12:28:28 PM --- So there's more to making your bike faster than just running synthetic oil and race fuel?
--- End quote ---
Lots of stickers!
--- Quote --- A higher-octane fuel, under identical combustion chamber conditions, will burn slower than a lower number.
--- End quote ---
Flame front burns at the same speed, it's just a little harder to get it to start burning.
--- Quote --- As the piston, quickly squeezing the fuel/air mixture into a small space, it can generate enough heat of compression to ignite the fuel well before the spark plug fires, with unpleasant results... Detonation....
--- End quote ---
Abnormal combustion before the plug fires is pre-ignigtion.
--- Quote ---
If the fuel prematurely ignites while the piston is on its way up, the burning of the fuel, in conjunction with the rising piston, creates even more pressure, resulting in a violent explosion.
This explosion is equivalent to hitting the top of the piston with a very large hammer. If you want to be able to see through the top of your piston, ignore those sounds that are usually called: "pre-ignition", "ping" or "engine knock".
--- End quote ---
A very good description of detonation.
--- Quote --- Premium grades of fuel often contain more energy per gal/ litre due to the composition of the fuel as well as increased octane.
--- End quote ---
BTU/gallon is the same.
Friar, You been hit'n the egg nog already? :-D
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