How much power dose a water pump take?

[Markh]

just a thought but how much power dose a water pump use? and more to the point is it worth fitting an electric one

[GreenV8S]

Markh said:

just a thought but how much power dose a water pump use? and more to the point is it worth fitting an electric one

The power goes up sharply with revs, at the top I think it peaks at around 4-5 BHP on a serpentine setup, maybe a bit less preserpentine.

The only reason I can see for the extra expense, complication and unreliability of an electric water pump is that you think you don't need all that water flow and would prefer to have the few bhp available to drive the car. But if you're in that situation you could expect to be pushing the car hard, in which case absolutely the last thing you want to do is compromise the cooling system. Now this implies you are replacing the mechanical pump with an equivalent electric one, which means you're looking at a very big and expensive pump. It is very hard to justify the time and money to do that conversion given that ultimately the electrical power to drive the pump has to be drawn from the crank.

[Mark Adams]

I remember dyno testing HarryW's grunty 4.0 V8S (pre-serpentine motor) when it threw the fanbelt. This happened at around 4500 RPM and the power trace jumped by 8 BHP, although this obviously includes the alternator.

One of my test cars is currently being fitted with the larger Craig-Davies electric water pump, so I'll let you know how I get on when the car is on the road again. The point about reliability is a serious one, and you can't escape the fact that mechanical pumps are very well proven...

[spend]

Why not just alter the gearing to suit your cooling reqs & rev range?

I suppose care in flowing the heads and stat housing etc might reduce load on the water pump? Ive always smoothed the waterway bits when I've had heads / inlets off, must admit just as a distraction whilst I've considered other things TBH..

I just happen to have a pre-serp 'water pump' modded for an external pump if anybody wants to try one (impeller & pulley removed + welded up).