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Date: Tue, 19 Oct 2004 16:38:52 -0400
From: echristley@nc.rr.com
Subject: Re: [FlyRotary] Re: EWP
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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----- Original Message -----
From: Al Gietzen <ALVentures@cox.net>
Date: Tuesday, October 19, 2004 10:29 am
Subject: [FlyRotary] Re: EWP


> As for HP savings, these pumps don't pull much
current, and it's 
> hard to
> imagine that an extra few amps of load on an
alternator is going to 
> costmore than a tiny fraction of a HP. 
> 

I was looking at Summit Racing's selection, trying
to find the one with the lowest current draw.  They
had a couple at 5A, but most ranged 7-9A.

At 13V and 9A, that's 117W*.00134Hp/W=.15678Hp

Even at 50% efficiency, you're only talking about
1/3Hp pulled off the engine.

> 
> 
> I'm still interested to know how much the stock
water pump takes to 
> run at
> high rpm.  
> 

So am I.  I look forward to your test results 8*)

> 
> 
> I understand the EWP has higher efficiency than
the stock pump - does
> someone know how much? (I may have missed it
because I haven't 
> followed this
> issue very closely).  

The argument is that the mechanical pump is designed
to flow sufficient water even when the engine is
slowly lugging up a mountainside.  At cruise RPM, it
is doing a lot of unecessary (and possibly
counterproductive) work, as flowing the water faster
doesn't cool any better after a certain ?unkown?
point.  The EWP efficiency claim is that it
decouples water flow from engine RPM.

The efficiency argument is highly debatable.  The
configuration options that it provides in my case
are clear and straightforward.