VEMS Community Forum

Technical => Fuel Injection => Topic started by: eraezer on May 23, 2008, 05:14:39 PM

Title: How do I change the stochiometric value?
Post by: eraezer on May 23, 2008, 05:14:39 PM
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?
Title: Re: How do I change the stochiometric value?
Post by: gunni on May 23, 2008, 06:05:50 PM
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.
Title: Re: How do I change the stochiometric value?
Post by: gox on May 25, 2008, 04:00:53 PM


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


Title: Re: How do I change the stochiometric value?
Post by: mattias on June 25, 2008, 10:13:39 AM
Like gunni said, why even bother? You have the lambda value which is what you want, it is true regardless of fuel.
Title: Re: How do I change the stochiometric value?
Post by: eraezer on July 16, 2008, 10:11:24 AM
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.
Title: Re: How do I change the stochiometric value?
Post by: [email protected] on July 16, 2008, 10:29:18 AM
Thanks for the info, what sort of differences in the reading are you getting?
Title: Re: How do I change the stochiometric value?
Post by: gunni on July 16, 2008, 01:48:56 PM
E85 AFR will not be the same as normal gasoline
So itÃ,´s not right to assume E85 lambda and gasoline lambda will be the same amount of fuel
Title: Re: How do I change the stochiometric value?
Post by: [email protected] on July 16, 2008, 02:43:34 PM
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.
Title: Re: How do I change the stochiometric value?
Post by: eraezer on July 16, 2008, 09:40:23 PM
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.
Title: Re: How do I change the stochiometric value?
Post by: [email protected] on July 16, 2008, 10:04:10 PM
Lambda 1.0 *IS* stochiometric, the values either side are a function of it:

L = AFR/AFRstoich

What are you looking for exactly?

Rob
Title: Re: How do I change the stochiometric value?
Post by: gunni on July 17, 2008, 01:04:48 AM
exactly.

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