AVGAS is good...

[Steven]

I've read some anti-avgas posts and seen pictures of broken pistons blaming avgas so I thought I'de share my findings.

I've been runnung chevron avgas 100LL for 10 months of weekend riding. 98% track and 2% trail.

The bike is my 440ex with a Ross piston at about 11.5:1. I run it hard at the motocross track and putz around on the trails.

I pulled it apart this weekend to check the internals.

Piston looks great! Valves look great! Cylinder looks great!

What can I say?

How does this gas hurt others bikes?

I just don't understand... is is just improper jetting?

[F-16Guy]

I swear by it. I've done hours of research on fuels, both their similarities and differences, and I've found nothing to suggest that there is anything in avgas that would harm an atv engine. The quality standards are unsurpassed, the vapor pressure is far more stable compared to automotive fuels, and there is actually an additive to scavenge the lead from the combustion chamber during combustion (to inhibit build-up). As for how super oxygenated it is, it isn't. Aircraft have mixture control, whether it be automatically through the fuel injection or manually controlled by the pilot. Small aircraft use the same type of internal combustion engine as an atv, so the notion that avgas is dryer (less lubricating properties) is a little rediculous. Actually, the lead insures that the metal parts are more lubricated and cusioned. I have yet to have any problems and I will continue to run it.:cool:

[hondafox440]

You guys may want to check this link out. It gives a good view on both sides of the issue..

http://www.dirtbike.com/forums/topic.asp?TOPIC_ID=11945


The only thing I question about AV gas is the burn rate of it, and the distillation curve. It's designed to burn in engines that are constantly run at 2500RPM, not around 10,000RPM. Airplanes don't need great throttle response either, unlike ATVs.

[airheadedduner]

I called one of the tech lines for on race gas company. I think it was either VP or Nutech. I was told that airplane motors are designed to run at a high constant RPM. At a high constant RPM there is not much load on the motor. Its when you see varried RPM like our quads see taht lots of load is put on the motor and it is in risk of preignition. Avgas is not formulated to stand up to that. The fact that your 11.5:1 440 was okay is it was getting enough octane that it was running okay, mine is 11:1 and it runs fine on pump. Its when you get to higher compression that you run into problems. Avgas is not a substitute for race gas. I am not 100%, but I think he also said it was rated differently.

[2004TRX450R]

I think the biggest problem with it is the way it burns. It was designed to run at very high altitues in engines that run in a completely different set of parameters. Will it work? Probably. Is it a bandaid for what should be run? More than likely. People like it because it is cheaper than race fuel and has a higher octaine than pump gas but it isn't the best thing to run in an ATV engine. Just because the internals of your engine are OK doesn't necessarily mean it is good to run. It may not fry your engine but it doesn't burn like it is designed to.

[RUNMYTA]

I have run AVgas for over 3 years in both my Ported banshee @215lbs of compression and my LRD 300 at 240lbs of compression with no problems. At every rebuild the pistons look clean and show know signs of pre ignition. I race both bikes XC and have abused them during the races and AVgas has never let me down.

Bottom line: It is as good if not better than race fuel for half the price.:macho

[seven]

I have run only av gas since 98 and have had no motor failures. Thumbs up from me.

[zephead400ex]

Most of the guys in our big group, most have buggies, run avgas in their buggies b/c it burns clean and supposedly it creates more power. They swear by the stuff but I have never ran it in my quad. My $.02.

later

[nacs400ex]

:confused: I guess there is no straight answer. Some people say good, some people say bad. I need to know if its gunna be safe to run in the 265 because I dont want it buggering up on me.:mad:

[seven]

I have a 310R that has run only Av gas for the past 3 years. The only issue you might have is it will generally make your quad run a little leaner. Av gas has a higher oxygen content then regular gas so you bump rour main jet up one size. Other then that run it!

[Steven]

Did you guys know that...

Avgas is designed to operate best between sea leval and about 8500 feet. Average cruizing level for any aircraft that uses Avgas is 3500 to 4500 feet. Above that, the air starts to get thin and the pressure can get uncomfortable. Not sure what you meant by its designed to run at "high altitudes." Its not, jet fuel is....

Also Avgas is a more refined fuel which better resists chemical change after age, heat, cold, ect... the C.A.B. (civil aironotics board) requires it be that way for obvious safety reasons. It is a signifigantly more refined and chemicaly superior fuel to pump gas. The BP/Amoco home page FAQ backes that up nicely as they rebadge it as thier race gas. Its the same stuff.

Not saying its better than race gas fellas but for the application in my Honda, its been effective and a cost saver.

Try it.

[JOEX]

Thanks for the update Steven:) Good info;)

Next question, is all AVgas the same?

Joe

[airheadedduner]

Originally posted by Steven
Did you guys know that...

Avgas is designed to operate best between sea leval and about 8500 feet. Average cruizing level for any aircraft that uses Avgas is 3500 to 4500 feet. Above that, the air starts to get thin and the pressure can get uncomfortable. Not sure what you meant by its designed to run at "high altitudes." Its not, jet fuel is....

Also Avgas is a more refined fuel which better resists chemical change after age, heat, cold, ect... the C.A.B. (civil aironotics board) requires it be that way for obvious safety reasons. It is a signifigantly more refined and chemicaly superior fuel to pump gas. The BP/Amoco home page FAQ backes that up nicely as they rebadge it as thier race gas. Its the same stuff.

Not saying its better than race gas fellas but for the application in my Honda, its been effective and a cost saver.

Try it.
Thats a good point but don't take the octane rating on av gas for what its worth. It is rated differently. Normal and race gas use the RON or MON testing to figure octane rating. RON is reasearch octane number and mon is Motor octane number. I think the RON number is just what they belive the composition of the fuels octane should roughly be, the MON is an actual test where they highly stress the fuel untill they create a condition that it will detonate. The MON test is very brutal. American pump ratings take the RON and MON, and them together and divide by 2 to get that average, a good compromise being the MON number is usually lower. From what I have red avgas put under 2 different supercharger tests. Thats whay you see a rating on avgas like 100/130. I stay away from avgas is that I can't compare it to race gas. Untill I know what avgas octane means in car/bike fuel octane ratings I won't use it. THe spacific gravity is also diff. But not enough to effect a whole lot. Maybe a little jetting. I am reading out of an older book so things may be different. It was revised mid 90's I belive.

[F-16Guy]

Originally posted by airheadedduner
Thats a good point but don't take the octane rating on av gas for what its worth. It is rated differently. Normal and race gas use the RON or MON testing to figure octane rating. RON is reasearch octane number and mon is Motor octane number. I think the RON number is just what they belive the composition of the fuels octane should roughly be, the MON is an actual test where they highly stress the fuel untill they create a condition that it will detonate. The MON test is very brutal. American pump ratings take the RON and MON, and them together and divide by 2 to get that average, a good compromise being the MON number is usually lower. From what I have red avgas put under 2 different supercharger tests. Thats whay you see a rating on avgas like 100/130. I stay away from avgas is that I can't compare it to race gas. Untill I know what avgas octane means in car/bike fuel octane ratings I won't use it. THe spacific gravity is also diff. But not enough to effect a whole lot. Maybe a little jetting. I am reading out of an older book so things may be different. It was revised mid 90's I belive.
I posted this a while back, but I think it may have some information that you'd find interesting. Especially note the octane, chemistry, and additives sections.
http://www.eaa.org/education/fuel/autogas_vs_avgas.pdf

[airheadedduner]

Originally posted by F-16Guy
I posted this a while back, but I think it may have some information that you'd find interesting. Especially note the octane, chemistry, and additives sections.
http://www.eaa.org/education/fuel/autogas_vs_avgas.pdf
Can't get the file to load:(
I found through some reading 110/130 avgas is roughly equal to 100 ocatne leaded racegas. But for what it cost me to cut 110 with premium it is about the same price. About 3.50/gal.

[AndrewRRR]

Originally posted by RUNMYTA
I have run AVgas for over 3 years in both my Ported banshee @215lbs of compression and my LRD 300 at 240lbs of compression with no problems. At every rebuild the pistons look clean and show know signs of pre ignition. I race both bikes XC and have abused them during the races and AVgas has never let me down.

Bottom line: It is as good if not better than race fuel for half the price.:macho

100 octane AvGas at 240psi? Have you had your compression gauge checked? lol
I've always heard above 165psi or so you need race gas and above 200 you need alcohol. My R reads 125psi on my gauge, 208psi on my friend's gauge, and 185psi on my engine builder's (very expensive) gauge. I run 110 race gas.

[Aceman]

Originally posted by AndrewRRR
100 octane AvGas at 240psi? Have you had your compression gauge checked? lol
I've always heard above 165psi or so you need race gas and above 200 you need alcohol. My R reads 125psi on my gauge,

AndrewRRR, you either have a bad gauge or didn't take your compression reading correctly. If it was 125 psi your quad would make no power. You would pretty much be pull starting it to get it to run. My chevy pickup has 155 psi of compression and runs fine on 87 octane. There is no way you need race gas at 165 psi, probably more like 190 psi and above.

[AndrewRRR]

Originally posted by Aceman
AndrewRRR, you either have a bad gauge or didn't take your compression reading correctly. If it was 125 psi your quad would make no power. You would pretty much be pull starting it to get it to run. My chevy pickup has 155 psi of compression and runs fine on 87 octane. There is no way you need race gas at 165 psi, probably more like 190 psi and above.

I know it's not 125psi, it's a leg-breaker. I'm just illustrating how much variance there are between compression gauges.

[Aceman]

You didn't happen to buy that gauge at a Wheeler Dealer did you?:D Sounds like it's only good for a paperweight now.

[F-16Guy]

Originally posted by airheadedduner
Can't get the file to load:(
I found through some reading 110/130 avgas is roughly equal to 100 ocatne leaded racegas. But for what it cost me to cut 110 with premium it is about the same price. About 3.50/gal. Because of the difference in the way the octane ratings are determined, auto gas is rated about 5 points higher than it would be using the aviation fuel method. Avgas would be rated at about 105 octane using the RON+MON/2 method used for auto gas. The two different numbers (80/87 for example) are determined during testing and indicate the anti-knock value during lean and rich operating conditions.

[Steven]

Correct.

100 avgas is well over 100 when using the same octane rating as pump gas.

Airheadedduner has got it backwards...

[airheadedduner]

Its what I got out of the book, I think andrewRRR has the same book, A. Grahm Bell: Two Stroke Performance Tuning. It is in the carburation chapter. He also says that 115/145 avgas is also somtimes labled as 108 race gas. From what I understand out of it the MON testing is much more harsh then the Supercharge test that av gas is certain but it obvious now that everything that is read needs to be considered a little more carfully. To each his own:o

[JBBSPEED]

I have just started using Av gas in my Cannondale. I did some research and what I have found about the belief that Av gas is bad for quads is a myth. When people say that the gas is made for high altitudes only, they have no idea what they are talking about. I guess you are going to tell me most biplanes fly really high all the time right! Ha... or planes never use Av gas to take off, they switch to Av after they get to 1000 feet. Ha.... Look a normal stock motor does not need to see any gas over 100 octane but a high compression racing motor only needs to be jetted correctly so it can run Av or Race gas. A local drag racer sent 3 samples of 100 octane Av gas form the Airport down the street to NC State and had it tested to see what octane it would be for cars. The samples all came back 116 octane. when asked if there was anything in the gas that would hurt a non airplane motor the answer was no. They also said that the lead would be burned away by a chemical in the gas. The only thing that could be hurt by this gas is a catalytic converter ( I probably spelled that wrong) and I do not know about you guys buy neither my Dale or 400Ex as one of those. You do not want to use Av gas thats your choice but please do not spread false truths.

[AndrewRRR]

If AvGas is 116 octane why in the world are the thousands of engine builders and millions of performance enthusiasts wasting money on race gas? Are they all stupid?
Yes, leaded gas clogs catalytic convertors and fouls 02 sensors.

Maybe we need those scientist dudes from the discovery channel to test AvGas for us in an automotive or ATV application :D

Oh, and yes my compression gauge is junk, it was a cheepie from Harbor Freight Tools. Although it did show 220psi for our race car which is about right (15:1). My friend's gauge showed my banshee and R at 208psi, which i'm pretty sure is high. My engine builder, who's gauge I trust since it's a really nice one, got 185psi.
The point isn't my compression, it's that there is a TON of variance among different gauges.

[airheadedduner]

Originally posted by JBBSPEED
You do not want to use Av gas thats your choice but please do not spread false truths.
Thats not what I am intending, I am just shareing what info I do have on the subject. I like learning all this new info, means I can get corrected and don't sound like an idiot later. Isn't that what learning is about?:blah: My source:

Pages 154-160
A. Grahm Bell:Two Stroke Performance Tuning
Second Edition 1999

To respond to some of the things you have said:
The race gas availible to me in my area has all been leaded so far, lead is a great lubricant, the environutz got it banned for auto aplications though, and yes it is the cadiletic(sp?) converter taht it fudges up, clogs it up I think.

From what I understand planes run on one fuel type, they have a mixture adjustment control that allows them to richen or lean the fuel/air manually as they see fit.

Is the 116 RON or MON??

From my source I am reading no diff in avgas and race gas, they are just rated differently.

F-16guy, The way I understand it the first number is the rating of the fuel which simulates a supercharged engine running a chemically corect fuel/air ratio as when crusing at a constant RPM. The second rating is simulating a rich condition and a higher load as in under takeoff. Thats what it says anyway:rolleyes:

Oh and andrewRRR, LRD told me under 180psi is okay for pump, 180-190 around 100 octane, 190-up you need to run strait race gas over some number I don't remember. My buddies R ran 215psi, he ran strait 110, we accidently dumped 50/50 110 and premium in it once and holed the piston:blah:

[AndrewRRR]

Originally posted by airheadedduner
Thats not what I am intending, I am just shareing what info I do have on the subject. I like learning all this new info, means I can get corrected and don't sound like an idiot later. Isn't that what learning is about?:blah: My source:

Pages 154-160
A. Grahm Bell:Two Stroke Performance Tuning
Second Edition 1999

To respond to some of the things you have said:
The race gas availible to me in my area has all been leaded so far, lead is a great lubricant, the environutz got it banned for auto aplications though, and yes it is the cadiletic(sp?) converter taht it fudges up, clogs it up I think.

From what I understand planes run on one fuel type, they have a mixture adjustment control that allows them to richen or lean the fuel/air manually as they see fit.

Is the 116 RON or MON??

From my source I am reading no diff in avgas and race gas, they are just rated differently.


Isn't that a great book?! I'm gonna read it again now that i'm finished.

Oh and everybody, I just posted the AvGas vs. Race gas idea to Mythbusters on discovery channel. Lets see if they'll settle it for us! :D

[wilkin250r]

Every fuel "expert" that has ever made a testimonial on the subject has always said "Do not use AV gas as a substitute for Race gas!" I would have to believe they are all saying the same thing for a reason.

AV gas has a lower specific gravity than race gas. This has two problems. First, it changes the jetting. You cannot swap between AVgas and race gas without rejetting. Because of the different weights of the fuels, your jetting will change.

Second, a lower specific gravity means it does not do as well with pre-mix oil. The oil will not stay suspended in AVgas, and will eventually separate and settle.

The thing you most often hear is that AVgas is formulated for high-altitude and low rpms, but what does that mean? The high altitude aspect means lower specific gravity to atomize in thinner air, and also oxygenating additives. Low RPMs mean that the fuel can have a much slower burn rate without causing problems. You obviously need a much faster burn rate at 12,000rpms than you do at 2,500rpms to achieve maximum power.

For those that have given their personal testimonials that they have run AVgas and haven't had any problems, I absolutely believe you. AVgas has higher octane than pump gas, and the quality is controlled much tighter than pump gas. It has additives to eliminate lead build-up, as well as improve the oxygen content. In reality, all fuel is a collection of hydrocarbons, and they aren't THAT much different from each other. I can run pre-mix in my four-stroke and still run fine and dandy, but that doesn't mean I'm getting maximum performance. As for testimonials, I've also seen many people that have said their throttle response was terrible with AV gas, so we have some good and some bad experiences with AV gas.

Bottom line is, AV gas may give you some benifit, but it's not the best. The increase in octane may prove useful if you are running a higher compression, so it is possible that you can extract more power from your engine with AV gas. However, AVgas is not formulated for high-rpm offroad use, and will not give you maximum performance.

[JBBSPEED]

Originally posted by AndrewRRR
If AvGas is 116 octane why in the world are the thousands of engine builders and millions of performance enthusiasts wasting money on race gas? Are they all stupid?


That is what I am saying exactly.. We all have been wasting our Money! I was using VP Racing Gas.

One more thingy The Cannondale's Fuel injection changes the fuel to air mix on it own by way of computer. But you carb users only need to rejet.

[AndrewRRR]

Originally posted by wilkin250r
Second, a lower specific gravity means it does not do as well with pre-mix oil. The oil will not stay suspended in AVgas, and will eventually separate and settle.


Trust me I found out about that the hard way! I ran VP C-14 in my R and it was running unusually lean at florence. After tearing the carb all apart I realized the fuel was separating from the premix quick enough that you could shake it up and watch the oil settle to the bottom of the float bowl in a matter of seconds. The specific gravity was too low to keep the oil suspended. I switched to Unocal's 110 competition (and saved $150 per drum as well).

[airheadedduner]

Originally posted by AndrewRRR
I switched to Unocal's 110 competition (and saved $150 per drum as well).
Thats what I am running now. I thought that with the C-dale fuel injection that it measured the incoming airflow and metered the proper volume of fuel to get the right mixture. So even with fuel injection the different specific gravity could throw it off. The difference in spacific gravity is like .05-.06.

I think wilkin hit the nail on the head.

[AndrewRRR]

Originally posted by airheadedduner
Thats what I am running now. I thought that with the C-dale fuel injection that it measured the incoming airflow and metered the proper volume of fuel to get the right mixture. So even with fuel injection the different specific gravity could throw it off. The difference in spacific gravity is like .05-.06.

I think wilkin hit the nail on the head.

With a 4 stroke the C-14 should work fine since you don't need to mix oil in. If course I haven't seen a C-dale with compression high enough to need 114 octane. We actually switched to the 110 in the race car since it's so much cheaper and it hasn't had any problems with detonation at 15:1.

[JBBSPEED]

Originally posted by AndrewRRR
With a 4 stroke the C-14 should work fine since you don't need to mix oil in. If course I haven't seen a C-dale with compression high enough to need 114 octane. We actually switched to the 110 in the race car since it's so much cheaper and it hasn't had any problems with detonation at 15:1.

You are right i do not need octane that High so I do the following I mix the 116 rated Av gas with Amoco 93 at a 50/50 which = 104.5 even if the Av gas looses some of its octane (which it will not) it would have to drop all the way below 107 for my final mix to get below 100. I have been running my Cdale with racing gas and or Av gas from the first day I bought it in 02-05-02. I have kept the octane between 100 and 107 the whole time. The only Plug I fouled was the first one that came in the quad and I switch from a 10 to a 9 hotter plug and have not had any issues.

I know I have opened up another can of worms with mixing my fuel but I have talk to some very smart people and done my own research and this turned out to be the best for me. One thing I have learned is that my quad would not benefit form octane above 107 what that means any thing higher would not be more power. So that is why I mix my gas plus it SAVES a lot of MONEY for me in the long run.

2002 Cdale Racegas/avgas No updates to the motor... run in XC and MX races carrying an over weight guy of 260lbs. I even plan on racing some TT this year for the first time.

I must admit I never check on if the Av gas would mix with Oil for 2 strokes... This may be a big issue for them but for me and my Dale its Peachy.

[airheadedduner]

Originally posted by JBBSPEED


I know I have opened up another can of worms with mixing my fuel
I do that too, no point in running strait when you don't need to. If you go to far with high octane you can severly hurt performance. I can almost get away with pump gas but it runs way hot and it detonates under high loads.

[AndrewRRR]

When I found out the C-14 wouldn't mix with premix oil I took the 10 gallons I had left and threw in 10 gallons of 91 octane (thats the best we have here :( ). The brought the spec. gravity up high enough to run premix oil. Unfortunately the octane rating was now only like 104 (I have a mixing chart from VP) so I gave my cousin the gas for $2 a gallon (hey, sure beats pump gas!)

[F-16Guy]

I agree with what you guys are saying with regard to performance. Avgas may not give you optimum performance when compared to purpose blended race fuel, but is it a suitable substitute? I think in the hands of an informed rider and used in a bike which really requires the extra octane, avgas is a safe alternative to high priced and sometimes hard to find race fuel. Avgas does contain more long chain hydrocarbons which evaporate slower and therefore reduce vapor pressure, but does that really dramatically effect atomization? Fuel used in California is also required to maintain a maximum vapor pressure similar to avgas, and you don't hear about cars melting down because they were running too lean. It seems to me that the short chain hydrocarbons (aromatics) that are used in automotive fuel now are only used because the federal government outlawed the use of lead. Back in the day, I'd bet that the chemical makeup for auto gas was pretty similar to avgas because lead is much cheaper and more effective at raising the octane rating than aromatics such as toluene.

[JBBSPEED]

Man very awesome points made in last post.

[airheadedduner]

Originally posted by F-16Guy
I agree with what you guys are saying with regard to performance. Avgas may not give you optimum performance when compared to purpose blended race fuel, but is it a suitable substitute? I think in the hands of an informed rider and used in a bike which really requires the extra octane, avgas is a safe alternative to high priced and sometimes hard to find race fuel. Avgas does contain more long chain hydrocarbons which evaporate slower and therefore reduce vapor pressure, but does that really dramatically effect atomization? Fuel used in California is also required to maintain a maximum vapor pressure similar to avgas, and you don't hear about cars melting down because they were running too lean. It seems to me that the short chain hydrocarbons (aromatics) that are used in automotive fuel now are only used because the federal government outlawed the use of lead. Back in the day, I'd bet that the chemical makeup for auto gas was pretty similar to avgas because lead is much cheaper and more effective at raising the octane rating than aromatics such as toluene.
100% agree. Most people don't research it that well and don't know what they are getting. I think thats why some people and myself:rolleyes: jump on them when they say they run avgas. If you understand what you are getting it is a good alternitive.

[wilkin250r]

Originally posted by F-16Guy
I agree with what you guys are saying with regard to performance. Avgas may not give you optimum performance when compared to purpose blended race fuel, but is it a suitable substitute? I think in the hands of an informed rider and used in a bike which really requires the extra octane, avgas is a safe alternative to high priced and sometimes hard to find race fuel. Avgas does contain more long chain hydrocarbons which evaporate slower and therefore reduce vapor pressure, but does that really dramatically effect atomization? Fuel used in California is also required to maintain a maximum vapor pressure similar to avgas, and you don't hear about cars melting down because they were running too lean. It seems to me that the short chain hydrocarbons (aromatics) that are used in automotive fuel now are only used because the federal government outlawed the use of lead. Back in the day, I'd bet that the chemical makeup for auto gas was pretty similar to avgas because lead is much cheaper and more effective at raising the octane rating than aromatics such as toluene.

This becomes a really gray area, with several overlapping issues. There is obviously more to power than just compression and octane.

I've never personally run race gas, so this is pure speculation. Since the makeup of AV gas truly is not optimized for the conditions of offroad engines, I would imagine that in a stock engine, AV gas will make less power. However, most likely by increasing the compression to the highest possible limit allowed using AV gas (obviously beyond the ability of pump gas) you can extract more power from your engine.

If you have two extremes, on one side you get less power with AV gas, and on one side you get more power with AV gas, it makes sense that somewhere there is a crossover. The benifits of AV gas depend on which side of that crossover you are at. There are also factors such as RPM range and throttle response to consider. So much like a politician, I'll just give a general, non-committal answer. Whether AV gas is suitable as a cheap alternative to Race gas really depends on the specific makeup of the engine, as well as the demands of the rider.

Did I skirt the real issue enough? Maybe I should run for political office! :D