Move coolant through the engine and the radiator at a rate high enough to carry the heat away.
A Pierburg CWA100-3 electric centrifugal pump. It spins a motor to move coolant across the system. Running an electric pump rather than the engine-driven OEM pump means flow is independent of engine speed, so the system still circulates at idle and in the pits.
Mounted at the lowest point in the system, which is what keeps it primed. Purchased rather than designed; selection is a cost and flow-rate decision.
Cost. Current draw against the vehicle's electrical budget.
Data sheet from purchase, cross-checked against a pump curve. Current draw measured on the car: maximum 11 A, average 9.73 A, roughly 3 A more than the EWP80 it replaced. From the design reports and one-pagers: CR22 used a Davies Craig EWP115 sized from the manufacturer pump curve, with water flow assumed at 59 L/min from the current draw seen in the ECU rather than measured directly. System pressure was found with a general head loss calculation across the engine, radiators, lines and swirl pot. The report flags that testing was still needed to find actual flow through the system, and records the pump as oversized for the application in hindsight.
Purchased.
Purchased unit.
Air gets trapped in the pump. This is the long-running complaint and is why the thermostat was removed and the system is bled. Fault Vault, 2026-06-07, CR26I, Operational Errors, Performance Failure. Improper bleeding techniques led to an excess of air in the cooling system. Two contributing causes were identified: the pump duty cycle was too high, so it spun too fast for air to be released, and the pump's PWM control did not enable until the engine was running. Recorded fix: change M1 Build to allow cooling bleed tests, or vacuum fill the system. The previous EWP80 pump leaked and had to be swapped regularly, which is what drove the move to the Pierburg CWA series.
Recorded fix for the bleeding problem: change M1 Build so cooling bleed tests can be run, or vacuum fill the system. PWM control so the pump always runs at the rate that rejects maximum heat is the other standing improvement.
Operating voltage 8-16 V. Weight approximately 1.0 kg. Current consumption 8.5 A maximum, approximately 0.2 mA standby. Nominal differential pressure at or above 0.75 bar. Flow rate approximately 30-35 L/min at 0.75 bar, 40-45 L/min at 0.50 bar. Speed approximately 7000 rpm. Temperature range -40 to 110 C water, -40 to 120 C ambient. Estimated 40-50 L/min in the CR26I installation. From the design reports and one-pagers: CR22 pump: Davies Craig EWP115, 12 V, roughly 2.03 lb, AN-16 inlet and outlet pipes. Chosen over the EWP80 for higher flow rate. From the cost report drawings and CAD: Dimensions called out on the cost report drawings. These are the figures printed on the drawing, not a labelled specification; open the drawing itself for what each one refers to. Coolant Pump (mm): 128.2, 80.0, R13.8, 20.0 Source: Cost report drawings: CR26E/Powertrain - EV/Design/Cost Report Drawings/Cooling/Coolant Pump.pdf Quantity per car, as costed: 1