Pump Performance Testing

The pump used in the CORSAIR Hydro XD5 is a Xylem D5, which means it already has a history of reliable and good performance backing it. But as with every product we receive, it was put through the full test suite. To test a D5 pump, I use a reference D5 top from XSPC (XSPC D5 Bay Res) and the pump separately after disassembly. This is to help decouple the pump's performance from the pump top's performance as part of the reservoir, which is tested separately. Given this is a PWM pump, the first thing to test is its RPM response, and to do so, I used the pump in a simple loop of reservoir-in to reservoir-out, with pump power from an EVGA SuperNova 1300G2 PSU and PWM control from an Aquacomputer Aquaero 6 XT, which also provided RPM monitoring.


There have been a few years of inconsistency when it comes to PWM control with the Xylem D5 pump, especially as a result of it not conforming with Intel PWM spec 1.3. A few manufacturers took it upon themselves to work around it, and a few others claimed to be working with Xylem to resolve this once and for all. Whatever the reason, we see a nice linear response of the pump's speed with the PWM signal. As generally expected with PWM duty cycle control in the PC DIY sector, there is an increased range of control at the lower end and a full-speed operation when no PWM signal is provided relative to the older D5 PWM pumps. The rated RPM for this pump is 4800 RPM with a 20%–100% PWM duty cycle, which the measured numbers match very well indeed.

In order to see how the pump performs, I used it in the same loop as before, but with a Dwyer 490-1 wet-wet manometer to measure pump head in PSI and a King rotameter to measure average flow rate in gallons per minute (GPM). This P-Q curve for a pump provides extremely useful information as it shows the average flow rate in a loop when any flow restriction is added from blocks and radiators, under others. To produce an ideal but realistic data set, the P-Q curves below are thus for the pumps in a closed loop with minimal flow restriction.


I have included other pumps that have been developed within the few last years, and have at the same time removed the DDC-style pumps from consideration to keep to a more D5/flow-optimized pump comparison. This keeps the plots as clean as possible and makes for direct comparisons. A lot of the more budget-oriented pumps introduced lately aim to match the Xylem D5 Vario in Position #3, which corresponds to the D5 PWM at 70% PWM duty cycle. As such, I have included that setting as well, in addition to 100% PWM. The Alphacool VPP755 is a newer "D5-replacement" pump sold by Alphacool with a different design but based in a similar housing as the Xylem D5, and it ends up outperforming the D5 PWM pump in the CORSAIR Hydro XD5 (w/XSPC top) ever so slightly while having a considerably less favorable history of operating reliably. The rest of the lot are hovering around the lower end with only the XSPC X2O 420 in the XSPC Ion and the Topsflo TDC doing better.