R1-2 Pump Noise 35X vs PMP450 vs PMP400+Top

Posted: February 27, 2011 in Pumps

Special thanks to Tim from Koolance.com for sponsoring the Koolance pumps and tops!

Also a special thanks to Gabe from Swiftech.com for sponsoring the Swiftech MCP-35X plus reservoir top!


This was a direct comparison of the Koolance PMP-400(DDC3.25) + COV-RP400 top vs PMP-450 (D5 Vario).  There seems to be many opinions about noise between these two model pumps and I’ve set out to “Attempt” to measure differences.  It’s proving to be fairly difficult and the results are typically within that “3dbA is not perceptible” range, but I’m trying anyhow.

First the video:

I have charted results for this video captured in round 2 below, but the above video contains the entire sweep on the PMP400 and PMP450 pumps


This was adding in the Swiftech MCP-35X+Reservoir combo to see both how the PWM handles range, but more specifically to see how the reservoir weight changes the results. Here are the charted results:


For those that insist on the absolute lowest noise, you’ll need to find a good way to decouple the pump from any direct metal or solid contact.  I used a piece of eggcrate as my test case, although there are a variety of alternatives.  The more “Free Floating” the pump is from the case, the better.

1" Egg-Crate Foam Decoupler


The DDC series pumps are performing slightly better with their aftermarket tops, and the 1″ foam decoupler is most effective with the lighter weight unit.  It should also be noted the amazing range that PWM is offering the MCP-35X.  The 35X takes the crown for lowest possible noise although that is a very small amount of pumping power.  For medium to high settings loosing the reservoir allows the foam decoupler to work a bit better.

The other apparent trend is the rise in noise levels from medium speeds to high speeds.  There are relatively minor benefits going much slower than medium speed, but very good reductions in noise going from high to medium on all of the pumps.


This is for those that are not all that concerned with pump noise and perhaps either directly bolt the pump down, or have very minimal decoupling.  I allowed the pump to sit directly on sheet metal as is without any foam decoupling.


Direct Metal Contact

The direct contact results seem to tell a few different things.  While the weight of the reservoir of the 35X may have been making the foam decoupler less effective, it’s also serving to assist in keeping noise vibrations in check much better than the lighter top only pumps when in direct metal contact.  Mass/weight alone does appear to have some benefit to reducing vibration transfer noises.  The other interesting trend with the direct contact is the undulating “Harmonics” results.  This will obviously depend on the exact installation, but in a solid type installation it appears there would be benefit to “tuning” the rpm and avoid those peaks as much as possible.  I would also suggest reservoirs and high mass in instances where pump decoupling isn’t being used, that appears to be another benefit.


And here is the video including the 35X comparison to the previous two pumps tested so far:

You might notice I had a small leak from the side plugs in the 35X test that took me a while to notice  (I forgot to tighten the top plug).  Whoops! yet another operator error!  I fixed it in the middle of the test.

Obviously next on my list is to test the 35X without the reservoir.  Theoretically without the reservoir weight, it should equal the PMP-400+top results except have that added PWM extra range.  I’ve also got the PMP450S and a need to test the PMP450 with COV-RP450 top to see if there is some noise benefit to the stock vs top element.

Lots of unexplored areas to keep working on here, but I hope it’s been interesting and of some value so far.

  1. […] pump noise testing and video Also posted on my new blog site, but here is the summary: ROUND 2 MCP 35X has been added This was adding in the Swiftech […]