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I'm looking for a person who exactly know how the s7/s8 emissions system works.
due to emissions regluations in my country, I want to program my aftermarket ECU(haltech elite 2000) to control the ACV and the Airpump.
Unfortunatly the s7/8 does not have the "classic" ACV which not has the following components:
Switching, Relief 1, Relief 2, Port Air Bypass, Split Air Bypass.
The newer models ACV only has the Relief 1 (air returns back into filter) and the switching valve (air switches between Port and Catalytic Converter).
I only have the diagram below for the classic ACV from the s6 model:
When idling, the air pump is running and the air is completly injected into the port.
But to reach lambda 1 (14.7) in idle, the car has to run SUPER rich, about 0.75 Lambda. This 0.75 lambda plus the air from the pump makes Lambda 1 and the sensor and catalytic converter.
Any ideas what wents wrong? How should the pump and ACV be controlled to get Lambda 1 in idle. Maybe it works to PWM Control the Air relief to get a percentage of the air not in the port.
PWM controlled switch would dump a percentace of the air into the converter, this will also change the lambda reading of the emissions tester away from lambda 1 and I will fail.
The factory ECU knows when the air pump is injecting air into the exhaust manifold and knows that it skews the readings the O2 sensor sees. It modifies the numbers to compensate. This is why on a car with a stock ECU if you remove the air pump the car will idle rough and will be rough on/off throttle, it's trying to compensate the O2 sensor output when it doesn't need to.
There may not be an easy way to do this with an aftermarket ECU, you would have to define ranges where the air pump runs and change the O2 target for those areas.
