I have a stock waterpump with RX8 Performance underdriven pulley on it. I'm erroring on the side that the waterpump is original to the engine, so 60k. This is for a plane engine so be sitting at 7000rpm cruise most of it's life. Max 8500rpm

I've read mixed reviews on the Mazmart, that some say it's worth it, some say it's not. Stock flows more at low rpm but cavitates at high rpm (~7000rpm). Mazmart doesn't flow as much, but doesn't cavitate. I want to get a new water pump so trying to decide if I stay underdriven stock, or go with Mazmart. I messaged them on ETA of their pumps, but haven't heard back. I messaged RX8 to see what % they are underdriven, but haven't heard back either from them. I do have an rpm handheld laser gauge that I'll measure if I can't find out. Basically if the pulley is 20% u/d, then at 8500rpm the waterpump would be at is under 7000rpm which would be safe. If it's 15%, then probably not the best and should go with Mazmart instead.

 

What about an S2 water pump?
The cavitation thing is a bit debatable. What coolant pressure are you running?

 

One or two bolt holes don’t align properly with an S2 water pump on an S1 front cover

 

I've come across a few posts saying what TeamRx8 said, 1 or two holes need to be wallowed out. But haven't seen anyone actually do it. At this time I'm not looking to experiment. Basically stock S1 underdriven pulley vs Mazmart with stock pulley. What people's thoughts are on that.

I have a 1.3bar (19psi) pressure cap on my expansion tank, but at full power my coolant is averaging around 28psi. I don't think it's cavitation because the signal gets noisy for oil, fuel and coolant psi at fuel power. Still need to trouble shoot if it's the alt or cas that's injecting the noise. Or my 5volt rail is noisy.

 

What is the consensus with the group already running rotaries in planes? What has been tested before?

 

Really isn't much consensus. Lots of trial and error. Most only run 7700rpm max, where I have a new setup that allows me to run up to 8500rpm now.
I just went ahead and ordered the Mazmart. I can do apples to apples comparisons this way, stock underdriven vs their. Doesn't take long to swap, so much room to work

 

I have pump similar to Mazmar
Oe pump retro fit With CNC blade
my friend who had similar cooling mod like I have
His water temp will stay Around 102-105
My stay at 98c at same track day

I do need to use two waster pump gasket to prevent, shaft jam to housing

 

Honestly, if you aren't having overheating problems with your current setup, I'd just check the water pump impeller periodically for erosion and not worry about it.

According to Legot's modeling, the Mazmart pump reduces cavitation by moving less water per RPM. You're doing the same thing by underdriving it.

 

I thought they didn’t recommend underdriving their impeller for that reason. Paul would need to confirm.