QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

[Clem Z.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

The heating value of the fuel is net of the energy required to break the original bonds of the specfic molecule.

From Taylor (rather than Obert) the lower heating value of benzene is 17,270 BTU/lb, iso-octane is 19,080 and gasoline is listed at 18,900.

Duke

why did the auto union race cars back pre WW II use benzine ? i have a book somewhere that had their fuel formulas

[Duke W.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

Benzene is the German word for gasoline in addition to being the English word for a specific aromatic molecule - C6H6. Though benzene has a relatively low heating value, it has a very high octane rating - about 110 MON - and a moderate boiling point - 177F, so it's a very good blending agent for high octane.

Toluene (C7H8) and Xylene (C8H10) are also members of the aromatic family with similar heating values and high octane - 104 to 105 MON - and boiling points of 231 and 285F, respecitively, so they are good for lowering vapor pressure.

In a pinch on the road if one has a detonation problem you can buy either of the above at hardware stores and add it to your fuel tank.

IIRC the pre-WW II GP cars used an exotic fuel blend of mostly methanol and included some acetone, which is a very powerful organic solvent.

Duke

[Clem Z.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

Benzene is the German word for gasoline in addition to being the English word for a specific aromatic molecule. Though benzene has a relatively low heating value, it has a high octane rating. IIRC the pre-WW II Formula 1 cars used an exotic fuel blend that even included some acetone, which is a very powerful organic solvent.

Duke

i used some of the mixes in my 2 stroke go kart race engines.

[Michael W.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

I am using a fairly modified 350. Stock looking from the outside, it has been built to produce 400hp and does, at least on the engine dyno. I occasionally get what I believe is spark knock under rapid heavy acceleration. I was considering using an avgas/mogas blend to see if that would help. I rarely hot-rod the engine, but it would be interesting to me to see if the avgas made a difference here.

If your engine is truly experiencing spark knock under the stated conditions, the problem might well be with the ignition advance curve and not with fuel octane levels.

As seen above some believe that Avgas is a sort of miracle fluid that does everything but cure the common cold, but except as a last gasp alternative, there's much better and more logical avenues to explore.

Becoming dependant on a fuel that's expensive, difficult to get and illegal to use on the street makes little sense to me.

[Duke W.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

Most OE engines that experience detonation on modern gasoline can usually be tamed by reducing spark advance a few degrees - usually in the form of decreasing initial timing.

But if you have to reduce initial timing to the point that total WOT advance is more than about 6 degrees less than optimum, then you are loosing a fair amount of torque/power, increasing fuel consumption, and possibly increasing operating temperatures.

In these cases, blending in higher octane fuel is something to consider.

I think most vintage Corvette owners that experience detonation have modified engines - whether they know it or not - but some big blocks that got out of Tonawanda with deck clearances on the low end of the range can also experience detonation.

Duke

[Domenic T.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

The only way I can keep the pinging away when I have the correct Innition timing is a 50/50 blend of avgas.
I have used it since 1975 with NO problems and have found that the engines that I have with more than 9to1 compression will ping when timed to manufactures specs.

DOM

[Ciro A.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

Hey Brad,

I'm not going to have to get a siphon out on the next layover if we ever fly together!
Ciro

[Brad H.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

Fortunately,
My 69 lives in my hanger at the airport, so avgas is pretty easy to get...at least for now.
Thanks everyone for the discussion, it has been very helpful!
Brad

[Domenic T.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

Brad,
So do my cars and the high wing planes you park under help getting the fuel to the car.
It's funny that I have reversed my usage of fuels in my cars and aircraft.
I am putting auto fuel in one side of my aircraft and aircraft fuel in my cars now.

DOM

[Brad H.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

Dom,
It surely seems that way. I'm going to dabble in the avgas just to see if there is an improvement. I can't use mogas in my airplane or I would.
See ya,
Brad

[John D.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

Another benefit of Avgas is the life span, pump gas will go bad much faster. I have ran it in my 1960 FI for over 30 years and the fuel bowl stays "clean as a whistle." Also fuel percolation (sp?) when re-starting in hot weather (common FI problem) is much more managable - ask John D. Don H.

Hi Don, Just back from Fall Carlisle and behind on the posts here. Sorry that I cannot read all the AV gas posts right now.

Well the show season is over for me for my fuel injection business. Trailer goes into winter storage shortly. To prep it one of the things I do is run the generator until it runs out of the crappy ethanol gas. Then I will put in 100LL and run the generator for a few minutes. Now come April the thing will start right up.
I would be scared to death to leave corn fuel in my generator for long periods of time.

Personally I could care less if they take the lead out of aviation fuel. You gear heads out there know that lead causes dirty engines. A lot of the old time racers refused to use it. My Dad NEVER used leaded gas in the old days. Dad was born in 1911 and passed in 1994. Dad only used Amoco white gas as he called it. Meanwhile the subject isn't about lead.

When I am working the shows if someone comes up and says some bad stuff about 100LL I don't argue. I just smile and say thank you very much. Then when they leave I don't clog my old brain with their info and ignore their comments.
My 63 the LWC is a trailer gueen. Don't drive it and never plan on driving the car. It's just a toy to me and not a car. I use 100LL in it and have no issues.
Test all the FI's I restore with 100LL too as don't know how long they will sit in the box without being used. For example. A guy came up to me a Fall Carlisle and said I restored his FI unit 11 years ago and now he is going to install it. Whew!!! Yes it was tested with 100LL as I have only been using it since 1990. JD

[Clem Z.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

Hi Don, Just back from Fall Carlisle and behind on the posts here. Sorry that I cannot read all the AV gas posts right now.

Well the show season is over for me for my fuel injection business. Trailer goes into winter storage shortly. To prep it one of the things I do is run the generator until it runs out of the crappy ethanol gas. Then I will put in 100LL and run the generator for a few minutes. Now come April the thing will start right up.
I would be scared to death to leave corn fuel in my generator for long periods of time.

Personally I could care less if they take the lead out of aviation fuel. You gear heads out there know that lead causes dirty engines. A lot of the old time racers refused to use it. My Dad NEVER used leaded gas in the old days. Dad was born in 1911 and passed in 1994. Dad only used Amoco white gas as he called it. Meanwhile the subject isn't about lead.

When I am working the shows if someone comes up and says some bad stuff about 100LL I don't argue. I just smile and say thank you very much. Then when they leave I don't clog my old brain with their info and ignore their comments.
My 63 the LWC is a trailer gueen. Don't drive it and never plan on driving the car. It's just a toy to me and not a car. I use 100LL in it and have no issues.
Test all the FI's I restore with 100LL too as don't know how long they will sit in the box without being used. For example. A guy came up to me a Fall Carlisle and said I restored his FI unit 11 years ago and now he is going to install it. Whew!!! Yes it was tested with 100LL as I have only been using it since 1990. JD

i hope you told him he will have to send it back to be rebuilt because of the ethanol in the gasoline will attack the parts you installed back then.

[Ronald L.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

Lead and Ethanol, two villains, two different issues.

The lead put in clogs up the valve seats in a huge way. I had engine parts come back that you could not believe, deposits built up that essentially close up the combustion chamber. Don't have pics from so long ago but the fuel manufactures are supposed to put another highly toxic compound in to "get the lead out" of the combustion chamber. I'd have to break out that Org Chem E book to think back that far.

By the mid to late 70's most GM engines I am aware of had heat induction hardened valve seats and lead was no longer needed.

So - eliminating lead from av gas - welcomed.

Alcohol - meant for anything but the gas tank. When that was first introduced, most likey it was a combination of poor underground storage as well as incompatibility of the fuel system components. We had lines coming back, the tern coat all clogged up carbs corroded beyond all belief and recognition and more. Alcohol is a powerfull solvent, hygroscopic, that means it sucks up water from the air, or any other source. In those days, on the cusp of the EPA, it was very common to have water runoff get into the underground tanks, worse salt water run off in the winter. So that mix of alcohol, a little water and dissoved salt in my opinion was why we have such a "time" with the turn coat coming off and plugging new car fuel systems to the max. If you think about it, it was not until the late 80's and into the 90's that service station testing was in full force and EPA clean up required for leaky tanks. That helped clean up the fuel supply considerably.

However, on a 44 year old car that never saw alcohol before in any concentration, by the time I got to the second tank the fuel sender was shot and we'd find later the power valve in the carburetor too. It was at that point I bucked the gov't corn lobby imposition and move to the pure stuff.

[Doug L.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

I have one additonal prespective on this question. 100 low lead gas has remained available for aircraft use because there are a LOT of reciprocating aircraft engines out there that were built before the 1970s. My Beech Bonanza was built in 1961. It has always been my understanding that those old engines need lead for valve lubrication and that they were designed to run on 100 octane gas. In any event every aircraft type was put through some pretty rigorous testing to obtain FAA certification. If something changes on the plane, even something like a change of fuel type, the certification goes out the window and the process starts again. I can not legally run anything but 100L in the Bonanza. If 100LL goes away there will be big headaches for a lot of general aviation owners, probably in the form of their aircraft being grounded. Pilot-Owner groups will fight the FAA on this.

Will 100LL gas work in a pre-70's Corvette engine? Why not. 100 leaded was available back then.
Doug

[Ronald L.]

Re: QUESTION ON AVIATION GAS COMPATIBILITY for Duke and all

It will purr like a very content kitten, check that - tiger!

A couple 6 gallon jugs go a long way if all you do is get out on the sunny days in the mid west.