Hi,
You only need fancy drive circuitry if it's a flight engine where weight and endurance are important.
Phils radial engine circuit has issues, particuarly the 0.47uF capacitor across the gates of the MOSFETs. This stresses the mocrocontroller outputs and keeps the MOSFETs in their linear region longer increaing heating and battery consumption. Fo a simple sequential switch a couter decoder like a CD/HEF 4017 or 4022 would be easier to use.
For a flat four I'd run the plugs series / parallel. Put a link / busbar between the two plugs on each side then connect the battery (or other source), with a voltage twice the rating of each plugs, between the two links. The crankcase will be at half battery voltage but as long as the battery is isolated tthat is not an issue.
For bench running a transfomer can be used, glow plugs don't mind if power is AC or DC.
Robert G8RPI.
Edited By Robert Atkinson 2 on 12/07/2020 11:34:34