MEMS

[Rich M]

Date: Wed, 13 Oct 1999 18:41:28 +0100
From: Ade + Lamb Chop <alaw at mrc.soton.ac.uk>
Subject: Re: DIY_EFI Digest V4 #576

At 15:00 12/10/99 -0400, you wrote:
>>All MEMS systems use as a minimum the following sensors:

>>Additional sensors , depending on application, include:
>>Knock

>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.

>>Fuel rail temperature

>Why?

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.

>>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.

Rich