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Date: Fri, 15 Jun 2007 10:00:05 -0400
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From: "Bill Wade" <dhc1@gwi.net>
References: <list-2103542@logan.com>
Subject: Re: [LML] Re: Boost Pump
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Bob-
         Thanks for catching that, I misread the label. It is indeed 35 GPH.
 35 GPM *would* tend to overload the return, wouldn't it?
 What are you barbecuing?
 I think this has been suggested before but I'm thinking about using an ON 
[low]-OFF-(MOM) [high] switch for the boost with a separate guarded ON-OFF 
switch wired in parallel for the high side marked something like "Emergency 
Boost". Now to see if I could remember that five years from now when I get 
to that point...
 The Lancair circuit includes a primer solenoid that's energized at high 
boost. The TCM schematic shows a primer that diverts flow from the spider to 
a primer nozzle, and includes an oil pressure switch to disable the primer 
circuit when the engine is running. Is this the same setup that Lancair 
uses?
  Thanks-  Bill Wade

----- Original Message ----- 
From: "bob mackey" <n103md@yahoo.com>
To: <lml@lancaironline.net>
Sent: Thursday, June 14, 2007 10:53 PM
Subject: [LML] Re: Boost Pump


>
>> I'm looking at a Dukes pump that's rated 11.0 PSI low and 25 PSI
>> on high. Flow rate is 35 GPM @ 21.0 PSI. I don't know how this
>> compares to the pumps being used in Lancair installations, but
>> wouldn't seem that the Dukes could overload the system, especially
>> if  the engine-driven pump was inoperative.
>> If you were idling and hit the high boost, yes. At full TO power it 
>> should
>> be less than the engine-driven output. My question is: could the output 
>> of
>> the two pumps combine and overwhelm the return line causing pressure and
>> thus fuel flow to go out of limits?
>
> Bill:
> You might want to check those specs... you wrote that the
> Dukes pump is rated at 35 GPM (gallons per MINUTE)
> while the engine uses 32-36 GPH (gallons per HOUR).
>
> If you can really fill a 5 gallon can from the Dukes pump
> in 8.57 seconds, it can probably flood an IO-550.
>
> I use a system that flows 35 GPM liquid propane at about 200 psi.
> That generates a flame about 100 feet high. That kind of flow
> might be excessive even in an Lancair IV.
>
>
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