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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-2874281@logan.com>
Subject: Re: [FlyRotary] Re: Electric Water pumps - Interesting
Date: Sun, 27 Apr 2008 12:48:52 -0400
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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/
>
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