av gas and reg gas info i found

[suzuki2903]

heres two link i found while doing some searching for info on using av gas... maybe someone else can use this info as well.

 

http://www.groupk.com/tec-gas96.htm

 

 

http://www.groupk.com/tec-gas97.htm

[dawarriorman]

Aviation gasoline (or "av gas") is blended specifically for use in small aircraft. It's also commonly used by many high performance engine owners because of it's high stated octane rating (usually 100-110) and the relatively low price compared to racing fuel. Unfortunately this fuel is not all it appears to be. Avgas octane is rated on a different scale than gasoline's intended for ground level use. What is 100 octane "av", is not necessarily 100 octane "ground level". Besides this, there is also a big chemical difference. Normal ground level race fuels are made up of gas molecules that have a "light end" and a "heavy end". The light end of the molecule ignites easily and burns quickly with a low temperature flame (as a piece of thin newspaper would burn). The heavy end of the molecule is not so easily ignited, but it burns with a much more intense heat (as an oak log would). This heavy end of the gasoline molecule is responsible for the hotter, more powerful part of the combustion process.

 

Small aircraft are constructed as very weight conscious vehicles. That's because their somewhat weak engines often have difficulty taking off with any extra weight. To help reduce this weight problem, aviation gasoline's are blended with no heavy molecule end. This makes a gallon of avgas weigh substantially less than a gallon of ground level fuel. Since small plane engines turn very low rpms and produce so little power, the omission of the heavy end is not a horsepower issue. However, for high output pwc racing engines, there is defiantly a compromise in power. This, despite the fact that many pwc owners experience the desirable cooler operating temperatures that avgas offers. In addition, some blends of avgas will quickly separate from some oils used in premix situations. For the above reasons, we do not recommend the ongoing use of 100% avgas, and we will not prepare any "avgas" engine kits.

 

Despite all this bad news, running avgas (accepting the slight power loss) is usually a better choice than burning down a high output engine on regular pump gas. In this situation, the best choice is usually a 50/50 mix of pump and avgas. That provides "some" heavy molecule ends for the engine.

Aviation fuels - One affordable way to get away from the problems associated with oxygenated fuels "used to be" the use of "av" gasoline. However, now all "av" gasoline's are also oxygenated. Despite this, running a 50/50 mix of avgas with 92 octane pump gas is still a very effective way to raise octane and reduce operating temperatures.

I've done enough research on this, contacted people, got numbers from people at the airport. Most of what this guy says are the same reasons that everyone else uses. They make some sense logically, but they aren't based on any fact.

 

As for his "heavy end light end" theory:

The specific gravity (density, weight per unit volume) of most race gasolines is somewhere in the .700 - .750 range. I can't remember the exact number off the top of my head, but both BP and Shell 100LL AV gas are above .700. So it weighs the same as other race gase, and also won't seperate any more than the next gas.

 

Its not oxygenated either.

Edited February 4, 2008 by dawarriorman

[wesw]

i ran 100LL on my stock jug 4mm for over a yr and ran the piss out of it. never had an issue

 

 

with my cub it seems to not like it as much but too much compression and other factors like a possible crank turnign on the pin it it didnt seem to like it. not sure but on stock jugs it works good.

[suzuki2903]

ive ran 50/50 av an dpump gas an dnever had a problem either. i just found some of the info intersting and thought id share it.