cold start problems (frequency valve?)

[Ti Kan]

Mike_Buckham at ptk.pioneer.co.uk writes:
> Older UK spec cars do not have O2 sensors to perform fine calibration of
> the fuel mixture. Mine is a 1989 200qta with a MAC-12D ECU. There is no O2
> sensor and the O2 sensor inputs to the ECU are disconnected (where they
> would usually be connected on a MAC11 ECU). So I was wondering... why do
> these cars still have a frequency valve to adjust the fuel pressure? What
> is the ECU using to change the duty cycle on this valve, as there doesn't
> seem to be any input which it could use to make any adjustments?

I am not sure, but the ECU might also uses the frequency valve for
fuel enrichment purposes when under turbo boost.

-Ti
2003 A4 1.8T multitronic
2001 S4 biturbo 6-sp
1984 5000S turbo
1980 4000 2.0 5-sp
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