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  #1  
Old 12-11-2019, 02:30 AM
svyolo svyolo is offline
 
Join Date: Oct 2017
Location: bellingham, wa
Posts: 197
Default Boost pump running continuously

I saw a couple responses to running boost pumps (EFII, Andair, AFM) continuously. I saw a couple pros and cons of running them continuously, vs turning them on and off.

External fuel pumps do run warm. If you run them continuously, will the bypassed and returning fuel gradually warm up, and cause the pump to get hot? Sort of a slow motion thermal runaway? Or at least till the pump gets hot enough to radiate/conduct/convect enough heat to reach equilibrium?
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  #2  
Old 12-11-2019, 04:31 AM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
Posts: 1,972
Default Efii

The EFII system is a full flow return setup; when the pump is on, fuel is drawn from the tank, pumped through the fuel rail and regulator, then back to the tank. I doubt pump heating would be an issue as the pump has a large supply of fuel to cycle...it does not recirculate within the pump...
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  #3  
Old 12-11-2019, 11:50 AM
svyolo svyolo is offline
 
Join Date: Oct 2017
Location: bellingham, wa
Posts: 197
Default

Bob;
I understand that about EFII EFI fuel injection. But they sell a boost pump setup for Bendix style mechanical FI. It has a bypass when it is off so fuel goes straight to the engine driven fuel pump, but pumps fuel to the engine driven pump, and recirculates excess fuel from the outlet, back to the inlet, when the boost pump is selected on.

Just wondering if the pump would overheat if left on continuously. The pumps run warm, and if they impart heat to the fuel, and the fuel is returned back to the pump, will the pump keep getting hotter. At idle or close, almost all the fuel is returned.
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  #4  
Old 12-11-2019, 01:03 PM
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Wunderon Wunderon is offline
 
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Location: Seattle (Edmonds) and Iowa
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Default

Perhaps check with the manufacturer ?
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  #5  
Old 12-11-2019, 02:28 PM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
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Default

Quote:
Originally Posted by svyolo View Post
Bob;
I understand that about EFII EFI fuel injection. But they sell a boost pump setup for Bendix style mechanical FI. It has a bypass when it is off so fuel goes straight to the engine driven fuel pump, but pumps fuel to the engine driven pump, and recirculates excess fuel from the outlet, back to the inlet, when the boost pump is selected on.

Just wondering if the pump would overheat if left on continuously. The pumps run warm, and if they impart heat to the fuel, and the fuel is returned back to the pump, will the pump keep getting hotter. At idle or close, almost all the fuel is returned.

I did not see that you were referring to the mechanical FI...
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Bob
Aerospace Engineer '88

RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
EFII System 32 - Done
297 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful
Wiring...

Dues+ Paid 2019,...Thanks DR+
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