How do I change the stochiometric value?

[eraezer]

Hi,
I want to change the stochiometric value (or z-value) to be able to read the lambda right.
I have searched and searched but I have not found anything about this.

I want to change from 14,7:1 to 9:1 (gasoline to ethanol).

VEMS spec.:
Vems v3.3
1.0.73


Any Ideas?

[gunni]

Vems reads the lambda value from the sensor. so the lambda you see is the real lambda.
neither the sensor or the vems sees air fuel ratio.

[gox]

Lambda (V)    Ethanol A/F ratio
   0.70              6.3
   0.75              6.8
   0.80              7.2
   0.85              7.7
   0.90              8.1
   0.95              8.6
   1.00                 9.0
   1.05              9.5           
   1.10              9.9
   1.15              10.4
   1.20              10.8
   1.25              11.3
   1.30              11.7

[mattias]

Like gunni said, why even bother? You have the lambda value which is what you want, it is true regardless of fuel.

[eraezer]

Compared to this: http://www.etas.com/en/products/la4_lambda_meter.php the VEMS setup shows the wrong lambda while running the car on E85.

[rob@vems.co.uk]

Thanks for the info, what sort of differences in the reading are you getting?

[gunni]

E85 AFR will not be the same as normal gasoline
So it´s not right to assume E85 lambda and gasoline lambda will be the same amount of fuel

[rob@vems.co.uk]

It will be a different mix of fuel, but lambda 1.0 is stoichometric burn which means a reading of 1 for any fuel means that its the perfect AFR.

[eraezer]

lambda 1 is the same, but it will be wrong when going up or down and therefor do I need to change the stochiometric value, hence this thread.

[rob@vems.co.uk]

Lambda 1.0 *IS* stochiometric, the values either side are a function of it:

L = AFR/AFRstoich

What are you looking for exactly?

Rob

[gunni]

exactly.

Lambda 0.8 is 80% of Lambda 1 So it´s totally irrelevant to AFR , everytime.