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Discussion Starter · #1 ·
My shop is at the airport in my hanger and I pretty much use avegas in my cars (100 octain low led). Even use it in my model A. The cars have seemed to really like it , and the real reason I use it is because it does not break down or does not gum up the carbs or fuel lines even if it sits for 2 or 3 years. It is 100 octain and I was wondering about the engine set up, as in timeing. Also was questioning the led as there is a little lead still in avegas. Maby like foueling plugs, or a littli more carbon build up in the combustion chamber. In the aiplane I have to lean aggressively during taxie and then in cruse we run very lean, in fact quite a bit lean of peak EGT. I was thinking it would tend to foul plugs a little more since there os no way to lean auto engines without changeing jets. Any thoughts out there. Sharkey 5557.
 

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My shop is at the airport in my hanger and I pretty much use avegas in my cars (100 octain low led). Even use it in my model A. The cars have seemed to really like it , and the real reason I use it is because it does not break down or does not gum up the carbs or fuel lines even if it sits for 2 or 3 years. It is 100 octain and I was wondering about the engine set up, as in timeing. Also was questioning the led as there is a little lead still in avegas. Maby like foueling plugs, or a littli more carbon build up in the combustion chamber. In the aiplane I have to lean aggressively during taxie and then in cruse we run very lean, in fact quite a bit lean of peak EGT. I was thinking it would tend to foul plugs a little more since there os no way to lean auto engines without changeing jets. Any thoughts out there. Sharkey 5557.
Just stumbled across this. Octane is just a resitance to detonation - so higher octane does not require more lean or advance - it merely allows it. We used to run avgas in the race cars and the only diff when we went to a track that had a pump gas rule was to take about 4 degrees off the timing all the way through the curve. Yes we SHOULD have raised the jets one or two - but chose not to - saw no issues.
So I would think the reverse is that if you are right at the lean edge with pump gas going to av should allow a couple degrees of timing to cure a fouling issue IF one arises (or go to a colder plug). (just don't forget to back it off if you have to dump pump gas in for any reason)

Most important is the specific gravity difference (I do not recall the comaprison). If the AVgas has a lower specific gravity than the pump gas - less fuel will make it in from the pressure applied by the air bleeds. At which point you may not WANT the extra advance. I would do a plug check run as is with avgas, make sure you ain't too lean and go with the av if all looks good- that is as long as you got a proper niner to charge the sale to - big fine without it now a days.
 

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My shop is at the airport in my hanger and I pretty much use avegas in my cars (100 octain low led). Even use it in my model A. The cars have seemed to really like it , and the real reason I use it is because it does not break down or does not gum up the carbs or fuel lines even if it sits for 2 or 3 years. It is 100 octain and I was wondering about the engine set up, as in timeing. Also was questioning the led as there is a little lead still in avegas. Maby like foueling plugs, or a littli more carbon build up in the combustion chamber. In the aiplane I have to lean aggressively during taxie and then in cruse we run very lean, in fact quite a bit lean of peak EGT. I was thinking it would tend to foul plugs a little more since there os no way to lean auto engines without changeing jets. Any thoughts out there. Sharkey 5557.
Don't get caught using Avgas in your car....using any leaded fuel on the highway could get you a $10,000 fine.

"From 1 January 1996, the Clean Air Act banned the sale of leaded fuel for use in on-road vehicles. Possession and use of leaded gasoline in a regular on-road vehicle now carries a maximum $10,000 fine in the US. However, fuel containing lead may continue to be sold for off-road uses, including aircraft, racing cars, farm equipment, and marine engines.[16] Similar bans in other countries have resulted in lowering levels of lead in people's bloodstreams.[17][18]"
 

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Don't get caught using Avgas in your car....using any leaded fuel on the highway could get you a $10,000 fine.

"From 1 January 1996, the Clean Air Act banned the sale of leaded fuel for use in on-road vehicles. Possession and use of leaded gasoline in a regular on-road vehicle now carries a maximum $10,000 fine in the US. However, fuel containing lead may continue to be sold for off-road uses, including aircraft, racing cars, farm equipment, and marine engines.[16] Similar bans in other countries have resulted in lowering levels of lead in people's bloodstreams.[17][18]"
Key word Highway - on the trailor, in the parking lot or at the race track. Lots of winks room there ... but as you typed I was hunting down the code myself...

lol

Just don't try to use the farm use thing. Your wife may not appreciate the imnplications. I know mine did not.
 

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Just stumbled across this. Octane is just a resitance to detonation - so higher octane does not require more lean or advance - it merely allows it. We used to run avgas in the race cars and the only diff when we went to a track that had a pump gas rule was to take about 4 degrees off the timing all the way through the curve. Yes we SHOULD have raised the jets one or two - but chose not to - saw no issues.
So I would think the reverse is that if you are right at the lean edge with pump gas going to av should allow a couple degrees of timing to cure a fouling issue IF one arises (or go to a colder plug). (just don't forget to back it off if you have to dump pump gas in for any reason)
Higher otane fuel actually burns slower than lower octane fuel. That's what causes the resistance to detonation at higher compression ratios where the fuel would want to burn too fast. So ichangine the octane of the fuel in a given engine could actually drive a timing change to optimize combustion. I would think you would want to increase the timing advance slightly to account for the slower burning fuel.
 

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Higher otane fuel actually burns slower than lower octane fuel. That's what causes the resistance to detonation at higher compression ratios where the fuel would want to burn too fast. So ichangine the octane of the fuel in a given engine could actually drive a timing change to optimize combustion. I would think you would want to increase the timing advance slightly to account for the slower burning fuel.
Yea - but on a street machine just how fine is that optimun line? But as I always have gone with as much adv as possible anyway - I agree I would want to adv. But would someone else who does not want to retune with every different tank - such as loaded with av and driving to show 100 miles away and having to top off at a foreign pump. SO maybe eve a split the diff tune.

WRANING - ADVICE IS NOT legal for on highway use
 

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Discussion Starter · #7 ·
Interesting posts. Really the only reason I use it is because of the stability issue, Maby its not a good idea. Besides its a couple bucks + per gallon more. Avegas is not going to be available much longer anyway. Thanks for the come backs. Sharkey 5557.
 
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