The legendary Martin has the best explanation on pump curves and how to decipher the results, and most of the following information comes from his site, I paraphrased a portion of the explanation from the legend.

Pump Curves or P/Q (P is pressure, Q is flow) curves are derived from two measurements, flow and pressure, and the P/Q curve is just a visual representation of the relationship between flow and pressure. For the curve, maximum flow rate (GPM or LPM) is the X axis and Pressure (PSI, mH2O, ftH20, mBar) is the Y axis.

Almost every pump specification I have ever seen comes with a defined maximum head (or lift) and maximum flow rate. Problem with these curves is they are based on perfect world conditions, where no restriction or resistance are factored into the data and resulting P/Q curve. The key for testing is setting up a test fixture to collect data for all capable ranges of the pump and top in order to develop a real world P/Q which uses the common components in a PC Liquid Cooling System, and that is exactly my goal for each Pump and Top test performed in the lab, we aim for real world scenarios and the resulting data.

One other item to note on P/Q curves is the Trendlines used on the scatter plots. DDC's trendline has a best fit polynomial using a 3rd Order, where as D5's have a best fit with 4th or 5th Order. Now the problem I am running into with Excel is a defect that has been around since Excel 2000 and polynomial trendlines. Sometimes no matter what you do, the trendline will not work on a best fit, the code inside Excel is not consistent. As a result, some of the trendlines you see on the individual test reports will not represent the proper trendline. Additionally, I did not forecast or predict ahead on the compiled P/Q curves for all results, some did not have the Excel bug and some did.

In short, dynamic head pressure is the pressure measurement at the outlet minus the pressure at the inlet or the differential. Dynamic head pressure is a better measurement for the actual pressure the blocks will see in the loop. Many other pump tests have only measured the outlet pressure, which does not take into account the inlet pressure and does not represent a true pressure measurement for your cooling loop. Dynamic head pressure is quite easy to add to the Pump test fixture and requires a T fitting at the pump inlet and a T fitting at the pump outlet. The pump inlet T is hooked up to the negative side of the manometer and the Outlet T to the positive side of the manometer.

I took Martin's lead on this measurement and included these in the individual test results that you will find at the bottom of each speed setting graph. For each flow setting the voltage was regulated to 12.00 volts as set on the DC Power Supply and verified on the multimeter hooked up for all tests. In addition, the current (amps) draw was recorded for each flow setting, luckily the DC power supply I have has a display for amp draw, initially I had a multimeter hooked up but as tests went on the two displayed identical readings. As with Martin's tests, the voltage regulation and amp draw data recording is really used for the efficiency charts, but power consumption is displayed on the P/Q curve charts for your reference as well.

No shocker here, another test result that was started by Martin and I only feel that it is right to continue providing the information. The efficiency charts are simply a graphical depiction of the water horsepower to break horsepower of the pump at the given flow rate, showing which flow rate the pump (and pump top) will perform with the best efficiency.

Here is a scatter plot for each of the five speed settings that the D5 Vario is capable of. The following scatter plots show the pump curve of the stock Laing D5 and the D5 with the Detroit Thermo Top. The Performance Results Intro section of this page explains how to read the charts and the explanation of the data. The full test report for the Detroit Thermo top and Stock D5 are available as links below each of the scatter plots for that specific speed setting. Enjoy!

The Detroit Thermo top provides a nice performance boost to the stock D5 top. If you notice in the scatter plots, the Detroit Thermo top provides a slight increase in flow rate over the stock top, all while increasing the Total Dynamic Head Pressure at almost every flow rate tested, only below 0.5GPM does the stock top outperform the Detroit Thermo top. However, that amount of restriction is not a "real world" loop. Anyone with that amount in their loop should really look at adding a second loop, as the cooling performance in their loop is greatly degraded...but that is completely different topic.

Besides performance, the feature that I like most about the Detroit Thermo top is the ability to use the stock D5 mounting bracket or other compatible brackets. This feature allows for anyone with an existing D5 mounted in their case to perform an upgrade and not have to worry about drilling new mount holes into their case.

I only have one very small complaint about the Detroit Thermo top, this was even adjusted in a revision that was sent to me. When using the (UN)Designs bracket the bottom gromet becomes compressed and slips out the bottom slightly, I am almost certain that this was not accounted for in the design of the top. Like I said, a very small complaint and cannot be listed as a con since the (UN)designs bracket was not used as part of the design criteria.

Overall, the Detroit Thermo top was a pleasure to have on the test bench. The performance gains are worth the upgrade, the simple installation and ability to use the stock or (UN)designs bracket make the Detroit Thermo top an excellent product.