Most of us who have bog standard Rover Flapper Efi Systems know we must adjust our throttle pot to be 0.325 volts above zero at the idle position of the throttle?

It's not Zero nor 1.0 volts. It's 0.325 Volts. But WHY?

I cant recall ever seeing a written explanation (reason) in any "Rover" documentation and although I have heard a few different opinions none ring true.

UNTIL NOW!

In another forum I was explaining that the Rover ECU "FULL LOAD ENRICHMENT CIRCUITS" are triggered when the throttle pot reaches 4.3 volts at 90 degrees of rotation, or full throttle.

Feedback from some members indicated this was not common knowledge yet that fact is clearly described in the original Rover Technician Training Manual. See below, a scanned image from page 14 of that manual.

It then dawned on me that to guarantee the ECU would see a full 4.3 volts at 90 degrees of rotation, a small offset at idle position is needed.

So, if normal tolerances for analog circuit components (say 5%) apply, then, if for some circuit tolerance reason the full load enrichment circuits saw something lower than 4.3 volts, they may not be triggered.

Now, 0.325 volts is 7.5% of 4.3 volts so by specifying a 7.5% offset, this would ensure that the circuits were always triggered at full throttle providing there were no overt mechanical reasons preventing full 90 degree rotation.

For the first time in 14 years, and without the benefit of the designers' knowledge or reasons, this seems like a good explanation of why the setting is so specified.

Can anyone throw a different light on this subject?

Interesting. Mine never gets that high (only around 3.5v) for some reason. The throttle plate opens fully and I've had the pot apart and it's clean and not worn through the track.

Perhaps I'll adjust it sometime to to give 4.3v at full deflection and see what happens.