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Aviation Gas

Discussion in 'The Hokey Ass Message Board' started by Russ Gaylord Fontana, Sep 23, 2008.

  1. badlefihand
    Joined: Apr 20, 2007
    Posts: 318


    Will burn valves if you burn it straight,but not right now. Mix it with reg gas ,needs a little lube in there.I run it half and half for a number of years .You wont have any ping thats for sure.
  2. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    Old wive's tale.
  3. smcquaggjr
    Joined: Jun 19, 2009
    Posts: 28

    from Georgia

    Boy that brings back memories, except we used the 115 supplemented with tolulene and a richer mixture. When they went 100LL, we stopped using it as we no longer felt it was an advantage.
  4. Truckedup
    Joined: Jul 25, 2006
    Posts: 3,975


    Low octane fuel is traditional :D Reading vintage engine tuning info from the late 40's and early 50's it seems 80-90 octane pump gas was all you could get.So mixing gas with stuff like acetone ,methanol and so on was used as an octane boost when needed.
  5. D-fens
    Joined: Aug 30, 2007
    Posts: 369

    from Huntsville

    My old man had a Hemi Satellite that he bought from some street racer dude. The motor was supposed to be somewhere up around 13 or 14:1 compression, maybe not but you could tell the shit was up there. Probably the harshest motor I've ever heard. Sounded like a damn funny car at idle.

    Dad had to run the car on 115/145 because there was a small rural airport nearby that was a hell of a lot closer to the house than anyplace that sold race gas. I think they mixed the avgas with a little bit of 2-stroke oil to help save the valves (this was late 70's - early 80's).

    My uncle had to do a lot of tuning and tweaking to make the motor happy on avgas, nit really sure what he did but they spent a lot of weekends working on it. Uncle had a cropdusting service, so it wasn't a problem for him to buy drums of avgas.
  6. spiderdeville
    Joined: Jun 30, 2007
    Posts: 1,134

    from BOGOTA,NJ

    the higher the octane , the slower it burns
    racing gas will slow you down if it is used in a low compression stocker
    I used to mix 20% Xylene with sunoco ultra to make cheap fuel to pull my race car in and out of the shop . xylene used to be an easily available solvent and an aromatic
  7. Chally
    Joined: Dec 18, 2006
    Posts: 155


    The chart below shows the octane requirements for the compression of your engine...


    Not enought octane can cause detonation problems. Too much does not hurt anything but is really just a waste of your money. My octane booster is real lead additive and not a lead subsitute. Fill with pump gas and add the required amount of lead additive to make your own leaded gas at the octane number that you want...


    ...and drop ship anywhere in the contiguous 48 states UPS ground...
    Last edited: Aug 18, 2011
  8. bbc 1957 gasser
    Joined: Aug 3, 2007
    Posts: 685

    bbc 1957 gasser

    5 gal of 94 sunoco to 1 gal e-85 =106 octane..
  9. with.disdain
    Joined: Apr 10, 2009
    Posts: 29


    I do know that avgas octane ratings are measured differently than auto fuel. Most importantly, the octane number is given for a lean mixture (cruise conditions). 100LL has a rich mixture octane rating of around 130. I'm not certain of the test altitude.

  10. stlouisgasser
    Joined: Sep 4, 2005
    Posts: 670


    The fellow who assembled a high compression race engine for me about 20 years just got really upset and chewed me out when he thought I was using Av-Gas in a motor he put together for me. He explained the while the octane rating is slightly higher than pump gas, it's major claim-to-fame was the fact that it is ultra-filtered, more than anything. It makes sense, after all would you want you engine to stumble at 15,000 feet because of a clogged fuel filter? Not me!
  11. 29NashRod
    Joined: Jan 18, 2009
    Posts: 66

    from Portland

    You can't pump avgas into any vehicle that's not an airplane. You can pump it into portable containers, though.

  12. Pete1
    Joined: Aug 23, 2004
    Posts: 1,919

    from Wa.

    Av gas is no different than any exotic racing fuel. You have to understand what it is and tune the engine for it. I have been running it in racing applications since the early 50's.
    Back then we could get the 115/145 purple stuff and ran it in engines up to 13-1 compression. On the dyno in an engine setup for it,there would only be about 5% less power than alcohol. We even ran it in an Offy with 14-1 compression. When you added
    20% nitropropane or 10% picric acid things really happened and I don't mean blowup.
    Av gas needs to be run richer and the spark needs to be advanced. I have found one range
    colder plugs are needed also.
    I have a small block Chev crate engine in my current vintage circle track roadster and have been running av gas in it for 4 years. The 100LL won't stand as much compression as the old purple stuff but we don't race for money any more.
    Several local airports here have no problems with us pumping into barrels or cans.
    I have several friends that run it in their Friday night drive-in racers.
  13. Mmmm, I love the smell of Av Gas in the morning !!

    Ran it for yeasrs in my street/strip Mopar, with bigger jets and slightly advanced timing. I was taught back then (80s) that the specific gravity of the fuel was different to gasoline and so needed richer jetting.

    Here its illegal now to runit in street cars - back then Id drive my Charger to the local Airport and theyd pump it into my car. Then this changed for safety reasons and they would only fill it into jerry cans etc.

    Now, its illegal thanx to the tree huggers, EPA and the scare mongerer wanker, carbon footprint, global warming control freaks.

    Its was fun while it lasted.....some guys still use it but they have connections to get it.

  14. petritl
    Joined: Jul 31, 2006
    Posts: 950

    from Marion, TX

    My dad turned me on to running AV gas in anything engine powered that is used seasonal or occasional use. The fuel has a usable life measured in years instead of months

    Between my dad and I we have been running AV gas in our snow blower, emergency genset, power washers for years with no problems.
  15. The Shocker
    Joined: Dec 30, 2004
    Posts: 3,538

    The Shocker

    I raced my 10 to 1 Dodge a month ago on some 100 Exxon race gas ,it ran well .I drained it out when i got home and raced it Friday on some plain pump 93 (in hotter worse conditions).The only difference it made was $5.99 versus $2.50 a gallon (the performane et wise was too close to call).I know people that have that mentallity of "if your racing ,you need race gas period ".Good luck just my .02 .I think its like was said by many earlier ,the fuel octane rating should fit your compression ratio...
  16. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    I think it's a good idea to "over octane" when you a margin against detonation - especially when tinkering with blown applications.

    When I was a kid, I used to occasionally run 50/50 avgas in my old Mustang, I couldn't really tell performance difference (I did like the smell!), but the engine ran ever so slightlly cooler - not much, but definitely noticeable. Years later, someone explained it was the 'slower burn' of higher octane...
  17. richardlw
    Joined: Jun 26, 2009
    Posts: 21


    Since regular gas here runs between 74 and 80 octane and my 88 BMW 325ic requires something like 92, I run a mixture of 25% ave gas with the regular.
    It is what is run in all the race cars here, and with my membership I'm allowed to buy it, so I take a drum or a couple of 5 gallon containers.

    With straight regular the car almost doesn't run. I used 50% for a while, but when there was a shortage I started skimping, and eventually found that 25-28% ran the best mileage and the best acceleration.

    Every once in a while one of the local stations gets a load of 90 octane and I try it, but get about 10% less mileage and hard starting with the premium.
  18. ken1939
    Joined: Jul 5, 2008
    Posts: 1,558


    av gas is closer to kerosene
  19. garcoal
    Joined: Nov 15, 2006
    Posts: 277


    av gas and cam 2 are 2 different gases .av gas is blended for low rpm and high altitude use planes fly at a constant rpm usually high load , cars run at higher rpm 2 differnt blends hence the difference in cost they smell the same but they are way different,
  20. Darwin
    Joined: Oct 14, 2002
    Posts: 505


    Aviation fuel has a significantly higher vapor pressure rating than conventional gasoline. At altitude this reduces the tendency for problems related to over vaporization of the fuel. At low levels this higher pressure is handled by specific aviation carburetor/fuel injection designs which means mods are usually in order on ground bound vehicles. Kerosene based aviation turbine fuels have higher vapor pressures yet since they operate at much higher altitudes than piston engines. In fact some jet fuels, JP-7 for instance which is used in such as the Blackbird spy plane, have such low vaporization tendencies that at sea level they essentially produce no vapor at all. Rumor is that you can toss a match into a pool of JP-7 without effect although obviously that's not a super-smart thing to do. Basically jet fuel is simply Diesel fuel with a different additive package and its higher BTU content means that less fuel needs to be carried by hungry turbine engines for a given range. Conventional gasoline could probably be made with vapor pressures adequate for high altitude use but it would still have less energy content per pound than kerosene.

    Piston aircraft engines in general operate at quite high cylinder pressures and at continuous high throttle settings which makes a higher octane rating desirable. The main reason for this is that aero engines develop max power at relative low rpm ranges to match the power delivery characteristics of propellors which can only turn so fast before serious tip-speed problems occur. For average sized two bladed props this means rpms of 2500-3000 so an engine must make its max power at far lower revs than an equivalently sized car engine. Consequently you get very high cylinder pressures and the need for higher octane fuel to combat detonation.

    These engines also have to be lightweight and very rugged at the same time so they are very expensive with new powerplants costing well over 20K. Overhaul periods are also lengthy with 2000 hours between major overhauls being common. That's roughly equivalent to 200,000 miles of travel. Not bad at all and even at that many aircraft engines have little wear on them even when the mandated overhaul period is over. Consider how long the average SBC would run if it spent nearly all of its running time developing 75% of its rated power. This is also why many single engine aircraft seem to get relatively poor mileage--they are running nearly flat out for hours on end. A Cessna 172 typically cruises at about 120-130mph. What kind of mileage would you get in your ride at that speed?
  21. Rusty Kustoms
    Joined: Feb 5, 2006
    Posts: 238

    Rusty Kustoms

    WRONG, jet fuel is closer to kerosene. Av gas is totally different than pump gas or racing gas. This is a never ending discussion, you will always have the people who have run it and "claim" to get more performance, just like those who think that running their '96 honda on premium gives them more performance. The facts are that you should use a fuel and octane rating that suits your engine, Av gas has its uses but a street or race car is not one of them. More octane does nothing for and engine that doesn't have the compression to warrant it. Also, anyone who is currently buying av gas without a tail (aircraft registration) number WILL get the seller in major trouble some day, it is only a matter of time before the FAA finds out.
  22. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    Jet-A, Jet-B, F-34, JP-4, JP-5, JP-8 are more similar to kerosene (some are actually kerosene based), but 80/87, 100LL, 100/110, 115/145 are not and are more like automotive gasoline...

    Different? Yes. Way different? No. Beyond the additive packages that reduce vapor pressure issues, there's little difference in a comparable octane racing gas with regards to how it burns in the engine.

    Not entirely true. There are situations where aviation engines are used outside of aircraft (ie - no tail number) and AVGAS is allowed to be sold to support this - airboats are just one example.
  23. gasser
    Joined: Mar 3, 2001
    Posts: 149


    Mike just run super unleaded and get some Power Pour octane additive from Webster Racing if you are worried. 10:1 is not enough to start buying race or AV gas IMHO.

    Also remember that the Octane ratings here in the UK are slightly different from those in the USA / Canada. I think it goes something like our ours is RON (research octane number)and the American one is an average between RON and MON (motor octane number)There is maybe a couple of points difference I think, it's been a while since I raced.

    Seriously wouldn't worry about it for 10:1 try the power pour it works, just don't get it on your paint.
  24. I use 100 LL in my 406 SBC with Weber carbs. Absolutely love it because it will not varnish up the carbs. It starts up after sitting for 2 months with a flick of the start. I have 4 - 48 IDF carbs. basically 1 barrel per cylinder. I have been told to add "marvel mystry oil" to the gas to help lubricate the internals of the carbs. 100 LL AvGas is a very dry fuel and have heard it will dry out cork type gaskets over time.

    1. I use it because it doesn"t get stale.
    2. smells great .
    3. Webers respond well to it.

  25. Any new comments on the ever-evolving avgas situation or new experiences?

    I've got a big ol' Chrysler crossram car with a 26 gallon tank. I just filled a 5 gallon can with avgas 100LL at my local small airport and was going to run that 5 with 20 gallons of 93 octane Shell pump gas which today is 10% ethanol. Yes, I used a registration number of one of the planes sitting at the field so the pump would work. It was $4.66 per gallon.

    I personally don't see how I can hurt anything. While the 100LL is probably around 102-104 octane, my mixture should be around 95 octane with a little lead and I have a 10.5:1 compression ratio.

    There is NO race gas station within 75 miles of me or I'd be using it.

    Interested in all y'all's comments.........
  26. RichFox
    Joined: Dec 3, 2006
    Posts: 10,003


    I have run Av gas in my roadster and in the 150. Never hurt either one of them. Roadster was a little faster with ERC 110 than with LL100 on back to back test.
  27. flatoutflyin
    Joined: Jun 16, 2010
    Posts: 385


    In the mid '80's, I ran straight 100LL in an old '76 Harley shovelhead. Someone had stroked it a bit, it had a solid lifter cam, and it detonated on pump gas unless you really backed off on the timing. Our local airport sold 100LL for $2.00 or $3.00 a gallon, and would let you pump it into anything. It seemed to work fine, and the bike had a deep, smooth, mellow sound, and pulled very well. Maybe the fact that it was a long stroke, low RPM application suited the gas. The only problem was poor mileage with 3 gallon fatbobs.
  28. Flatheadguy
    Joined: Dec 2, 2008
    Posts: 2,037


    "av gas is closer to kerosene".....posted above.
    I do not want to muddy the waters with more technical information, but......a few words of caution. Do NOT run a heavy mix of or pure 100LL in any car that has a catalytic converter. After a few thousand miles, you'll find out why.
    Also, I read (above) that you can only pump aviation fuel into aircraft, not cars. There is NO FAA issued advisory circular, or other FAA document, that mentions it. That can only be your local airport manager or FBO policy.
    Some of these comments are very accurate and informative.
    Quite a few are horse pokey.
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  30. davidwilson
    Joined: Oct 8, 2008
    Posts: 595

    from Tennessee

    plugs read funny on that stuff

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