Quote:
Originally Posted by Bill in Houston
Yeah, it would use electricity from the alternator, but it would pump the right amount of water, instead of 6 times what you really need, so it would save that way. It's the same idea as the electric cooling fans, really. It would run at "low" speed most of the time, and kick up to "high" if it needed to.
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I agree, it should help. On the other hand:
1) A mechanical pump is a direct mechanical-to-mechanical drive. With an electric pump, you're converting from mechanical to electrical (via the alternator/battery) and then from electrical back to mechanical (via the electric water pump). The losses in both conversions will limit the possible gain.
2) I imagine most hypermilers run lower revs in general, so the gains from "as needed' pumping may be less for us than for the typical lead-foot.
Plus I read someone's test where they completely removed the drive belt(s) -- taking out the alternator, A/C compressor, etc. (not sure if the water pump was on that list) -- and only reclaimed about 3HP.
I have no doubt that an electric water pump would help.
How much it would help is an interesting question, though.
On the third hand
you're talking exactly the same parameters for electric fans versus mechanical drive, and haven't we determined that offers a usable improvement? I would think a water pump conversion would be similar.
Unrelated to FE but still an issue: If the water pump is driven by the timing belt, then if one switched to an electric pump, wouldn't they need either an idler to take the place of the mechanical pump, or a different (shorter) timing belt (if such a beast even exists)?
I'm not trying to be argumentative here -- just tossing in some reasons why the switch to an electric water pump may not offer the level of benefit we might like.
Now, someone show me I'm wrong and we're actually talking about a 10%-15% gain potential here so I can get one ordered.
Rick
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