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  #11  
Old 04-28-2018, 12:55 PM
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mfleming mfleming is offline
 
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Quote:
Originally Posted by vic syracuse View Post
Well, the RV-12iS has 2 boost pumps that have to run continuously, as there is no engine-driven pump on the iS engine.
I haven't noticed the fuel overheating.

Vic
The pump recycles fuel internally...not back to the tanks like in the electronic fuel injection systems.

The manufacturer of this pump says that due to constant fuel recycling while on, it is not suitable for continuous duty. I didn't realize that until after I purchased the pump.

The manufacture states that this pump is a good choice for my installation (-7 IO-360), just not continuous.

I tried to get information on how long it could run before trouble arose and what that trouble might be. The answer I received was pretty non technical:

"If you are using the Boost Pump as a backup to the engine driven mechnical pump, then you will not have any problem."

That might be correct but still...I'm trying to figure out if I bought the right pump.

I haven't named the pump because I don't want to malign the pump do to my uncertainty.
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RV-7 Slider #74572
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  #12  
Old 04-28-2018, 12:59 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by mfleming View Post
The pump recycles fuel internally...not back to the tanks like in the electronic fuel injection systems.

The manufacturer of this pump says that due to constant fuel recycling while on, it is not suitable for continuous duty. I didn't realize that until after I purchased the pump.

The manufacture states that this pump is a good choice for my installation (-7 IO-360), just not continuous.

I tried to get information on how long it could run before trouble arose and what that trouble might be. The answer I received was pretty non technical:

"If you are using the Boost Pump as a backup to the engine driven mechnical pump, then you will not have any problem."

That might be correct but still...I'm trying to figure out if I bought the right pump.

I haven't named the pump because I don't want to malign the pump do to my uncertainty.
You still haven't told us which pump you are referring to. How are we to help without this info. There are different kinds of pumps.

Larry
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  #13  
Old 04-28-2018, 01:05 PM
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mfleming mfleming is offline
 
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Quote:
Originally Posted by lr172 View Post
You still haven't told us which pump you are referring to. How are we to help without this info. There are different kinds of pumps.

Larry
Yes, I know...I was hoping to not bring up the pump manufacture. But your right.

The pump is the EFii BPM-1
I'm very pleased with the customer service and the pump looks like it top notch quality. I'm just trying to make sure this is the right pump for my service (-7 IO-360)
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Joseph, OR
sagriver at icloud dot com

RV-7 Slider #74572
Started 11/2016
Empennage completed 11/2016 (sans fiberglass)
Ailerons and flaps completed 3/2017.
Wings completed 12/2017 (sans fiberglass)
Started on QB fuselage 01/2018
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  #14  
Old 04-28-2018, 01:09 PM
rv7charlie rv7charlie is offline
 
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Mike,

It sounds like the rest of the sentence is 'as long as your primary pump is working properly.'

If it's not suitable for continuous operation, it's not suitable as a backup pump. The vendor shouldn't be selling it as a backup pump, if that's what he told you.

In the interest of everyone's safety, my opinion, FWIW, is you should share the written communication you had with the vendor, and the brand.
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  #15  
Old 04-28-2018, 01:15 PM
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mfleming mfleming is offline
 
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Quote:
Originally Posted by rv7charlie View Post
Mike,

It sounds like the rest of the sentence is 'as long as your primary pump is working properly.'

If it's not suitable for continuous operation, it's not suitable as a backup pump. The vendor shouldn't be selling it as a backup pump, if that's what he told you.

In the interest of everyone's safety, my opinion, FWIW, is you should share the written communication you had with the vendor, and the brand.
I'm pretty sure the problem is just with my understanding of how the boost pump can be operated.
Many people recommend these pumps on VAF. Here's a link to the pump description on the manufactures website.
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Joseph, OR
sagriver at icloud dot com

RV-7 Slider #74572
Started 11/2016
Empennage completed 11/2016 (sans fiberglass)
Ailerons and flaps completed 3/2017.
Wings completed 12/2017 (sans fiberglass)
Started on QB fuselage 01/2018
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  #16  
Old 04-28-2018, 01:52 PM
lr172 lr172 is offline
 
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That Walbro pump is designed for continuous duty, though typically with an external return (the fuel flowing through it cools the pump). That setup does return into it's own inlet, however, as long as you have a reasonable net fuel flow I don't see how the fuel can overheat, as it is constantly pulling in fresh, cool fuel from the inlet to support the net flow. Somewhere around 30% of the moderately heated fuel returned will go out the outlet on the next pass, so you have a constant dilution of the heated, retun fuel. Further, the pump doesn't introduce much heat to the fuel on each pass through. It would take many passes through the pump before the fuel got to hot and the constantly dilution with cold fuel should keep the pump temp well in check.

I can see how overheating can possibly occur at very low fuel flows, such as typical at idle, but don't see how the fuel can overheat much with moderate fuel flows, like at cruise.

The severity of this issue is based upon the flow capacity of the walbro pump (they make many different pumps with different flow ratings). An application like this should use a flow rate around 125% of the max required (35 GPH is a good general number for GA) at 25 PSI. You may want to check the pump part number. Walbro makes some pumps with a LOT of flow and I don't know whether to trust that EFII got it right. The greater the pump's volume, the more return flow that it creates.

Larry
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Last edited by lr172 : 04-28-2018 at 02:11 PM.
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  #17  
Old 04-28-2018, 01:57 PM
rightrudder rightrudder is offline
 
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If you've got a boost pump and engine-driven pump plumbed in series, just use the boost pump for priming, takeoffs, landings and emergencies. Some like to use it when doing practice maneuvers and when switching tanks.

Leaving it on all the time is just wearing out the pump. I switch mine off at about 1500' agl after takeoff and turn it on as part of my landing check. Pretty much SOP.
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  #18  
Old 04-28-2018, 04:39 PM
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RV7A Flyer RV7A Flyer is offline
 
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Quote:
Originally Posted by rightrudder View Post
If you've got a boost pump and engine-driven pump plumbed in series, just use the boost pump for priming, takeoffs, landings and emergencies. Some like to use it when doing practice maneuvers and when switching tanks.

Leaving it on all the time is just wearing out the pump. I switch mine off at about 1500' agl after takeoff and turn it on as part of my landing check. Pretty much SOP.
I think that's pretty much what everyone does, but the OP was asking how long it *could* run without an issue. The general response here seems correct: a backup pump should be able to run continuously for an indefinite time with no issues.

And frankly, even if you left it on *all the time*, it should be able to operate with no issues...unless you're flying thousands of hours per year, I doubt you'd exceed any pumps operating lifetime (which should be 10s of thousands of hours, not 2000).
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  #19  
Old 04-28-2018, 04:49 PM
TS Flightlines TS Flightlines is offline
 
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'Probably' 2500+ continuous flight hour operation, based on the automotive installs and driving miles those pumps get before replacement is necessary.

Tom
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  #20  
Old 04-28-2018, 05:32 PM
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mfleming mfleming is offline
 
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Quote:
Originally Posted by RV7A Flyer View Post
I think that's pretty much what everyone does, but the OP was asking how long it *could* run without an issue. The general response here seems correct: a backup pump should be able to run continuously for an indefinite time with no issues.

And frankly, even if you left it on *all the time*, it should be able to operate with no issues...unless you're flying thousands of hours per year, I doubt you'd exceed any pumps operating lifetime (which should be 10s of thousands of hours, not 2000).
The manufacture say's not to be used continuous. And doesn't say for how long I can run it otherwise. (I asked twice, two different emails).
Not having much boost pump experience and this is a popular pump, I guess I was looking for clarification from VAF.

Quote:
Originally Posted by TS Flightlines View Post
'Probably' 2500+ continuous flight hour operation, based on the automotive installs and driving miles those pumps get before replacement is necessary.

Tom
Apparently the continuous running restriction is not the electric motor but the fact that the fuel is in constant recycle while running, which according to the manufacturer can heat up.

The manufacture said to me in an email "If you are using the Boost Pump as a backup to the engine driven mechnical pump, then you will not have any problem"...
I was looking for something more concrete...Oh well

The last thing I want to do if I have a engine fuel pump failure is try and keep track of how long my electric boost pump has been on.

But hopefully thats what the manufacture was trying to say in above quote...no worries during a emergency.
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Michael Fleming
Joseph, OR
sagriver at icloud dot com

RV-7 Slider #74572
Started 11/2016
Empennage completed 11/2016 (sans fiberglass)
Ailerons and flaps completed 3/2017.
Wings completed 12/2017 (sans fiberglass)
Started on QB fuselage 01/2018
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