| Hi Dave
My understanding (questionable) is:
1. The Series 1 Rx8 Renesis pump had known cavitation problems around 7K and a redline of 7500. 2. That cavitation could be accentuated by removing the restriction of the thermostat reducing pressure at the entry to the pump. 3. The series 2 Renesis engine had a modified pump impeller, which I understood was to reduce cavitation at the new higher 8500 redline.
The series 1 has a pressed metal impeller and the series 2 a plastic more efficient design. The aftermarket pumps are milled aluminium. I also understood that they changed the bolt pattern of the series 2 pump, so not easily allowing us to use a series 2 pump on a series 1 engine, therefore the opening in the market for an aftermarket pump for series 1 engines.
My experience was that on removing a restriction in the flow leaving the engine to the radiator, we encountered a significant rise in coolant temp which I came to believe was caused by cavitation. This was my decision point to install an after market pump, seeking to maintain flow rate without cavitation.
However my research on questionable lists, my presumptions of what was going on in the cooling circuit, and my decisions could well be faulty.
Thanks for adding your experience Dave, you’ve been so helpful over the years.
Steve Izett
On 22 Aug 2023, at 4:11 am, David Leonard wdleonard@gmail.com <flyrotary@lancaironline.net> wrote:
Steve, In my experience the stock pump works great at least to 7500rpm... (racing at Reno). Stock Pully size... Isn't the redline in the stock car over 8k? David Leonard.
Here is a page with various year water pumps from MazdaTRix.
here is a link to some of their water pulleys
Rotary_Ed
------ Original Message ------
Date 8/18/2023 4:16:53 AM
Subject [FlyRotary] Re: Waterpump Rpm
Hi guys
The pumps that I am aware of are:
I do not remember the pulley size on our alternator. I can remember ordering it from the Eastern States of Aust. I’ve put it on my todo list to measure when I’m at the hangar, possibly Sunday.
If I could be assured of the reliability of the latest water pumps I’d go with electric and get the benefits of modulating the pump speed for automatic temp control at cruise. The cowl flap gives some control but it can still get too cold in cooler weather.
Cheers Steve
Steve, What company in New Zealand had this stuff? What dia pulley and where from on alternator? Inquiring minds want the specs? Marc On the Renesis I’ve put a race pump on to ‘reportedly’ reduce cavitation as the basic pump is reported to cavitate at the rpm’s we operate in during take off. When I took out a restrictor in the return to the radiator on one flight tamper went up considerably and I reasoned this was caused by cavitation. In response I purchased a race pump from New Zealand. My water pump is running at OEM speed, but I slowed my alternator with a larger pulley. Hi : What is the optimum waterpump rpm for the 13B as i can modify the
pulley diameter and ratio’s for my set - up The data i have is that at the standard ratio is 1:1.18 at 6500 rpm for the 13B the pump flo is round about 150 - 160 L per minute.
So my question: If i run on 6500 rpm for take off then the waterpump impellor turns 6500 x 1.18 ???
Must i put on a bigger diameter pully on the pump for a flo of round about 100 L per minute.?
Don’t know ?
If somebody can help me with that
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