Boxster (986) F6-2.7L (2000)
Oxygen Sensor: Description and Operation
Diagnosis of Oxygen Sensing System Mixture Adaptation
Diagnosis Of Oxygen Sensing System Mixture Adaptation
General
The adaptive oxygen sensing system corrects longer lasting deviations of the fuel/air mixture of lambda = 1 by changing the anticipatory control
calculated in the DME control module and the injection timing altered as a result.
Through mixture adaptation, the anticipatory control is multiplied and augmented in such a way that corrections to the oxygen sensor (FR) itself can be
kept to a minimum, and the mixture remains within the range lambda = 1 even during open-loop (as opposed to closed-loop) control.
This process is based on the following assumptions:
Over the life span of the engine and through different tolerances, two basic faults may occur:
The multiplicative fault and the additive fault per time unit (false air). At idle speed the false air fault dominates (low air flow rate, low rpm); with a high
air flow rate the multiplicative fault dominates.
A combination of multiplicative and additive faults is compensated correctly when a corrective value is adapted in its dominant range. Therefore, there
are three major adaptation ranges:
System description
The adaptation values can be read out with the Porsche System Tester 2.
The key to the adaptation values is as follows:
RKAT = Adaptation in range close to idle Cylinders 1 - 3
RKAT2 = Adaptation in range close to idle Cylinders 4 - 6
FRAU = Adaptation in lower load range Cylinders 1 - 3
FRAU2 = Adaptation in lower load range Cylinders 4 - 6
FRAO = Adaptation in upper load range Cylinders 1 - 3
FRAO2 = Adaptation in upper load range Cylinders 4 - 6
FR = Oxygen sensor for cylinders 1 - 3
FR2 = Oxygen sensor for cylinders 4 - 6
FUNCTION:
After the DME control module has been disconnected from constant B+, the numerical values are at 1.00 (FRA) or 0 (RKAT). After the engine is
started, first the programmed map is displayed.
Example:
Range 1:
RKAT:
0 %
RKAT2:
0 %