Air Plane Fuel

[jlwelding]

My son races dirt track and we were talking the other day about the cost of race fuel. Any way his motor is not real high in compression somewhere about 160 psi. I made the comment that we used to run airplane fuel in our hot rods back in the day we just went to the airport and top off with 110 octane.
You get about 50/50 from people who say no you cant run aircraft fuel it will hurt your eng. and you here people say I been running it for years with no problem.
What are your thoughts?
Thanks
 

[Mopar1973Man]

The higher octane is going to work better for high compression engines with heavy timing advancement. Higher the octane the slower the fuel burns more like diesel fuel and also contains more BTU's. Like I've got a Goldwing under my desk with excessively high compression pressure (the heads where milled excessively) and the only way to keep it from overheating is using double shot of 104 Octane boost.

[jlwelding]

The higher octane is going to work better for high compression engines with heavy timing advancement. Higher the octane the slower the fuel burns more like diesel fuel and also contains more BTU's. Like I've got a Goldwing under my desk with excessively high compression pressure (the heads where milled excessively) and the only way to keep it from overheating is using double shot of 104 Octane boost.

Ok but is small air craft fuel still the same as back in the 70's with lead or have they removed it from everything. Because there are still a lot of older planes out there from the sixtys that needed the leaded fuel. The lead kept the valves from beating the heck out of the seats and piston damage.

Race fuel is 10.00 gal and air craft is 4.50. big diff. He's not really that high in compression to require 115 octane which is race fuel. He also cant run additive due to IMCA rules. Rules say pump gas, but nothing about ari craft fuel, which is pump gas. They test for additive.

thanks

[MnTom]

You can still get leaded gas at most airports. The EPA is working on that 'problem' but it sounds like there are too many older piston engines to eliminate all of it.

[mulcher812]

I know the aircraft fuel helps the engine run a lot cooler. I have a 14' sand rail that as a 98 SOHC subaru engine in it and all i run in it is aircraft fuel to help keep the heat down. It feels like its running on some really good race fuel though. I can pull a wheelie the distance of a football field.

[IBMobile]

100LL is the only aviation gas to be found at most airports. The LL stands for low lead and was introduced in the mid 70s so it has been around for a while. The lead is used as a lubricant in gas somewhat like the sulfur is in diesel fuel.  In the 80s when leaded fuel for cars was discontinued pre 1975 engines were having valve problems. The valves would wear into the valve seats or as we called it "valve rescission". The fix for this was a valve job and replace the seats with harden ones.

The ave gas around here is as low as $5.37/gal at Borrego Springs, CA to $8.20/gal at San Diego International. They won't sell it in a can, it has to go in the wing of the plane. It has to due with the road tax that hasn't been paid on it.  

[Kotta390]

I have done the research here cause I too have a racetruck (avatar) and I have been running 110octane fuel for awhile. I only need around 98-100octane but that's the lowest I can get in leaded conditions. It's about $2.00/gal more if I go with 100 unleaded and my truck doesn't have cats or 02 sensors so the leaded is fine.110octane is a

Slower burn than 100LL and also has a slightly cooler charge from atomization. It is more expensive and has slightly more lead. 100LL is great but is not as fuel efficient as 110octane in the fact that it actually has less BTUs per gallon than 110 because it is not as dense for use at much higher altitudes. You can get the same basic results between both fuels but you will need to run the 100LL a but richer to achieve the same goal. Also it is usually about $3-4/gal cheaper than 110 and sometimes EGTs are slightly cooler with 100LL. All in all it depends on what you want to run. I have ran both and the 110 actually runs just a hair better in my race truck than 100LL but I'm only talking about .05-.07 better on average between the two fuels on the same day.

[ISX]

My dad researched this with our dirt bikes and he said if the octane is a lot higher than the compression can allow then a lot of fuel doesn't burn and it washes the rings out and ruins compression.  One kid I ride with runs it and sure enough you can just set your boot on the kick start and it just goes all the way down.  My dads bike I can put all my weight on and it barely goes down.  I just jump on his going down a hill rather than trying to kick it.  Maybe that kid was just coincidence but it makes sense to me