Water pump....questions (summary)

[amalventano@sc.rr.com (Allyn)]

ok, so here is the summary:

subj: electric water pump in place of mechanical

pros:
- one less pulley driven, reduction in total pulley friction (think tire
rolling resistance), one less bearing to turn.
- drop in engine total rotating mass (coolant momentum plays into this as
well).
- stable, constant rate of coolant flow, killing any idle-overheat issues
you may have had. more importantly, power consumption of a centrifugal pump
rises to the third power as compared to pump speed. You simply do not need
the flow rate that the pump provides (>~4k), to maintain sufficient cooling.
The electric pump keeps the system at an efficient flow rate all the time,
which adds up.
- ability to install in reverse coolant flow mode (cold water to head
first).
- ~same life as mechanical driven pump.
- failure of electrical driven pump doesnt cause loss of coolant (as most
are hermetically sealed). when our normal pumps fail, teh bearing goes,
taking the seal with it.
- ability to kill alternator load for short bursts (i.e. WOT).

cons:
- must fabricate some parts (connection to block, re-routing of belts, etc).
- expense/weight of electric pump/plumbing.
- not as good as a drag setup (as they have no alternator). even if we
remove electrical loading from the alternator, it is still a hunk of metal
that must be accelerated, contributing to overall rotating mass of the
engine.
- higher loading on alternator overall, resulting in slight drop in
alternator efficiency due to hysteresis losses (that one is for you, haygood
:).

notes:
- for reverse flow configuration, pump must be between radiator/head vs.
radiator/block. this keeps the pump in the coolest point of the system.
- can install mechanical clutch on alternator if you *really* want that drop
in rotating mass.

p.s. if they dont break the bank, twin will have 2 cross-connectable
electric water pumps, mounted in the center of the car.
hth
Al

Allyn Malventano, ETC(SS), USN
87 Rieger GTO Scirocco 16v (daily driver, 180k, rocco #6)
86 Kamei Twin 16V Turbo Scirocco GTX ('it has begun', rocco #7)
86.5 Occo 16v Trailer (dotting 'i's across the country, rocco #8)
87 Jetta 8v Wolfsburg 2dr (wifes daily driver, 285k, 0 rattles)

From: "Haygood" <haygood@aemail4u.com>
> OK, so I tried.   The next challenge is for someone to work the word
hysteresis into the conversation.  Geesh.  Good night all!
> BH

mission completed.