Its been a while since talking about this topic, and I'd like to get back to it. This time though, I'm thinking about putting this setup on the Metro. It already has a
deep cycle battery in it and an
alternator disable mod done to it. The only thing left being powered on the crankshaft's accessory belt is the water pump... so lets fix that.
So, first things first, how fast does the Metro spin its water pump? Well, the crank pulley is 5" and the water pump has a 5-3/8" diameter. So, it has a 1:0.93 ratio. I threw the numbers into excel to get this chart. At idle, our lowest water pump rpm is 700 (assuming 750 rpm idle speed).
For now, I'll probably consider 700 to be the low end of what is needed once the car is up to temp. This sounds somewhat logical to me, your two cents is welcome.
The high end will ideally be determined by the speed at which the water pump starts to cavitate. Getting rpms up there will be interesting though. The electric motor only spins 1250 rpm at 12V. I'd imagine I'd want a max water pump rpm of around 2000. That means I'll need a 8" diameter pulley which is pretty large period... I may have to look into making a new water pump pulley too and reducing its size.