PeachParts Mercedes-Benz Forum - View Single Post

duxthe1 · #5 12-01-2008, 08:26 PM

The idea behind the project is to be able to make adjsutments to the fuel mixture on the fly while in closed loop. With the lambda set to ~50% for normal unadjusted driving, the controller should be able to move the lambda up or down ~30% in 5% increments. So with a good 50% basic adjustment you could adjust the lambda to either a maximum of 80% or a minimum of 20%. I didn't see any situations where a normal engine (non forced induction)would want or be able to operate outside of those tolerances.

The controller adjusts the mixture richer by outputting an O2 sensor voltage that is leaner than it actually is, thus allowing the CIS-E to adjust it richer. The inverse is also true, if you want to adjust the mixture leaner then the controller outputs an O2 signal that is interpreted as rich allowing the CIS-E to adjust itself leaner. The CIS-E module tries to oscilate the mixture around 50%. The controller is designed to basicly allow you to select different values (other than 50%) around which it's adjustments are centered. Such that if I want to center the CIS-E around 40% then I decrease the O2 sensor's voltage by 10%. This lower O2 sensor voltage is interpreted as 10% lean, and the CIS-E will adjust it 10% richer. All the while the CIS-E thinks it's still centering around 50%

The concept behind the controller is to be able to dial in a bit more fuel at the stoplight when there is a BMW next to you, or to be able to dial the mixture leaner when you are on the highway at a nice cruise, and then be able to set it so there is no adjustment for general putzing around. All with just a turn of a knob.