Marc Wiese wrote:

  I just wanted to see if many of you agreed with this advice

on Mazda

 Competition's web site:
 "If you are using a stock (cast-iron) water pump, we recommend

"gutting"

 the stock thermostat, leaving just the thermostat casing. Because

some

 "restriction" is helpful, generally removing the thermostat is

not as

 effective as using a gutted thermostat or restrictor. It is also
 important to plug the thermostat housing's water bypass. This can

be

 done very easily by tapping the hole (1/2" pipe tap) and

installing a

 plug."<<
 You plan on using the remnants of the thermostat, Paul, or

running wide

 open, just using the cowl flaps?
 Marc Wiese

I think you get the same benefit running a 20 or 24  psi pressure

cap

without the pump HP loss in the restrictor. I always thought
a restrictor to up the pressure in the block and the pump was a

dumb idea.

And of course closing down the cowl flaps at cruise speed lowers

the cooling

drag.
Paul Lamar

Hi Guy

 Would increasing the pressure in the system do two thing's, one

raise the boil temp of the water and reduce pump efficeicy.

Yes on the boiling temp but I think it would raise pump efficiency by
doing away with the flow restriction.

Would it not be better to reduce all loss in  pump flow and control

our temp's through air control through air flaps.

I think this is easier.
Regards Don Dunbar

Yes I agree Don.
Paul Lamar

Hi again all,

As I see it any restiction in the system should only be to reduce max

flow of water throught the at full RPM or max  HP so the water flow does not
exceed  say 7ft per second.

What is the flow rate of the 13B and of velocity in a 13B cooling

system?

Regards Don

We have no idea Don. We think the pump is pumping about 35 gallons per

hour as

I recall.

Paul Lamar

Finally getting caught up on a backlog of e-mail and came across this
thread.

Centrifugal pumps will have a single point of best efficiency, although they
can be made to run over a broad range of flows.  Decreasing the system
resistance (i.e. gutting the thermostat) will increase flows, but may well
put the pump beyond it's best efficiency point.  This probably isn't a big
deal.  Just more hp consumed per pound of water moved, but not a huge
difference.

More of a problem could be pump cavitation, particularly with a cold system
that hasn't pressurized yet.  With a "wide open" coolant system that does
not prevent cavitation of the pump at atmospheric pressure, it will be
absolutely essential to get ALL air out of the system.  The system needs to
start pressurizing as soon as the engine is started so that by the time you
do the run-up, there is enough pressure to keep the water pump from
cavitating.  Trapped air will act as a cushion and minimize the system
pressurization.  Another very good reason to have a cooling system pressure
gauge.

BTW:  Cavitation is a slow insidious killer of single stage pumps.  With a
soft metal like aluminum it will start eating holes in the pump casing and
nibbling at the pump impeller.  Final failure could well be when you least
want it.  With an acoustic pickup on the pump casing you could well hear it:
With an engine pump it probably sounds like you are pumping pea gravel
through it.

I will probably have some pump outlet restriction and keep drilling it out
larger if need be until I got sufficient cooling flow but also kept some
backpressure on the pump.

Tom Kendall

 
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