AV-GAS or how ever you spell it

[mybeatupford]

today a neighbor came by and gave my friend 5 gallons of this stuff, his dad said he used to run it into his 56 chev gasser, but what the hell is so great about it? does it have a higher octane or what?

[Hot Rod To Hell]

It's High octane, but it's set up for High altitude... It won't work as good as regular old "Race Gas" in a car anywhere near sea level!

[mortecai]

When I was in the service I had a 57 chev convertible that ran like hell on AV gas I stold from the base. Only it burned the valves up in no time flat.

[55olds88]

I was using as a lead booster over here with pump unleaded (as we can't buy leaded any more) from memory its higher octane then race gas and more lead too....mmmm lead http://www.jalopyjournal.com/ubbthreads/images/graemlins/smile.gif

[mybeatupford]

i see we put some of it into my friends peek-up and he tried to say it had more power but i didn't think so but my lil straight 6 peek up did a better burn out than his v-8 did on av-gas http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif hehe

[FWilliams]

[ QUOTE ]
It's High octane, but it's set up for High altitude... It won't work as good as regular old "Race Gas" in a car anywhere near sea level!

[/ QUOTE ]


excuse my ignorance, but how do you "set up" a fuel for high altitude?

[Hot Rod To Hell]

I don't remember all of the details, because I discussed it with my HS CHemistry teacher, but something about the specific gravity and the oxygen content being different to account for the different air density at altitude.

[mybeatupford]

ehhh CHemistry that was the first class of the day for me, lets just say i never made it because of my hangovers,so i have no ideal how to do that stuff he's talkin about

[OldCarPilot]

Damn you are getting to complicated with this. Avgas is just Aviation Gas. Its 100LL (Low Lead). It is like 110 octain fuel in cars. Airplanes run at a much higher compression than cars so need a higher octain fuel. Hence 100LL. Has nothing to do with the altitude that airplanes run.
It runs fine in older cars, especially the ones that were built to run regular gas.

[FWilliams]

http://www.jalopyjournal.com/ubbthreads/images/graemlins/smirk.gif

[dehudso]

[ QUOTE ]
Damn you are getting to complicated with this. Avgas is just Aviation Gas. Its 100LL (Low Lead). It is like 110 octain fuel in cars. Airplanes run at a much higher compression than cars so need a higher octain fuel. Hence 100LL. Has nothing to do with the altitude that airplanes run.
It runs fine in older cars, especially the ones that were built to run regular gas.

[/ QUOTE ]

Compression ratio, or cranking compression?
Not trying to be a jerk.
Just trying to learn, as the Cessna I fly has a 8.5:1 compression ratio.

[OldCarPilot]

I don't know on that one. But your cessna is a big(ish)motor running a low HP at a low RPM. I think the 180 horse engine is a 360 cu in engine. It makes full power at about 3200 or so? Haven't flown one in a while so I don't remember the exact #. The airplane engine hasn't changed in a LONG time so still uses lead as a lubricant.
The lower HP engines don't NEED the high octain fuel. If you look into it you'll see that there are conversions for those so you can run car gas in them.
BUT the larger engines NEED the hight octain fuel. Look at the bonanza (sp?) or something with a higher performance engine that doesn't have a turbo. They make more power from compression.
I've done a bunch with round (radial) engines where if you don't run at LEAST 100LL than the engine will kill it self.

[thirtytwo]

detination can also accur from timing... not just compession ratio...

[Scotch]

Come on guys...this one's easy.

There's less oxygen at altitude, so higher octane makes teh most of what's there.

AvGas isn't recommended for high rpm use because it's brewed to burn at a slow rate.

What RPM do you cruise at in that Cessna? Pretty low compared to a race car, isn't it? And, I assume you set the throttles at one speed and it's pretty much constant.

AvGas is a good fuel additive, but I wouldn't want to run it "straight" in a high rpm race motor.

Mix it 50/50 and a high compression mill will love you. You'll be able to give it more timing.

Lots of info on the 'Net about this...

Scotch~!

[29EHV8]

We run Av gas in our stock car and sportsman car.
We mix it 5 gallons av gas,5 gallons premium gasoline and 1 gallon of tolulene.It runs bitchin.The tolulene makes it cold.Makes great horsepower.Never ever have had a problem.
The mill is a 406 stroker with 13 to 1 compression ratio.....Shiny

[Kev Nemo]

Im my days as a line service tech at Raytheon, I ran avgas in my 3.1 v6 and it screamed. Basically not recommended for cars with computers because it burns out oxy sensors. 50/50 is defintely the best way to go. I loved running this at the track-made me feel all mad scientest and what not http://www.jalopyjournal.com/ubbthreads/images/graemlins/cool.gif

[zman]

[ QUOTE ]
Damn you are getting to complicated with this. Avgas is just Aviation Gas. Its 100LL (Low Lead). It is like 110 octain fuel in cars. Airplanes run at a much higher compression than cars so need a higher octain fuel. Hence 100LL. Has nothing to do with the altitude that airplanes run.
It runs fine in older cars, especially the ones that were built to run regular gas.

[/ QUOTE ]

It's not just high octane, the burn rate is different from that normally used in automotive gasolines. It is brewed to have a high flashpoint that would not explode in the aircraft's tanks, but this also makes the fuel hard to ignite within the engines themselves. It is so hard to ignite, particularly at the low pressures encountered at high altitudes, they use a chemical called tri-ethyl borane (TEB) To counter this, which burns at a high temperature when it is oxidized (combined with air).

It's not just higher compression..... a good source of info is http://www.cs.uu.nl/wais/html/na-dir/autos/gasoline-faq/.html
&
http://members.shaw.ca/costall/1000Q/answers-gasoline.htm

[Hot Rod To Hell]

Hmmm. Maybe my Chem teacher wasn't as wrong as some people think! http://www.jalopyjournal.com/ubbthreads/images/graemlins/smirk.gif

[Roothawg]

It's only 100 octane.
They don't sell the good stuff anymore. 100 lowlead is the standard.

The high altitude stuff is bs.
There are guys getting stc's all day long to run automotive fuel in their airplanes.

[Rand Man]

Don't use high octane, AV-gas, or any special fuel unless you have problems with what you get at the pump.

[zman]

[ QUOTE ]

The high altitude stuff is bs.
There are guys getting stc's all day long to run automotive fuel in their airplanes.

[/ QUOTE ]

Gonna have to call you on this one there Root. There is a difference. Now if those guys aren't going very high, that's their deal, or if they have a low compression engien maybe. But the way the 100LL is formulated as to the burn rate and everyhting, there is a difference. Maybe you shouldn't have napped in those Chem classes http://www.jalopyjournal.com/ubbthreads/images/graemlins/wink.gif

[dehudso]

Yeah the engine makes 180hp at 2700rpm, with the 8.5:1 ratio. I was under the misunderstanding that it was because of the load these engines see sometomes.

[stealthcruiser]

on the altitude question,
i seem to remember something about av gas having a different"reid vapor pressure",or some other such horse shit as that,to compensate for it's use at altitude.
it was prolly' some over engineering on someones part.
as the Root Meister said,lots of planes running fine on auto gas.

[Flat Ernie]

[ QUOTE ]
There are guys getting stc's all day long to run automotive fuel in their airplanes.

--------------------------------------------------------------------------------

Gonna have to call you on this one there Root. There is a difference. Now if those guys aren't going very high, that's their deal, or if they have a low compression engien maybe.

[/ QUOTE ]

There are many, many STC (supplemental type certificates) for various aircraft & engines to run MOGAS (automotive gasoline). It has nothing to do with altitude...directly. These are typically low performance engines in low performance planes. They don't fly high because they're inefficient up high - not because they don't want to.

Many of the old radials used the Red 80/87, but these are typically the lower compression radials in transport versions. An R-1830 isn't always the same - the 'dash' numbers of the engine could indicate a different induction setup, exhaust, timing, compression, etc. The engines required different fuels based on application & dash number.
An R-1830 in a C-47 (DC-3) might require 80/87 (Red)
An R-1830 in something else might require 110/115 (Green)
An R-1830 in a high-performance application (none I'm aware of) might require 130/145 (Purple)

These days, it's extremely difficult to find anything other than 100LL (Blue).

Even though it's labled "Low Lead", it has about 8 times the lead of old Leaded Regular (pre 1980). If you are silly enough to run it in a car with an oxygen sensor or catalytic converter, it will destroy them quickly.

Everyone always says to run the lowest octane fuel you can get away with. However, higher octane, while not producing any more power in the same engine, will usually run cooler...

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