Lambda/Afr/Eq Ratio Chart

[jmac636]

This chart is based on a Stoich of 14.7 AFR in a perfect world where ethanol is not added to delute our fuel!

Lambda AFR EQRATIO
0.686 10.08 1.45
0.696 10.23 1.43
0.706 10.38 1.41
0.716 10.53 1.39
0.727 10.69 1.37
0.739 10.86 1.35
0.750 11.03 1.33
0.762 11.20 1.31
0.774 11.38 1.28
0.787 11.57 1.26
0.800 11.76 1.24
0.814 11.96 1.22
0.828 12.17 1.20
0.842 12.38 1.18
0.857 12.60 1.16
0.873 12.83 1.14
0.889 13.07 1.12
0.905 13.31 1.10
0.923 13.57 1.08
0.941 13.84 1.06
0.960 14.11 1.04
0.980 14.40 1.02
1.000 14.70 1.0
1.037 15.25 .96
1.078 15.84 .92
1.121 16.48 .89
1.169 17.18 .85
1.220 17.93 .81
1.276 18.76 .78
1.337 19.66 .74
1.405 20.66 .71

Stoich Afr / commanded Afr = Eq Ratio
Example: 14.7 /13.07 = 1.12

Let me know if this needs any corrections. I looked around and couldn't find a simple chart so I put this together for me and others to use.

[EagleMark]

That would be helpful!

Since most fuels out now are E10 another chart with 14.2 (or whatever) to Lambda 1. and eq ratio 1 would be useful.

[c.u]

Simple chart.

[CalEditor@pcmcalibrators]

That is not correct at all.

Lambda = the Stoich for the given Fuel --- E10% is 14.1
You can have a commanded AFR of 14.68 and you will have Lambda on E10%in closed loop.
You can have a commanded AFR of 14.14 and you will have Lambda on E10%in closed loop.

EQ is another story when E is in the system

The O2 sensor is not use the way most people think. The PCM drives the injectors to drive the O2 sensor to a given voltage on some vehicles and the driven the oposite dirrection. On some vehicles they use a switching point without the high low setting, but it has other settings also.

Swap the O2 sensors connectors and see how the engine runs.

[jmac636]

Simple chart.

Great chart but it doesn't show Eq ratio. You still have to make calculations which would obviously depend on the fuel and the blend of ethanol thats added.

[CalEditor@pcmcalibrators]

I guess my point is the AFR doesn't realy mater

I have a question for you. Will a narrow band O2 sensor work on with an AFR of 8 to 1?

[EagleMark]

Not on any fuel I know of? Stoich of fuel would have to be 8 to 1 AFR...

On to E10, I've seen stoich of 14.1 to 14.3? Is there really that much difference in fuels that these numbers seem to change? State to state or?

[excessive]

This is the best chart available for afr/ eq ratio...

[LSxpwrdZ]

Forget AFR all together... the only time you need AFR is when you are setting what fuel type you have for it's stoich ratio. After that Lambda or EQ is easiest to use and universal. Lambda and EQ are the same only the inverse of one another. 1/Lambda = EQ and 1/EQ = Lambda.

[LilJayV10]

Forget AFR all together... the only time you need AFR is when you are setting what fuel type you have for it's stoich ratio. After that Lambda or EQ is easiest to use and universal. Lambda and EQ are the same only the inverse of one another. 1/Lambda = EQ and 1/EQ = Lambda.

LSx, I am brand new to this whole tuning thing. I have seen others say that Lambda is better to use than AFR. Why is that? Thanks.

Jason

[Dusty05]

Can we add NGC commanded afr in here? That's a horrible think to calculate all the time.��

[joshuafarwel]

This is very very helpful. Thanks for making it. Going in my notes permanently

[joshuafarwel]

From the study i was trying to read about lean burn mbt.

Table 6. MBT spark advance for all fuels.
Fuel- MBT, eqr=1.0 MBT, eqr=0.83. [?CA BTDC]
Gasoline 26 36
iso-Octane 29 45
Ethanol 25 32
Butanol 25 34
B16 25 35
B25 25 35
E25 25 35
B16I84 29 40
B25I75 27 38
E25I75 28 41