E85 for dummies
05-15-2011, 02:23 PM
#16
Nordschleife Master
The usage of E85 allows a much wider range of AFR than does petrol. While "Stoich" for Ethanol is an actual 9.6 or 9.7 (or 14.7 on a petrol scale) when its E85, its important to understand that number is not going to be what is best for power.
In fact, unlike petrol, ethanol, when made richer, continues to add torque ALL THE WAY down to 6.75.
It IS a different fuel, and it does need to be treated differently.
What the OP is suggesting is technically true, as you need to start thinking in Lambda so there is no problems with "scales" and such. If you can practice divergent thinking, then, fine, but it can help some.
The turbo people in this forum can REALLY benefit. Since the volume and therefore mass of fuel is higher in the combustion process, ethanol has the possibility of spooling the turbos faster and earlier.
I believe more tuning and better tuning needs to be done because of this wider spectrum of possible AFR ratios in a normal car. Cruising can be tuned past stoich for better gas mileage on the lower-btu ethanol, and at part throttle increasing cruise, you can add more duty cycle to assist acceleration without so much throttle input. At BARN burning WOT, you would want to go full past rich to add that additional amount of torque.
The issues that arise when ethanol (or methanol) is burnt is that the amount of mass in the combustion process is past the task of many stock OEM ignition systems. Remember, that at the "nth degree" or in the extreme, methanol needs essentially a mig welder in the combustion chamber to ignite the mixture. So to a lesser degree, one must be aware of the amount of mass inside the combustion chamber that must be ignited for proper combustion and power.
In fact, unlike petrol, ethanol, when made richer, continues to add torque ALL THE WAY down to 6.75.
It IS a different fuel, and it does need to be treated differently.
What the OP is suggesting is technically true, as you need to start thinking in Lambda so there is no problems with "scales" and such. If you can practice divergent thinking, then, fine, but it can help some.
The turbo people in this forum can REALLY benefit. Since the volume and therefore mass of fuel is higher in the combustion process, ethanol has the possibility of spooling the turbos faster and earlier.
I believe more tuning and better tuning needs to be done because of this wider spectrum of possible AFR ratios in a normal car. Cruising can be tuned past stoich for better gas mileage on the lower-btu ethanol, and at part throttle increasing cruise, you can add more duty cycle to assist acceleration without so much throttle input. At BARN burning WOT, you would want to go full past rich to add that additional amount of torque.
The issues that arise when ethanol (or methanol) is burnt is that the amount of mass in the combustion process is past the task of many stock OEM ignition systems. Remember, that at the "nth degree" or in the extreme, methanol needs essentially a mig welder in the combustion chamber to ignite the mixture. So to a lesser degree, one must be aware of the amount of mass inside the combustion chamber that must be ignited for proper combustion and power.
That's the thing though, you don't need to change any way of thinking.
Your wideband has no idea how much fuel is actually going into your engine. All it knows is stoich mixture is 1 lamda. So, when you see 14.7 on your wideband gauge, its actually showing you the stoich mixture of whatever fuel you are using.
If you want to tune your e85 to be perfectly stoichiometric, you tune to 14.7 on your wideband gauge. The actual amount of fuel/air mixture going into your engine will be 9.7:1....which is 1 lamda, which your wideband shows to be 14.7.....
So, in essence, you really don't tune it any differently than you tune gas. Cruise at 14.7, and boost at 11.5 (very rough example to show a point), so your thinking doesn't need to change. Don't make it harder than it actually is.
05-15-2011, 02:25 PM
#17
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And to add to that ^^^^^ a tighter spark plug gap goes a long way. Also, there is no need to run a "hotter" spark plug. which is misleading because it is trying to run colder.... So if you have a higher heat range plug in your engine and are running Ethanol, drop back down a range or two If you are having ignition problems.
05-15-2011, 02:46 PM
#18
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What plugs are you using? I pulled my plugs out yesterday and they were very clean and I haven't run that much with E85. It also burns with a different smell, much easier to handle then a rich gas smell.
05-15-2011, 02:55 PM
#19
Race Car
yes it is much easier to tolerate than petro, especially when rich. When it is tuned lean it starts to smell very dry similiar to methanol. In normal conditions it is pretty sweet smelling.
Another thing to think about while on the subject of using lambda vs petro scaling is IMO the petro scaling adds a bit of visual resolution for tuning while driving. You are not just looking for 7.something or 8.something. You are looking for 11. something up to 17.something. Much easier to distinguish IMO while driving.
I run NGK br7es plugs myself.
Another thing to think about while on the subject of using lambda vs petro scaling is IMO the petro scaling adds a bit of visual resolution for tuning while driving. You are not just looking for 7.something or 8.something. You are looking for 11. something up to 17.something. Much easier to distinguish IMO while driving.
I run NGK br7es plugs myself.
05-15-2011, 03:14 PM
#20
Nordschleife Master
Love the smell of burning alcohol.... It used to be my favorite part of going to the drag races when I was a kid.
Except for the smell of nitromethane. That is a smell I could get hooked on
Except for the smell of nitromethane. That is a smell I could get hooked on
05-15-2011, 03:46 PM
#21
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And to add to that ^^^^^ a tighter spark plug gap goes a long way. Also, there is no need to run a "hotter" spark plug. which is misleading because it is trying to run colder.... So if you have a higher heat range plug in your engine and are running Ethanol, drop back down a range or two If you are having ignition problems.
A higher heat range plug takes less voltage to jump the gap (or can fire easier in more pressure/mass of air and fuel).
Therefore, since a colder, and higher octane charge is good insurance against detonation, one should use a hotter plug with e85 (to insure against misfires).
05-15-2011, 03:52 PM
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05-15-2011, 04:48 PM
#24
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Google: Ethanol has only about 2/3 the energy of gasoline
The lower heating value (LHV) of conventional gasoline = 115,500 Btu/gallon
The lower heating value (LHV) of ethanol = 76,000 Btu/gallon
Hence it takes 115.5/76 = 1.52 gallons of Ethanol to replace the energy in one gallon of gasoline. since E85 is a blend, you wind up with injector increase of 25-30% to run E85.
Last edited by Bri Bro; 05-15-2011 at 05:08 PM.
05-15-2011, 04:59 PM
#25
Three Wheelin'
Ethonal carries oxygen it it molecule. That is why at AFR is 9/1 vs 15/1 for gas. Look at the BTUs of gas and Ethanol, you will see that Ethanol is 2/3 of gasoline..
Google: Ethanol has only about 2/3 the energy of gasoline
The lower heating value (LHV) of conventional gasoline = 115,500 Btu/gallon
The lower heating value (LHV) of ethanol = 76,000 Btu/gallon
Hence it takes 115.5/76 = 1.52 gallons of Ethanol to replace the energy in one gallon of gasoline. These values can be found here.
Google: Ethanol has only about 2/3 the energy of gasoline
The lower heating value (LHV) of conventional gasoline = 115,500 Btu/gallon
The lower heating value (LHV) of ethanol = 76,000 Btu/gallon
Hence it takes 115.5/76 = 1.52 gallons of Ethanol to replace the energy in one gallon of gasoline. These values can be found here.
05-16-2011, 12:36 AM
#26
Rennlist Member
Ethonal carries oxygen it it molecule. That is why at AFR is 9/1 vs 15/1 for gas. Look at the BTUs of gas and Ethanol, you will see that Ethanol is 2/3 of gasoline..
Google: Ethanol has only about 2/3 the energy of gasoline
The lower heating value (LHV) of conventional gasoline = 115,500 Btu/gallon
The lower heating value (LHV) of ethanol = 76,000 Btu/gallon
Hence it takes 115.5/76 = 1.52 gallons of Ethanol to replace the energy in one gallon of gasoline. since E85 is a blend, you wind up with injector increase of 25-30% to run E85.
Google: Ethanol has only about 2/3 the energy of gasoline
The lower heating value (LHV) of conventional gasoline = 115,500 Btu/gallon
The lower heating value (LHV) of ethanol = 76,000 Btu/gallon
Hence it takes 115.5/76 = 1.52 gallons of Ethanol to replace the energy in one gallon of gasoline. since E85 is a blend, you wind up with injector increase of 25-30% to run E85.
Let's pick a random # of air ingested into an engine: let's say 30 lbs/min of air.
-divide that by 9.8 for e85 = 3.06 lbs of fuel/min
-divide that by 14.7 for gasoline = 2.04 of fuel/min
(these are both roughly lamda = 1)
To me, it sure looks like you need about 50% more fuel with e85.
(There's a small difference in mass of the two fuels, but that would constitute only a very small volume change of flow through the injectors)
The lower heating value and BTUs/lb are irrelevant.
05-16-2011, 01:28 AM
#27
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Actually, it would be the other way around.
A higher heat range plug takes less voltage to jump the gap (or can fire easier in more pressure/mass of air and fuel).
Therefore, since a colder, and higher octane charge is good insurance against detonation, one should use a hotter plug with e85 (to insure against misfires).
A higher heat range plug takes less voltage to jump the gap (or can fire easier in more pressure/mass of air and fuel).
Therefore, since a colder, and higher octane charge is good insurance against detonation, one should use a hotter plug with e85 (to insure against misfires).
Ethonal carries oxygen it it molecule. That is why at AFR is 9/1 vs 15/1 for gas. Look at the BTUs of gas and Ethanol, you will see that Ethanol is 2/3 of gasoline..
Google: Ethanol has only about 2/3 the energy of gasoline
The lower heating value (LHV) of conventional gasoline = 115,500 Btu/gallon
The lower heating value (LHV) of ethanol = 76,000 Btu/gallon
Hence it takes 115.5/76 = 1.52 gallons of Ethanol to replace the energy in one gallon of gasoline. since E85 is a blend, you wind up with injector increase of 25-30% to run E85.
Google: Ethanol has only about 2/3 the energy of gasoline
The lower heating value (LHV) of conventional gasoline = 115,500 Btu/gallon
The lower heating value (LHV) of ethanol = 76,000 Btu/gallon
Hence it takes 115.5/76 = 1.52 gallons of Ethanol to replace the energy in one gallon of gasoline. since E85 is a blend, you wind up with injector increase of 25-30% to run E85.
Last edited by 95ONE; 05-16-2011 at 01:52 AM.
