Howdy Ernie,

On 17 Oct 2002, at 22:14, Ernest Christley wrote:

>
> The EWP is the same game.  Pump a lot of water and restrict what you
> don't need.  Simple old school thinking.  Don't hink of the EWP as 57
> times more efficient, think of it as only pumping the 1/57th of
> coolant that is actually needed at 6000RPM vs 800RPM.

This 57 times or 1/57th seems to have taken on a life of its own
without any one questioning the (unfounded) assumptions that the
mathematically challenged individual made when he arrived at this
figure.

Anyway,  one good thing about all this banter is that it has given
me MANY MANY excellent points upon which to write an article for
one or more of the local magazines,  and correct a LOT of
misconceptions,  and closely held prejudices..  

I will write it all up during my break over the next 4 weeks. and post
it here for comments.  Once I have my repeatable test data in 6
weeks,,  I will include those data with the text and pix,  and submit
for publication.  You guys will see it first.

But like I said somewhere else,  running the mechanical water
pump at 6,000 RPM and throttling it with a thermostat to control
the flow rate is the same a driving around with your left foot on the
brake!!  Totally inefficient.  It not only wears out pads,  but it
wastes a LOT of fuel as well!!  

Moreover,  throttling a centrifugal water pump is exactly how a
water brake dyno works!!  The one on my mate's SuperFlo 901 can
absorb over 1,000 BHP,  and boy does it shift some water!! Fire
hose stuff!!

The EWP pumps 80 Litres per minute open flow.  That's more than
a full RX7 fuel tank every minute.  It uses 7.5 amps @ 13.8 V to do
so.

If you only need to pump 20 litres a minute,  the pump controller
slows the pump down so that the temp outlet remains at whatever
temp at which you set it.  

There are NO restrictions,  and therefore NO pressure head  except
the for cooling passage boundary layer drag.  (The insides of most
cooling systems are not exactly smooth).

In a cooling system with NO head,  it will pump 80 litres per
minute.  Assuming about 3" of head,  allowing for cooling system
boundary layer friction,  it will still pump about 75 litre a minute at
full tilt. (which is still about a full RX7 tank of water every minute!!)

The main reasons for using an EWP are
1.  weight,  and
2.   cowl clearance.  

The fact that you DO get a slight increase in power,  be it 10 watts
or several BHP,  depending on a LOT of variables, like relative
pulley sizes and engine speed,  and thermostat opening size IS
BESIDE THE POINT.

The trick to having an efficient cooling system is NOT pumping a
gazillion gallions a second though the engine.  It has ALL to do
with the efficiency of the heat exchanger.  The more efficiient the
heat exchanger,  the less flow you need to extract a certain
amount of heat (which is how a thermostat works).

That's why we can cool 1,000 BHP turbo and blown ski boat V8's
on the dyno with an EWP.  The cool side of the heat exchanger,  
using resevoir water  and is usually between  20 - 30 Deg C.

Same applies with aircraft.  If your heat exchanger set-up is
marginal, (and I think air conditioning cores are!!),  you can have a
1000 BHP water pump flowing 1,000 litres a minute and it will still
overheat on a hot day.  On a clod day,  you will not notice a
problem.  The heat exchanger MUST be able to reject the heat
produced in the engine.

It is NOT the FLOW of water through the engine or the heat
exchanger that is the issue.  It's the differential temp of the coolant
and the engine block and the efficiency with which the heat
exchanger rejects the heat either into the atmosphere or into the
river.  

If the heat exchanger can't get rid of the heat,  then engine will
OVER heat because the differential temp between the block and
the coolant is not sufficient to extract sufficient heat away to keep
the engine at a stable temp!!


Best wishes & kindest regards,

Leon Promet

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