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Re: [Fot] Nuerburgring Nordschleife 400 km race

To: "MadMarx" <tr4racing@googlemail.com>
Subject: Re: [Fot] Nuerburgring Nordschleife 400 km race
From: Bill Babcock <Billb@bnj.com>
Date: Thu, 2 Oct 2008 11:21:37 -0700
Certainly possible, but you'd have to run a huge pulley to reduce the  
pump RPM significantly. According to my crappy memory the one that  
comes in the typical thin-belt kit is about 10% bigger than standard.  
I tried to find an old pulley to measure but I don't seem to have one.  
I think most people look at reducing the pump RPM as a way to increase  
horsepower rather than limit cavitation.

You should be able to see signs of cavitation on the pump blades. They  
should erode enough to show marks if you had serious cavitation. It  
would be nice if someone did a real impeller, with arched blades.  
Blades that curve away from the direction of rotation are much slower  
to cavitate. But even if you had gross cavitation in the pump you'd  
still see some pressure and flow, it just becomes unstable and noisy.  
I'd look elsewhere, like perhaps a suction hose collapsing, or too  
much pressure drop across your radiator, before I'd worry too much  
about pump rotation speed. Even if it is cavitation reducing the  
system flow, anything that decreases the suction pressure will make it  
worse.

I eliminated a consistent high RPM cooling problem on Peyote with more  
hard aluminum piping, using flexible hose only for the joints.

On Oct 2, 2008, at 7:05 AM, MadMarx wrote:

> Henry,
>
> can you tell me the sizes of your crank and water pump pulleys?
> I have the stock water pump with that sharp edged impeller. I really  
> suspect
> the impeller to cavitating when turning longer at high revs. I hold  
> 6000 for
> about 30-40 seconds in on go.
>
> Chris

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