Dumb down lambda
03-27-2012, 03:27 PM
#2
All oxygen sensors sense lambda values, and lambda remains the same regardless of fuel used. To put it simply, lambda = 1.0 is stoich for any fuel used.
Most people are used to looking at air/fuel ratios though, and that's where it gets confusing. The stoich AFR for gasoline is 14.7 (lambda = 1.0 at this AFR), but for something like E85, the stoich AFR changes to around 9.76 (but lambda is still 1.0 at this AFR for E85). So if you have a WBO2 gauge calibrated for gasoline, it will take the lambda value and convert it to an AFR based on the assumption that you are using gas that has a stoich AFR value of 14.7. If you are using E85, this gauge reading would then be inaccurate, but not because of the sensor...the sensor only knows the world in terms of lambda, so it is operating correctly regardless of the fuel used. It's how the gauge interprets it that makes a difference.
Tuning for lambda takes the fuel type used out of the equation, so it wouldn't matter if you used regular gas, E10, E85, etc, the lambda values would all be the same...the fuel required to reach the desired lambda values would change depending on fuel though (it would take more E85 to obtain a lambda value of 1.0 than regular gas, etc.).
Most people are used to looking at air/fuel ratios though, and that's where it gets confusing. The stoich AFR for gasoline is 14.7 (lambda = 1.0 at this AFR), but for something like E85, the stoich AFR changes to around 9.76 (but lambda is still 1.0 at this AFR for E85). So if you have a WBO2 gauge calibrated for gasoline, it will take the lambda value and convert it to an AFR based on the assumption that you are using gas that has a stoich AFR value of 14.7. If you are using E85, this gauge reading would then be inaccurate, but not because of the sensor...the sensor only knows the world in terms of lambda, so it is operating correctly regardless of the fuel used. It's how the gauge interprets it that makes a difference.
Tuning for lambda takes the fuel type used out of the equation, so it wouldn't matter if you used regular gas, E10, E85, etc, the lambda values would all be the same...the fuel required to reach the desired lambda values would change depending on fuel though (it would take more E85 to obtain a lambda value of 1.0 than regular gas, etc.).
03-27-2012, 07:12 PM
#3
Thinking lambda is dumbing down because it is so much easier to use.
You can think of a fuel correction as a %
You can scale your changes using afr but if you are logging lambda error
there is no math involved.
You can think of a fuel correction as a %
You can scale your changes using afr but if you are logging lambda error
there is no math involved.
