Restriction / Pressure Drop (PQ)
When building your loop there should be a list of things that come to mind, flow and pressure should be near the top of that list. Pressure drop is the measurement of inlet pressure minus outlet pressure, or the pressure loss of flow through the block. In order to measure restriction, we have a few tools at the ready…
I have the line from my washbasin in the mudroom hooked up to the gate valve controlling flow, which then runs into the King flow meter. The bottom port on the flow meter is the inlet, top port is the outlet. The outlet runs down to the Delrin T which I have Bitspower 1/2″ barbs on for the normal flow, and the negative pressure line connects via an EnzoTech 1/4″ fitting. After the negative pressure T, the component in testing is attached. I always use Bitspower 1/2″ fittings, which keeps everything on a common test platform…well from a fitting perspective anyhow. At the outlet of the component is the positive pressure T fitting, again with Bitspower 1/2″ fittings and an EnzoTech 1/4″ fitting for the pressure line. The tubing the runs back into the washbasin and down the drain. I control flow with the valve in 0.25GPM increments, up to a safe flow rate. By safe, one that will not exceed the rating of the manometer and a flow rate that does not scare me with my head less than 1ft away from it taking measurements and controlling flow with the valve.
Being in the photo-sharing mood, a few snaps of the blocks during pressure drop testing. The lighting is awful in that room, just makes the photos difficult to color balance.
Pressure Drop Data
With the tests completed, we have the compiled table for all of the blocks in our roundup. You will notice not all blocks have data up to 5.0GPM, the restriction of the block exceed the level of what I was comfortable running any higher. Not to worry though, there is more than enough data to build the curves for charting purposes.
This time around, we had a request to include the PQ from a few common pumps; the two gray lines represent a D5 and DDC. To note, the chart does not include other loop components, just the pump PQ and the block restriction.
Danger Den captures the high flow label for this round, having the lowest restriction of the blocks by a large margin. On the other end of the spectrum, we have Aqua Computer and EVGA with the bulk of the other blocks within a few PSI of each other. Even with the higher restriction of the AC and EVGA blocks, I still do not see any cause for pump over kill in an SLI setup with those blocks. Just something to keep in mind as you are parting together your loop though.
Loop Flow Rates
With pressure drop covered, how about the test loop and resulting flow rates… Well, I am glad you asked but will say we are presenting a chart before we cover the test method and spec where you will get the lowdown on the entire loop. But yeah, we have a chart for you.
First, let me point out the Danger Den blocks are the same, the flow rates recorded during testing just averaged out slightly lower when we tested the block with all TIM instead of thermal pads. No surprises here after digesting the PQ chart prior, overall the blocks are quite free flowing and remember you can always setup your multiple GPU blocks in parallel if restriction is a concern.
Since I have already mentioned the test method and spec, you can probably guess what is waiting for you on the next page…