Posted By: BradH
Max power air-fuel ratio for e10 fuel? - 03/20/13 05:05 PM
I know that straight gas is generally expected to produce peak power with an air-fuel ratio in the range of 12.8 - 13.2. What about the typical 10% ethanol blend that everything local to me sells year around now? With the addition of a wideband O2 setup once The MoPig is back on the street, I'd like to have a general idea of what's "normal" for e10 pump gas. Thanks!
Posted By: YO7_A66
Re: Max power air-fuel ratio for e10 fuel? - 03/20/13 06:24 PM
Brad,
I have been running the O2 sensors for the last two years and I have been reading everything that I can to try and determine what the best A/F might be for my steup on E10. From what I have gathered, there might be a "range" to shoot for and then tweak from there.
Since there are so many variables (outside temperature, octane, compression, timing, altitude, vehicle combo, etc.), I have been testing with 12.5-13.0 WOT A/F's for my WOT range. I do think that the "seat of the pants" shows that 12.8-13.0 feels quicker for my street car.
You will find that there are some people who will aim for 12.0 and some that will aim for 13.4. I was finding so many different opinions on what number to aim for, so I started testing different A/F numbers and found what my car seemed to like. Two years ago I aimed for 12.8-13.2. Last year I aimed for 12.4-12.8. This year I will aim for somewhere in the middle around the 12.8-13.0 range.
Posted By: Dunnuck Racing
Re: Max power air-fuel ratio for e10 fuel? - 03/20/13 06:54 PM
Stoich X 90 percent is a good general guideline .
So approximately12.6 to 1 for E10. If you get a chance ,read my A/F article in the May Mopar Muscle. I gave some of the information there,on the track and dyno.
Keith
Posted By: Dunnuck Racing
Re: Max power air-fuel ratio for e10 fuel? - 03/20/13 07:19 PM
I just checked and its not on their website yet. It should be pretty soon,they usually post tech articles about a month after the print issue.
Basically,I showed the effects of varying A/F ratios against power on the dyno with race fuel and then tested E10 on a street/strip car at the track.
Keith
Posted By: Thumperdart
Re: Max power air-fuel ratio for e10 fuel? - 03/20/13 07:21 PM
Cool, maybe post it when it`s ready.
Posted By: Dunnuck Racing
Re: Max power air-fuel ratio for e10 fuel? - 03/20/13 08:15 PM
Brad,
I will look at the article and my original draft and notes. Some things get editing for space and may have had something like that happen.
Usually the the 90% of stoich is a good starting point for max power. But how good the base fuel is that the ethanol went into and gown efficiently the engine can use the fuel matters too.
The track testing was done on a low compression stock bottom end 440 with aluminum heads and a custom solid lifter cam. Certainly not the best quench I have ever seen to help with efficiency.
Keith
Posted By: Dunnuck Racing
Re: Max power air-fuel ratio for e10 fuel? - 03/20/13 08:49 PM
Something else to keep in mind with E10, just like E85, is that it doesn't necessarily contain10% exactly. By law if it states 10 % ethanol on the pump,it must contain a minimum of 6% and out of 10 stations I tested fuel from,only one was above6%
I have been testing a few different carburetors and doing some emulsion circuit tuning lately with pump gas and there is a lot of power to be found getting the mixture where the engine likes it everywhere.
Keith
Posted By: BradH
Re: Max power air-fuel ratio for e10 fuel? - 03/20/13 09:22 PM
I'm 100% with you on there not being a "magic number" for everyone. I was looking for a general range that e10 seems to perform best at.
Your comments on how much ethanol the pumps labeled as 10% really contain reminded me that I was looking for some type of ethanol tester to check the local stations. I know Quick Fuel markets one targeted towards the e85 crowd, but I'd like to be able to run spot checks on the e10 stuff to see what it really shows and how consistent it is from fill-up to fill-up...
Posted By: 440Jim
Re: Max power air-fuel ratio for e10 fuel? - 03/22/13 03:38 PM
Brad,
One other thing to remember...
The wide band oxygen sensor actually measures Lambda, the ratio of actual mixture to stoichiometric mixture and it doesn't care what fuel you are running (100% gas, 95% gas, 90% gas, E85, alcohol, etc. i.e. it already accounts for the percent alcohol. The display device can be programed to show Lambda, or A/F based on the stoichiometric ratio you input.
I still like to talk in A/F ratio. So I convert Lambda to A/F based on 100% gasoline stoichiometric ratio of 14.7, this is called using the gasoline scale.
Gas: Lambda 0.85 x 14.7 = 12.5 A/F
E85: Lambda 0.85 x 9.76 = 8.3 A/F
Alky: Lambda .85 x 6.40 = 5.4 A/F
And E10 might have a stoichiometric ratio around 14.3, FWIW.
From running all those fuels, the "best" Lambda is not significantly different for any of those fuels. So leave your display in gasoline scale and shoot for 12.5-13.0
Posted By: Dunnuck Racing
Re: Max power air-fuel ratio for e10 fuel? - 03/22/13 04:09 PM
Stoich for E10 is closer to 14.1
The 360 mule I am testing with right now ,makes its best power and torque at 12.1-12.2 with 5 different carburetors I have been testing with. This is another non efficient combination though,8.8 to 1 compression aluminum heads,Comp Thumper cam.
How well the mixture is prepared can make a big difference. Part throttle tuning with different carburetors has been pretty revealing as far as rich/ lean conditions vs torque
Keith
Posted By: Dragula
Re: Max power air-fuel ratio for e10 fuel? - 03/22/13 04:25 PM
On my pump gas rides I am running between 12.2-12.6...No leaner at WOT. I used to use 12.7-12.9, but with E10 that is too lean.
