[Diy_efi] Digifant (was:This turbo assist stuff...)

[Mike]

At 10:55 AM 1/3/03 +0800, you wrote:
>If you think that odd - schematics for earlier cars show a 10A fuse
>to power the ECU relay coil; and nothing else! Looks like the ECU
>was originally powered entirely via the ignition switch and somebody
>though better of it, putting a relay in to take the bulk of current.
>
>But the coil is still running via the ignition switch!
>
>Maybe that's deliberate - the extra cable length (inductance) may be
>being used to isolate the ECU from voltage fluctuations induced by
>the coil.

Nop, its the same on my car. The reason seems to be the ECU releases
the relay when its done, but the ignition can be 'killed' ad therefore
there isnt a 'hold' time. The other reason is the ECU is then compatible
with the hot wire AFM burn requirement. Inductance at those frequencies
is not an issue IMHO. My schematic has a capacitor, I am speculating
yours is in your 'bosch amp' - which if old may be marginal causing
erroneous early and overly sensitive determination of engine knock.
The ECU may also have an eeprom which may need an update time after
ignition off, mine holds for about 12 seconds after ignition removed,
but thats mostly for AFM burn, though there is a small eeprom in the
bosch/hitachi ecu.

Onw thing which I dont understand with your setup given the point
you mentioned that your ECU occasionally does a knock sensor test
to drive the ignition excessively advanced to test the sensor etc.

How does the ECU determine the difference between a slight knock
and a severe knock or are you implying it just doesnt care ?


Rgds

Mike
Perth, Western Australia
Some power/auto stuff here:-  http://www.iinet.net.au/~erazmus


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