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aviation fuel mix with gasoline?

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It's headlight fluid, gosh get it right! :P

 

Perhaps you're confusing AVgas with Jetfuel, which will give you tons of extra power... right before your engine melts. :lol:

 

Down to business - So, is there a legitimate reason you're wanting to run this stuff? Potential for increased timing, reduced knock, higher boost, a cheaper (???) solution to other high octane fuels?

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Avgas is just simply higher octane fuel. Which pretty much means that the burn will be much more steady and consistent. This is great for turbo cars, because they can run more boost without detonating. As far as NA applications go, unless you're running really high compression, you probably won't notice a staggering difference. Although if you can afford it, better gas never hurt anyone. Especially since avgas is so refined and filtered its ridiculous.

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You guys are being needlessly rough.

 

What you want to do will raise the overall fuel octane. More av gas then pump gas and the higher the octane goes. You are essentially making premium gas.

 

But unless your car NEEDS premium gas, you won't get any extra power out of it. Turbo cars can dial up the boost or timing to make more power with higher octane gas, but like mentioned above there is only so much you can do to a non turbo car to make better use of the octane.

 

And leaded gas is no more hazardous then unleaded, except to your catalytic converter, if you have one.

 

Oh, and jet fuel is just low quality kerosene. Your car won't run at all on kerosene.

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I have not spent the time to research the accuracy of the following, but Gene Berg wrote it and his success speaks for itself (underlines are mine)...

 

"Aircraft fuel is often considered as a high octane fuel that may be used in a high performance car engine. When talking to the engineers at one of the major refineries I was rather shocked to find that they use a totally different octane rating system. Aircraft engines are rarely ran over 2500 RPM so the piston pressure is changed far less than that of the auto engine that has a wide RPM change. The higher the performance usually means even a higher RPM range. They also rate the octane according to the rich or lean mixture device on the dash of the airplane. The aircraft fuels octane ratings were considerably lower compared to the automotive fuel rating system and should never be used for automotive applications. In fact, one of the new big things for aircrafts is to use automotive unleaded gas."

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Well Ron you are right.

 

My plane was certified to run unleaded gas, so I was bringing my Canister at the pump and filling the plane with them. Cost was a lot lower. I was only doing this in the winter, in the summer it was not going as well if the plane was heavy.

 

I guess with the unleaded gas, the plane was more sluggish, had less torque/power.

 

Dayz

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Well when my engine pinged on 92, I cut it with 100LL and the pinging went away. Car made a lot more power as I was able to adjust the timing to something close to "proper" as well. I've also run leaded race gas cut with 92, and Tolulene and Xylene cut with 92. I've also bent over at the race track and paid big bucks for unleaded race fuel.

 

All of these solutions worked. For my engine my butt dyno said the 112 leaded race gas and the 100LL cut with 92 worked best. I don't doubt that its true that the octanes are rated differently, but when I calculated it out I needed about 95 octane with car gas to keep from pinging. That's what I shot for with the AVGas not knowing that it is rated differently, and it didn't ping either.

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Higher octane fuel contains less BTU/gallon than lower octane fuel. plain and simple. Unless you can make up for this loss of energy somehow like listed above, there are no advantages to running higher octane fuel. Given the fact that there is less overall energy in a given amount of fuel, in turn makes it more stable for combustion. Add more boost, change ignition timing, raise compression, One might be able to use this to their advantage to achieve more overall power. With that said, Ill go out on a limb and say that an engine in a given state of tune, will make more power on 87 octane pump gas, than it will on 100 octane race gas. Personally, I run the lowest octane rating that I can without pinging.

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I’ll throw in my $.02 as well.

 

Back in the mid ‘90’s one of our flag ship engine projects we built for Justin Boice and his unlimited class white water endurance race boat, (Wade was owner of the shop overseeing, planning, ordering parts, etc, for this project, I merely machined and assembled it). That engine was run only on 100LL Av-gas. This was a Twin Turbo, 540 CID Big Block, 10:1 static compression ratio, 12 lbs of boosts, water to air intercooler, (IAT after the intercooler was only 85 degrees), and on the engine dyno at Sunset Engine Development produced 1168 HP at 5800 RPM! Engine was not revved past 6200 RPM, (that is what we told Justin to keep it under, whether or not he did?) This engine would run at WOT for 80+% of the time during the race for stints exceeding an hour at times, set many records down and UP several rivers, (lower Rogue, Snake, etc), and would run a whole season between tear downs. I still have the pistons and Rods from the first season here in the shop. Pistons look great, under side shows no signs of coking, rings all show very little wear and could’ve easily ran another season, bearings look like new.

That is one application where Av-Gas appeared to work.

 

Also as a certified Aircraft and Power-plant technician and private pilot, I also know that Av-Gas is not formulated like auto gas, i.e., they are quite different. Av-Gas is formulated for longer shelf life as some air planes will sit for extended periods between fill ups. Av-Gas is also formulated to withstand the extreme temperatures of higher altitude and for many other factors that is not taken into account with auto gas.

This different formulation alters Av-Gas so much that its specific Gravity is much less than that of Auto Gas. That means for given volume, there is actually less mass, (less dense, i.e., in a running engine, Av-gas burns leaner for a given jet size/injector pulse width compared to auto gas). With that means for us Auto guys, is that if you just switch to Av-Gas from auto gas, you will have to run slightly larger jets in the carb or slightly longer pulse widths for the injectors if the engine is fuel injected. You may have heard old timers talk about running Av-Gas in their cars, motorcycles, lawn mower, etc and mention that the Av-Gas is so much hotter that they burned a valve or melted a piston! Uh, yeah they burned the valves and melted pistons, but not from Av-gas being hotter. Av-Gas is NOT hotter, i.e. no more BTU in Av-gas vs Autogas, it is less dense, those bone heads didn’t compensate for that and as such, their engines were running too lean and THAT is what burned their valves and melted their pistons. wink.gif

Another attribute that Av-Gas has a slower burn rate, ie. flame speed. I have only read this in one other place, but the source was credible so I believe it to hold water. A slower flame speed could be a hindrance at elevated engine speeds as the rate at which pressure rises due to combustion is slower and therefore depending on the combustion chamber size, the engine could become less efficient at making power the higher it revs, i.e. burn event is not happening fast enough in the time available at high RPM.

 

 

In summation;

 

1) Don’t mix Av-gas with auto gas. nono.gif They are very much different. Use one or the other, but don’t mix unless you are a gasoline engineer and know what you are doing. Most of us just are not that savvy to know so we are better off not mixing.

 

2) Auto gas is known to work in auto engines as well as Air craft engines just fine. Av-Gas is for Air planes, (yet I have been know to run it in my … )

 

3) If you plan to run Av-gas in a race car, I feel it is ok so long as it is not in a high revving engine with a large bore, but do not forget to tune for it, i.e. make darn sure the mixture is correct, do NOT just tune for auto gas then switch over to Av-Gas without retuning the fuel map.

 

4) Automotive Race gas works just fine and is actually formulated for high RPM, high compression auto engines, though it is generally more expensive. If Race gas is too expensive for you, then to be perfectly honest, racing in general is too expensive and you should just sell the car as the price of gas should NOT be the determining factor of whether or not you can race. cool.gif

 

 

That is my $.02

 

Paul

 

 

ad...

 

Higher octane fuel contains less BTU/gallon than lower octane fuel. plain and simple. Unless you can make up for this loss of energy somehow like listed above, there are no advantages to running higher octane fuel. Given the fact that there is less overall energy in a given amount of fuel, in turn makes it more stable for combustion. Add more boost, change ignition timing, raise compression, One might be able to use this to their advantage to achieve more overall power. With that said, Ill go out on a limb and say that an engine in a given state of tune, will make more power on 87 octane pump gas, than it will on 100 octane race gas. Personally, I run the lowest octane rating that I can without pinging.

 

Very well said. bgiorno.gif

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In summation;

 

1) Don’t mix Av-gas with auto gas. nono.gif They are very much different. Use one or the other, but don’t mix unless you are a gasoline engineer and know what you are doing. Most of us just are not that savvy to know so we are better off not mixing.

 

Actually from what I can tell different types of race gas have different specific gravities and need to be tuned for when you have a motor on the edge. Probably not something you'd worry about in a normal auto engine. But something still to think about.

 

Cary

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Can someone post a link or list of the specific gravities of various fuels listed here.

 

I am also interested in how Toluene and Xylene rate in comparison, Either pure or mixed.

 

Just for kicks and hazard prevention... what about the poor fella who mixed up his brake cleaner and his carb cleaner one day? I know there are variations of each.

 

Also what effect do normal dosages of Marvel's MO, other preservatives, and top cylinder oils have on the fuel performance?

 

Alcohol is EVERYWHERE... uhhhh?

 

For you Aircraft guys.. I have read in Smithsonian's "Air and Space" a story of how a pilot lost his life due to large quantities of Marvels' Mystery oil in the fuel tanks. Not a very good preservative in his case...

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Higher octane fuel contains less BTU/gallon than lower octane fuel. plain and simple. Unless you can make up for this loss of energy somehow like listed above, there are no advantages to running higher octane fuel. Given the fact that there is less overall energy in a given amount of fuel, in turn makes it more stable for combustion. Add more boost, change ignition timing, raise compression, One might be able to use this to their advantage to achieve more overall power. With that said, Ill go out on a limb and say that an engine in a given state of tune, will make more power on 87 octane pump gas, than it will on 100 octane race gas. Personally, I run the lowest octane rating that I can without pinging.

 

But the whole point IS to modify the engine to make maximum use of the fuel. The availability of higher octane gas will allow you to build a higher HP motor.

 

And even though much has been made of the different methods of measuring octane in av gas, no one has posted anything to say what the actual octane of pump and av gas is. Except Jon, who posted some empirical result that supports the idea that av gas does increase octane.

 

Plus I am not seeing the "don't mix av gas and pump gas" warning. Don't see much to support that contention.

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Plus I am not seeing the "don't mix av gas and pump gas" warning. Don't see much to support that contention.

 

Been following this thread for kicks, but this Q I might be able to give some input on.

 

I believe his "don't mix" warning was based on the fact that over time two substances with different enough specific gravities will separate, and at any one point you might be running a higher concentration of one or the other, or just have an unpredictable mixture.

 

Assuming that's correct, I didn't know the various fuels would have a different enough specific gravity to make a serious difference. Shows what I know! Now back to the experts...

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…..

Plus I am not seeing the "don't mix av gas and pump gas" warning. Don't see much to support that contention.

 

 

Ok, I retract my “no mixing” statement. Everyone can mix the two all you want, for whatever special elixir you guys feel that it then becomes.

Personally, there is enough of a difference in their formulation that I see no reason to “mix” them. Either you want the benefits of the formulation that Av-gas affords or you do not. Like mixing Chevron Super unleaded and Texaco regular unleaded to meet some sort of goofy middle ground. I don’t see the point . Just use one or the other and be done with it. Better yet, if your motor was built to take advantage of high octane fuel, just use Race gas! No guessing or speculating.

 

 

But the whole point IS to modify the engine to make maximum use of the fuel. The availability of higher octane gas will allow you to build a higher HP motor.…..

.

 

 

Yeepsie doodle. I agree…

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IMO, Toluene is a good fuel additive if your car is boosted, but it takes more than you'd think to get at a useable increase in detonation resistance. Also the price of it has increased greatly over the past few years (used to be 3.99/ gallon @ Sherwin Williams). On my car, I experienced ping pretty bad at 13 psi on a 95* summer day with 93 octane. It drove me nuts to have to retard the timing & lower boost to be able to drive around in that ambient temperature without the power I had been used to on cooler days. I found a website that explained the mixtures needed to achieve octane increases but I didn't save the link. Essentially the formula is as follows: (gallons of gas x octane of gas) + (gallons of toluene x 114[octane of toluene]) / total number of gallons. In my car, I mix a 30% ratio & can now run 18psi on hot days. For example, I use 12 gallons of 93 octane gas and 6 gallons of toluene (18 gallons total). Here is how you'd figure my total octane: 12 x 93 = (1116) + 6 x 114 = (684) or 1800 / 18 gallons = 100 octane. The car ran great & runs absolutely awesome on cold winter days. All the guys here make good points about Aviation fuel (ie. lead content, slower flaming) so I wouldn't advise using it. But the penny pinching aspect of toluene (8.00/ gallon) is very good. For 12 gallons of 93 & 6 gallons of toluene I currently pay $85 for a tank. Versus $144 for 100 octane race gas. The biggest drawback is carrying a funnel to the gas station & it taking 15-20 minutes to fill up, LOL! Talk about pissed off rednecks!

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Personally, there is enough of a difference in their formulation that I see no reason to “mix†them. Either you want the benefits of the formulation that Av-gas affords or you do not. Like mixing Chevron Super unleaded and Texaco regular unleaded to meet some sort of goofy middle ground. I don’t see the point . Just use one or the other and be done with it. Better yet, if your motor was built to take advantage of high octane fuel, just use Race gas! No guessing or speculating.

The only reason to mix gas is if you can't run what you can buy at the pump, but you don't need the 100 octane or whatever you're buying. You can mix a $3/gal pump gas with a $7 or $8/gal high octane gas and split the cost and get the octane needed without spending more than you have to.

 

Also as mentioned previously, there should in theory be more hp to be had with the lowest octane fuel that can be used without pinging while at the optimal amount of advance.

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I filled up at the local airstrip 15 years ago. The airport technician said that I cannot use containers, I had to directly fill the tank. I told him that there was no restrictor plate in my old car and he said ""as long as you can pump it straight into the vehicle then no problem".

 

It did not make any noticable difference, and it was a pain to go to the airport every week.

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Here is the skinny folks;

 

The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing these results with those for mixtures of isooctane and n-heptane.

 

There is another type of octane rating, called Motor Octane Number (MON) or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON. Normally fuel specifications require both a minimum RON and a minimum MON.

 

In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, would be 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90-91 US (R+M)/2, and even deliver 98 (RON) or 100 (RON).

 

The octane rating may also be a "trade name", with the actual figure being higher than the nominal rating.[citation needed]

 

It is possible for a fuel to have a RON greater than 100, because isooctane is not the most knock-resistant substance available. Racing fuels, straight ethanol, AvGas and liquified petroleum gas (LPG) typically have octane ratings of 110 or significantly higher - ethanol's RON is 129 (MON 102, AKI 116) reference[2]. Typical "octane booster" additives include tetra-ethyl lead and toluene. Tetra-ethyl lead is easily decomposed to its component radicals, which react with the radicals from the fuel and oxygen that would start the combustion, thereby delaying ignition. This is why leaded gasoline has a higher octane rating than unleaded.

 

CJames you are incorrect;

 

A premium motor fuel will often be formulated to have both higher octane as well as more energy.

 

Compression is directly related to power (see engine tuning), so engines that require higher octane usually deliver more power. Engine power is a function of the fuel as well as the engine design and is related to octane ratings of the fuel. Power is limited by the maximum amount of fuel-air mixture that can be forced into the combustion chamber. At partial load, only a small fraction of the total available power is produced because the manifold is operating at pressures far below atmospheric. In this case, the octane requirement is far lower than what is available. It is only when the throttle is opened fully and the manifold pressure increases to atmospheric (or higher in the case of supercharged or turbocharged engines) that the full octane requirement is achieved.

 

Many high-performance engines are designed to operate with a high maximum compression and thus need a high quality (high energy) fuel usually associated with high octane numbers and thus demand high-octane premium gasoline.

 

The power output of an engine depends on the energy content of its fuel, and this bears no simple relationship to the octane rating. A common understanding that may apply in only limited circumstances amongst petrol consumers is that adding a higher octane fuel to a vehicle's engine will increase its performance and/or lessen its fuel consumption; this may be false under most conditions — while engines perform best when using fuel with the octane rating for which they were designed and any increase in performance by using a fuel with a different octane rating is minimal or even imaginary, unless there are carbon hotspots, fuel injector clogging or other conditions that may cause a lean situation that can cause knocking that are more common in high mileage vehicles, which would cause modern cars to retard timing thus leading to a loss of both responsiveness and fuel economy. This also does not apply to turbocharged vehicles, which may be allowed to run greater advance in certain circumstances due to external temperatures.

 

Using high octane fuel for an engine makes a difference when the engine is producing its maximum power or when under a high load such as climbing a large hill or carrying excessive weight. This will occur when the intake manifold has no air restriction and is running at minimum vacuum. Depending on the engine design, this particular circumstance can be anywhere along the RPM range, but is usually easy to pinpoint if you can examine a printout of the power output (torque values) of an engine. On a typical high-revving motorcycle engine, for example, the maximum power occurs at a point where the movements of the intake and exhaust valves are timed in such a way to maximize the compression loading of the cylinder; although the piston is already rising at the time the intake valve closes, the forward speed of the charge coming into the cylinder is high enough to continue to load the air-fuel mixture in.

 

When this occurs, if a fuel with below recommended octane is used, the engine will knock. Modern engines have anti-knock provisions built into the control systems and this is usually achieved by dynamically de-tuning the engine while under load by increasing the fuel-air mixture and retarding the spark. Here is a link to a white paper that gives an example: [5] . In this example, the engine maximum power is reduced by about 4% with a fuel switch from 93 to 91 octane (11 hp, from 291 to 280 hp). If the engine is being run below maximum load, the difference in octane will have even less effect. The example cited does not indicate at what elevation the test is being conducted or what the barometric pressure is. For each 1000 feet of altitude the atmospheric pressure will drop by a little less than 11 kPa/km (1 inHg). An engine that might require 93 octane at sea level may perform at maximum on a fuel rated at 91 octane if the elevation is over, say, 1000 feet. See also the APC article.

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if you kill yourself with the stuff be sure to let us know... jk, how would it give you more power????

 

Make sure to check your bumper fluid, before adding all that power.

 

It's headlight fluid, gosh get it right! :P

 

Is there a legitimate reason you're wanting to run this stuff? Potential for increased timing, reduced knock, higher boost, a cheaper (???) solution to other high octane fuels?

 

Perhaps you're confusing AVgas with Jetfuel, which will give you tons of extra power... right before your engine melts. :lol:

 

Are you really sure you want to run leaded gas in your car that is not designed for it? If yes, then do it!

 

I'm more than alittle disappointed in the above answers to an otherwise good question. If you don't have anything good to say, intellegent or otherwise, then don't bother. Hybridz isn't like the other sites you visit where that kind of activity is condoned. I hope you all get the hint. :wink:

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