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Date: Sun, 27 Apr 2008 10:56:20 -0600
From: Bob White <bob@bob-white.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Electric Water pumps - Interesting
Message-Id: <20080427105620.9166b1ed.bob@bob-white.com>
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My memory finally kicked in.  I was using was the Meziere WP337S rated
at 55 GPM, so you can see that flow rates are much lower than the spec
once installed in the system.

I still don't know where my flow tests data is.  I seem to recall the
"free flow" that I measured as being more like 20 GPM.

Bob W.


On Sun, 27 Apr 2008 12:48:52 -0400
"Ed Anderson" <eanderson@carolina.rr.com> wrote:

> Thanks for the report, Bob.  I suspected that the flow rates were based on 
> best - obtainable (no flow restrictions).  But, even so and as suggested by 
> your experience (marginal cooling) EWP may not provide the best answer.  OR 
> perhaps a different EWP (they do seem to vary quite a bit in claimed flow 
> rate and power consumed) might provide the answer.
> 
> Will be interested to see how it works out in your car.
> 
> Ed
> ----- Original Message ----- 
> From: "Bob White" <bob@bob-white.com>
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Sent: Sunday, April 27, 2008 12:40 PM
> Subject: [FlyRotary] Re: Electric Water pumps - Interesting
> 
> 
> > Hi Ed,
> >
> > I did some testing on the EWP's.  The rating is the free flow rating,
> > but my measurements seemed to indicate that number was overly
> > optimistic.  I will have to dig around to see if I can find the stuff I
> > did on it.  With just a short hose on the inlet and outlet plus a flow
> > meter, I got substantially less flow.  The 3.8 hours I flew was with
> > the EWP exclusively.  As I recall, the in system flow rate was around
> > 10 gpm.  Using calculations based on Bill Shertz' work I had wanted 15
> > GPM.
> >
> > The 3.8 hours I flew was in 50F to 60F temps and cooling was adequate
> > but marginal.  I believe I had seen 220 on the oil temps once in
> > climb.  Water temps were a little lower.  When I leveled off and pulled
> > the power back, temps would drop below 200 pretty quickly.  I know the
> > air flow through my oil cooler was poor, and was on my short list to
> > modify.  Air flow through the radiators may not have been as good as
> > it could have been either.
> >
> > Now let me propose a theory as to why the simple argument that the EWP
> > wont work because it doesn't consume enough HP may be incorrect.  The
> > stock pump on the engine definitely uses 5 to 10 HP.  But does it
> > need to?  The stock pump has to provide adequate cooling sitting at a
> > stop light in 120F temps (Phoenix in the summer).  HP goes up as the
> > second or third power of RPM (one of the things I need to look up
> > again).  So to get adequate cooling flow at idle, the cooling flow at
> > cruise may well be more than adequate.  As mentioned earlier, I had
> > calculated that I needed 15 GPM.  The air flow needed to be sufficient
> > to give the delta T's I was using in the calculation.  The EWP has the
> > advantage of providing full flow at all speeds, so the use in a car
> > seems quite doable since there are very few times full power is
> > sustained for any length of time.
> >
> > This is all just a theory, and it's not a theory like the "Theory of
> > Gravity".  It's the hypothesis kind of theory.
> >
> > I will be using the exact same setup in the Alpine with the EWP.  I
> > will at least be able to report on how well it does in the car.
> >
> > Bob W.
> >
> >
> >
> > On Sun, 27 Apr 2008 10:31:47 -0400
> > "Ed Anderson" <eanderson@carolina.rr.com> wrote:
> >
> >> I was just thumbing through a recent catalog from Summit Racing and came 
> >> across a couple of pages on electric water pumps.  There has always been 
> >> a degree of interest (and some debate {:>)) regarding the use of electric 
> >> water pumps in aircraft.   It was interesting to read some of the 
> >> descriptions, but basically the current consumed ranged from 4 - 9 amps 
> >> and the quoted flow rate (presumably without back pressure) was from 
> >> 16-35 gpm.
> >>
> >> So if you take 9 amps at say 14 volts = 126 watts = 0.167 HP to get that 
> >> flow.  However, some of them indicate you can save 15 - 20 engine HP at 
> >> HIGH rpm.  So why the difference?
> >>
> >>   Apparently (my best guess) is that they are advertising their product 
> >> to best advantage (surprise?).  I would suspect that the flow rates shown 
> >> are without back pressure and that when attached to a real engine coolant 
> >> system that :
> >>
> >> 1.  The flow rates would decrease
> >> 2.  The current requirements would increase.
> >>
> >>  However, not to the point the electric pump would be required to make 
> >> 10HP or more to provide the required flow.  I suspect there are 
> >> considerable losses (such as pump cavitation and pressure drops through 
> >> the cooling galleys)with mechanical pumps  at high pump rpm as driven by 
> >> a high revving engine which accounts for the high power requirements. 
> >> Whereas the electric driven pumps may operate at lower and more efficient 
> >> rpm without the majority of those losses.
> >>
> >> That said, the pumps cost range from around $200 - $400 and while no 
> >> weights were given, basic on the photographs showing the heavy electric 
> >> motors and additional plumbing  would not appear to offer any significant 
> >> weight savings over the proven, reliable mechanical pumps most of us are 
> >> using.
> >>
> >>  So while certainly interesting and perhaps of value in some aircraft 
> >> installations(how would you like to gain an additional 10 HP on 
> >> takeoff?), I remain confident in my old 86 13B water pump housing and 
> >> cartridge which is still going strong after 10 years.  I have moved it 
> >> from my first 86 N/A engine to my current 91 turbo block, so it has 
> >> performed for over 10 years in two different engines without any problem.
> >>
> >> Interestingly, of  the  11 electrical water pumps advertised, only one 
> >> was specified for drag race use only - and it had the lowest current 
> >> drain - 3.5 amps.
> >>
> >> Ed
> >>
> >> Ed Anderson
> >> Rv-6A N494BW Rotary Powered
> >> Matthews, NC
> >> eanderson@carolina.rr.com
> >> http://www.andersonee.com
> >> http://members.cox.net/rogersda/rotary/configs.htm#N494BW
> >> http://www.dmack.net/mazda/index.html
> >
> >
> > -- 
> > N93BD - Rotary Powered BD-4 - http://www.bob-white.com
> > 3.8 Hours Total Time and holding
> > Cables for your rotary installation - http://roblinstores.com/cables/
> >
> > --
> > Homepage:  http://www.flyrotary.com/
> > Archive and UnSub: 
> > http://mail.lancaironline.net:81/lists/flyrotary/List.html
> > 
> 
> 
> --
> Homepage:  http://www.flyrotary.com/
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-- 
N93BD - Rotary Powered BD-4 - http://www.bob-white.com
3.8 Hours Total Time and holding
Cables for your rotary installation - http://roblinstores.com/cables/