Ideal wide band o2 reading
- Thread starter m6z
- Start date
The wide band doesn't measure AFR's it measures lambda
lambda 1 is stoichiometric for all fuels
so when your wideband says 14.7:1 its actually at 9.7:1 if you are running e85. Below is a cut and paste of a chart showing the differences. As you can see the max power rich and max power lean for gas and E85 are pretty close. You may have to run a slightly richer wideband reading on e85 than gasoline at WOT.
Fuel AFRst FARst Equivalence
Ratio Lambda
Gasoline stoichiometric 14.7 0.068 1 1
Gasoline max power rich 12.5 0.08 1.176 0.8503
Gasoline max power lean 13.23 0.0755 1.111 0.900
E85 stoichiometric 9.765 0.10235 1 1
E85 max power rich 6.975 0.1434 1.40 0.7143
E85 max power lean 8.4687 0.118 1.153 0.8673
E100 stoichiometric 9.0078 0.111 1 1
E100 max power rich 6.429 0.155 1.4 0.714
E100 max power lean 7.8 0.128 1.15 0.870
lambda 1 is stoichiometric for all fuels
so when your wideband says 14.7:1 its actually at 9.7:1 if you are running e85. Below is a cut and paste of a chart showing the differences. As you can see the max power rich and max power lean for gas and E85 are pretty close. You may have to run a slightly richer wideband reading on e85 than gasoline at WOT.
Fuel AFRst FARst Equivalence
Ratio Lambda
Gasoline stoichiometric 14.7 0.068 1 1
Gasoline max power rich 12.5 0.08 1.176 0.8503
Gasoline max power lean 13.23 0.0755 1.111 0.900
E85 stoichiometric 9.765 0.10235 1 1
E85 max power rich 6.975 0.1434 1.40 0.7143
E85 max power lean 8.4687 0.118 1.153 0.8673
E100 stoichiometric 9.0078 0.111 1 1
E100 max power rich 6.429 0.155 1.4 0.714
E100 max power lean 7.8 0.128 1.15 0.870
.714 lambda is going to read 10.45 to one on a gasoline scale. I'm experimenting with .70 lambda with methanol (10.2 to one on the gasoline scale) and it feels pretty good. E.T. slips are promising. The a/f number you end up with is really going to depend on your particular combination. Start rich and work it around until you find what your engine likes.
If you have to know what your actual a/f ratio is with E85 and you're using a wide band O2 that's calibrated to readout with gasoline related numbers, this is what you do.
First you must know what the stoich ratios are for the 2 fuels you are dealing with.
The wideband is calibrated to readout with gasoline related numbers. Gasolines stoich ratio is 14.7.
E85 is the fuel you are actually burning. E85s stoich ratio is 9.7 according to Dave.
After making a pass you have a readout of 11.7 on your meter. You want to know what the actual a/f ratio is.
First convert your meter value to a lambda value. Divide the meter value by the stoich value for gasoline. 11.7 / 14.7 = .796 lambda.
Now take your lambda value and multiply it by the stoich value of your actual fuel. .796 x 9.7 = 7.72 actual a/f ratio for E85.
I do this math all the time with the methanol I burn. My datalogs and O2 readings are all calibrated for gasoline readouts. Don't make the mistake I did by assuming the optimum gasoline ratios for power were a good target for my actual fuel. Methanol, and I'm sure E85 have their own particular optimum ratios for full power. It is up to the tuner to find out what that number is.
First you must know what the stoich ratios are for the 2 fuels you are dealing with.
The wideband is calibrated to readout with gasoline related numbers. Gasolines stoich ratio is 14.7.
E85 is the fuel you are actually burning. E85s stoich ratio is 9.7 according to Dave.
After making a pass you have a readout of 11.7 on your meter. You want to know what the actual a/f ratio is.
First convert your meter value to a lambda value. Divide the meter value by the stoich value for gasoline. 11.7 / 14.7 = .796 lambda.
Now take your lambda value and multiply it by the stoich value of your actual fuel. .796 x 9.7 = 7.72 actual a/f ratio for E85.
I do this math all the time with the methanol I burn. My datalogs and O2 readings are all calibrated for gasoline readouts. Don't make the mistake I did by assuming the optimum gasoline ratios for power were a good target for my actual fuel. Methanol, and I'm sure E85 have their own particular optimum ratios for full power. It is up to the tuner to find out what that number is.
- Joined
- Feb 18, 2006
Ya I would have to say that my car likes to be rich when running meth.
afr's in the high tens.
It's definitely a science and I agree, it's up to the individual to find the sweet spot.
afr's in the high tens.
It's definitely a science and I agree, it's up to the individual to find the sweet spot.
I'm not sure if this has been discussed already, but this thread sort of begs for it, so here it goes.
This is for the guys that are mixing fuels. That includes the people that are injecting methanol as a combustion coolant for their gasoline engines.
Some may not realize it yet, but in all reality you are mixing two very different fuels. Each with their own optimum a/f ratios for max power. You are not just spraying a coolant like water. Spraying water will not affect your target a/f ratio much. The only way it will is in how it will allow for a leaner mixture if before the water injection you were running excessively rich to combat detonation, using the extra gasoline as the actual coolant.
It would be best if you forgot the notion that you're filling your auxiliary injection bottle with a coolant and got used to the fact that you're filling your extra fuel tank or cell with another fuel. When you get used to that idea, you'll start to look at that bottle and its related plumbing and components with a little more respect and hopefully with more safety concerns.
To get back on track. You need to realize that when mixing two fuels with very different optimum a/f ratios, you're going to end up with a totally new optimum target a/f ratio for your mix. I emphasize YOUR because not everyone mixes these fuels with the same mix percentages. Even when the one individual, who has spent hours upon hours to find the optimum a/f ratio for the particular amount of methanol spray he's using, will find that if he increases the mix ratio by cranking up the methanol spray, he will have to retune his setup to find a new optimum a/f ratio. To assume that one optimum a/f ratio is going to be the best for everyone is a big mistake. Everyone tunes their methanol spray differently. Some now have two nozzles. That is going to change the target a/f ratio drastically.
The trend is, the more methanol you mix with your gasoline, the richer the optimum a/f ratio will have to be.
This is for the guys that are mixing fuels. That includes the people that are injecting methanol as a combustion coolant for their gasoline engines.
Some may not realize it yet, but in all reality you are mixing two very different fuels. Each with their own optimum a/f ratios for max power. You are not just spraying a coolant like water. Spraying water will not affect your target a/f ratio much. The only way it will is in how it will allow for a leaner mixture if before the water injection you were running excessively rich to combat detonation, using the extra gasoline as the actual coolant.
It would be best if you forgot the notion that you're filling your auxiliary injection bottle with a coolant and got used to the fact that you're filling your extra fuel tank or cell with another fuel. When you get used to that idea, you'll start to look at that bottle and its related plumbing and components with a little more respect and hopefully with more safety concerns.
To get back on track. You need to realize that when mixing two fuels with very different optimum a/f ratios, you're going to end up with a totally new optimum target a/f ratio for your mix. I emphasize YOUR because not everyone mixes these fuels with the same mix percentages. Even when the one individual, who has spent hours upon hours to find the optimum a/f ratio for the particular amount of methanol spray he's using, will find that if he increases the mix ratio by cranking up the methanol spray, he will have to retune his setup to find a new optimum a/f ratio. To assume that one optimum a/f ratio is going to be the best for everyone is a big mistake. Everyone tunes their methanol spray differently. Some now have two nozzles. That is going to change the target a/f ratio drastically.
The trend is, the more methanol you mix with your gasoline, the richer the optimum a/f ratio will have to be.
Ya, but I was refering to E85, not E100. That's where my 9.7 figure came from.
Doh!
Sorry Dave. Didn't have my thinking cap on.
A point that comes to mind. E85 is a mixed fuel. Gasoline and Ethanol. We should know by now that by mixing fuels with different optimum a/f numbers, you end up with a product that will have its own optimum a/f ratio and that will depend on exactly what the mix percentages are for the particular mix.
How reliable is E85 when it comes to the consistency of the mix? We're pretty sure that the ethanol side of the mix will be pretty consistent. What about the gasoline side? Do they just mix in any gasoline thats readily available at the time or is the formulation strictly controlled?
Without a consistent mix, a tuner could end up chasing his tail with every new tank full. What has been the experience from people burning E85? Has anyone experienced a bad batch?
Sorry Dave. Didn't have my thinking cap on.A point that comes to mind. E85 is a mixed fuel. Gasoline and Ethanol. We should know by now that by mixing fuels with different optimum a/f numbers, you end up with a product that will have its own optimum a/f ratio and that will depend on exactly what the mix percentages are for the particular mix.
How reliable is E85 when it comes to the consistency of the mix? We're pretty sure that the ethanol side of the mix will be pretty consistent. What about the gasoline side? Do they just mix in any gasoline thats readily available at the time or is the formulation strictly controlled?
Without a consistent mix, a tuner could end up chasing his tail with every new tank full. What has been the experience from people burning E85? Has anyone experienced a bad batch?
E85 mixtures
That is a very important issue if you are running a high power tune. If you just want a good safe daily driver tune (high 90+ octane fuel) you don't need to worry all that much about it.
E85 can actually have a range of fuel blends depending on where you live and what season it is. Just like pump gasoline E85 blends change with the season.
E85 fuel ethanol content seasonal changes
The recommended dates for changing E85 fuel blends are listed in a chart in the E85 handbook on page 22, which is in the "E85 Fuel Specification" tab.
The Volatility class specifications are broken down on page 10.
Volatility class 1 --- minimum ethanol 79%
Volatility class 2 --- minimum ethanol 74%
Volatility class 3 --- minimum ethanol 70%
As you can see each region has a different start date and recommendation for seasonal blends depending on local weather climate.
Here on the high plains east of the rockies in Colorado we run the class 1 fuel blend from mid June -- mid Sept, run class 2 fuel from mid Sept -- mid Oct and run the class 3 fuel blend from Mid Oct -- mid April, then back to the class 2 blend from mid April to mid June. In short here in Colorado near Denver we are already on the winter blend, but there is latitude in the standard, so the standard only specifies a minimum ethanol content. If it is cheaper for the fuel blender to add more he can. Ethanol content is bottom line driven by local weather conditions, and cold starting problems for local drivers just a gasoline blends are modified to give easier starting in cold weather.
In the Southern part of Texas they would never go to a class 3 blend, and in Wisconsin, they would only have the class 1 blend for about 2 months in the summer. In Florida they would be on class 1 almost all year long and in North Dakota and Wyoming and Montana, they would be on class 3 almost all year long.
If you are running a serious tune and high boost you want to be cautious during the season change periods. I know a couple people with turbocharged imports that test the fuel and tweak their tune accordingly.
If you have a wide band simply watch your AFR's at light throttle cruise, if the blend changes you will see it there as the mixture should be very stable in that light load part of the tune. Perhaps pick a certain rpm and gear and learn what your tune does on each.
As the blend goes to lower Ethanol content in the fall the mixture will go rich as you are running more gasoline in the blend to improve cold starting. This is a safe change in mixture for most folks unless you are right on the edge with your tune and need every octane point you can get. In the spring time as the mixture moves back to higher blends of ethanol it is more dangerous as you will lean out a bit, so be cautious on big power tunes when you first trot the car out for sunny spring run.
The standard gasoline added to the fuel is "natural gasoline", ie just the raw gasoline that comes off the first pass at the refinery, but some dealers may not have ready access to that, and will cut the E98 with normal UL pump fuel to get the right mixture.
E85 will probably like richer mixtures than your max power gasoline blend by a small amount. If in doubt take your max power rich gasoline mixture and fatten it up just a bit.
Max power mixtures on gasoline (if you have enough octane) is usually about 25% rich of stoichiometric mixture. That works out to between 12.5 - 11.8 AFR on most cars. Max power mixtures on ethanol can go as high as 40% rich of stoich. That means on a gasoline calibrated wideband you would see about 11 - 10.5 AFR's. My WRX was very happy at a gasoline calibrated AFR of 11.5 but makes just a bit more power at lambda 0.72-0.76 which is a gasoline calibrated AFR of 10.5 - 11.2.
Hope that helps.
Larry
That is a very important issue if you are running a high power tune. If you just want a good safe daily driver tune (high 90+ octane fuel) you don't need to worry all that much about it.
E85 can actually have a range of fuel blends depending on where you live and what season it is. Just like pump gasoline E85 blends change with the season.
E85 fuel ethanol content seasonal changes
The recommended dates for changing E85 fuel blends are listed in a chart in the E85 handbook on page 22, which is in the "E85 Fuel Specification" tab.
The Volatility class specifications are broken down on page 10.
Volatility class 1 --- minimum ethanol 79%
Volatility class 2 --- minimum ethanol 74%
Volatility class 3 --- minimum ethanol 70%
As you can see each region has a different start date and recommendation for seasonal blends depending on local weather climate.
Here on the high plains east of the rockies in Colorado we run the class 1 fuel blend from mid June -- mid Sept, run class 2 fuel from mid Sept -- mid Oct and run the class 3 fuel blend from Mid Oct -- mid April, then back to the class 2 blend from mid April to mid June. In short here in Colorado near Denver we are already on the winter blend, but there is latitude in the standard, so the standard only specifies a minimum ethanol content. If it is cheaper for the fuel blender to add more he can. Ethanol content is bottom line driven by local weather conditions, and cold starting problems for local drivers just a gasoline blends are modified to give easier starting in cold weather.
In the Southern part of Texas they would never go to a class 3 blend, and in Wisconsin, they would only have the class 1 blend for about 2 months in the summer. In Florida they would be on class 1 almost all year long and in North Dakota and Wyoming and Montana, they would be on class 3 almost all year long.
If you are running a serious tune and high boost you want to be cautious during the season change periods. I know a couple people with turbocharged imports that test the fuel and tweak their tune accordingly.
If you have a wide band simply watch your AFR's at light throttle cruise, if the blend changes you will see it there as the mixture should be very stable in that light load part of the tune. Perhaps pick a certain rpm and gear and learn what your tune does on each.
As the blend goes to lower Ethanol content in the fall the mixture will go rich as you are running more gasoline in the blend to improve cold starting. This is a safe change in mixture for most folks unless you are right on the edge with your tune and need every octane point you can get. In the spring time as the mixture moves back to higher blends of ethanol it is more dangerous as you will lean out a bit, so be cautious on big power tunes when you first trot the car out for sunny spring run.
The standard gasoline added to the fuel is "natural gasoline", ie just the raw gasoline that comes off the first pass at the refinery, but some dealers may not have ready access to that, and will cut the E98 with normal UL pump fuel to get the right mixture.
E85 will probably like richer mixtures than your max power gasoline blend by a small amount. If in doubt take your max power rich gasoline mixture and fatten it up just a bit.
Max power mixtures on gasoline (if you have enough octane) is usually about 25% rich of stoichiometric mixture. That works out to between 12.5 - 11.8 AFR on most cars. Max power mixtures on ethanol can go as high as 40% rich of stoich. That means on a gasoline calibrated wideband you would see about 11 - 10.5 AFR's. My WRX was very happy at a gasoline calibrated AFR of 11.5 but makes just a bit more power at lambda 0.72-0.76 which is a gasoline calibrated AFR of 10.5 - 11.2.
Hope that helps.
Larry
Pronto
Believe nothing you hear and half of what you see.
- Joined
- Dec 9, 2002
Good question. Any ideas?
Pronto, I just drilled another hole in the fire wall 3/4" dia and put a grommet
in the hole, the hole is about in the center of the firewall but a tad closer to
the DS , there is kind of a raised area there you will see it on the fire wall, it is about 6" to the right of the ground strap for the heater core. hth.
Ron
in the hole, the hole is about in the center of the firewall but a tad closer to
the DS , there is kind of a raised area there you will see it on the fire wall, it is about 6" to the right of the ground strap for the heater core. hth.
Ron
