Chris S

Put simply, a major factor is cost. Four cylinders is cheaper.

Not if the receive path was conductive.

For a long time now this question has bothered me. I have a classic car, and I want to know how the rate of flow of coolant affects cooling. Could I make a simplified model to show how engine temperature varies with coolant flow? Obviously zero flow would halt the cooling effect. But does engine temp continue to reduce with increase in flow or is there a point where it stabilises or even drops? As an electrical engineer I dont have the tools to make such a model.

I spent a lot of time on a project to control dc pm motors. A pm (permanent magnet ) motor has two wires, and speed will vary with applied voltage. If you just want to manually vary the speed, buy a cheap adjustable voltage regulator off ebay. But if you want the speed to be accurate, that is a different ball game.

I retired about 12 years ago but I still take an interest in engineering. As an analogue engineer, I had to do a fully toleranced design analysis on one project to prove in theory that our design should work. To do this manually would have been tedious, and very time consuming, so I used spice modelling. For anything non trivial I dont see any alternative to using a computer.