First of all: the stock water pump is rubbish. I have learned a lot about the design of fluid pumps in university and the impeller shows almost none of the beneficial design features, we learned about. It's completely rudimental and doen't show any intention of reaching a sophisticated level of performance. It was intended for 55 or 65 HP in road use. Three times the power output (or more) in racing environment requires a much higher cooling performance, of course.
In my case, an additional issue is that we had a small leak in the radiator at the last race. We used liquid sealant, because we didn't want to miss the race. But that means that water channels inside the engine and radiator can get pluged by the sealant. This reduced the cooling performance in addition. The consequence at my latest drive to an oldtimer meeting in 2018: Water Temp. higher than 95°C and oil temp below 50°C, because of the very low reving driving on the road. Even at the last race, we had to drop the RPM and "lift and coast" into many corners to keep the temperature below 100°C. As far as I know, the max. pressure (before blowing off) inside the cooling circuit allows water temperatures up to 110-115°C (before boiling), but the car had to survive four hours, thus we didn't risk too much.
All this is too much of a compromise and has nothing to do with racing. This is just carrying my fuel around a circuit. I don't want to waste any more money for that.
That's why I'm going to replace the crucial parts of the cooling circuit as the first important upgrade before the car goes on a track for the next time.
