Race Fuel
05-14-2011, 10:18 AM
#16
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In addition, since higher octanes hamper detonation as Scott correctly says, they also can be used to cool the cylinder head(s) in very high operating temperatures such as high RPM tracks in summer. This can be especially useful for high mileage motors that don't even require above 93 octane. For example, when I track in hot weather here in Texas, I will mix some 98 or 100 octane unleaded with 93 in my 101,000 mile M3 (even though the car gets no adaptation/ignition advance benefits from the octane) just to help protect the engine. $9/gallon every once in a while is a lot less expensive than a top end rebuild!
05-14-2011, 01:19 PM
#17
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Scott and others who have pointed out that the octane rating has nothing to do with the "burning speed" or "power" a fuel produce are exactly right. You can buy high octane fuel that burns quickly once it is ignited. And, you can buy high octane fuel that burns relatively slowly once it is ignited. Everyone who is considering running racing fuel should at least educate themselves on the "Four Key Properties of Fuel" (octane, burning speed, energy value and cooling effect) as outlined here: http://www.vpracingfuels.com/page469659.html
The thing I like about running race fuel is that once you pick the right fuel for your application, you can count on the race fuel being blended the same every time. Whereas, when you buy pump gas at any given gas station, the blends are always changing (primarily for emissions reasons) and you never really know exactly what you are getting unless you stay in touch with the gas station owner / supplier to find out exactly which blends they are buying. For example, how much ethanol is blended in? What other emissions chemicals are being blended in during seasonal changes? Etc, etc.
Regarding alcohol based fuels, the most common type of alcohol used as "alcohol racing fuel" is methanol and it produces approximately half the amount of heat energy per unit of volume when compared to a gasoline fuel. Therefore, you need to burn approx two gallons of methanol to get the same amount of energy as burning one gallon of gasoline. In other words, you typically need injectors that are twice as big.
The other main alcohol fuel is ethanol and it produces approximately two thirds the amount of heat energy per unit of volume when compared to a gasoline fuel. When you do the math for E85 (which is 85% ethanol blended with 15% gasoline), you get approx 70% of the heat energy per unit of volume meaning you need to burn 1.4 gallons of E85 to get the same amount of heat energy as burning 1 gallon of gasoline. Therefore, to burn 100% E85, you need to program your ECU properly and probably run larger injectors.
Jeff
The thing I like about running race fuel is that once you pick the right fuel for your application, you can count on the race fuel being blended the same every time. Whereas, when you buy pump gas at any given gas station, the blends are always changing (primarily for emissions reasons) and you never really know exactly what you are getting unless you stay in touch with the gas station owner / supplier to find out exactly which blends they are buying. For example, how much ethanol is blended in? What other emissions chemicals are being blended in during seasonal changes? Etc, etc.
Regarding alcohol based fuels, the most common type of alcohol used as "alcohol racing fuel" is methanol and it produces approximately half the amount of heat energy per unit of volume when compared to a gasoline fuel. Therefore, you need to burn approx two gallons of methanol to get the same amount of energy as burning one gallon of gasoline. In other words, you typically need injectors that are twice as big.
The other main alcohol fuel is ethanol and it produces approximately two thirds the amount of heat energy per unit of volume when compared to a gasoline fuel. When you do the math for E85 (which is 85% ethanol blended with 15% gasoline), you get approx 70% of the heat energy per unit of volume meaning you need to burn 1.4 gallons of E85 to get the same amount of heat energy as burning 1 gallon of gasoline. Therefore, to burn 100% E85, you need to program your ECU properly and probably run larger injectors.
Jeff
05-15-2011, 04:27 AM
#18
Rennlist Member
In addition, since higher octanes hamper detonation as Scott correctly says, they also can be used to cool the cylinder head(s) in very high operating temperatures such as high RPM tracks in summer. This can be especially useful for high mileage motors that don't even require above 93 octane. For example, when I track in hot weather here in Texas, I will mix some 98 or 100 octane unleaded with 93 in my 101,000 mile M3 (even though the car gets no adaptation/ignition advance benefits from the octane) just to help protect the engine. $9/gallon every once in a while is a lot less expensive than a top end rebuild!
loss of compression? static or dynamic?
so, you mix 93 with 100 octane for what? do you really think higher intake air temps are going to increase your propensity to knock? since air density and fuel used will go down substantially with higher track temps, if you were on teh edge at 80f, you probably will be ok at 105 degree track temps with the same gas features.
Now, here you go again. using suspecion as fact. as a side note, i race and help build up a buddy's M3 engine that is near 11:0 compression and he runs 91 pump gas, even at 105 degree track temps. on the dyno, it shows no signs of detonation either. at near 350flywheel hp, if that e36 euro motor can do it, your street/track m3 should be able to handle it . You probably are just tossing money down the drain for an unneeded insurance policy.
Here is what I found, that has made me decide not to use AVGas. This and Scott's post.
"Avgas is less dense than most racing gasolines. Instead of weighing about 6.1 to 6.3 pounds per gallon like racing gasoline, it weighs 5.8 to 5.9 pounds per gallon. The racer must compensate for this by changing to richer (larger) jets in the carburetor when changing from racing gasoline to avgas.
The other major difference is octane quality. Avgas is short on octane compared to most racing gasolines. Many racing engines with "quick" spark advance curves or with no centrifugal advance have more spark advance at low rpm than avgas and some racing gasolines can handle. The result is detonation, especially during caution periods in circle track racing because all of the spark advance is "in", rpm is low, and part throttle air fuel ratios are too lean for the operating conditions. If the driver does not "work" the throttle back and forth, pistons can be "burned" which melts away part of the aluminum piston material. Inadequate octane quality is one of the quickest ways to destroy an engine. Pistons can be severely damaged during one acceleration where detonation is present and the racer may not know what is happening until it is too late.
For maximum performance and power from a racing engine, racing gasoline will normally provide better performance than avgas. Avgas can be a good gasoline for some applications, but since most racers do not know the octane requirement of their engines, they would be better off with a "real" racing gasoline that will give them the overall resistance to detonation that they need to protect their investment. If someone has spent from $15,000 to $50,000 or more on their racing engine, it is foolish to cut corners on gasoline be sure you have a gasoline with adequate octane quality."
"Avgas is less dense than most racing gasolines. Instead of weighing about 6.1 to 6.3 pounds per gallon like racing gasoline, it weighs 5.8 to 5.9 pounds per gallon. The racer must compensate for this by changing to richer (larger) jets in the carburetor when changing from racing gasoline to avgas.
The other major difference is octane quality. Avgas is short on octane compared to most racing gasolines. Many racing engines with "quick" spark advance curves or with no centrifugal advance have more spark advance at low rpm than avgas and some racing gasolines can handle. The result is detonation, especially during caution periods in circle track racing because all of the spark advance is "in", rpm is low, and part throttle air fuel ratios are too lean for the operating conditions. If the driver does not "work" the throttle back and forth, pistons can be "burned" which melts away part of the aluminum piston material. Inadequate octane quality is one of the quickest ways to destroy an engine. Pistons can be severely damaged during one acceleration where detonation is present and the racer may not know what is happening until it is too late.
For maximum performance and power from a racing engine, racing gasoline will normally provide better performance than avgas. Avgas can be a good gasoline for some applications, but since most racers do not know the octane requirement of their engines, they would be better off with a "real" racing gasoline that will give them the overall resistance to detonation that they need to protect their investment. If someone has spent from $15,000 to $50,000 or more on their racing engine, it is foolish to cut corners on gasoline be sure you have a gasoline with adequate octane quality."
true, dentonation can happen, before a driver knows what happens. its what tuning is for. the idea of av gas, and racing fuel is to slow the burn rate, so that you dont get pre ignition or detonation. you always want a rapidy expanding flame front, which pushs the piston down. thast the idea. Diesel engines run with near 18:1 compression ratios and no spark plugs and are in a constant state of knock or detonation. Diesel, is more like carosene than gasoline. Its more like Jet fuel, than gasoline.
the entire idea of higher octane fuels , is that you need to tune around them. this means, you would advance the timing, to beable to gain more mass flow. even though the energy potential is less with higher octane fuels, (Dave, you get less power by mixing 93 and 100octane to protect your M3 engine) you get more mass flow and more energy in the end by burning more of it. thats its goal. as an equally important goal, preventing pinging its function as well. However, contrary to the engine scientists here, its done by reducing the speed at which the fuel burns by use of octane. also, due to this characteristic, its abilty to be ignited is less.. both are related. Lead is used to do part of this in Avgas as well.
you say, "no its not". "get my facts straight"
so, you are saying that resisting detonation has nothing to do with burn rate.
in otherwords, do you know the difference??
Better do some research on octane my friend.
Mark
Last edited by mark kibort; 05-15-2011 at 05:08 AM.
05-15-2011, 04:46 AM
#19
Rennlist Member
Scott and others who have pointed out that the octane rating has nothing to do with the "burning speed" or "power" a fuel produce are exactly right. You can buy high octane fuel that burns quickly once it is ignited. And, you can buy high octane fuel that burns relatively slowly once it is ignited. Everyone who is considering running racing fuel should at least educate themselves on the "Four Key Properties of Fuel" (octane, burning speed, energy value and cooling effect) as outlined here: http://www.vpracingfuels.com/page469659.html
The thing I like about running race fuel is that once you pick the right fuel for your application, you can count on the race fuel being blended the same every time. Whereas, when you buy pump gas at any given gas station, the blends are always changing (primarily for emissions reasons) and you never really know exactly what you are getting unless you stay in touch with the gas station owner / supplier to find out exactly which blends they are buying. For example, how much ethanol is blended in? What other emissions chemicals are being blended in during seasonal changes? Etc, etc.
Regarding alcohol based fuels, the most common type of alcohol used as "alcohol racing fuel" is methanol and it produces approximately half the amount of heat energy per unit of volume when compared to a gasoline fuel. Therefore, you need to burn approx two gallons of methanol to get the same amount of energy as burning one gallon of gasoline. In other words, you typically need injectors that are twice as big.
The other main alcohol fuel is ethanol and it produces approximately two thirds the amount of heat energy per unit of volume when compared to a gasoline fuel. When you do the math for E85 (which is 85% ethanol blended with 15% gasoline), you get approx 70% of the heat energy per unit of volume meaning you need to burn 1.4 gallons of E85 to get the same amount of heat energy as burning 1 gallon of gasoline. Therefore, to burn 100% E85, you need to program your ECU properly and probably run larger injectors.
Jeff
The thing I like about running race fuel is that once you pick the right fuel for your application, you can count on the race fuel being blended the same every time. Whereas, when you buy pump gas at any given gas station, the blends are always changing (primarily for emissions reasons) and you never really know exactly what you are getting unless you stay in touch with the gas station owner / supplier to find out exactly which blends they are buying. For example, how much ethanol is blended in? What other emissions chemicals are being blended in during seasonal changes? Etc, etc.
Regarding alcohol based fuels, the most common type of alcohol used as "alcohol racing fuel" is methanol and it produces approximately half the amount of heat energy per unit of volume when compared to a gasoline fuel. Therefore, you need to burn approx two gallons of methanol to get the same amount of energy as burning one gallon of gasoline. In other words, you typically need injectors that are twice as big.
The other main alcohol fuel is ethanol and it produces approximately two thirds the amount of heat energy per unit of volume when compared to a gasoline fuel. When you do the math for E85 (which is 85% ethanol blended with 15% gasoline), you get approx 70% of the heat energy per unit of volume meaning you need to burn 1.4 gallons of E85 to get the same amount of heat energy as burning 1 gallon of gasoline. Therefore, to burn 100% E85, you need to program your ECU properly and probably run larger injectors.
Jeff
You might be taking the website verbage a little out of context.
Burn speed depends on many factors, but all things beng equal, higher octane will resist its abiltiy to be ignited, and also slow the flame front speed. sure, flame front speed is effected by many other factors. (turbulence in the combustion chamber, can increase or decrease flame front speed)
If you understand the differences in octane scale, you should be safe in using avgas in a race motor.
This is from
http://horsepowercalculators.net/e85...e85-calculator
The advantage of using a higher octane fuel is that the in-cylinder flame front travel rate of a higher octane mixture is slower than that of a lower octane mixture. snip
Having a higher octane mixture, slows down the burn rate. This means that we can increase our boost level, our compression ratio, or our timing advance and return the mixture to a normal burn rate similar to that of gasoline, having a similar level of ’safety’ in the cylinder, a similar mixture volatility, but albeit at a higher power level.
also, Steve Poole, having a lot of experience working with 76 racing fuels and av gas, seems to agree as well. (from my quotes above) He said:
Remember this...OCTANE is a measure of a fuels ability to resist detonation/preignition. 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.
05-15-2011, 09:04 AM
#22
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are you sure the comparison is not avgas (jet fuel) vs av gas (internal combustion fuel)?
true, dentonation can happen, before a driver knows what happens. its what tuning is for. the idea of av gas, and racing fuel is to slow the burn rate, so that you dont get pre ignition or detonation. you always want a rapidy expanding flame front, which pushs the piston down. thast the idea. Diesel engines run with near 18:1 compression ratios and no spark plugs and are in a constant state of knock or detonation. Diesel, is more like carosene than gasoline. Its more like Jet fuel, than gasoline.
true, dentonation can happen, before a driver knows what happens. its what tuning is for. the idea of av gas, and racing fuel is to slow the burn rate, so that you dont get pre ignition or detonation. you always want a rapidy expanding flame front, which pushs the piston down. thast the idea. Diesel engines run with near 18:1 compression ratios and no spark plugs and are in a constant state of knock or detonation. Diesel, is more like carosene than gasoline. Its more like Jet fuel, than gasoline.
Jet A is close to kerosene.
05-15-2011, 09:18 AM
#23
Rennlist Member
what does a high mileage motor have to do with not requiring higher octane?
loss of compression? static or dynamic?
so, you mix 93 with 100 octane for what? do you really think higher intake air temps are going to increase your propensity to knock? since air density and fuel used will go down substantially with higher track temps, if you were on teh edge at 80f, you probably will be ok at 105 degree track temps with the same gas features.
Now, here you go again. using suspecion as fact. as a side note, i race and help build up a buddy's M3 engine that is near 11:0 compression and he runs 91 pump gas, even at 105 degree track temps. on the dyno, it shows no signs of detonation either. at near 350flywheel hp, if that e36 euro motor can do it, your street/track m3 should be able to handle it . You probably are just tossing money down the drain for an unneeded insurance policy.
loss of compression? static or dynamic?
so, you mix 93 with 100 octane for what? do you really think higher intake air temps are going to increase your propensity to knock? since air density and fuel used will go down substantially with higher track temps, if you were on teh edge at 80f, you probably will be ok at 105 degree track temps with the same gas features.
Now, here you go again. using suspecion as fact. as a side note, i race and help build up a buddy's M3 engine that is near 11:0 compression and he runs 91 pump gas, even at 105 degree track temps. on the dyno, it shows no signs of detonation either. at near 350flywheel hp, if that e36 euro motor can do it, your street/track m3 should be able to handle it . You probably are just tossing money down the drain for an unneeded insurance policy.
Multiple facepalms posted here on my behalf, thanks, guys!
05-15-2011, 09:21 AM
#24
Lifetime Rennlist Member
Scott and others who have pointed out that the octane rating has nothing to do with the "burning speed" or "power" a fuel produce are exactly right. You can buy high octane fuel that burns quickly once it is ignited. And, you can buy high octane fuel that burns relatively slowly once it is ignited. Everyone who is considering running racing fuel should at least educate themselves on the "Four Key Properties of Fuel" (octane, burning speed, energy value and cooling effect) as outlined here: http://www.vpracingfuels.com/page469659.html
The thing I like about running race fuel is that once you pick the right fuel for your application, you can count on the race fuel being blended the same every time. Whereas, when you buy pump gas at any given gas station, the blends are always changing (primarily for emissions reasons) and you never really know exactly what you are getting unless you stay in touch with the gas station owner / supplier to find out exactly which blends they are buying. For example, how much ethanol is blended in? What other emissions chemicals are being blended in during seasonal changes? Etc, etc.
Regarding alcohol based fuels, the most common type of alcohol used as "alcohol racing fuel" is methanol and it produces approximately half the amount of heat energy per unit of volume when compared to a gasoline fuel. Therefore, you need to burn approx two gallons of methanol to get the same amount of energy as burning one gallon of gasoline. In other words, you typically need injectors that are twice as big.
The other main alcohol fuel is ethanol and it produces approximately two thirds the amount of heat energy per unit of volume when compared to a gasoline fuel. When you do the math for E85 (which is 85% ethanol blended with 15% gasoline), you get approx 70% of the heat energy per unit of volume meaning you need to burn 1.4 gallons of E85 to get the same amount of heat energy as burning 1 gallon of gasoline. Therefore, to burn 100% E85, you need to program your ECU properly and probably run larger injectors.
Jeff
The thing I like about running race fuel is that once you pick the right fuel for your application, you can count on the race fuel being blended the same every time. Whereas, when you buy pump gas at any given gas station, the blends are always changing (primarily for emissions reasons) and you never really know exactly what you are getting unless you stay in touch with the gas station owner / supplier to find out exactly which blends they are buying. For example, how much ethanol is blended in? What other emissions chemicals are being blended in during seasonal changes? Etc, etc.
Regarding alcohol based fuels, the most common type of alcohol used as "alcohol racing fuel" is methanol and it produces approximately half the amount of heat energy per unit of volume when compared to a gasoline fuel. Therefore, you need to burn approx two gallons of methanol to get the same amount of energy as burning one gallon of gasoline. In other words, you typically need injectors that are twice as big.
The other main alcohol fuel is ethanol and it produces approximately two thirds the amount of heat energy per unit of volume when compared to a gasoline fuel. When you do the math for E85 (which is 85% ethanol blended with 15% gasoline), you get approx 70% of the heat energy per unit of volume meaning you need to burn 1.4 gallons of E85 to get the same amount of heat energy as burning 1 gallon of gasoline. Therefore, to burn 100% E85, you need to program your ECU properly and probably run larger injectors.
Jeff
Octane is NOT resistance to what is generally called pre-ignition vs. knock. It is resistance to knock. There is a difference between pre-ignition (as the term is usually used) and knock.
Flame travel speed is not the main determinant in anti-knock properties and, as Jess said, there are different flame propagation speeds across different octanes and they do not correlate.
Alcohol (both ethanol and methanol) have higher resistance to knock - both due to their direct anti-knock and due to the fact that the latent heat of vaporization differs from gasoline.
Alcohol has a much lower energy content (BTU/LB) than gasoline. It has a higher density than gasoline which partially offsets this difference. Due to different molecule size, when you mix 1 gallon of gasoline and 1 gallon of alcohol, you get less than 2 gallons.
But WTF do I know - I didn't get my information from the INTRAWEB, I actually did combustion and knock research in college.
05-15-2011, 01:23 PM
#25
Mark,
If anything I said was wrong, it was slight. I should have said "before spark propagation" instead of "before spark". When I was typing, that is what I intended to type. I was not talking about pre-ignition. I was talking about detonation. Pre-ignition is quite uncommon. You would have to use a really bad fuel to get that.
Regardless, the actual point of my post was that octane has nothing to do with burn speed, which is fact.
Scott
If anything I said was wrong, it was slight. I should have said "before spark propagation" instead of "before spark". When I was typing, that is what I intended to type. I was not talking about pre-ignition. I was talking about detonation. Pre-ignition is quite uncommon. You would have to use a really bad fuel to get that.
Regardless, the actual point of my post was that octane has nothing to do with burn speed, which is fact.
Scott
05-15-2011, 01:38 PM
#27
Lifetime Rennlist Member
Mark,
If anything I said was wrong, it was slight. I should have said "before spark propagation" instead of "before spark". When I was typing, that is what I intended to type. I was not talking about pre-ignition. I was talking about detonation. Pre-ignition is quite uncommon. You would have to use a really bad fuel to get that.
Regardless, the actual point of my post was that octane has nothing to do with burn speed, which is fact.
Scott
If anything I said was wrong, it was slight. I should have said "before spark propagation" instead of "before spark". When I was typing, that is what I intended to type. I was not talking about pre-ignition. I was talking about detonation. Pre-ignition is quite uncommon. You would have to use a really bad fuel to get that.
Regardless, the actual point of my post was that octane has nothing to do with burn speed, which is fact.
Scott
05-15-2011, 01:42 PM
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Although I do work in the energy industry, I need to clarify that I am not a liquid fuels engineer. I am simply the type of guy who tries to properly educate myself through reading material written by authoritative sources and talking with individuals who I believe are authoritative sources. My knowledge was obtained by reading a number of publications and talking at length with fuels engineers from Sunoco Racing Fuels, VP Racing Fuels and TORCO Racing Fuels.
Regarding Mark’s observation as stated above, I would like to politely point out that I have educated myself about race fuels MUCH more thoroughly than simply “taking the website verbiage a little out of context.” To me, various race fuel engineers have given me fairly complex explanations of both detonation (or “knock”) and pre-ignition which as SundayDriver correctly points out are two very different things. To keep it simple, additives to increase a fuel’s octane rating generally raise that fuel’s temperature of ignition BUT ONCE THE FUEL IS IGNITED, THE SUSTAINED TEMPERATURE OF COMBUSTION IS QUITE A BIT HIGHER THAN THE TEMPERATURE OF IGNITION OF THE SURROUNDING AIR/FUEL MIXTURE AND THAT FUEL WILL BURN AS FAST OR SLOW AS THE FUEL WAS DESIGNED TO BURN.
Some examples:
1. A fast burning fuel (higher percentage of “light” hydrocarbons which tends to produce a lower specific gravity fuel) with no additives to increase its octane rating will ignite at a low temperature and will burn “fast”.
2. A slow burning fuel (higher percentage of “heavy” hydrocarbons which tends to result in a higher specific gravity fuel) with no additives to increase its octane rating will ignite at a low temperature and will burn “slow”.
3. A fast burning fuel with the proper additives to increase its octane rating will ignite at a higher temperature and will still burn “fast” once it is ignited.
4. A slow burning fuel with the proper additives to increase its octane rating will ignite at a higher temperature and will still burn “slow” once it is ignited.
Therefore, a fuel’s temperature of ignition (or generally, it’s resistance to detonation) and its speed of combustion are two very different things and are mutually exclusive. The temperature of ignition of any given fuel is always below that fuel’s temperature of combustion, once it is ignited. Therefore, the temperature of ignition can be viewed as the “hurdle temperature” and once you are over that hurdle, the fuel will combust at the same speed regardless of what its ignition temperature is. Make sense?
Mark, if you want to get into a very specific debate about taking the exact same fuel blend and discussing whether or not the addition of additives to raise its octane rating has some effect on its burn speed, that is a VERY different debate and does not apply in this discussion. This discussion is about the comparison of “non-race fuels” that you buy at a gas station on the street (where you never know the blend unless you talk with the station owner / supplier) to high quality “race fuels” that use very different blends that are known with precision. For anyone to generally state that higher octane race fuels burn slower and/or produce less power than lower octane street fuels is WAY off base.
Regarding pre-ignition, the simple explanation is that this is generally caused in an engine that has some condition that develops internal “hot spots” which “pre-ignite” the fuel before the spark. One example is internal carbon deposits that become glowing red little hot spots inside the combustion chamber or another example is slight imperfections (or sharp edges) on the pistons or valves or cylinder head that are prone to become hot spots. As VR has correctly pointed out, on an engine that has high miles on it, it is much more likely to have one or more of these conditions that can cause pre-ignition and it is a VERY good idea to run a blend of the proper high octane race fuel to give you some extra margin of safety. In addition, VR probably also has properly recognized that race fuels have a known cooling effect in the combustion chamber, whereas, the cooling effect when using street fuel blends is difficult to determine because you never know what blend you are getting.
Jeff
Jeff, you might be taking the website verbage a little out of context. Burn speed depends on many factors, but all things beng equal, higher octane will resist its abiltiy to be ignited, and also slow the flame front speed. sure, flame front speed is effected by many other factors. (turbulence in the combustion chamber, can increase or decrease flame front speed).
Some examples:
1. A fast burning fuel (higher percentage of “light” hydrocarbons which tends to produce a lower specific gravity fuel) with no additives to increase its octane rating will ignite at a low temperature and will burn “fast”.
2. A slow burning fuel (higher percentage of “heavy” hydrocarbons which tends to result in a higher specific gravity fuel) with no additives to increase its octane rating will ignite at a low temperature and will burn “slow”.
3. A fast burning fuel with the proper additives to increase its octane rating will ignite at a higher temperature and will still burn “fast” once it is ignited.
4. A slow burning fuel with the proper additives to increase its octane rating will ignite at a higher temperature and will still burn “slow” once it is ignited.
Therefore, a fuel’s temperature of ignition (or generally, it’s resistance to detonation) and its speed of combustion are two very different things and are mutually exclusive. The temperature of ignition of any given fuel is always below that fuel’s temperature of combustion, once it is ignited. Therefore, the temperature of ignition can be viewed as the “hurdle temperature” and once you are over that hurdle, the fuel will combust at the same speed regardless of what its ignition temperature is. Make sense?
Mark, if you want to get into a very specific debate about taking the exact same fuel blend and discussing whether or not the addition of additives to raise its octane rating has some effect on its burn speed, that is a VERY different debate and does not apply in this discussion. This discussion is about the comparison of “non-race fuels” that you buy at a gas station on the street (where you never know the blend unless you talk with the station owner / supplier) to high quality “race fuels” that use very different blends that are known with precision. For anyone to generally state that higher octane race fuels burn slower and/or produce less power than lower octane street fuels is WAY off base.
Regarding pre-ignition, the simple explanation is that this is generally caused in an engine that has some condition that develops internal “hot spots” which “pre-ignite” the fuel before the spark. One example is internal carbon deposits that become glowing red little hot spots inside the combustion chamber or another example is slight imperfections (or sharp edges) on the pistons or valves or cylinder head that are prone to become hot spots. As VR has correctly pointed out, on an engine that has high miles on it, it is much more likely to have one or more of these conditions that can cause pre-ignition and it is a VERY good idea to run a blend of the proper high octane race fuel to give you some extra margin of safety. In addition, VR probably also has properly recognized that race fuels have a known cooling effect in the combustion chamber, whereas, the cooling effect when using street fuel blends is difficult to determine because you never know what blend you are getting.
Jeff
05-15-2011, 01:46 PM
#29
Rennlist Member
Mark,
If anything I said was wrong, it was slight. I should have said "before spark propagation" instead of "before spark". When I was typing, that is what I intended to type. I was not talking about pre-ignition. I was talking about detonation. Pre-ignition is quite uncommon. You would have to use a really bad fuel to get that.
Regardless, the actual point of my post was that octane has nothing to do with burn speed, which is fact.
Scott
If anything I said was wrong, it was slight. I should have said "before spark propagation" instead of "before spark". When I was typing, that is what I intended to type. I was not talking about pre-ignition. I was talking about detonation. Pre-ignition is quite uncommon. You would have to use a really bad fuel to get that.
Regardless, the actual point of my post was that octane has nothing to do with burn speed, which is fact.
Scott
Hey, ill be the first to admit that Im not a fuel engineer. never claimed to be. but, now this group all claims to be experts now. octane has "NOTHING" to do with flame front propagation. is that what you all are saying? ive heard that it did and quoted a 76 engineer, as was quoted by someone else as well and both are a little contradictary, dont you think. Is Steve Pool right or Tim Wusz.
anyway, VR can pump in an extra $20 a tank full so that he feels better about his M3 motor on DE days.
most of the time, race gas is dumped in to get preceieved gains and its usually just robbing pwer. the smart guys mix it to protect their 11.5:1 compression ratio motors, and the real race engines need it to stop the chance of detonation, or knocks. Does octane do it by making it harder to ignite the fuel load, or slow propagation of the flame front, I dont know for sure. you think you do. two quotes say it will. in the end, this thread is about race gas vs av fuel. it has been used by racers for years and there are some subtle differences that should be looked at.No need to be insulting, and imature about it. this is a discussion, not some text that will live forever to be tapped on by future generations. You need to sit back and pretend we are talking and discussing this over a Beer or at the track and stop getting so damn arrogant! you comment like you have small man's complex.
05-15-2011, 01:52 PM
#30
Rennlist Member
Tim Wusz, says: http://www.osbornauto.com/racing/race2avgas.htm
or this 76 representiive steve poole
Real info on Race Gas/Av Gas...
My experience comes from 7 years as the western states representative for 76 Race Fuel, Unocals 40 hours Advanced Products course, Working personally with Tim Wusz (senior performance products Rep for Unocal, Tim was responsible for Unocals 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 Unocals 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, F;ashpoint, 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/TetraEthylLead (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 gasolines.
Shelf life is NOT better. The reason pump gas won't last as long is because street gas has extremely lightend 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/preignite causing detination. 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 harden valve seats. There is no need for lubrication of the valve seats. All engines have come with harden 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 your running commercial grade gasoline, more timing can cause detonation/preignition quit 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/preignition. 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
both of these guys worked together but have a slightly different take on octane.
which is right??
or this 76 representiive steve poole
Real info on Race Gas/Av Gas...
My experience comes from 7 years as the western states representative for 76 Race Fuel, Unocals 40 hours Advanced Products course, Working personally with Tim Wusz (senior performance products Rep for Unocal, Tim was responsible for Unocals 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 Unocals 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, F;ashpoint, 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/TetraEthylLead (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 gasolines.
Shelf life is NOT better. The reason pump gas won't last as long is because street gas has extremely lightend 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/preignite causing detination. 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 harden valve seats. There is no need for lubrication of the valve seats. All engines have come with harden 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 your running commercial grade gasoline, more timing can cause detonation/preignition quit 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/preignition. 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
both of these guys worked together but have a slightly different take on octane.
which is right??