Silenced TJ07 (D5 and DDC 2 in same loop)

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Leak test time!

I have everything plumed and filled with distilled for leak testing as this is posted. It’s been running for about two days now, and I’ve been able to fix any issues except for the res leaking. The Koolance res’s don NOT like to seal very well, so I’m unable to test just by pressure with my gauge.



Also the Koolance Res-Top does not bleed easily as the flow does not pass through the top chamber. After running over night most of the bubbles are out, but an odd number stick to the side of the res like in the pic below.



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Performance Testing:

With the two unlike pumps in this system, I want to show that it’s a load of bull that one cannot do such. Normally it’s stated that one will “over speed” the second pump or starve the second one of flow depending on how they are matched.

That’s not quite how it works in most cases. As long as you are not pushing more flow thought he second pump then it’s 0 head flow rate (max flow), you cannot over speed it from doing this. Also as long as you don’t have a negative relative to atmosphere pressure going into the second pump, then you are adding to “flow” by increasing total pressure, not restricting it.

Right now I have a Compound Pressure gauge with a range of +10 to -15PSI in the system at the inlet to the second pump. With this gauge, one can judge how the two pumps are working together. System flow wise it’s like this:

Res -> D5 W/Koolance top -> RX360 rad -> Koolance 5-way port (pressure tap here) -> DDC-2 with XSPC top -> extremely restrictive loop

I’ll be comparing this pressure, minus the presumed pressure drop of the rad, to the following graph that Martinm210 produced in the thread ” Some Laing D5 Testing, 13.1-24V is the same” back in 2007.


Graph of D5 flow vs pressure at various settings by Martinm210.

First, a zero PSIG point must be put into the loop to ensure accuracy of the gauge. Thus, I put a brass ¼” BSPP breather port into my fill port to bring the res pressure (and pump 1 inlet pressure) to 0 PSIG.



Next we need to see what the gauge thinks 0 PSIG looks like


So it’s at about 0 PSIG = .25 PSI on this gauge. The adjustment screw is not accessible, so I’ll just leave it like this. What can you really expect form a $10 harbor freight kit?

Now with just the D5 on, and at setting 5.


This gives a little under 5PSIG, and if you subtract out the offset and presumed loss in the rad you can presume this to be 4.5PSI as the outlet pressure of the D5. Looking on the graph, this comes out to be some were around 1GPM on the “5” setting.

Now let’s try with just the DDC2 on.


Here we can see a slight vacuum at the pump inlet. Taking out the offset, it’s about 2 in Hg, or about -1 PSIG at the pump inlet here. It’s hard to tell, but looking at the pressure drop graphs for the RX360, this is as least 1GPM of flow.

Now let’s try both on full blast.


This is about 3.60 PSIG on the gauge, or right around 4 PSI after you take into account offset and pressure loss through the rad (a little less then .5PSI @ 2GPM). 4PSI at setting 5 on Matrianm’s graph above would put the total flow output just under 2GPM, so that’s quite good with the components I have. The GT 220 it’s dropping over 2PSI at 2GPM, the MCP-60 1PSI, and I cant find graphs on the Heatkiller 3.0.

Now let’s tune this thing for silence by adjusting the D5’s speed. I have the 10-turn port that I can finely adjust the speed on until the pressure and noise levels are were I want them.


This is at about setting 2 on the DDC, and both the D5 and the DDC are much quieter at this operating point. They aren’t that loud at full blast, but I’m gunning for silence here. Pressure at the DDC is a little above zero (.25 to .5 PSIG), so I’m still getting a performance boost and it’s still high enough to give cool the system if the DDC2 decides to bite the dust.

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Due to a request by another user, i made a few addition pics of the top rad. I'll post them here as well: