NefMoto

I think this info will help out a lot of people.

(http://i.imgur.com/ZUbak.jpg)

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
0.740   7.222   10.878
0.750   7.320   11.025
0.760   7.418   11.172
0.770   7.515   11.319
0.780   7.613   11.466
0.790   7.710   11.613
0.800   7.808   11.760
0.810   7.906   11.907
0.820   8.003   12.054
0.830   8.101   12.201
0.840   8.198   12.348
0.850   8.296   12.495
0.860   8.394   12.642
0.870   8.491   12.789
0.880   8.589   12.936
0.890   8.686   13.083
0.900   8.784   13.230
0.910   8.882   13.377
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
1.210   11.810   17.787
1.220   11.907   17.934
1.230   12.005   18.081
1.240   12.102   18.228
1.250   12.200   18.375
1.260   12.298   18.522
1.270   12.395   18.669
1.280   12.493   18.816
1.290   12.590   18.963
1.300   12.688   19.110
1.310   12.786   19.257
1.320   12.883   19.404
1.330   12.981   19.551
1.340   13.078   19.698
1.350   13.176   19.845
1.360   13.274   19.992
1.370   13.371   20.139
1.380   13.469   20.286
1.390   13.566   20.433
1.400   13.664   20.580
1.410   13.762   20.727
1.420   13.859   20.874
1.430   13.957   21.021
1.440   14.054   21.168
1.450   14.152   21.315
1.460   14.250   21.462
1.470   14.347   21.609
1.480   14.445   21.756
1.490   14.542   21.903
1.500   14.640   22.050

 ;)

Page 15 of Engine Management Advanced Tuning by Greg Banish has a similar diagram. He quotes AFR of between 13.2 and 13.4:1 (lambda approx. 0.95) is ideal for best power. Similarly, he quotes AFR of about 15.5:1 (lambda approx. 1.05) for best economy.

Doug

Unfortunately,

a lot of that goes out of the window on knock limited turbo cars!

That's for NA cars.

For Audi 5v stuff you want 11.6-12.4 under load and 14.7-15.5 at cruise depending on economy desired.

16 - 17 is too lean.

what afr do you want on decel?  i've been seeing wideband afr values of 22+ on high rpm decel...

what tables would we need correcting to fix decel afr?

thats because of the fuel cut

Rick: agreed. I'm finding 11.5 to 12 is appropriate for pump gas (91/93oct, US)

On race gas, what do you think is optimal?

Yes this is for NA. For turbo under boost you want to run 12. Any richer is just a waste.
I run 1.1156 on my (non-boosted) 12v (16.4) for part throttle. Add timing to make up for lack of power while running lean on part throttle ;)

I thought that second chart was a nice addition since its a nice way to convert AFR to Lambda and vice versa.

On 91oct, I find richer than 12 gives me a bit more timing and a lot less knock, especially with high IATs.

YMMV.

I only use 93  :P
You can go a lil richer. Depends on gas and other factors like IAT, etc.

Edit: 99.9% of all my tuning work revolves around 1.8T. 2.7T might like to be a little richer.

Could you possibly explain this more or give me an idea of where to read about it?

Thanks Rick!

injectors and spark turns off on decel.

you're assuming every engine is the same.. it's not...

Also you're making very general statements... the more boost you run the more chance of knock, the more fuel you will need to run to cool the charge and keep knock to a minimum... the problem is you get to a point where combustion suffers when going too rich (usually lower then 11.3 or so) and you actually start to misfire from too much fuel.

16.4:1 is too lean IMO... some car might be ok with it.. but generally that is pretty rare, and if they are they're completely stock.

That's the impression I got from the OP, but didn't really want to upset anyone by stating that...  :'(

At the fundamental level, there will always be an AFR just before or just after stoichiometry which corresponds to the ideal mixture for best power or best economy, but as we all know, there are so many other factors (enrichment for component protection or enleanment for a stratified charge regime) that cause it to be modified, it's hardly merits a new thread.

Doug

Your assuming that my comments were general statements. They aren't.

Read:

Take all of my posts with a grain of salt, just like you should with every other statement on an internet forum. The only way to figure out the best AFR for your setup is to do a custom tune. I'm just saying what works for ME, and I wanted to contribute something to this forum.

In internal combustion engines there is a lot of factors that dictate what AFR you should run. In fact, just engine wear could affect that. Some like to be a little lean, some like to a little rich. The first graph I posted was for NA applications. For turbo applications you obviously want to go a little richer but it still gives you a good starting point.

Also my 12v doesn't seem to mind being lean. I use only 93+ though.

Stratified injection engines are another beast. You can go leaner on a stratified injection engine (TFSI/FSI) than on a 1.8T/2.7T and make good power.

ok so this isn't dangerous then?  thanks for the info btw...  could we put a link on the wiki for this?

no it's no dangerous... it prevents unburnt fuel getting to the catalytic(s).  Every FI car does this (some very early fuel injection cars don't but that is still very rare).

As above,

it's been a feature of pretty much any ECU built in the last 25 years. 

It's a cat saving and fuel saving device. 

Nyet, I have done some work with leaded race fuel, which is pretty much completely knock proof, but I haven't come to a definite conclusion yet.  I suspect though that best power will be around 12.5:1, and pretty flat from 11:1 to 13:1.  ECUplot is really helpful for stuff like this :)

Rick

I am running for some time now lambda 1.10 at low load part throttle conditions and i am decreasing it as the load goes higher than 80% to stock 1.00. I have a noticable fuel economy without any problems until now. Do you think that this it too lean? I have an 1.8t engine 180 ps.

No you should be OK :)

What is stock AFR for under load and partial load, for the 2.7t?

stock 2.7T is 14.7 nearly everywhere, unless you're deep into 4th/5th gear during a long pull.