Pump Testing

Robert removed the coolant pump setup to give him more space to fit the motor, so I took the opportunity to bring the assembly home and get some testing done to make sure the pieces I had stashed away will actually work. The Pierburg CWA50 pumps were sourced from EVTV and were used in the same Ford Transit Connect vehicle that provided the Siemens motor and DMOC inverter.

I put together a test rig in the garage initially with a piece of clear vinyl hose recirculating back into the catch tank. I can watch the fluid pass through the hose to verify it's actually pumping, then try to vary the pump speed and therefore the flow rate.

My friend Tim Catellier worked through the use of a Pierburg pump last year on his beautiful BMW Z3 conversion. Although Jack Rickard runs the pumps at full speed, 30 liters/minute, Tim notes that more water is not necessarily better. The DMOC calls for 13 to 16 liters/minute, about half the flow rate this pump is capable of. The pump does provide for speed control by a PWM (plus width modulation) signal, so a PWM signal generator is needed. 

Tim built his own, but since Radio Shack has gone out of business, I let my fingers do the walking and found this tiny contraption on eBay. It was really a shot in the dark, but at only $4.65 each plus $1.50 shipping from Hong Kong, there wasn't much to lose.

I'm pleased to report that it works just fine. Turning the little brass screw on top varies the speed from full bore to just barely moving. 

The pump is almost silent at all speeds, so won't be intrusive. I did notice that it seems to aerate the water and not sure what that's about or if it's any cause for concern. I don't have hose clamps on it, so it may just be an air leak somewhere in the short loop.

A more pressing question is how to measure the flow rate and set it to about half. Once the screw is set, it will stay at that speed, just need to figure out what that is. So buckets and a stopwatch figure to be a big part of my weekend.