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Old 07-24-2007, 01:54 PM   #11
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Originally Posted by Bill in Houston View Post
Really, I was just thinking out loud and hoping to give you something to go on so that YOU could generate the actual good ideas. :-)
Hahaha... way bad move... trust me on this one...

I'm not sure how much hp a car's water pump draws...
Well, even the small incremental stuff adds up. I just made my DRLs switchable even though that's at best a tenth of a horsepower. I posted the question because you never know when someone's going to say something like, "Yeah, have them put on a DRZ52A pump from a Mk2 Jetta instead of the Mk3 Golf version, it's the same mount and will cool things okay but it's 20% smaller and puts less load on the engine..."

With it being under the timing belt, I think it goes beyond the level of complexity that I would want to attempt.
And me as well, I'm not worth much under the hood. I've swapped batteries, replaced broken heater hoses, exchanged starter solenoids, stuff like that. Anything of significance I leave to people who know what they're doing. In fact I'm letting the dealer do this one (even though that will mean big bucks ).

I do want to dive in and start tinkering once the VW is no longer my daily driver or vital to my making a living. I love this little car and it'd be fun to see just how much FE I can wring out of it. But for now I'm limiting it to air dams (coming next), fender skirts (I hope), switchable DRLs, hunting for the control lines so I can turn the cruise control into a throttle lock... things that can't get me into too much trouble.

Oooo, and have a Prius thermos thingy...
Actually, with as much stop-and-go as I do during a business day, that might pay off in the Winter. Hmm...


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Old 07-24-2007, 02:26 PM   #12
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Originally Posted by Bill in Houston View Post
Hey, wait a minute. I don't know how many people know this, but restricting the outlet on a centrifugal pump will generally reduce the amount of power it draws (which I know is counterintuitive). So if one could restrict the water pump outlet, one could reduce the amount of drag the pump causes.

But you would want for it to be controllable in case you REALLY DID pull a 5000 pound trailer 100 mph up a hill on a 110 degree day...

Anyway, something for one of the genuises here to figure out - an easy, adjustable way to restrict the outlet of the water pump...

Someone with experience with pumps come to bat for me here too - centrifugal pumps draw less current or use less power when the outlet is restricted, right? I know someone is going to try to smack me around for suggesting such a thing.
Bill your correct a centrifugal pump requires less energy to spin when its dishcharge is restricted, it also produces more pressure when restricted.

Low flow rates require less energy, high flow rates require more energy. If you look at it from the flow rate perspective it makes perfect sense. More flow = more mass moved = more load.

Controlling the flow rate of a belt driven pump would require another valve and thats not going to be easy to rig. Installing a variable speed electric would be the best way to go with a temperature controller running the pump.

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