Warning: Bypassing the Heater Matrix - DON'T DO IT!

[Xud Missile]

That's a good point. The pond pump I was using has a fixed flow rate which I can't alter, unlike an engine at different revs. I also don't know what pressure the water is at in the engine (which will also change with temperature), the pump I'm using is low pressure, high volume. Rigging it up on the engine, like you say, would definitely give the best 'real world' results. Would use a lot of water Outside workshop: pallets, empty IBCs, use of a forklift...