<... "up to 30 HP." ... current drain
is .134 HP ... Maximum flow rate of [the EWP is] only 88L/min compared
with a maximum of 240L/min for the same engine using an older mechanical
water pump design ...>
Beware people with an agenda - like
"... figures don't lie, but liars figure ...
Most folks with an agenda will exaggerate
to make a point. There are instances on record where a proponent
of this or that point of view will lie shamelessly and/or deliberately
ignore important factors to make a point. HORRORS!! I won't
name any names, but I got off that list years ago ;o)
As for the EWP, I am a believer, so
keep that in mind. My position is that EDWP is designed for the worst
case scenario - idle, AC on, hot day, etc. That's under 1000 rpm,
pumping a decent volume of water. Think cc water per rpm or something
like that. At 150-200 kts in cool air at 6000 rpm, that pump is going
crazy, cavitating, thrashing it's brains out trying to pump 400 gpm past
a [mostly closed?] thermostat creating useless big time head pressure (just
between the impeller and the thermostat) and generally operating waaaay
outside its design envelope. Damn right that's going to absorb a
bunch of power. 30hp? How the hell does anyone quantify that
with ANY degree of accuracy? EDWP is ENGINE DRIVEN. That means,
it's going to do what the engine does whether it wants to or needs to or
not - and nearly always (in our application) it DOESN'T need to.
EWP OTOH is master of it's own agenda.
The engine is the client of the WP, not the owner/driver. It decides
what it needs to do and does just that, no more. It could really
care less what the engine's doing. That's where the efficiency happens.
PL can run his mouth 'till hell freezes over (and probably will ;o) but
he does not (never has?) and perhaps never will have an actual engine of
his own flying in an airplane of his own performing what it performs.
Some things haven't changed since 1953.
Bullshit is still three dollars a ton ... Jim S.
Barry Gardner wrote:
Guys,
let me play the role of skeptic here. I'm not Paul Lamar's lockstep disciple
but I thought his argument sounded good. Can you guys help me understand
why the EWP works with such less power? I
looked at the Davies Craig website, which claimed that substitution of
the EWP for the mechanical variety could save "up to 20 HP." A tech article
inside the site looked at the improvement on a drag car which estimated
the HP addition of lessening the load on the crank at 30 HP. So, the claims
are that the EWP saves 20 to 30 HP load on the engine. By
Ed's law--I mean Ohm's law--below, the EWP current drain is .134 HP. So
why the difference? 1)
The pumps could have differing efficiencies. That's possible but it doesn't
explain the magnitude nor why auto manufacturers would persist with an
inferior pump design if reverse engineering a Davies Craig pump could yield
such superior results.2)
Electric motors are more efficient than internal combustion engines. While
this is true, the 20 HP savings is measured at the crank of the gas engine
so the efficiency loss of the internal combustion engine (i.e., the heat
balance and all that stuff) has already been taken into account.3)
???
|