[Aaron]

Undoubtedly you will have seen the Focus Audio Control stalk (or bear paw as it’s called in Renault land) that has integrated Cruise Control buttons. It looks suspiciously like it would mount in place of the Fiesta unit.

As far as Arduino etc powered Cruise control it’s pretty simple logic, apply that fuzzy logic you’re reacquainting yourself with into a simple 8x8 matrix or two and keep other I/O interrupts simplified. ie Brake/Clutch/Cancel is the “same”, That leaves you with “Up speed” and “Down Speed”. “Set” puts your code into its loop of chasing target roadspeed (or rather input sensor frequency). EHPAS only needs a “is engine turning/is roadspeed below 40km/h” as a minimum type of loop, although it depends how much granular Control you have over pump output.

I do worry that your EHPAS idea is going to way overstress the electrical generation capability of the Fiesta with the constant high draw. Shifting anything up to 1kw of “load” from the crank to the alternator at low RPM during low speed manoeuvres is going to be “a thing”.

It may be worth checking the current output of the MPS3/MPS6 alternators (bolt in same location as an XR4) and see if there’s extra amps available there. A spec check between EHPAS Focus Alternator and the XR4 stock unit would be worth it. The MPS alternators are in 2 and 3 wire versions, I think the XR4 is 3 wire, so MPS6 is more likely to be that direct donor.