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Muscle-Milk-KTM Muscle-Milk-KTM
5/22/2018 8:08 AM

I can get hold of Avgas 100LL from my local airport. Do I run this straight or mix it 50/50 with Super Unleaded?

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exbmxmx exbmxmx
5/22/2018 8:53 AM

Either will work in a stock bike. You will most likely get more power from a 50:50 mix in a properly jetted stock bike.

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Muscle-Milk-KTM Muscle-Milk-KTM
5/22/2018 9:06 AM
exbmxmx wrote:

Either will work in a ...more

Spoke to a guy I know & he said its more of an aggressive fuel & its meant for low rpm engines. He said it doesn't mix well with oil. He recommended a race fuel.

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BobPA BobPA
5/22/2018 9:20 AM
exbmxmx wrote:

Either will work in a ...more

Muscle-Milk-KTM wrote:

Spoke to a guy I know ...more

He is drunk. AV Gas is absolutely fine. What are you running it in? Keep in mine it is only 100 Octane, so do not compare it to a 110 octane fuel....

Tomac and/or Anderson for 2020.....

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Muscle-Milk-KTM Muscle-Milk-KTM
5/22/2018 9:23 AM
exbmxmx wrote:

Either will work in a ...more

Muscle-Milk-KTM wrote:

Spoke to a guy I know ...more

BobPA wrote:

He is drunk. AV Gas is ...more

YZ 125

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exbmxmx exbmxmx
5/22/2018 9:27 AM

Not sure what he means by aggressive fuel? Avgas is made up with 100% hydrocarbons and has no oxygenates. Mix it with pump fuel if you are concerned about mixing it with 2-stroke oil or spend the money and buy the VP T2. The Avgas/Ethanol Pump fuel mix is the cheapest way to get 96ish octane fuel and have no issues with 2-stroke oil mixing at high oil:fuel ratios.

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murph783 murph783
5/22/2018 10:05 AM

It isn’t designed for low rpm, isn’t designed for high altitude, yadda yadda yadda. Run it, jet it/map it richer to compensate for slow burn, give er hell

RPM Performance
CT
783

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exbmxmx exbmxmx
5/22/2018 10:31 AM
murph783 wrote:

It isn’t designed for low ...more

Yea but if Fuel A can give you 5% more power than Fuel B, that's 5% more hell you can give er!

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murph783 murph783
5/23/2018 2:55 AM
murph783 wrote:

It isn’t designed for low ...more

exbmxmx wrote:

Yea but if Fuel A can give ...more

Can’t fault that logic! Lol

RPM Performance
CT
783

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Brett Campbell Brett Campbell
5/23/2018 5:32 AM

Nice read from another forum listed below.

https://www.race-dezert.com/forum/threads/100ll-avgas-ok-to-run.44599/


Real info on Race Gas/Av Gas...

My experience comes from 7 years as the western states representative for 76 Race Fuel, Unocal's 40 hours Advanced Products course, Working personally with Tim Wusz (senior performance products Rep for Unocal, Tim was responsible for Unocal's race fuel development for 30+ years). I have also met and discussed fuels/motors with just about every engine builder in every facet of racing in the western United States. I also conducted Educational Seminars at the Fred L. Hartley Institute in Brea in which we would invite Engine Builders for a tour of Unocal's testing facilities and do live octane tests on any gasoline they would choose to bring to the seminar. Included in the training we would demonstrate live tests how Distillation curve, Reid Vapor Pressure, Specific Gravity, Octane Rating, Flashpoint, etc. are conducted and the importance of these numbers. Some of you will remember me from contingency with my 76 Racing Gasoline hospitality trailer in the 1990's.

Through the 50's, 60's, 70's and 80's Av gas was the base product used for most racing "gasoline". VP, f&L, Turbo Blue, and Trick all used AV gas as the base product. They would buy a tanker (8000 gallons of Av Gas) than add other hydrocarbons/Tetra Ethyl Lead (TEL) to the base, drive around the block stopping and accelerating the truck/trailer until they felt the product was mixed well. Obviously this was not science, but it worked for most racers only because most racers use a higher rated octane than they actually need.

In the mid to late 1990's VP graduated to buying there own base product and do there blending of products in a much better fashion. Turbo Blue and Trick have since been bought Sunoco and are blended by Sonoco. Trick was purchased by Phillips 66 and has continued to be blended by Phillips 66.

The only two companies I am aware of who "cracked" there own base product is Sunoco and 76. And as we all know, 76 race fuel is no longer available, leaving only one true manufacturer of Racing Gasoline....Sunoco.

AV Gas has a MOR (motor octane rating) of 96, R+M/2 rating of 100, and ROM (Research Octane Rating) of 106.

AV Gas is lighter than racing gasoline thus more fuel/larger jetting is required. Jetted correctly you should not experience a lean burn at WOT.

I would not use AV Gas as a cleaner. The amount of TEL (2 grams/gallon) and other hydrocarbons makes it extremely carcinogenic. Same goes for all other racing gasoline's.

Shelf life is NOT better. The reason pump gas won't last as long is because street gas has extremely lightened hydrocarbons to help your car start and idle. Racing Gasoline does not have these light end hydrocarbons needed for idle and starting, hence the reason race motors start and idle poorly.

Av Gas is NOT designed for low RPM motors. AV Gas is designed to not detonate/pre-ignite causing detonation. This would be the same design as race fuel. If you compare the "distillation curve" of AV Gas to Race Gas, you will find they are almost identical. The "distillation curve" controls the speed of burn across the combustion chamber.

You will only "spit" gas out the exhaust pipes if you run to rich or include a supercharger/turbocharger on your engine and "overdrive" the blower. Example would be the bitchin flames you see at the starting line of a drag race on normally aspirated engines and the long flames you see on all "blown" engines.

The LEAD (TEL) added to AV Gas is to increase the octane rating only. All heads these days have hardened valve seats. There is no need for lubrication of the valve seats. All engines have come with hardened seats since the late 60's.

AV Gas is not formulated for High Altitude. and will have very little, if not any performance differences vs racing gasoline. On the other hand, commercial grade fuels (87, 89, 92) will definitely enhance your performance due to the commercial fuel being oxygenated. The Oxygen enhancers added to commercial fuel is only for California Smog laws.

Advancing timing on your motor will definitely help with AV Gas and Race Gas due to its slow burn characteristics. On the other hand, be careful if you're running commercial grade gasoline, more timing can cause detonation/pre-ignition quite quickly.

AV Gas does not go BAD faster. It is extremely consistent. The MOR is only 96, whereas Sunoco Purple or VP C12 is 104. A rating of 96 is good for up to 10:1 on Steel heads and 12:1 on Aluminum heads with water cooling. Air cooled motors run much hotter.

Buying a higher octane for a $20-50K motor is the cheapest insurance available.

Remember this...OCTANE is a measure of a fuels ability to resist detonation/pre-ignition. The higher the Octane number, the slower the fuel burns. Technically speaking 87 Octane fuel will develop more power than 118 Octane fuel. With this said, you should see gains in throttle response and HP by mixing commercial fuel and AV Gas/Race Gas. You now have some light end Hydrocarbons for throttle response and heavy hydrocarbons/TEL for detonation resistance.

Bottom line... use the most consistent fuel you can find and create horsepower by moving as much air as possible though the combustion chamber.

I have no reason to be bias here as I have moved on to much greener pastures. See you on the race course.

Good Luck,
Steve Poole

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exbmxmx exbmxmx
5/23/2018 8:25 AM

Take the above article with a grain of salt...several things are not correct, especially when discussing motorcycle racing fuels.

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Brett Campbell Brett Campbell
5/23/2018 9:22 AM
exbmxmx wrote:

Take the above article ...more

Please...enlighten us!!

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exbmxmx exbmxmx
5/23/2018 7:04 PM

1) "Remember this...OCTANE is a measure of a fuels ability to resist detonation/pre-ignition. The higher the Octane number, the slower the fuel burns."
This is a common misconception of octane because a fuel's octane rating does not mean the rate of burn or flame front speed. As defined above, octane is a measure of a fuels ability to resist detonation/pre-ignition, which is the fuel's ability to start the combustion reaction process. Fuel combustion is a series of chemical reactions initiated by the atoms of the molecule reacting with a radical of oxygen, which occurs when a minimum reaction energy is met. When you add Tetra Ethyl Lead, for example, the combustion process now chooses to react with the lower energy reactant of Lead, and thus delays the combustion process with the hydrocarbon fuel. So when the octane of a fuel is high, it requires more reaction energy to start the combustion process which means that the fuel does not ignite until the spark plug fires. Once the ignition occurs, then the flame front speed is determined by the structure of the molecule being burned and the thermodynamics of the reaction rate. This is why the high end motorcycle racing fuels are so expensive, because great care is taken to match the compounds in the fuel with the speed of the engine being used.

2) "Technically speaking 87 Octane fuel will develop more power than 118 Octane fuel."
The main factor for power production of a fuel in an engine is the BTU content of the fuel applied against the optimum air:fuel ratio. Hydrocarbon only fuels may have a high BTU content per weight or lb, they also have a higher air:fuel ratio. Although oxygenates have lower BTUs than hydrocarbons, you must increase the air:fuel ratio to maintain the correct stiochiometry for optimum combustion. When an oxygenated fuel is correctly jetted with the optimum air:fuel ratio, the net BTUs that the engine burns is higher and thus the engine makes more power.
Think about this way...if you took a fuel and added enough lead to go from 87 to 118 octane with no other changes, would the power of the engine change? No, because the energy content per weight has not changed. And if the 87-octane was enough to prevent detonation, then so is 118-octane and guess when the fuel ignition occurs in both cases? Exactly when the spark plug fires it off. The piston still has the same amount of time to burn the fuel because the flame speed has not changed because the composition of the fuel has not changed.
When a guy decides to add race gas to his stock bike that is designed (and jetted) to run on oxygenated pump fuel and he adds basic non-oxygenated 110-octane fuel, the bike loses power. Not because of octane but because the net BTU the engine sees has changed in a negative direction.

I'll just stop here for the night as I'm sure everyone's eyes have glazed over by now...







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Brett Campbell Brett Campbell
5/24/2018 6:15 AM

I have been running a 50/50 mix of 93 non-ethanol pump gas and avgas ll100 for years. I recently did a top end rebuild on my CR480 and everything looked great. If properly jetted It will work fine. It stopped the detonation in my bike, which is known to have this problem.

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Tracktor Tracktor
5/29/2018 3:58 PM
exbmxmx wrote:

1) "Remember this...OCTANE ...more

Feel free to continue. I dig reading about this stuff as I think the small details are often over shadowed by urban myth.....

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