Ravenous T\A

iTrader: (12)

Is there a difference in racing gas and airplane fuel. I thought I read somewhere that its not good to run in a car. If its ok I'd run it in my 70 GTX cause the compression is way to high! I was wondering since I live close to a small airport, that be way better then driving to the track to get it.

Scott99Z

I think the only reason you would want to shy away in a new car is that 100LL is not unleaded (LL - low lead, but leaded none the less).

Ravenous T\A

iTrader: (12)

So in a 70 Gtx with forged pistons runnin well over 11:1 maybe close to 12:1, airplane fuel should be fine.

x phantom x

iTrader: (14)

He's got it. Airplane gas is leaded, while reg car gas is not. I know it is not good to use in a newer car as it will wreak havoc on your sensors ... however I am not sure if it would be okay to use it for your exact application.

pimpmaro

I wouldn't do it. I used to be a lineman at an airport. First, that fuel may be low lead, but it's still got quite a bit of lead in it. Secondly, it's illegal for the airport to sell that fuel to you. All in all, it's ok to put in your car every now and again but you don't want to run it on a normal basis.

Ravenous T\A

iTrader: (12)

I was thinkin of running a half and half mixture. Either with racing gas or airplane fuel. 50/50 with reg gas and race gas thing.

trackbird

iTrader: (4)

Do not run AV Gas in a car with oxygen sensors and convertors (cats, not transmission). It will ruin both! I worked for an avionics company that also had a fueling station at the airport.

Also, AV gas octane is measured differently than car gas. It is measured for knock resistance at cooler temperatures (it's colder at 8,000 feet) and as I remember, they only use the Motor Octane Number (MON) and don't do an average of the Research Octane Number (RON) like car gas does (meaning the octane rating is not comparable to a car rating...they can be very different). Also, Av Gas is designed to vaporize at low pressure and temp, so it will really vaporize at warmer temps (on some cars, carbed of course, it will vapor lock real easy). And, if all this isn't enough, it burns "slow". Meaning that some reasearch indicated that at 7000 RPM the piston could be pulled down the bore faster than the "flame front" is traveling, meaning that you are burning fuel, but the pressure in the cylinder moves slower than the piston and therefore makes "no" horsepower. Aircraft engines typically don't exceed 3500 rpm, if that.

With all that said, I have a friend who is a pilot and uses it in a vintage race car. It runs ok. But, one day we ran out of AvGas and had to use race gas. This actually required rejetting the carb (for the difference in density) and the car ran much, much better after the switch. We basically proved that it is not a "great" auto fuel with that accidental experiment.

Just my thoughts.


Besides, why do you want more octane? The LS1 is an all aluminum, EFI motor that will run very well up to 11.0:1 or higher. If you are mostly stock and have stock compression, there is not much need for extra octane. If you just want to run it because it "smells cool", then prepare to start replacing an expensive batch of oxygen sensors and your Cats.....

My thoughts.

Ravenous T\A

iTrader: (12)

This is for a 1970 Plymouth GTX with a really built motor that I built but when I did I didnt measure the Piston to deck height with a set of 10.5:1 pistons and my machinist had also decked my block without telling me and also the company I got the heads from had shaved them to insure straightness, so all those combined turn it into a High compression motor. Learn something new everytime, I was wondering if runnin it 50/50 mix would help the burn issue.

L-EATER

iTrader: (2)

I run avgas all the time in my 494 cubic inch 1972 Buick Skylark at 12.2 compression with no problems. I have ran race gas with no performance difference noticed either way. I do run straight 116 race gas when spraying but when off the juice I use the avgas. This discussion is like the old "which oil is better" everybody has an opinion and an experience to share. I suggest trying it and if it works for you cool if not run some race gas.

trackbird

iTrader: (4)

Cool. It runs ok in the 1971 Mach 1 road race car, but the car runs better on race fuel. The density is different enough to require rejetting if you change the fuel mix ratio. It may vapor lock on a hot start...and not start. And it is illegal to put it in your car (you have to convince the airport you fly....and use fuel jugs). Other than that, it will probably do what you need.

Kevin

Ravenous T\A

iTrader: (12)

cool thanx for the info guys. Now I just have to get my LS1 to out run my old toy. So far it smokes my a$$ at half throttle. Hope my TR224 helps that out. (end of this month, thank god)

x phantom x

iTrader: (14)

Everything he said is right on. Airplane engines usually redline around 2-3,000 rpms ... not high at all.

Cal

iTrader: (1)

Good thread . . . interesting information.

Pro Stock John

iTrader: (34)

Best avgas vs racegas comments I have ever seen, I learned quite a bit.

Texas_WS6

iTrader: (9)

If the GTX heads still have the old style stock seats in them I would think it would be a good idea to be running leaded fuel in the car. I had a 76 455 TA that I put some ram air three 400 heads on. Plus it was built for drag racing. We had 12.5 to 1 compression. Pump fuel will not run in these cars. The new cars have knoch sensors to pull timing out when it starts to detonate. The old GTX has nothing like that in it. My car preformed very well with the AV Gas. I tried a 50/50 mix with 92 octane pump fuel but it did not work. 100% Av Gas was the answer. I did also try to use racing fuel. I never saw any difference in the plugs or the time slip to make me think it ran better with the race fuel. It is not illegale for them to sell you the AV Gas. You do not pay road taxes on it and because of that and the fact it does have lead in it, it is illegal for you to run it on the street. It is not illegal for you to use it for off-road use. But don't worry about that stuff though, unless you live someplace like California. I would most definatly try it out. See what you think of it. I know it will not hurt the GTX engine as long as it does not Detinate.

Thats my two cents.

ChrisB

Yep, trakbird prety much covered it - the avgas is formulated to run at different operating conditions than "normal" gas. You could possibly tune your car to work better with it, but the flame speed is something you can't tune around that much. This could actually be a good thing in a high boost FI car, but it may not be also - it is highly dependant on your combination.

Yes you can run it if you aren't worried about the lead content, but it is not going to be a "high octane replacement fuel" like 104, etc. - it will change the way the combustion process is working.

pimpmaro

Trackbird is all over it. He covered every aspect of why you don't run avgas in a car. Great thread.