Re: [ST] AVGAS

[david.funk@xxxxxxxxxxx]

I agree with what Emile says.
But there is more to octane then just additives. True that AVGAS uses additives for high altitude and other special airplane conditions.
The difference between regular gas and premiun has a great deal to do with the blend of hydrocarbons that make up the "gas".
Kerosene is not the same as diesel.
High octane gas has the same energy as low octane gas, at least for pump gas.
Racing fuels are different. You know this because of the rules to control racing fuel.

David W. Funk

-------------- Original message -------------- 
From: "Emile Nossin" <Emile@xxxxxxxxxx> 

> >From: BrettWilson21@xxxxxxx 
> >I imagine it would be like running racing fuel e.g. 10% or 20% methanol. 
> >When you twist the throttle - hang on! 
> 
> That would be nice, but avgas 100 LL is just regular gasoline but 
> with extra additives to prevent pinging and knocking at high 
> altitudes, high temperatures and high power settings. A C172 
> engine is just an aircooled 4 cilinder boxer, imagine it running 
> full power climbing to 10.000 feet in thin air on a hot day, for 
> at least half an hour with hardly any forward speed (the prop 
> cools of course). 
> 
> The Avgas 100LL is probably only gonna make your engine only run 
> (slightly?) worse because of these extra anti pinging additives. 
> "Premium" gas with higher octane all sounds cool, but the higher 
> octane just indicates it will be safer to run IF your engine 
> has a tendency to ping / predetonate etc. If it won't ping on 
> lower octane, it will probably run better on that because it has 
> less (safety, not "power") additives. 
> 
> Of course the current BMW bikes have enflamed the myths about 
> higher octane again. As always, they require a higher octane 
> fuel because they would otherwise be pinging all the time. But 
> you can now set the chip in such a way that the engine can actually 
> run on lower octane fuel, but it will retard the ignition in such 
> a way that it won't ping. Of course, that will make the engine 
> run with less performance. But now people see that as a confirmation 
> that higher octane means more power, making them again suckers for 
> the "premium" and "super" marketing value that surrounds fuel with 
> anti pinging additives. 
> 
> Kerosine won't make the bike run better either, that's just diesel. 
> And diesel / kerosine is cheap, because it goes into engines that 
> can burn anything without problems (jets, diesel engines). That's 
> why, in general aviation, they are slowly trying to introduce 
> diesels. They are more efficient and nowadays a lot lighter as 
> well, plus you can run them on kerosine which is cheap and has 
> much better availability than avgas 100LL. In Holland the diesel 
> revolution is not getting thru to general aviation yet, but my 
> aeroclub ( www.klmaeroclub.com ) will modify it's cessnas and 
> piper to run on regular automotive gas (MOGAS). It will be quite 
> a lot cheaper and the airplanes will run the same, after the 
> small modification, except when you'd taking them at extreme 
> high altitudes over the Alps (in that case you can fill it up 
> completely with avgas 100LL), but they almost never do that. 
> 
> Emile 
> www.piloot.com 
> 
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