Cam chain tensioners

Randy Grein randygrein at
Sun May 17 19:42:38 PDT 2009

An interesting idea, but consider that there will be an 'optimum'  
coolant velocity through the system beyond which there will be little  
improvement in heat exchange. Further the power draw from the pump  
will go up as to what - the cube of engine RPM. More, trimmed blades  
will make a very inefficient pump - big loss in flow with just a  
little reduction in power draw; the rest goes into water eddies  
(heat). A variable ratio pump would be a great idea - if it were  
simple and efficient. I do know the electric water pump idea is not  
unique; the idea is common in NASCAR where they actually do experiment  
with such things.

Final bit about this is that a really clever racer might configure the  
alternator so that it stopped producing power during full throttle  
application. Even with an SV much of the circuit is run under part- 
throttle operation. Cutting the alternator to run off the battery  
(temporary total loss) might give the best of both worlds for  
endurance racing - during the daytime anyway. (grin)

Randy Grein, WMRRA #41

On May 17, 2009, at 7:07 PM, Beth wrote:

> On Sun, May 17, 2009 at 6:43 PM, Randy Grein  
> <randygrein at> wrote:
>> Alternator.
> I wonder if that's the most efficient approach. You're using an
> inefficient source (50% loss at the alternator) to power something
> that normally is powered probably much more efficiently by the engine
> itself. I wonder if simply trimming the blades the OEM pump's impeller
> to decrease drag but get enough flow to keep the engine cooled would
> be more effective. Frictional losses of the gear that drives the water
> pump may be less than 50%. I would bet that somebody has tried it
> already.
> Wish wish wish I had the money and time to commit to putting real data
> behind these thought experiments.
> -Beth

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