Author Topic: How do I change the stochiometric value?  (Read 10178 times)

Offline eraezer

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How do I change the stochiometric value?
« 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?

Offline gunni

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Re: How do I change the stochiometric value?
« Reply #1 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.

Offline gox

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Re: How do I change the stochiometric value?
« Reply #2 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


« Last Edit: May 25, 2008, 04:03:28 pm by BMW 325i »
E30 2.7 - VEMS,KKK K27.2,Schrick,1bar

Offline mattias

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Re: How do I change the stochiometric value?
« Reply #3 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.

Offline eraezer

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Re: How do I change the stochiometric value?
« Reply #4 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.

Offline rob@vems.co.uk

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Re: How do I change the stochiometric value?
« Reply #5 on: July 16, 2008, 10:29:18 am »
Thanks for the info, what sort of differences in the reading are you getting?

Offline gunni

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Re: How do I change the stochiometric value?
« Reply #6 on: July 16, 2008, 01:48:56 pm »
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

Offline rob@vems.co.uk

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Re: How do I change the stochiometric value?
« Reply #7 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.

Offline eraezer

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Re: How do I change the stochiometric value?
« Reply #8 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.

Offline rob@vems.co.uk

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Re: How do I change the stochiometric value?
« Reply #9 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

Offline gunni

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Re: How do I change the stochiometric value?
« Reply #10 on: July 17, 2008, 01:04:48 am »
exactly.

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