The Outlander motor is oil cooled, while the Prius inverter is cooled by traditional engine coolant (water + additive). This means right now we will need two cooling systems, unless we can maybe run oil through the inverter. This feels like a bit of a gamble though with lots of maths required around flow rates, viscosities and thermal transfer. So for now, my plan is to stick with two cooling systems.

With the combustion engine removed and no drive belts to take power from, this will require a couple of additional coolant pumps as well as an additional oil cooler (not sure if the donor car has one of these yet). These can be quite pricey so I started an eBay watch early on and came across a fairly high spec Mocal oil pump going for relatively little. Some fastest-finger-first bidding later and I’d nabbed it for £51 including shipping – about a third of its retail price. Picture to follow when it arrives.

Specs are as follows (from the MOCAL website):

Pump has integral cooling fan, 12 or 24volt motor. Ports are 3/8NPTF and may be rotated in 90° increments to simplify plumbing. The pump body is made of lightweight nylon, care must be taken when tightening tapered adapters not to over tighten and crack housing.
Perfomance: 2 UK gals/10 litres per minute with 7 amps current draw. Temperature constant use up to 130°C, intermittent up to 150°C.
Dimensions: Weight: 1.5kg/ 3.3lbs

I will need to rig up some sort of temperature switch so the pump kicks in not to early and not too late – somewhere around 70°. I could do this with a simple 12v temperature switch but I’ll more likely use the coil temperature readings from the motor and have this switched on a relay using logic on a microcontroller somewhere (I will likely need something to act as a vehicle control unit (VCU), replacing the onboard logic for the car).