Discussion topic.
From Wiki ...
At some point, as the engine speed increases, the DME energizes the VANOS solenoids pushing the solenoid pistons forward applying hydraulic pressure to the back of the VANOS pistons and advancing the camshafts via the helical gears to which they are attached. This reduces fuel consumption and lowers emissions according to Wiki. I prefer to think of this in terms of improving fuel consumption efficiency because the phrase is less ambiguous.
So here's the thing. During the emmissions test a gas analyzer is shoved up the tailpipe and the gases are analyzed.
The test is conducted in two phases. At idle and at 2500 RPM and the vehicle has to pass both tests.
It is reasonable, given what I have just laid out, to assume that the emmissions recorded during the 2500 RPM test have to be less than those of idle.
In which case if the VANOS isn't working as it should, advancing the camshafts, then it is going to impact on the emmissions readings of the 2500 RPM test, leaving them more in line with teh idle test, and therefore may impact those readings to the point where the emmissions are greater than expected resulting in the car failing the second test.
How does that sound? Does that make sense?
More importantly, has anyone had an emmissions failure that has been corrected by a VANOS rebuild?
From Wiki ...
As an assumption I would expect the rest state of the VANOS solenoids to be at engine idle ie: lowest RPM = de-energized VANOS solenoids. The default position of all components. That makes sense to me.
At some point, as the engine speed increases, the DME energizes the VANOS solenoids pushing the solenoid pistons forward applying hydraulic pressure to the back of the VANOS pistons and advancing the camshafts via the helical gears to which they are attached. This reduces fuel consumption and lowers emissions according to Wiki. I prefer to think of this in terms of improving fuel consumption efficiency because the phrase is less ambiguous.
So here's the thing. During the emmissions test a gas analyzer is shoved up the tailpipe and the gases are analyzed.
The test is conducted in two phases. At idle and at 2500 RPM and the vehicle has to pass both tests.
It is reasonable, given what I have just laid out, to assume that the emmissions recorded during the 2500 RPM test have to be less than those of idle.
In which case if the VANOS isn't working as it should, advancing the camshafts, then it is going to impact on the emmissions readings of the 2500 RPM test, leaving them more in line with teh idle test, and therefore may impact those readings to the point where the emmissions are greater than expected resulting in the car failing the second test.
How does that sound? Does that make sense?
More importantly, has anyone had an emmissions failure that has been corrected by a VANOS rebuild?