MEMS

[Ade + Lamb Chop]

At 05:00 15/10/99 -0400, you wrote:
>>What does the knock sensor do? What does it mean if I don't have one
>
>Detects the onset of knocking and dynamically reduces the ignition
>timing advance to minimise it. Not all the systems implement knock,
>If you chose to use a system that does, but don't want to use it (or
>don't have anywhere to mount it) the best would be to have the sensor
>connected so that it doesn't create a sensor detection fault; the
>system will never see a knock signal, so will perform normally.

My Rover manual doesn't mention a knock sensor so it cannot have one. (and
we all trust rover don't we....yeah right) The manual says it plays with
the timeing at idle. But I presume that once it comes off idle it just uses
the map of MAP/REVs

>I think it's to do with hot start strategy when there could be the
>possibility of fuel vapourisation in the fuel rail. I've only seen this
>fitted on MPi applications, where the sensor is mounted on a boss, thermally
>attached to the fuel rail.

Sounds reasonable....

>>>All MEMS systems control ignition, either single coil or distributorless.
>>>All systems use a stepper motor controlled throttle stop for idle speed
>>>control.
>
>>Apart from the Mpi (97 on) minis which have a bypass valve which bleeds are
>>from the filter casing into the manifold.
>
>I wasn't aware of that - I've only ever seen steppers.... we live and learn.

It is a stepper motor. But instead of an adjustable butterfly endstop. It
is a 'pintle valve' (what ever that is) Which is adjusted by a stepper. The
valve is mounted to the manifold where it does the turn towards the head.
It has a hose that goes from the valve up to the filter side of the
throttle body. 

Ade