FireHead Posted March 7, 2007 Report Share Posted March 7, 2007 AV fuel is absolutely fine to run and will not hurt an engine at all. Its higher octane is is mostly achieved by the introduction of lead in the fuel. Lead retards detonation by absorbing shock waves at at molecular level and, as being a non-ferrous metal, absorbs heat readily. This means it will actually extract heat from the combustion cycle and carry it out the pipe. Lead also acts as a lubricant to further reduce the chance of detonation. Anytime you purchase a commercial fuel that must meet so many criteria and EPA guidelines, it has to have special additives. These additives lengthen shelf life, reduce fuel gel, minimize deposits, and so on. These additives can be as much as 15% of a given fuel by volume. These fillers do not contribute to the combustion cycle thus acting as "inert" fillers in the cycle. No good for HP but when your flying, fuel gel can be a much bigger concern. Racing fuels by design are refined with different guidelines and additives are drastically reduced thus allowing more burnable fuel in the combustion cycle. They generally have more lead as well to also raise the octane number as well. In short, race fuels are far superior to AV fuels, BUT, please keep in mind that as the octane of a fuel is raise, so is it's rate of combustion. This means DO NOT buy more octane than you need. Please use octane as a " safety" number as this is only the rating of a fuels resistance to pre-ignition. I think someone was asking about 175psi static with 4 degrees advanced. That setup at sea level might indicate a 21cc chamber with a stock port height and a corrected comp ratio of 6.8:1. That ratio is within the safe limits of standard pump fuel. Will someone make more power with AV fuel with that setup? NOPE. With race fuel? only if the ignition is further advanced to compensate for the slower burn rate. You have to "get the party started" a little earlier with race fuels. The nice thing with race fuels in thumpers is the slower burn rate really helps by applying for to the piston through most of the stroke, not just 20 degrees like pump fuels. Unfortunately, two-strokes do not have a long enough blow down time to take full advantage of this. In short, you should only use AV fuel over pump to supress detonation, not the make power. The big power gain is in Alky because it has extra O2 bonded in the fuels molecules thus acting like a small chemical supercharger. Methyl fuels will contain almost 50% O2 by molecular composition. Don't take the following the wrong way, I couldn't figure out a good way tp say any of this without being an ass. To avoid reponding to each in full, please do a search in this forum on this topic. :thumbsup: Your statements about lead in AVgas are misleading. AVgas is not always leaded. AVgas cna be an EPA controlled fuel depending on the fuel type. Race fuel is also not always leaded. Race fuels are also typically based on a different hydrocarbon string than AV or pump gas. Your commentary on how ignition advance ties in with the use of race fuel is misleading and mostly incorrect. Especially, the portion regarding the blow down time. You will not make any more power with pump, AV, or race gas if you make the assumption that you are using the lowest possible octane without detonation and the fuel does not have any oxygenation additives in it. The statements you made about alcohol is pretty much inaccurate as well. Quote Link to comment Share on other sites More sharing options...
grpark20 Posted March 7, 2007 Author Report Share Posted March 7, 2007 what part of washington are you from?? Spanaway, WA Quote Link to comment Share on other sites More sharing options...
grpark20 Posted March 7, 2007 Author Report Share Posted March 7, 2007 How does a person come to have this information about another person? One could only imagine..........I'm in Spanaway, WA Quote Link to comment Share on other sites More sharing options...
FireHead Posted March 7, 2007 Report Share Posted March 7, 2007 Spanaway, WA The Unocal station on Auburn's auto row sells Trick race gas from a pump and is by far the best value near you. Federal Way Cycle center sells race gas as does Kart-o-rama in Spanaway. :thumbsup: Quote Link to comment Share on other sites More sharing options...
grpark20 Posted March 7, 2007 Author Report Share Posted March 7, 2007 The Unocal station on Auburn's auto row sells Trick race gas from a pump and is by far the best value near you. Federal Way Cycle center sells race gas as does Kart-o-rama in Spanaway. :thumbsup: WOW!!!! Thanks for that info. I would have done the research myself, but at the time I'm in Iraq. Thanls alot Quote Link to comment Share on other sites More sharing options...
grpark20 Posted March 7, 2007 Author Report Share Posted March 7, 2007 AV fuel is absolutely fine to run and will not hurt an engine at all. Its higher octane is is mostly achieved by the introduction of lead in the fuel. Lead retards detonation by absorbing shock waves at at molecular level and, as being a non-ferrous metal, absorbs heat readily. This means it will actually extract heat from the combustion cycle and carry it out the pipe. Lead also acts as a lubricant to further reduce the chance of detonation. Anytime you purchase a commercial fuel that must meet so many criteria and EPA guidelines, it has to have special additives. These additives lengthen shelf life, reduce fuel gel, minimize deposits, and so on. These additives can be as much as 15% of a given fuel by volume. These fillers do not contribute to the combustion cycle thus acting as "inert" fillers in the cycle. No good for HP but when your flying, fuel gel can be a much bigger concern. Racing fuels by design are refined with different guidelines and additives are drastically reduced thus allowing more burnable fuel in the combustion cycle. They generally have more lead as well to also raise the octane number as well. In short, race fuels are far superior to AV fuels, BUT, please keep in mind that as the octane of a fuel is raise, so is it's rate of combustion. This means DO NOT buy more octane than you need. Please use octane as a " safety" number as this is only the rating of a fuels resistance to pre-ignition. I think someone was asking about 175psi static with 4 degrees advanced. That setup at sea level might indicate a 21cc chamber with a stock port height and a corrected comp ratio of 6.8:1. That ratio is within the safe limits of standard pump fuel. Will someone make more power with AV fuel with that setup? NOPE. With race fuel? only if the ignition is further advanced to compensate for the slower burn rate. You have to "get the party started" a little earlier with race fuels. The nice thing with race fuels in thumpers is the slower burn rate really helps by applying for to the piston through most of the stroke, not just 20 degrees like pump fuels. Unfortunately, two-strokes do not have a long enough blow down time to take full advantage of this. In short, you should only use AV fuel over pump to supress detonation, not the make power. The big power gain is in Alky because it has extra O2 bonded in the fuels molecules thus acting like a small chemical supercharger. Methyl fuels will contain almost 50% O2 by molecular composition. WOW!!! Sounds like a lot of info. Thanks for your advice/opinion, or facts. But with all the research I've been doing on this subject......there is no way I'm going to run 175psi with +4 timing @ sea level with 21cc domes on PUMP FUEL. Not saying you can or can't do it. Just sounds like to me the only person that would gain from this is Jeff @ F.A.S.T. But thankyou for sharing your info. I'm here to learn. Quote Link to comment Share on other sites More sharing options...
blowit Posted March 7, 2007 Report Share Posted March 7, 2007 WOW!!! Sounds like a lot of info. Thanks for your advice/opinion, or facts. But with all the research I've been doing on this subject......there is no way I'm going to run 175psi with +4 timing @ sea level with 21cc domes on PUMP FUEL. Not saying you can or can't do it. Just sounds like to me the only person that would gain from this is Jeff @ F.A.S.T. But thankyou for sharing your info. I'm here to learn. I guess I should not make generalizations here but "generally" speaking, most AV fuels ARE leaded and so are racing fuels. I am well aware of unleaded race fuels but I am not aware of any 110 octane unleaded fuels. You cannot achieve higher amounts than 100% iso-octane in a given fuel chain. Anything over 100 octane is a calculated "performance" number based on data back side of the 100 octane limit and the Engine test data. As I recall, most of this power 110, Trick 110, VP110, which I believe to all be the same fuel, all share the same specific gravity, and lead content which I think was 4.23 grams/gal. Yes sir, I do know what blow down time is and the term is used in two strokes as the port time in degrees in which the exhaust port is open and the transfers are not thus blowing down the pressure in the cylinder. I guess I should have used power stroke for you. Yes, you do need to light race fuel sooner because it burns slower. That is not my opinion, it is in the books. There are burn rates for every fuel out there and the lower the octane, the faster and less controlled it is. Fuel "tuning" is something that few people do but we have proven more power just by adding a few ounces of Acetone with some of our fuels, for example, and helps a bunch to speed the burn rate. I am very familiar with Alky and the O2 numbers are based on the H molocules bonded to that carbon. The reasoning behind the O2 content at any given time gets very exhaustive. I am sure you know that H is very attractive to O thus the reason it is a Hygroscopic fuel. This is also why it takes so darn much fuel when running methanol. It is also slightly acidic and likes to attack the oxide protective layer of Al. there are so many variables with gasolines like how the fuel was cracked, how it was blended, what additives were used. Also with race and AV fuels, you just have to know what you are buying. Alky on the other hand, is a very simple compound. Only drawback is it does not have as many BTU's/gal as gasoline. Quote Link to comment Share on other sites More sharing options...
blowit Posted March 7, 2007 Report Share Posted March 7, 2007 Oh, I did do a search and quit when I read a post that someone says that octane is the most explosive compound. Ouch, I don't want any then. I think Heptane and Octane got rather interlaced there. I would not that the hydrocarbon chaining of AV fuel is much closer to that of common race fuels than that of standard pump fuel. Either way, we still cannot use all the potential of Gasoline because we cannot break that darn fuel apart during combustion Quote Link to comment Share on other sites More sharing options...
burleybanshee Posted March 7, 2007 Report Share Posted March 7, 2007 I don't claim to be an expert in fuels, but i see that both Firehead and blowit do both have knowledge on this subject and both sound to be close, just picking a few words here and there, if they were in person they would communicate same things a little better I believe. I fly and have a general understanding of av gas. An piston powered aircraft normal operates in a 2000 rpm range for flight. The av gas is designed to provide anti-gel and water seperation qualities so the engine keeps running at 18,000 feet at -10 degrees. The burn rate is designed for lower rpm's of the aircraft engine and not 10,000-12,000 rpm like race engines that run race fuels. The fuels are similar in make up and octane but there are enough differences that you should run the race gas over av gas. Quote Link to comment Share on other sites More sharing options...
Snopczynski Posted March 7, 2007 Report Share Posted March 7, 2007 Yeah that Unocal is on Auburn Way by Auburn Chevrolet. I believe there is a sunoco place in Sumner also. Quote Link to comment Share on other sites More sharing options...
grpark20 Posted March 8, 2007 Author Report Share Posted March 8, 2007 I don't claim to be an expert in fuels, but i see that both Firehead and blowit do both have knowledge on this subject and both sound to be close, just picking a few words here and there, if they were in person they would communicate same things a little better I believe. I fly and have a general understanding of av gas. An piston powered aircraft normal operates in a 2000 rpm range for flight. The av gas is designed to provide anti-gel and water seperation qualities so the engine keeps running at 18,000 feet at -10 degrees. The burn rate is designed for lower rpm's of the aircraft engine and not 10,000-12,000 rpm like race engines that run race fuels. The fuels are similar in make up and octane but there are enough differences that you should run the race gas over av gas. Thanks for the simplified version. Was ready to break out the dictionary to figure out some of this stuff. The only reason I am thinking of running AV Gas is to prevent detonation from occuring. No power gain. But if it's worth doing, it's worth doing right...still doing some research though but keep the info coming!! Thanks again!! Quote Link to comment Share on other sites More sharing options...
grpark20 Posted March 8, 2007 Author Report Share Posted March 8, 2007 Yeah that Unocal is on Auburn Way by Auburn Chevrolet. I believe there is a sunoco place in Sumner also. What part of Washington are you from? Quote Link to comment Share on other sites More sharing options...
FireHead Posted March 8, 2007 Report Share Posted March 8, 2007 What part of Washington are you from? I grew up in Auburn by SIR (Pacific Raceways). :thumbsup: Quote Link to comment Share on other sites More sharing options...
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