e-85 a/f table

Questions specific to Megatune. (Only about the tuning software, not about MS1/MS2 code or code features)
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e-85 a/f table

Postby fffstang » Thu Jun 02, 2011 7:20 am

I need help figuring out how to set the air fuel table, for gasoline no problem. but for e-85 i need help. i understand that lamda is like .71 for ethanol. i set my req. fuel ( 342ci 8cyl 160lb inj 9.0a/f) does this have any effect on the a/f table? where in tuner studio can i set lamda to .71? is there an easier way to make sure my air fuel ratio is correct.(i will be usingmy wideband) im really not to happy with the information avail to those of us using forced induction and alternative fuels but maybe im not looking the right places any suggestions?
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Re: e-85 a/f table

Postby racingmini_mtl » Thu Jun 02, 2011 3:49 pm

Lambda for stoichiometric is always 1.0 no matter which fuel you use. That will translate into different air/fuel ratios but the O2 sensors work with lambda so there is no need to adjust anything. Use the same AFR table as if you were running gasoline.

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Re: e-85 a/f table

Postby fffstang » Fri Jun 03, 2011 7:58 am

I appologize for my stupidity but I'm new to this an trying to figure it out. but if the air fuel table reads naturally aspirated pump gas ratios and I'm running e-85 then where to i tell it to richen up the mixture if the not in the a/f table? Can i use the scaler and multiply by .61 since stoich for e85 is 9.0 / stoich for regular gas at 14.7 so 9/14.7 = .61 so then take the a/f table scaler and put .61 in there to correct the whole table or what do i do to make sure i' m running rich enough?
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Re: e-85 a/f table

Postby racingmini_mtl » Fri Jun 03, 2011 8:25 am

The req fuel value should take care of that. You may need to do some small adjustments to the AFR table but not to compensate for the difference between the 2 AFR but simply because E85 can work better at different lambdas.

It would be much simpler if everything was shown as lambda rather than AFR. But since that's not the case, you need to work based on stoic being 14.7 even if that's not the case. The only place you need to adjust for the real AFR is when computing the req fuel value. Everything else will be scaled correctly from that.

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Re: e-85 a/f table

Postby fffstang » Fri Jun 03, 2011 8:54 am

ok thank you that solves a lot of issues. in req. fuel i should be fine using 9.0 as stoich then correct?
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Re: e-85 a/f table

Postby t_cel_t » Mon Dec 19, 2011 4:55 pm

fffstang wrote:ok thank you that solves a lot of issues. in req. fuel i should be fine using 9.0 as stoich then correct?

no, you will still use 14.7 as the stoich.

if you still dont get it check this quick mspaint i did. its shows number lines, a vertical line shows what stoich would be for each fuel.


your wideband outputs a signal thats say .5-1.5 lambda, all the controller does it scale that according to what fuel its set up for. its doesnt care what fuel, it just measures the ammount of O2 passing the sensor.

you have your sensor set up for 10-20afr, 0-5v, with lambda being 14.7(think of it as being a round 15), thats 2 afr for every volt change, or 5v for 10 afr.
or you have your sensor set up for 6-12afr, 0-5v, with lambda being 9.0, thats a 6afr over 5v, or 1.2 afr for every volt change.
is just the scale you lay on top of the sensor voltage.
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Re: e-85 a/f table

Postby Swagon_wagon » Mon Aug 06, 2012 8:16 am

Does the lc1 work for e85? Afr only goes down to 7.3 on my gauge. What are good targets for power and while under boost? Same numbers as with gasoline cause 14.7 is really 9.0?
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Re: e-85 a/f table

Postby HidRo » Mon Aug 06, 2012 8:27 am

The number of the AFR Table, are just a "translation" for your eyes.
It's a lot easier to read 14.7 AFR and then 16.7 AFR than 1.0 and 1.2 or something.
So, the computing will all be done in lambda. Only for you to see, and it's easier to work with, the AFR will be shown.
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Re: e-85 a/f table

Postby racingmini_mtl » Mon Aug 06, 2012 10:44 am

Swagon_wagon wrote:Same numbers as with gasoline cause 14.7 is really 9.0?

That.
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Re: e-85 a/f table

Postby Swagon_wagon » Mon Aug 06, 2012 1:05 pm

Ok sweet. I though I needed to buy a special wideband.
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Re: e-85 a/f table

Postby cukali » Fri Dec 20, 2013 9:57 am

Sorry to jack the thread, but this question seams to confuse so many people. In a few other forums I have been run off by saying to ignore the fuel types and tune to the fuel guage. You cannot make your A/F guage read 9:1 and think its stoich if your using E85.

If the guage says 14.7:1 then its the correct mixture not matter the fuel used. I swear the problem is those people that dont actually tune themselves but read posts, make assumptions, and then teach the world.

Not talking about anyone in this forum or thread, just delighted to see some sanity here. After fueding for days on other forum about it I finally gave up trying to help.

Seriously though...Use a wideband, believe the wideband, and tune it just as you would with gasoline (reguardless of the fuel used) and youll be fine.

Cheers.
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