[Diy_efi] Power supplies Was: Digifant (was:This turbo assist

[Mos]

On Thu, 9 Jan 2003, Mike wrote:

> 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.
<snip>

On the majority of injected toyotas there is an EFI relay for the ECU and
fuel pump supply running pretty much off the alternator output directly,
whereas the injectors and coils/ignitors are run through the ignition
switch through 3-4 m of cable.

On toyota engines fitted with stepper motor idle speed controls the EFI
relay is activated by the ECU itself, and maintains power to the ECU for
about 3-5 seconds after turnoff to reset the position of the ISC motor to
the starting state.

Mos.

-- 
84 AE86, 90 ST185GrpA, 91 MX83Gr, Sydney, Oz.



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