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Air fuel or Lambda? For tuning.

haltechsupra

haltechsupra

New member
Joined
Jun 22, 2004
Location
Texas
I have been tuning my car using a/f both on the ve target maps, and on the wideband o2 gauge -innovate mtx-L. I know that Lambda is actual air fuel ratio divided by stoichiometric burn of the fuel used, and is a lot easier to formulate percentages of fuel added or subtracted to an engine-as well as consistant with what percentage is lean or rich, where as a/f is not . However I find it difficult to make the transition from a/f to lambda. For instance , my mtx gauge has a lambda function I can set up. However my Microsquirt does not have an option where I can change target Air fuel ratios, to lambda, that I can find. I would also like to change from pump gas to e85, so that I can continue to road trip my car and run pump fuel and turn the boost down when I cannot find e 85 stations. Of course I can use the flex sensor, but it doesn't do everything does it(?)-like recalibrate the stoich scale on ecu, o2, or gauge? Right now I have just saved two different fuel and spark maps, and change them when I have to.
I know that lambda doesn't change depending on what type of fuel used, and a/f does. For example a/f of a rich running engine on 93 octane may be 10.1, with the stoich of pump gas being 14.7.or .68 lambda. But, on e 85 , 10.1 is lean, because e 85 burns at theoretical perfect burn( stoichiometric) at 9.8.1, so any thing higher than that would read lean, giving us a lambda of 1.03 which is way lean, even though you think your running 10.1-your not! So the whole scale on the o2 sensor /gauge/ ecu needs to be reset according the stoich level of the fuel I am now burning. I get a little crossed up on the different calibrations of the wideband sensors and gauges, and a little confused about a gauge that is calibrated for 14.7 stoich reading for gas , on what that reading should translate into for a safe e 85 mixture, hence the reason for me wanting to switch to a lambda scale to begin with. Consistency. Thoughts?
 
The AFR readout on your gauge is already a translated lambda figure. Regardless of what fuel you're running, using the gasoline scale, 14.7 AFR indicated on the gauge always means 1 lambda. That goes for the entire scale, 12.0 indicated AFR is always 0.82 lambda, 17.0 indicated AFR always 1.16 lambda. This is why nobody really cares to use lambda when running on E85 because we already know that 12:1 indicated AFR is .82 lambda.

Standard E-10 oxygenated pump has as a stoich ratio of 14.0:1, yet nobody's trippin' that they're tuning for 14.7:1 at cruise. True AFR is still 14.0:1, because lambda is still 1.

BTW, lambda is piece of cake.

AFR=StoichAFR*Lambda
Lambda=TrueAFR / StoichAFR
 
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I have read your reply a few times and still barely grasping it. I guess what i am having a problem with is- lambda is on a 14.7 stoich scale for PUMP gas, and the e85 i am running is on a 9.7 stoich scale, how can the readings be even close to the same- with different stoich levels that are not accounted for?
What am I missing in this equation?
 
The wideband is technically already converting for it. Do not adjust any scale of anything, leave the wideband on pump gas (14.7:1) and just tune for the afr's you want.

I tried to switch over to using lambda as that is what my truck uses and tuner, my brain just couldn't adjust to the new numbers and conversion so i switched my WB gauge to show normal afr's.


Gross Polluter: are you sure that E10 is 14.0? I have run into a lot of people that state 14.2:1 for E10 fuels.
 
It's hard to get at first. Blame it on the old American drag race guys that didn't want to covert to lambda! 1.0 lambda is stoich for every fuel. It's reading oxygen that's left in the exahaut is all. So think of this. If you have an analog wide band with 14.7 as stoich, you can litteraly change the face plate so that it now reads 9.8 at the same location

We most just keep the gas wideband and use gas numbers because in a sense, they are the same thing. 12.0 gas afr is .80 lambda or 20% rich
 
thelostartof said:
Gross Polluter: are you sure that E10 is 14.0? I have run into a lot of people that state 14.2:1 for E10 fuels.
Click to expand...

I'm going by what GM puts in their flex-fuel ECU calibrations. I'm assuming they know more than I do.

Independent results and measurements will vary based on actual ethanol content and fuel composition.
 
I found this as well for easy comparison..
DISCLAIMER: I got this off of Yellowbullet from user "Drag Chevette". I cannot guarantee accuracy, but seems right as far as calculations go.


stay out of the RED.

Lambda E85 AFR Gas AFR
0.500 4.880 7.350
0.510 4.978 7.497
0.520 5.075 7.644
0.530 5.173 7.791
0.540 5.270 7.938
0.550 5.368 8.085
0.560 5.466 8.232
0.570 5.563 8.379
0.580 5.661 8.526
0.590 5.758 8.673
0.600 5.856 8.820
0.610 5.954 8.967
0.620 6.051 9.114
0.630 6.149 9.261
0.640 6.246 9.408
0.650 6.344 9.555
0.660 6.442 9.702
0.670 6.539 9.849
0.680 6.637 9.996
0.690 6.734 10.143
0.700 6.832 10.290
0.710 6.930 10.437
0.720 7.027 10.584
0.730 7.125 10.731 @ Max Power Multi Turbo
0.740 7.222 10.878
0.750 7.320 11.025 @ Supercharged/Turbo
0.760 7.418 11.172
0.770 7.515 11.319 @ Max Power NA
0.780 7.613 11.466
0.790 7.710 11.613
0.800 7.808 11.760 @ Consistant Race
0.810 7.906 11.907
0.820 8.003 12.054
0.830 8.101 12.201
0.840 8.198 12.348 @ Part throttle RACE
0.850 8.296 12.495
0.860 8.394 12.642
0.870 8.491 12.789 @ Idle
0.880 8.589 12.936
0.890 8.686 13.083
0.900 8.784 13.230
0.910 8.882 13.377 @ Part throttle STREET (economy)
0.920 8.979 13.524
0.930 9.077 13.671
0.940 9.174 13.818
0.950 9.272 13.965
0.960 9.370 14.112
0.970 9.467 14.259
0.980 9.565 14.406
0.990 9.662 14.553
1.000 9.760 14.700
1.010 9.858 14.847
1.020 9.955 14.994
1.030 10.053 15.141
1.040 10.150 15.288
1.050 10.248 15.435
1.060 10.346 15.582
1.070 10.443 15.729
1.080 10.541 15.876
1.090 10.638 16.023
1.100 10.736 16.170
1.110 10.834 16.317
1.120 10.931 16.464
1.130 11.029 16.611
1.140 11.126 16.758
1.150 11.224 16.905
1.160 11.322 17.052
1.170 11.419 17.199
1.180 11.517 17.346
1.190 11.614 17.493
1.200 11.712 17.640



HOPE THIS HELPS SOME PEOPLE OUT!
 
Hell, Ill run 12.5 afr with e85. It Intercools so well and has such knock resistant that I won't lift till then
 
I wonder if anyone's developed gas analysis charts for E85 like they have for Gasoline. I'm curious to see if E85 is capable of exceeding the thermal limits of the nitrogen boundary layer in the combustion chamber under high loads and lean mixtures.

Unless spark knock is occuring, gasoline won't get hot enough at high loads and lean mixtures to break that boundary layer.

My only concern with running E85 on the lean side is burning off that boundary layer and burning Pistons.
 
In Europe, i live in Holland we all do Lambda, easy ,no converting when you go on lpg or e85. Thats how we do it overhere .
 
gross polluter said:
I wonder if anyone's developed gas analysis charts for E85 like they have for Gasoline. I'm curious to see if E85 is capable of exceeding the thermal limits of the nitrogen boundary layer in the combustion chamber under high loads and lean mixtures.

Unless spark knock is occuring, gasoline won't get hot enough at high loads and lean mixtures to break that boundary layer.

My only concern with running E85 on the lean side is burning off that boundary layer and burning Pistons.
Click to expand...

less likely to burn pistons than it is to beat bearings out of the bottom end it seems. I would be curious about alcohol in general as it doesn't seem to burn as hot, yeah?

huh. maybe not. here's an interesting take on the subject
http://www.6speedonline.com/forums/...hot-cold-e85-vs-gas-theoretical-analysis.html


dat nitromethane doe
 
Its pretty easy in all honesty..

wb in my car reads in gasoline calibrated afr, wb in the wagon reads lambda... lower number is richer, higher number is leaner

In a stock lh car, you want to see cycling around 14.7 afr/ 1 lambda and at wot tend to see 11.5 afr or richer, 0.8 lambda or richer or in that neighborhood

on decel I see 19.9 afr/ 1.36 lambda

what's complicated about that?
 
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