Air/Fuel ratios with gasoline and alcohol mix.

[DblTrbl]

I'm looking for input.

Apparently, my AEM wideband O2 sensor is actually a lambda sensor not an Air/Fuel sensor. The output voltage is 0 to 5 volts and it is actually a Lambda value, not an air/fuel value. To calculate the equivalent air fuel ratio, you multiply the lambda by a different constant for each type of fuel. As it turns out, the sweet spot for gasoline air/fuel mixture is about 12 to 1. I've heard that the sweet spot for alcohol air/fuel is somewhere around 7 to 1. These both turn out to be the same (or very close) lambda reading on the Wideband O2 so, with the mix of alcohol and gasoline, I'm still tuning for 2.9 volts. This is equivalent to 12 to 1 A/F for gasoline and also equivalent to 7.3 to 1 A/F for Ethanol. I hope this is a valid theory.

So theoretically, no matter what the proportion of gasoline to alcohol, tuning for a wideband lambda of .82 which is equal to 12 to 1 A/F for gasoline and 7.3 to 1 A/F for Ethanol should yield good results??? If you have any input, please feel free to comment. I'd really like more info on this.

Below is the table from AEM.

Wideband Volts
.........Lambda,
.................Gasoline AFR
..........................Methanol AFR
..................................Ethanol AFR
.........................................Propane
0.000 0.570 8.351 3.688 5.13 8.95
0.156 0.580 8.497 3.753 5.22 9.11
0.312 0.590 8.644 3.817 5.31 9.26
0.468 0.600 8.790 3.882 5.40 9.42
0.624 0.610 8.937 3.947 5.49 9.58
0.780 0.620 9.083 4.011 5.58 9.73
0.936 0.630 9.230 4.076 5.67 9.89
1.092 0.640 9.376 4.141 5.76 10.05
1.248 0.660 9.669 4.270 5.94 10.36
1.404 0.670 9.816 4.335 6.03 10.52
1.560 0.680 9.962 4.400 6.12 10.68
1.716 0.690 10.109 4.464 6.21 10.83
1.872 0.700 10.255 4.529 6.30 10.99
2.028 0.710 10.402 4.594 6.39 11.15
2.184 0.730 10.695 4.723 6.57 11.46
2.340 0.750 10.988 4.853 6.75 11.78
2.496 0.760 11.134 4.917 6.84 11.93
2.652 0.780 11.427 5.047 7.02 12.25
2.908 0.800 11.720 5.176 7.20 12.56
2.964 0.820 12.013 5.305 7.38 12.87
3.120 0.840 12.306 5.435 7.56 13.19
3.276 0.860 12.599 5.564 7.74 13.50
3.432 0.880 12.892 5.694 7.92 13.82
3.588 0.910 13.332 5.888 8.19 14.29
3.744 0.930 13.625 6.017 8.37 14.60
3.900 0.960 14.064 6.211 8.64 15.07
4.056 1.000 14.650 6.470 9.00 15.70
4.212 1.040 15.236 6.729 9.36 16.33
4.368 1.080 15.822 6.988 9.72 16.96
4.524 1.130 16.555 7.311 10.17 17.74
4.680 1.180 17.287 7.635 10.62 18.53
4.836 1.240 18.166 8.023 11.16 19.47
4.992 1.330 19.485 8.605 11.97 20.88

[Frank]

This warents more research. Something doesnt make sense.... where is my book?


Frank

[turbometh]

You are correct. My innovate wide band reads lambda. It shows both on the screen but the actual measurement is lambda.
My sprint car(mech. fuel injection) on alcohol is tuned at around 4.5 to 5 to one. I have not checked it yet with my wideband but the engine machinist said he tunes then to around 4.5 to 5 on the engine dyno. I would assume this is a very safe rich tune. I change my oil after every race and there is alot of alcohol in the oil. However I would rather be rich than lean. Alcohol is not as forgiving as gasoline.

[DblTrbl]

Quote:

Originally Posted by Frank This warents more research. Something doesnt make sense.... where is my book? Frank

Thanks for looking into this. By the way, here's more info my my alky setup.

Carl's alky setup

Carl

[Frank]

Dont you have methanol, not ethanol? That changes everything! Methanol has the sweet spot of 7.1:1 a/f ratio, not ethanol which I dont know what the a/f is.

If it is methanol, then you will have 4.638volts if you ran that pure. Since you wont, you setup a percentage.... i would think. If you are running 80% gas, and 20% meth, it would be 80% of 2.96volts plus 20% of 4.64volts. I believe it should be 3.30volts for that combination.

Remember, the more meth you run, the more BTUs removed from the air, so the more timing you can run, etc. However the downside is that the more you turn up the meth, the less runs you can do exponentially since the required gph is drastically increased.


Frank

[Frank]

Some more information I have found....

Quote:

Methanol (CH 3 OH) is an alcohol fuel. Produced by a process using natural gas as a feedstock. The alternative methanol fuel can be used today in vehicles as M-85. Ethanol (ethyl alcohol, grain alcohol, CH3CH2OH) is a grain alcohol. Sold in hardware store as 'De-natured' alcohol. Not drinkable.

In addition, I believe Ethanol is 9:1 ratio. You will end up doing this in the same manner as the Methanol above. I did find this handy chart for ethanol, and closely applies for automotive use. Look up the precent blend you are using, then take the number on the y-axis (relative enleanment) and times that by the lambda/voltage value for your optimum gasoline which is 2.96volts. So if you are running 20% mixture, you will want 3.17 volts.



Does this sound cool?


Frank

[Frank]

Brian gave me crap that I was confusing, etc. So in turn, I have made a calculator that will give you all that you need. This is beta as it has not been tested, however I feel confident. Use at your own risk and watch those gauges. I would love to hear feedback.

http://www.***************/site/files..._alky_calc.xls


Frank

[Aries_Turbo]

makes total sense now!!!!!

Brian

[DblTrbl]

Very excellent!! A fellow excel junkie.

Two suggestions. More granualrity and a backwards vlookup that tells you what your A/F guage (since it's set to gasoline) should read.

On a seperate note, you may enjoy the spreadsheet I created to graph the results of the logs from my track runs. I'll post it sometime in the near future.

[Frank]

Quote:

Originally Posted by DblTrbl Very excellent!! A fellow excel junkie. Two suggestions. More granualrity and a backwards vlookup that tells you what your A/F guage (since it's set to gasoline) should read. On a seperate note, you may enjoy the spreadsheet is created to graph the results of the logs. I'll post it sometime in the near future.

Ahh... the same problem that Brian was having.... relating it back to the gasoline a/f. I can add that. What do you mean my more granualrity?


Frank

[DblTrbl]

Actually, I already changed my copy of your spreadsheet to incorporate my comments. I already had the AEM tables extrapolated with 4x the original detail. Let me know if you want the extrapolated tables or if you want to do it yourself.

Also to make thing easier, once you have Lambda, you can calculate A/F with the following:

Gasoline AFR = L * 14.65
Methanol = L * 6.47
Ethanol = L * 9
Propane = L * 15.7

Your spreadsheet rocks!

[DblTrbl]

Quote:

Originally Posted by Frank What do you mean my more granualrity? Frank

Volts Lambda
0.000 0.570
0.039 0.573
0.078 0.575
0.117 0.578
0.156 0.580
0.195 0.583
0.234 0.585
0.273 0.588
0.312 0.590
0.351 0.593
0.390 0.595
0.429 0.598
0.468 0.600
0.507 0.603
0.546 0.605
0.585 0.608
0.624 0.610
0.663 0.613
0.702 0.615
0.741 0.618
0.780 0.620
0.819 0.623
0.858 0.625
0.897 0.628
0.936 0.630
0.975 0.633
1.014 0.635
1.053 0.638
1.092 0.640
1.131 0.645
1.170 0.650
1.209 0.655
1.248 0.660
1.287 0.663
1.326 0.665
1.365 0.668
1.404 0.670
1.443 0.673
1.482 0.675
1.521 0.678
1.560 0.680
1.599 0.683
1.638 0.685
1.677 0.688
1.716 0.690
1.755 0.693
1.794 0.695
1.833 0.698
1.872 0.700
1.911 0.703
1.950 0.705
1.989 0.708
2.028 0.710
2.067 0.715
2.106 0.720
2.145 0.725
2.184 0.730
2.223 0.735
2.262 0.740
2.301 0.745
2.340 0.750
2.379 0.753
2.418 0.755
2.457 0.758
2.496 0.760
2.535 0.765
2.574 0.770
2.613 0.775
2.652 0.780
2.716 0.785
2.780 0.790
2.844 0.795
2.908 0.800
2.922 0.805
2.936 0.810
2.950 0.815
2.964 0.820
3.003 0.825
3.042 0.830
3.081 0.835
3.120 0.840
3.159 0.845
3.198 0.850
3.237 0.855
3.276 0.860
3.315 0.865
3.354 0.870
3.393 0.875
3.432 0.880
3.471 0.888
3.510 0.895
3.549 0.903
3.588 0.910
3.627 0.915
3.666 0.920
3.705 0.925
3.744 0.930
3.783 0.938
3.822 0.945
3.861 0.953
3.900 0.960
3.939 0.970
3.978 0.980
4.017 0.990
4.056 1.000
4.095 1.010
4.134 1.020
4.173 1.030
4.212 1.040
4.251 1.050
4.290 1.060
4.329 1.070
4.368 1.080
4.407 1.093
4.446 1.105
4.485 1.118
4.524 1.130
4.563 1.143
4.602 1.155
4.641 1.168
4.680 1.180
4.719 1.195
4.758 1.210
4.797 1.225
4.836 1.240
4.875 1.263
4.914 1.285
4.953 1.308
4.992 1.330

[Frank]

e-mail me your complete table with higher resolution, and i will incorporate it. i am going to incorporate some injector calculations so that you can approximate how much fuel you will be flowing so that you can better estimate blends.

Now we just have to prove that this works!


Frank

[Frank]

I am going to fix the spreadsheet when I get home today. I would do it today while at work, however its on my home computer... unless you feel like re-emailing it to me.


Frank

[aerosmith145]

Quote:

Originally Posted by DblTrbl the sweet spot for gasoline air/fuel mixture is about 12 to 1.

are we talking about stoichiometric? wouldn't 12:1 be pretty rich?