Help with avgas stoichiometric, facts only please
06-27-2011, 11:27 PM
#1
Help with avgas stoichiometric, facts only please Im finally seeing the light at the end of the tunnel on my YSI upgrade and need to get some final info on tuning. I need to know what the stoichiometric of 100LL avgas is because thats what I am going to have the car tuned on. If you have done this please share your experiences with it and how it runs vs c16 or 93 in a FI setup. The only real document I found online was that it is at about 15.1:1, is this correct?
06-30-2011, 08:45 PM
#3
Most people with EFI do not mess with leaded fuels due to the potential o2 sensor issues.
As for AV gas, I run it in my carbed big block Camaro & also in my quads. Just bought a bunch yesterday for $5.65 per gallon. Never noticed a big jetting difference over pump fuel.
As for stoic... it is probably around 14.7, but it doesn't matter. This is the cruise ratio. You need to tune for power & the correct number is what the car likes. Start around 11:1 & keep leaning slightly for best power. I probably would stay around 11.5 at the leanest for safety on a big power forced induction application.
Not sure if this answers your question.
As for AV gas, I run it in my carbed big block Camaro & also in my quads. Just bought a bunch yesterday for $5.65 per gallon. Never noticed a big jetting difference over pump fuel.
As for stoic... it is probably around 14.7, but it doesn't matter. This is the cruise ratio. You need to tune for power & the correct number is what the car likes. Start around 11:1 & keep leaning slightly for best power. I probably would stay around 11.5 at the leanest for safety on a big power forced induction application.
Not sure if this answers your question.
06-30-2011, 08:55 PM
#4
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man I'm getting old and cant remember all the facts. What I remember was having problems with nitrous and av gas due to the different burn rate it has and timing issues with it. Av gas (the one I had) is usually high altitude fuel. We switched to helicopter fuel which run at lower altitudes and it fixed our timing and nitrous problem. Don't remember which fuel it was as this was back in the mid to early 80's.
07-01-2011, 11:16 PM
#5
Most people with EFI do not mess with leaded fuels due to the potential o2 sensor issues.
As for AV gas, I run it in my carbed big block Camaro & also in my quads. Just bought a bunch yesterday for $5.65 per gallon. Never noticed a big jetting difference over pump fuel.
As for stoic... it is probably around 14.7, but it doesn't matter. This is the cruise ratio. You need to tune for power & the correct number is what the car likes. Start around 11:1 & keep leaning slightly for best power. I probably would stay around 11.5 at the leanest for safety on a big power forced induction application.
Not sure if this answers your question.
As for AV gas, I run it in my carbed big block Camaro & also in my quads. Just bought a bunch yesterday for $5.65 per gallon. Never noticed a big jetting difference over pump fuel.
As for stoic... it is probably around 14.7, but it doesn't matter. This is the cruise ratio. You need to tune for power & the correct number is what the car likes. Start around 11:1 & keep leaning slightly for best power. I probably would stay around 11.5 at the leanest for safety on a big power forced induction application.
Not sure if this answers your question.
man I'm getting old and cant remember all the facts. What I remember was having problems with nitrous and av gas due to the different burn rate it has and timing issues with it. Av gas (the one I had) is usually high altitude fuel. We switched to helicopter fuel which run at lower altitudes and it fixed our timing and nitrous problem. Don't remember which fuel it was as this was back in the mid to early 80's.
07-02-2011, 04:53 PM
#6
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If you are using a wideband, then stioch really doesnt matter. The wideband doesnt know or care what fuel you are using. The AFR you see on a display is purely a maths function.
AFR's relative to stioch will only change if you program the wideband to output a different number.
So in effect, you can just tune to typical gasoline AFR's, or lambda or whatever units you have chosen.
The only time you will need to use fuel specific AFR's is if you program the wideband to output for this fuel. But the wideband will still be reading the exact same thing.
And as stated, optimum/safe mixture will only be determined through proper dyno testing, and perhaps also monitoring EGT's
AFR's relative to stioch will only change if you program the wideband to output a different number.
So in effect, you can just tune to typical gasoline AFR's, or lambda or whatever units you have chosen.
The only time you will need to use fuel specific AFR's is if you program the wideband to output for this fuel. But the wideband will still be reading the exact same thing.
And as stated, optimum/safe mixture will only be determined through proper dyno testing, and perhaps also monitoring EGT's
07-04-2011, 11:37 AM
#7
If you are using a wideband, then stioch really doesnt matter. The wideband doesnt know or care what fuel you are using. The AFR you see on a display is purely a maths function.
AFR's relative to stioch will only change if you program the wideband to output a different number.
So in effect, you can just tune to typical gasoline AFR's, or lambda or whatever units you have chosen.
The only time you will need to use fuel specific AFR's is if you program the wideband to output for this fuel. But the wideband will still be reading the exact same thing.
And as stated, optimum/safe mixture will only be determined through proper dyno testing, and perhaps also monitoring EGT's
AFR's relative to stioch will only change if you program the wideband to output a different number.
So in effect, you can just tune to typical gasoline AFR's, or lambda or whatever units you have chosen.
The only time you will need to use fuel specific AFR's is if you program the wideband to output for this fuel. But the wideband will still be reading the exact same thing.
And as stated, optimum/safe mixture will only be determined through proper dyno testing, and perhaps also monitoring EGT's
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07-04-2011, 04:37 PM
#8
100ll 100 LL is only low lead only compared to the old 100/130, 2 grams/gal compared to 4 grams. Years ago I used to mix 100 LL 50/50 with 92 unleaded(no ethanol) and was able to drive a 72 pickup with a 12.2:1 compression ratio and a 350hp327 cam(about 222 @.50 if i remember right), on the street, safely without pinging. Would ping on the 92 alone. would ping on 92 with octane booster. Ran fine with 50/50 92 and 100LL. The extra lead gave the 92 a little kick in octane. I had water injection on the motor for trips away from my home radius, in which I used 50% methanol, 50% water. That with octane booster worked too. I fly, have a tank with 100 LL on premise, so it was not a hassle. At the time, My diesel supplier would bring me 1000 gal of 100 when he brought a tanker of diesel. At that time 92 was about 1.35 and I was getting 100LL for about 1.45.
The best part of the 100LL is extremely long shelf life, nice aroma, and it is always exactly the same. Since the amount of lead in it fouls spark plugs in low performance airplane motors I would think it would kill o2's in a heartbeat. It still has more lead than the old Sunoco 260. At the current 4.80 or so I pay for 100LL while gas is 3.40, I know I wouldn't go through the hassle for the small gain unless you already have it very handy. I think real race gas will make more power also. As stated the sensors read lambda, so they don't know or care the actual afr, only lambda and use the reciprocal( eq ratio) for calculating fueling.
That's not FI ls1 experience but I daily drove and towed a boat with that motor about 40,000 miles and kept it from knocking on that mixture, but I probably wouldn't use it unless I had it on hand a t todays prices. It will keep forever in a seldom driven vehicle however. Thats most of why it is good for airplanes. My tuner loves E85, about 2.50 currently at local ethanol plants, and provides better protection for forced induction, no sensor problems. Just my 2 cents. Computor will work fine til sensors foul, which will be rather quickly.
The best part of the 100LL is extremely long shelf life, nice aroma, and it is always exactly the same. Since the amount of lead in it fouls spark plugs in low performance airplane motors I would think it would kill o2's in a heartbeat. It still has more lead than the old Sunoco 260. At the current 4.80 or so I pay for 100LL while gas is 3.40, I know I wouldn't go through the hassle for the small gain unless you already have it very handy. I think real race gas will make more power also. As stated the sensors read lambda, so they don't know or care the actual afr, only lambda and use the reciprocal( eq ratio) for calculating fueling.
That's not FI ls1 experience but I daily drove and towed a boat with that motor about 40,000 miles and kept it from knocking on that mixture, but I probably wouldn't use it unless I had it on hand a t todays prices. It will keep forever in a seldom driven vehicle however. Thats most of why it is good for airplanes. My tuner loves E85, about 2.50 currently at local ethanol plants, and provides better protection for forced induction, no sensor problems. Just my 2 cents. Computor will work fine til sensors foul, which will be rather quickly.
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07-04-2011, 07:16 PM
#9
Hey thanks bsomm, this is a great post! I used a bunch a few years ago when I worked line service at the airport just putting the sumped fuel out of our refueling truck into my 99 trans am. I would mix like 2 gals with 87 gas. It ran great and after doing that for at least 6 months straight, I never fouled a plug or threw a bad 02 code. Obviously I will be running it straight in the camaro in question because I have to keep the consistency with the tune. As for getting it, I am a pilot so when I go to work I can take my barrels with me and have them filled up. Its about $5.50 a gal right now vs $8.99 for the 110 octane at the gas station down the road. I would love to do an e-85 tune because it would be way better, only thing is I dont have the fuel system to support it, and I have to drive almost 2 hours away to the east side of columbus to get it in barrels, so if I was out and ran out I would have no way to get any gas to get home. This is the unfortunate side, eventhough I am a very big fan of the e-85 until a gas station sells it where I am located it isnt feasable, and since everbody around here drive old shitboxes that arent flexfuel I doubt we will have it anytime soon.
07-05-2011, 10:11 AM
#10
Like Clint Eastwood said "Every man has to know his own limitations". I have 2 ethanol plants within 30 miles of me, here. I am a farmer, keep some gas for vehicles, lawn tractors, generators, pumps, etc. I don't use e85 as it draws moisture and won't keep as well as straight gas for extended periods. I do have neighbors that get straight ethanol and blend unleaded into e85. Easy to find here. The extra volume of liquid provides a great cooling effect on top of the increased octane. It also makes your gas tank get pretty small as you will burn almost 40% more of it, theoretically.
There is no road tax on 100LL, but there is an aviation trust fund tax. I don't know how much it is or when, where it is collected. Tankers will have 4 or 5 compartments in a tanker, one or two of them will be small (900 or 1100 gal). If you can set up a 1000 gal tank on running gear, you can probably talk someone into bringing you that small compartment considerably cheaper than an fbo. If you make it easy for them most will sell you fuel for pretty modest markup if the tanker doesn't have to go out of its way.
One other possibility is a marina that has 93 octane. Good marinas have straight unleaded for performance boats, the 93 straight unleaded is pretty good fuel. Some of them only sell to boats because of the road tax issue, but again a good jobber will get it for you if you're patient . It is much harder to find than 100 LL though. I usually only see it on the Missouri lakes with lots of offshore boats, or Oklahoma. I know Kansas and Missouri do not have to label whether or not ethanol is in gas, so a marina on a big lake is about the only source of non ethanol 93 around here. I know a couple people running reasonable amounts of boost on bbc's in offshore boats with 93, but those applications are very consitent ect's because of lake water cooling, and cold (lake)water to air intercoolers. More than 6 or 7 lbs of boost or too small of intercoolers gets into problems quickly.
I have a mildly modified Cr 250 dirt bike than does ok on 92 for motocross, but 50/50 92 and 100LL won't keep it happy in the Oklahoma sand dunes. They have 110 available there and it requires it in the dunes that pull hard and gets everything heatsoaked from the constant load. The ambient temperature and heat soak is the biggest variable on that bike for for jetting changes, fuel mix doesn't seem to change it much.
Don't know if any of that is useful, just my experience over the years.
There is no road tax on 100LL, but there is an aviation trust fund tax. I don't know how much it is or when, where it is collected. Tankers will have 4 or 5 compartments in a tanker, one or two of them will be small (900 or 1100 gal). If you can set up a 1000 gal tank on running gear, you can probably talk someone into bringing you that small compartment considerably cheaper than an fbo. If you make it easy for them most will sell you fuel for pretty modest markup if the tanker doesn't have to go out of its way.
One other possibility is a marina that has 93 octane. Good marinas have straight unleaded for performance boats, the 93 straight unleaded is pretty good fuel. Some of them only sell to boats because of the road tax issue, but again a good jobber will get it for you if you're patient . It is much harder to find than 100 LL though. I usually only see it on the Missouri lakes with lots of offshore boats, or Oklahoma. I know Kansas and Missouri do not have to label whether or not ethanol is in gas, so a marina on a big lake is about the only source of non ethanol 93 around here. I know a couple people running reasonable amounts of boost on bbc's in offshore boats with 93, but those applications are very consitent ect's because of lake water cooling, and cold (lake)water to air intercoolers. More than 6 or 7 lbs of boost or too small of intercoolers gets into problems quickly.
I have a mildly modified Cr 250 dirt bike than does ok on 92 for motocross, but 50/50 92 and 100LL won't keep it happy in the Oklahoma sand dunes. They have 110 available there and it requires it in the dunes that pull hard and gets everything heatsoaked from the constant load. The ambient temperature and heat soak is the biggest variable on that bike for for jetting changes, fuel mix doesn't seem to change it much.
Don't know if any of that is useful, just my experience over the years.
07-08-2011, 11:23 AM
#11
Like Clint Eastwood said "Every man has to know his own limitations". I have 2 ethanol plants within 30 miles of me, here. I am a farmer, keep some gas for vehicles, lawn tractors, generators, pumps, etc. I don't use e85 as it draws moisture and won't keep as well as straight gas for extended periods. I do have neighbors that get straight ethanol and blend unleaded into e85. Easy to find here. The extra volume of liquid provides a great cooling effect on top of the increased octane. It also makes your gas tank get pretty small as you will burn almost 40% more of it, theoretically.
There is no road tax on 100LL, but there is an aviation trust fund tax. I don't know how much it is or when, where it is collected. Tankers will have 4 or 5 compartments in a tanker, one or two of them will be small (900 or 1100 gal). If you can set up a 1000 gal tank on running gear, you can probably talk someone into bringing you that small compartment considerably cheaper than an fbo. If you make it easy for them most will sell you fuel for pretty modest markup if the tanker doesn't have to go out of its way.
One other possibility is a marina that has 93 octane. Good marinas have straight unleaded for performance boats, the 93 straight unleaded is pretty good fuel. Some of them only sell to boats because of the road tax issue, but again a good jobber will get it for you if you're patient . It is much harder to find than 100 LL though. I usually only see it on the Missouri lakes with lots of offshore boats, or Oklahoma. I know Kansas and Missouri do not have to label whether or not ethanol is in gas, so a marina on a big lake is about the only source of non ethanol 93 around here. I know a couple people running reasonable amounts of boost on bbc's in offshore boats with 93, but those applications are very consitent ect's because of lake water cooling, and cold (lake)water to air intercoolers. More than 6 or 7 lbs of boost or too small of intercoolers gets into problems quickly.
I have a mildly modified Cr 250 dirt bike than does ok on 92 for motocross, but 50/50 92 and 100LL won't keep it happy in the Oklahoma sand dunes. They have 110 available there and it requires it in the dunes that pull hard and gets everything heatsoaked from the constant load. The ambient temperature and heat soak is the biggest variable on that bike for for jetting changes, fuel mix doesn't seem to change it much.
Don't know if any of that is useful, just my experience over the years.
There is no road tax on 100LL, but there is an aviation trust fund tax. I don't know how much it is or when, where it is collected. Tankers will have 4 or 5 compartments in a tanker, one or two of them will be small (900 or 1100 gal). If you can set up a 1000 gal tank on running gear, you can probably talk someone into bringing you that small compartment considerably cheaper than an fbo. If you make it easy for them most will sell you fuel for pretty modest markup if the tanker doesn't have to go out of its way.
One other possibility is a marina that has 93 octane. Good marinas have straight unleaded for performance boats, the 93 straight unleaded is pretty good fuel. Some of them only sell to boats because of the road tax issue, but again a good jobber will get it for you if you're patient . It is much harder to find than 100 LL though. I usually only see it on the Missouri lakes with lots of offshore boats, or Oklahoma. I know Kansas and Missouri do not have to label whether or not ethanol is in gas, so a marina on a big lake is about the only source of non ethanol 93 around here. I know a couple people running reasonable amounts of boost on bbc's in offshore boats with 93, but those applications are very consitent ect's because of lake water cooling, and cold (lake)water to air intercoolers. More than 6 or 7 lbs of boost or too small of intercoolers gets into problems quickly.
I have a mildly modified Cr 250 dirt bike than does ok on 92 for motocross, but 50/50 92 and 100LL won't keep it happy in the Oklahoma sand dunes. They have 110 available there and it requires it in the dunes that pull hard and gets everything heatsoaked from the constant load. The ambient temperature and heat soak is the biggest variable on that bike for for jetting changes, fuel mix doesn't seem to change it much.
Don't know if any of that is useful, just my experience over the years.
07-11-2011, 06:51 PM
#12
Ok after a long day at the dyno shop on saturday the car has been successfully tuned on avgas. For anyone that is interested in ever doing this I can say that it is good stuff. With 18psi hitting the intake we were able to run 21* of timing and the computer never pulled any timing because of knock. It is just like c16 or whatever your favorite brand is, with the nice aroma and only 1/3 the lead. Anyway it put down 856rwhp with the YSI. Thanks for all the input, and I will leave this thread posted in case anyone has any questions. I will also put up a build thread with some pics of the setup in the next couple of days in the FI section.
07-13-2011, 01:42 PM
#13
I looked on an old tax return, form 4136, has a place for non aviation use of aviation fuel. If you take your receipts to your tax preparer, it is a simple form and will get you 19.3 cents per gallon refunded. Within 100 mile radius, I found 100 ll from 4.30 to 7.72 today on 100ll.com. I bet you could get it from a tanker for 4.00 easily if you get to using a lot of it, and .193 less than that after the refund. Less than the crappy 91 premium around here.
07-14-2011, 10:15 PM
#14
I looked on an old tax return, form 4136, has a place for non aviation use of aviation fuel. If you take your receipts to your tax preparer, it is a simple form and will get you 19.3 cents per gallon refunded. Within 100 mile radius, I found 100 ll from 4.30 to 7.72 today on 100ll.com. I bet you could get it from a tanker for 4.00 easily if you get to using a lot of it, and .193 less than that after the refund. Less than the crappy 91 premium around here.
07-16-2011, 04:57 PM
#17
Exacty.....
I had a state police officer pull into a gas station when I was dumping a can of fuel into my car to mix it with pump fuel & ask what I was doing.
I said... "My car wont run on that junk pump gas"
He said... "Guess you never break the speed limit either"
I said... "of course not" with a smile.... and then waited for him to leave before I did.
I had a state police officer pull into a gas station when I was dumping a can of fuel into my car to mix it with pump fuel & ask what I was doing.
I said... "My car wont run on that junk pump gas"
He said... "Guess you never break the speed limit either"
I said... "of course not" with a smile.... and then waited for him to leave before I did.
10-07-2012, 03:49 PM
#18
For anyone that reads this post. I can now say that I had the car successfully tuned on avgas and have been running it for over a year with no problems. I have NOT had to change my spark plugs or 02 sensors due to the very low lead content of avgas. If anyone has any questions they can pm me or reply here.
10-14-2012, 07:35 PM
#20
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my biggest issue with avgas is that its a "drier" fuel w/o as many topend lubricants. dont get me wrong it does work, id just rather have the safety factor of a proper fuel for the application