on na motors i know 12.8 to 13.1 is ideal for max power but with fuel having 10 percent ethanol in it now so should the numbers change?
e10
- Thread starter cobra916
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It depends on how you are measuring A/F.
Oxygen sensors read Lambda. (Basically the amount of burnt fuel vs amount of unburnt fuel)
If you are reading a wideband O2 sensor set to gasoline (14.64 Stoich) It doesn't matter what fuel you are running.
Follow along with the math. Gasoline Stoich = 14.64. So when tuning a NA motor for say 13.0 A/F you have a Lambda of .887978 (13/14.64) So basically 11.2% rich. Lambda of 1 = 100% perfect burn. Now the wideband just changes the Lambda to a number by multiplying so you read in A/F instead of Lambda.
So even if the fuel is E10 14.1 Stoich, the Lambda will still be the same to read 13.0 on that wideband.
Remember, a wideband is just a device that reads Lambda through voltage. It has no idea what fuel you run.
Let me know if you have any other questions.
Oxygen sensors read Lambda. (Basically the amount of burnt fuel vs amount of unburnt fuel)
If you are reading a wideband O2 sensor set to gasoline (14.64 Stoich) It doesn't matter what fuel you are running.
Follow along with the math. Gasoline Stoich = 14.64. So when tuning a NA motor for say 13.0 A/F you have a Lambda of .887978 (13/14.64) So basically 11.2% rich. Lambda of 1 = 100% perfect burn. Now the wideband just changes the Lambda to a number by multiplying so you read in A/F instead of Lambda.
So even if the fuel is E10 14.1 Stoich, the Lambda will still be the same to read 13.0 on that wideband.
Remember, a wideband is just a device that reads Lambda through voltage. It has no idea what fuel you run.
Let me know if you have any other questions.
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okay cool.. didnt know it worked like that.. so 13.0 a/f on gas is like 12.54 a/f on e10 right? 13/14.64= .8879 12.54/14.1= 889
Kevin, Shouldn't you at least change the base fuel stoich scalar in the tune to the actual stoich of the fuel burned.
Won't the ECM still think 14.64 is the stoich of the fuel even though it's 14.1 with E10 and give you a slightly false reading from what is truely happening with the A/F ratio?
Example: Base tune has fuel stoich scalar at 14.64. Thus when you tune for lambda at all levels it will be "right on" for NON E10 regualr unleaded.
But, for E10 you should set the base fuel stoich scalar to 14.1 making a true A/F ratio that's more accurate for the lambda tables to read from.
If you have the scalar for stoich set at 14.64 and the fuel burned is at 14.1 stoich, then you're not getting the true commanded lambda in the tune correct?
Sorry to highjack thead OP.
Won't the ECM still think 14.64 is the stoich of the fuel even though it's 14.1 with E10 and give you a slightly false reading from what is truely happening with the A/F ratio?
Example: Base tune has fuel stoich scalar at 14.64. Thus when you tune for lambda at all levels it will be "right on" for NON E10 regualr unleaded.
But, for E10 you should set the base fuel stoich scalar to 14.1 making a true A/F ratio that's more accurate for the lambda tables to read from.
If you have the scalar for stoich set at 14.64 and the fuel burned is at 14.1 stoich, then you're not getting the true commanded lambda in the tune correct?
Sorry to highjack thead OP.
Correct.
Yes. You would normally want the stoich in the tune set to he fuel you are running.
Although I have found there to be less fuel spikes with returnless systems leaving stoich @ 14.64 and rescaling the injector slopes and engine displacement accordingly. I have tried it both ways and it seems to work better for some reason. :shrug:
would it be a dumb question to ask the tuner what his wide band is set at? i know california has had e10 for awhile but i believe tuners are still sticking to the 14.7 rule..
I'm sure it is set to gasoline. I did on my E85 car just so I didn't have to change the gauge. I tuned for 11.7 on E85, wideband set to gasoline which is about 7.7 on an E85 wideband. .79918 Lambda. Or basically 20% rich.
omg so my 12.6 tune is more like a 12.1 tune?? what the french? gas in california is all e10. why dont the tuners pick up on this?
Because most tuners arent mathmeticians or chemists.
10% ethanol mix, in the grand scheme of things, doesnt look (to the everyday person) like its a necessity to fine tune and adjust values for, as opposed to E85, which combusts nothing like standard gasoline.
although that is an incorrect mentality, in my opinion...
+1 yea i dont get it
i dont know how i will be able to talk a local tuner into setting the a/f to 13.1-2 on a 14.7 stoich to get 12.7 ish on e10 omg.. these people already think im crazy from asking questions..
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push comes to shove, Id tell them point blank "I'm paying for the tune, set it how I ask" but you'll probably end up pissing them off lol
Don't sweat it! The tune is good.
You need to realize that in order to tune E10 you just need to input the correct mathmatics.
Your tune is GOOD at 12.6 on the gasoline calibrated wideband.
If your tuner put a E10 calibrated wideband on then the A/F would read closer to 12.1 at WOT.
You need to do the math in order to figure out the % off the gasoline wideband is in relation to the true tail pipe A/F ratio of E10.
Again your missing the mathmatics here.
Example: NON E10 stoich is 14.7 and true E10 stoich is 14.1
Now if you tune according to a wideband set to gasoline stoich of 14.7 and your running E10 in the tank then the following mathmatics need to be applied.
E10 stoich ratio/gasoline stoich ratio X Gasoline max power air fual ratio = E10 max power air fuel ratio.
14.1/14.7*12.6=12.09 So 12.09 is the power side of E10 which reads 12.6 on a gasoline calibrated(nonE10) wideband. QUOTE setting the a/f to 13.1-2 on a 14.7 stoich to get 12.7 ish on e10 QUOTE as you say is not the power side for E10 to be tuning to. It is 12.09 at Wide open Throttle. An air fuel ratio of 12.5-12.6 is the power side of non ethanol regular unleaded gasoline ONLY.
So on a wideband set to gasoline(non E10) stoich you still need to tune to the SAME gasoline's power side as well. To figure out what is truely coming out of the tail pipe you need to apply the above formula.
If you have your tuner set your E10 fueled engine tune to read 13.1 at WOT on a gasoline calibrated wideband then you'll end up running lean and buying new pistons.
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Interesting point. I never even thought of that.
Is that true even on the E85 side as well, leaving 14.64 as the stoich scalar and tuning from there?
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:beer: thanks
Yes. But only on returnless systems.
how did you get that 12.6 is ideal for pure gas? also with that math we are just getting a conversion from one fuel to another.. what is the ideal lambda for e10? i have read for fossil fuels .9 lamda makes the most power.. so that would put e10 at 12.7?
I just used 12.6 as an example for a power A/F ratio. Didn't mean to confuse you.
In reality it depends on how CLOSE you want to get to max power 13.1 A/F. To be on the safe side for regular gas 12.8 A/F is safe. Any higher and you better be spot on with your fuel delivery. Fuel hiccups could cause a lean spot.
As for the conversion table.. yes it is very much the same from what I've seen and read.
The ideal lambda wot power zone for ethanol is very similar to gasoline. If I'm wrong maybe Kevin will pipe in.
What you're trying to hit for power on the gas wideband will be converted for you to hit on E10/E85 etc....
Example: gas stoich 14.64 gas power 12.8 targeted lambda of .870
Converted E10 stoich 14.1 E10 power 12.33 lambda of .870
Converted E85 stoich 9.6? E85 power 8.38 lambda of .870
So yes if you are trying to hit .900 lambda on E10 then it would be 12.7 A/F on a E10 calibrated wideband.
On a gas calibrated wideband it will read 13.18 A/F ratio.
okay cool.. thanks again
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