aviation fuel mix with gasoline?

[nosebleedZ]

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!

[JMortensen]

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.

[bjhines]

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.

[dr_hunt]

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.

[dr_hunt]

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!

 

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.

 

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.

[TrumpetRhapsody]

If you don't have anything good to say, intellegent or otherwise, then don't bother.

I had a little bit of a positive contribution tucked in there . Guess I just countered with too much poking-of-fun. Hint taken, my apologies.

 

 

Anywho...

That is an interesting read about the specifics of the differences between countries and fuel rating systems. Didn't know that much went into the octane rating.

 

I've been told stories by a friend that owns a shell station, and always wondered how wal-mart style budget fuel stations can get away with selling lower quality gas. Based on that, I guess it makes sense to a degree since the octane rating is an average of two rating systems, and some preferential adjustment might be introduced to save costs.

[cjames]

Aviation gasoline

1 gal = 112,500 Btu

 

Gasoline:

1 Gal Gasoline (mid grade) = 125,000 Btu's

 

 

Yes I copy/pasted the above. and after the little bit of actual research I did to back up my first post, mid grade gasoline is commonly assumed to carry the above listed energy, in british thermal units. Make up your own mind.

 

In response to the original question, the answer IMO, is no, your stock engine, in stock tune will NOT make more power by simply filling up with 100 octane AVgas at the local airport. Nuff said outta me.

[cjames]

ok, one more, heres a neat link.

 

http://www.ior.com.au/ecflist.html

[dr_hunt]

Higher octane fuel contains less BTU/gallon than lower octane fuel. plain and simple.

 

It might seem odd that fuels with higher octane ratings explode less easily, yet are popularly thought of as more powerful. The misunderstanding is caused by confusing the ability of the fuel to resist compression detonation as opposed to the ability of the fuel to burn.

 

What you should be looking at is Btu/lb, not Btu/gallon. A simple explanation is that carbon-carbon bonds contain more energy than carbon-hydrogen bonds. Hence a fuel with a greater number of carbon bonds will carry more energy regardless of the octane rating. A premium motor fuel will often be formulated to have both higher octane as well as more energy. A counter example to this rule is that ethanol blend fuels have a higher octane rating, but carry a lower energy content by volume (per litre or per gallon). This is because ethanol is a partially oxidized hydrocarbon which can be seen by noting the presence of oxygen in the chemical formula: C2H5OH. Note the substitution of the OH hydroxyl group for a H hydrogen which transforms the gas ethane (C2H6) into ethanol. To a certain extent a fuel with a higher carbon ratio will be more dense than a fuel with a lower carbon ratio. Thus it is possible to formulate high octane fuels that carry less energy per liter than lower octane fuels. This is certainly true of ethanol blend fuels (gasohol), however fuels with no ethanol and indeed no oxygen are also possible.

 

 

 

Aviation gasoline

1 gal = 112,500 Btu

 

Gasoline:

1 Gal Gasoline (mid grade) = 125,000 Btu's

 

 

Yes I copy/pasted the above. and after the little bit of actual research I did to back up my first post, mid grade gasoline is commonly assumed to carry the above listed energy, in british thermal units. Make up your own mind.

 

 

Well, if your talking about a gallon of fuel, perhaps but that's not a correct analogy and that is the flaw in your statement, it's the stoichiometric ratio of fuel to oxygen as it's mixed in the engine that matters! So, if your going to make a point then we have to do it correctly. If gasoline is run at its preferred maximum power air/fuel mixture of 12.5:1, it will release approximately 20 MJ (about 19,000 BTU) of energy, where ethanol run at its preferred maximum power mixture of 6.5:1 will liberate approximately 25.7 MJ (24,400 BTU), and methanol at a 4.5:1 AFR liberates about 29.1 MJ (27,650 BTU), that is why oxygenated fuels make more power and VP and others are making oxygenated race fuels. It gets even better when you run Nitro!

 

I think that about covers it for this topic

[Kinked_Chrome]

the stoichiometric ratio of fuel to oxygen as it's mixed in the engine that matters! So, if your going to make a point then we have to do it correctly. If gasoline is run at its preferred maximum power air/fuel mixture of 12.5:1, it will release approximately 20 MJ (about 19,000 BTU) of energy, where ethanol run at its preferred maximum power mixture of 6.5:1 will liberate approximately 25.7 MJ (24,400 BTU), and methanol at a 4.5:1 AFR liberates about 29.1 MJ (27,650 BTU), that is why oxygenated fuels make more power and VP and others are making oxygenated race fuels. It gets even better when you run Nitro!

 

 

I think you you also sould point out the fact that methanol has only about 40% the energy density of gasoline. 19,800BTU/lb for gasoline and ~8500-9000BTU/lb for methonal, as i recall. Then ethanol is around 14,000BTU/lb.

[dr_hunt]

I'm going to summarize this one more time. Then I'm closing this thread.

 

Gasoline is what most of our cars came setup so it's usually what we stick with. Gasoline is a mixture of hydrocarbons. The petroleum distillate fraction termed "gasoline" contains mostly saturated hydrocarbons usually with a chemical formula of C8H18. The air fuel ratio, A/F Ratio, for complete combustion is 14.7:1, stoichiometric. The A/F ratio for maximum power is approximately 12.5:1 - 12.8:1. This means that a theoretcial engine at max power, 12.8:1, consumes 12.8 pounds of air for 1 pound of fuel. Gasoline has approximately 18,400 BTU/lb . Using the air flow calculator with the default inputs we will use a 355 SBC, so it consumes 567.53 cfm @ 6500rpm which is 42.64 pounds of air and consumes 2.89 pounds of fuel. Therefore if we are using gasoline our engine is producing 53,176 BTU's of energy at 6500 rpm.

 

 

Alcohol is usually used in the form of Methyl alcohol or methanol. CH3OH is the chemical formula. Methanol burns at a much richer mixture than gasoline does, between 5.0:1 - 6.0:1. That's 5 lbs of air to one pound of fuel. Methanol has approximately 9,500 BTU/lb. Using our 355, example above, SBC consumes 567.53 cfm @ 6500rpm which is 42.64 pounds of air and now at 6.0:1 ratio for Methanol is 7.11 pounds of fuel. Therefore if we are using Methanol fuel our engine is producing 67,545 BTU's of energy at 6500 rpm.

 

 

Nitromethane is a fuel that is used mostly in specialized drag racing classes, "nitro funny cars" and "top fuel". Nitromethane's chemical formula is CH3NO2. The oxygen in nitromethane's molecular structure means that nitromethane does not need as much atmospheric oxygen to burn, part of the oxygen needed to burn nitromethane is carried in the fuel itself. Typical A/F ratio for nitromethane is 1.7:1 and nitromethane has an energy content of 5,000 BTU/lb. Using our 355, example above, SBC consumes 567.53 cfm @ 6500rpm which is 42.64 pounds of air and now at 1.7:1 ratio for nitromethane is 25.08 pounds of fuel. Therefore if we are using Nitromethane fuel our engine is producing 125,412 BTU's of energy at 6500 rpm.

 

Clearly Nitro is the winner here. Methanol makes about 20% more power in the same engine than gas does. Hence the saying, Gas is for washing parts, alcohol is for drinking and nitro is for racing!

[808morgan]

Well Avgas has no ethanol, in an old carbed motor, that is a plus. I would think leaded gas was used in 1971 so it should be fine. There is a small airport near me and I am thinking of using Avgas in my 1953 m73 Dodge power wagon. 

[tube80z]

Did you notice this is a ten year old thread?