[DeTomaso] Meziere water pumps

[Ken Green]

Dave,
 
    I think with a PWM power supply the frequency can be in the kilohertz range (Dave Londry would know).  I would imagine the inertia of the water flow would keep the coolant flowing pretty steadily and that the pump never stop spinning.
 
Ken
 


________________________________
From: David Nunn <dnunn at telus.net>
To: detomaso at realbig.com 
Sent: Monday, January 16, 2012 11:34 AM
Subject: [DeTomaso] Meziere water pumps

Asa Jay,

About two years ago, I moved my Laminova heat exchanger from the engine
compartment to under the car. While I was at it, I decided to replace all of
my coolant tubing. Before doing so, I called both Stewart and Meziere and
asked their tech depts. for their advice on improving a Pantera's cooling
system. To my surprise, both tech guys were very familiar with the Pantera
and its cooling system. In fact, both guys had identical thoughts and
recommendations. Both felt the Pantera's biggest problem was the resistance
to flow that's inherent in pushing coolant through 22 feet of tubing. They
both told me that the Pantera's belt driven water pump cavitates badly at
high RPM's because there's simply too much resistance to flow. Both
suggested the same solutions: a single pass radiator and a remote, electric
booster pump, installed as close to the radiator's outlet as possible. I
decided to follow their recommendation and I went with a Stewart in-line
booster pump, for the simple reason that the Stewart pump creates zero
restriction in the cooling system when it's not running, whereas Meziere's
remote pumps create a substantial restriction when they're not running. 

Here's the part that was surprising to me: both tech guys advised me against
running an electric water pump as my only water pump, on a street driven
car, for two reasons: reliability and warm-up. The reliability matter is
what it is. Their concern with warm-up was that electric pumps simply flow
much more coolant at idle than a belt driven pump and so warm-up takes
longer and sometimes, much longer. I asked about controllers that regulate
the electric water pump until the engine is up to temperature but they both
did not like them because the way they work is to "stutter" the flow. That
is, they turn the water pump on and off at intervals that depend upon the
temperature of the engine. The problem, both felt, was that every part of
the cooling system gets "shocked" by cold coolant every time the controller
turns the pump "on" during warm up. It also takes a fraction of a second for
coolant to boil in a cylinder head, so the pump should never be "off". 

When they told me that, I immediately recalled reading, on the GT40 forum,
about owners with electric water pumps having radiator failures for unknown
reasons. It turned-out to be those "stuttering" water pump controllers. It
seems that aluminum rads don't like being warm, then getting hit with cold
coolant. 

Both companies said they were working on controllers that vary the voltage
to the electric pump, so they will operate continuously, with the speed of
rotation of the pump's impeller depending on temperature, but neither knew
when such an item would be available. Maybe they're available now? In my
case, with my booster pump, it's controlled by my EFI's ECU, so it stays off
until my engine temp hits 180 degrees. I also incorporated one of John
Taphorn's remote "high-flow" bypass thermostats into my revised cooling
system, but that's another subject entirely.

I hope this helps,

Dave        

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