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Boost Pump Operation

mfleming

Well Known Member
Patron
So I really did search high and low for this information but no joy.

I recently bought (but have not installed) a boost pump.
I've just learned that the pump cannot be run continuously. It seems the pump recycles fuel and eventually the fuel heats up.

I don’t have plans to run it all the time...just the normal takeoff/landing/fuel switching etc....

  • Are all boost pumps like this?
  • How long CAN I run the boost pump without worrying?
  • What happens its I run it too long due to distraction or perceived need?

I know there are experienced builders on this site who recommend this pump, so I'm pretty sure the pump is high quality and reliable.
I'm just confused on how to manage it and the consequences of running it to long.
 
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boost pump

Which pump? I've never forgotten to turn off the boost pump. :D /s
 
Who was your instructor? And which pump are we talking about?

Many instructors in the past 48 years ;)
No boost pumps involved except for last week and that instructor did not seem to be the guru on boost pumps :rolleyes:

I'm just trying to understand the how's and whys on boost pumps and if I made the right decision on my purchase.

PM'ed you some more info.
 
"Boost Pump" is also backup

to your engine-driven pump ---- I would expect mine to run continuously if my engine-driven pump failed.

Ron
 
Well, *I've* never forgotten to turn the boost pump off...as far as you know. :)

I have the Andair pump. Rated for continuous use. I'd expect pretty much all others are the same or else, as noted, they aren't really meeting the requirement of being a backup pump in case of engine pump failure, are they?
 
This is the primer war of the alt engine crowd (where should the regulator be, and where should the bypassed fuel go). For anyone considering auto style electronic injection, this thread's for you.

Just a minute; I'm going for some popcorn.

;-)
 
RV-12iS has 2

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
 
This is the primer war of the alt engine crowd (where should the regulator be, and where should the bypassed fuel go). For anyone considering auto style electronic injection, this thread's for you.

Just a minute; I'm going for some popcorn.

;-)

This pump is going in a -7 with a I0-360 with non automotive fuel injection.
 
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." :confused:

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.
 
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." :confused:

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
 
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)
 
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.
 
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.
 
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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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.
 
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).
 
'Probably' 2500+ continuous flight hour operation, based on the automotive installs and driving miles those pumps get before replacement is necessary.

Tom
 
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.

'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 :eek:

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.
 
Maybe I am way off here with my understanding, but if the manufacture of the pump says not for continuous duty then why would they sell a block off plate for the engine driven pump when installing their system?
I would not want a pump that I could not leave on continuous if needed? But that is just me. :)
 
'Probably' 2500+ continuous flight hour operation, based on the automotive installs and driving miles those pumps get before replacement is necessary.

Tom

This seems very low to me. I've had cars I've driven 200,000 miles and never never had to replace a pump.

Current vehicle is 4 years old...let's say approximately 2 hrs/day (more weekdays, less on weekends, but that's close) * 365 ~= 700/year * 4 years = 2800 hours so far :). Watch, now it'll fail next week LOL!

The Andair pump says right on the spec sheet: Continuous duty. That's what I want in an electric boost pump, so I don't worry if I ever forget to turn it off, and I know it'll be good if the engine-driven pump fails for at least enough time to get me safely on the ground no matter where I am.

This is Experimental aviation, though, so everyone can choose their own solutions. YMMV.
 
'Probably' 2500+ continuous flight hour operation, based on the automotive installs and driving miles those pumps get before replacement is necessary.

Tom

Pumps installed in automobiles use dedicated fuel return lines or return directly into the tank. Not the same application here, as in this application excess fuel is returned back to the pump inlet, creating the "potential" for overheating the pump motor. You can't apply the track record of those auto pumps in this application, eventhough the pumps are the same. I would be like saying the Subaru engine has a great track record in automobiles and therefore will provide that same reliability in an airplane. Its all about the application intended by the design and these auto pumps aren't designed for re circulation. They transfer their heat to the fuel passing through them and their design presumes that fresh, relatively cool fuel will be flowing through them at all times to absorb this heat.

If you don't believe me and you have one of these style of pumps, put your mixture at ICO and turn the boost pump on. Let me know how long it takes to fail. I would guess 30 minutes tops. That is tongue and cheek of course, as this would create a potential fire risk.

I am not saying these are bad. I have one of these style pumps in my plane. Just pointing out that it is not idiot proof and has failure scenarios that may not be obvious the user.

Larry
 
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Maybe I am way off here with my understanding, but if the manufacture of the pump says not for continuous duty then why would they sell a block off plate for the engine driven pump when installing their system?
I would not want a pump that I could not leave on continuous if needed? But that is just me. :)

It is continuous duty in their fuel injection setup, where fuel is returned directly to the fuel tank and not back to the pump inlet, not necessarily in the case when that pump is used as a boost pump on a bendix FI setup.

Larry
 
So I really did search high and low for this information but no joy.

I recently bought (but have not installed) a boost pump.
I've just learned that the pump cannot be run continuously. It seems the pump recycles fuel and eventually the fuel heats up.

I don’t have plans to run it all the time...just the normal takeoff/landing/fuel switching etc....

  • Are all boost pumps like this?
  • How long CAN I run the boost pump without worrying?
  • What happens its I run it too long due to distraction or perceived need?

I know there are experienced builders on this site who recommend this pump, so I'm pretty sure the pump is high quality and reliable.
I'm just confused on how to manage it and the consequences of running it to long.

Excellent question- most of the fuel pumps intended for 20-35psi fuel injection systems are adaptations or decendents of pumps designed for in-tank fuel-submerged applications. They are constant- displacement , meaning that they flow 25-50 gallons per hour(depending on model) through some sort of regulator or relief valve regardles of engine fuel flow, and consume 3.5-6 Amps continuous. This (and all)amperage flow can be expressed as BTU’s and these pumps are all designed to be fuel-cooled!

I personally regard adaptations of such pumps as “boost pumps” to be inherently dangerous as they accommodate this flow by recirculating fuel through a very short loop so they become fuel BOILERS if used continuously at low engine power settings. If you ever need to use one as emergency backup, be sure to fly at high-power/high fuel flow settings, and don’t be deceived into thinking that low power settings during this event are “babying” the pump. I’d suggest writting this into POH emergency proceedures.

These are well-designed pumps usually rated for continuous duty, but the ONLY way to safely operate them continuously is to have an adequately sized(i.e. 3/8” on RV’s), unobstructed, dedicated fuel-return line going back to the tank from the low pressure outlet of the regulator or relief valve.

These concerns do not apply to low-pressure, pulse-type pumps on engines with carbs- normal engine flows are completely adequate for keeping those cool, and anyway the carb float bowl vents any vapor that might be formed.- Otis
 
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user a timer for flashing light or buzzer

Perhaps a timer on the "fuel pump on" warning light or buzzer would solve your problem of possibly forgetting to turn off the boost pump? I found this one on amazon - probably lots of other ways to do this.

https://www.amazon.com/Timer-Delay-Relay-Hours-Cycling/dp/B00PD65UGA

I thought of a red light on all the time, but I don't like red lights unless there is a problem, and during takeoff and landing it's probably not a good idea to train yourself to ignore red lights. Having the warning light come on after say 10 minutes might be enough.

Or maybe just a green light when the fuel pump is on? Would not bother you too much during times when you really want it on, like takeoff and landing, and you would probably notice it in cruise if you forgot to turn it off.
 
Interesting. Lots of opinions, and not one little bit of temperature data.

A few points should be agreeable to all.

(1) To the OP's question, there cannot be a stated time limit for pump operation. If such an operating time limit exists, it depends entirely on outlet fuel flow. At low engine demand, the pump recirculates more, while high demand means less re-circulation.

(2) "Normal" operation of a typical Lycoming installation has the pump ON for departure and approach, OFF for the rest of the flight.

(3) Some run 'em at any low altitude ("low" meaning too low to get an engine restart if the engine driven pump goes TU), and for sure, it ain't worth having if it won't run continuously after engine pump failure.

Ok, let's get some facts. This is an easy-to-use temperature sensor:

https://www.digikey.com/product-detail/en/texas-instruments/LM34AH/LM34AH-ND/5055993

Wiring is just 12V power, ground, and sense. Connect an ordinary digital multimeter to sense and a common ground. Output is analog voltage, 10 mV per degree F, so (for example) 1.85 VDC on your meter is 185F.

To mount, solder the sensor's metal can to a small metal strip or square. Add a dab of heat-conductive silicone paste to the underside, and clamp the square to the pump body. Wrap the sensor in some kind of insulation, enough to minimize the effect of local air temperature.

Next time you fly, turn on the pump, and leave it on. Note the temperature, and start a clock. Note temp at intervals. Report back please.
 
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Joe--I was citing an 'average', and yes many do operate for more than 200,000 miles. My point was the Walbro motors can run for that long. Yep, in a full return system, the pump does run continuously, as in an automotive system.
I thought that was the original question. And perhaps my estimate of a failure time was 'off'. The life expectancy of the pump is when it quits.
If you want to test it, set it up LIKE the fuel system you plan to use, and let it pump and see how long it takes before it fails. Eat lunch first---

Sam probably has the correct answer-
Tom
 
Minor correction to Otis' earlier post: The Walbro pumps being used (and possibly the Airtex in other vendors' assemblies) are specifically designed for in-line use; not in-tank. Only reason for pointing this out is that immersing the entire pump in fuel obviously provides more cooling than just the flow through the pump.

And I agree with Dan's post; speculation isn't data. But shouldn't the vendor be able to supply the data and test conditions from his testing?

Just a minute; I've run out of popcorn...
 
It is not just temperature-

Interesting. Lots of opinions, and not one little bit of temperature data.



Dan- I don’t think the concern is exceeding any particular temperature- that is only one condition contributing to fuel vaporization. In fact, outright failure of the pump itself is unlikely and not even much of a concern.

There is no means of extracting fuel vapor in systems without return lines, and these pumps cannot effectively pump foam or vapor. If the incoming fuel is already warm and the pump assembly is heating up due to continued use while recirculating nearly all of the fuel it is moving, you could reach a point where output pressure falls below the minimum level required to sustain operation of the metering valve, distribution block and injectors. As net flow through the FWF plumbing subsequently falls off, the situation grows even worse, and there is literally nothing you can do to remedy it. That is why you would want to operate at the highest reasonable fuel flows if you found yourself relying upon the boost pump after failure of the engine driven pump.

It might be possible to set up and test conditions required for this, but doing it safely would require very careful planning.

Engine driven pumps are actually very reliable, but their failure modes can be quite grim and, ironically, use of a boost pump during some of them will make the situation worse. I’m now assembling a fully redundant dual electric pump setup with no single-point failure modes for the Airflow Performance FI system I’ll be installing on my 7A next Winter. It will include fuel return lines and a duplex valve that switches both feed and return lines between tanks. I will be completely removing the engine driven pump, and will document all on VAF.
 
Dan- I don’t think the concern is exceeding any particular temperature-

Neither do I. But perhaps we should both ignore what we think, and determine the actual worst case pump temperature. After all, in your next paragraph I see....

If the incoming fuel is already warm and the pump assembly is heating up due to continued use while recirculating nearly all of the fuel it is moving, you could reach a point where output pressure falls below the minimum level required to sustain operation of the metering valve, distribution block and injectors.

The scary supposition starts with a big 'ole if. You trying to say you don't know the pump temperature?

It might be possible to set up and test conditions required for this, but doing it safely would require very careful planning.

Apparently not.

BTW, what is unsafe about strapping a temp probe to a pump casing?
 
A few points on electric pumps:

Nomenclature differences- EFI engines don't use boost pumps. They are just fuel pumps. There is nothing to boost since they are the primary source of fuel flow and pressure. Most systems will have a second identical pump as a backup.

We've been using/ selling the Walbro pumps in question GSL392/393 for over 20 years and sold hundreds of them. I've never seen one fail or had to supply a new one to a customer who reported a failure except for 2 which were mounted improperly with the inlet facing up (both failed within a few hours).

Had a standard GSL255 pump in-tank mounted in our shop Nissan 240SX turbo for 18 years and around 5000 hours. Zero issues with a return circuit to the tank. Obviously from this rather long term use, they can be used either externally or in-tank.

Can the pump reliably be used in a Bendix type mechanical FI system as a boost pump with no tank return? That depends on a lot on recirculation rates, fuel temperature and fuel type.

Points to consider:

The boiling points of mogas and 100LL can be radically different.

The pump relies on fuel flow for cooling the motor and pump components.

Any vapor trapped in a non-return system has only one way out- through the injectors.

Cavitation or trying to pump liquid fuel plus vapor will destroy these pumps fairly quickly.

Any vapor introduced at the injectors will cause lean running and possibly complete engine shutoff depending on how much vapor is present.

The return fuel rate at idle is massive as these put out about a gallon a minute in the case of the commonly used 393 pump. Fuel heating will be become significant at idle, less so at high power settings. You probably need the pump mostly in flight where there is enough fresh flow through the system to keep the temps down but measurement is the only way to know for sure as Dan suggests.
 
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EFII boost pump or any other boost pump

There are some Lycoming engines that do not have provision for a mechanical pump on the accessory case. Sometimes people with these engines try to use a boost pump (EFII or otherwise) as the primary fuel pump for the engine.

This is not what these pumps are designed for.
This is the precaution that has been quoted by the OP.

This does not represent a shortcoming of, or a precaution in the use of these pumps when they are used as a boost pump.

A boost pump is a back up pump to the mechanical pump on the engine. Boost pumps are designed for temporary use such as during:
Take-off
Landing
Priming
Failure of the primary pump

If you are using a boost pump as a boost pump, there is not any problem or limitation with any of it's intended uses.

If you are trying to use a boost pump as the primary engine fuel pump, then you have chosen the wrong type of pump.

Robert
EFII
 
Data point for AFP pump

I know various pumps are being discussed, but here's one data point for the Airflow Performance pump on my plane (installed in 2001), which I understand is an automotive one:

I had it on for 1.5 hours during the long taxi at Oshkosh last year, save for about a 15 minute shutdown in the middle of that. Oil temps were 245, cht's about 300, OAT about 75 or 80F. My pump is mounted on the forward side of the spar, so I can easily reach down and touch it, which I did several times. Didn't seem warm to the touch.
 
There are some Lycoming engines that do not have provision for a mechanical pump on the accessory case. Sometimes people with these engines try to use a boost pump (EFII or otherwise) as the primary fuel pump for the engine.

This is not what these pumps are designed for.
This is the precaution that has been quoted by the OP.

This does not represent a shortcoming of, or a precaution in the use of these pumps when they are used as a boost pump.

A boost pump is a back up pump to the mechanical pump on the engine. Boost pumps are designed for temporary use such as during:
Take-off
Landing
Priming
Failure of the primary pump

If you are using a boost pump as a boost pump, there is not any problem or limitation with any of it's intended uses.

If you are trying to use a boost pump as the primary engine fuel pump, then you have chosen the wrong type of pump.

Robert
EFII

Robert, There are far more Bendix type FI systems flying than EFII, and all but a few of those are set up with the engine driven primary and an electric “boost/backup” pump. My point is that if you find yourself in the “backup” mode after an engine driven pump failure, you have now promoted the electric pump to “primary” for the duration of the flight. My further point is that electric bumps with short-loop recirculation systems are, in fact, NOT well suited to this role, and my post goes on to describe a scenario that could lead to engine stoppage without actual failure of the electric pump unless special proceedures are adhered to, and even then the best strategy is to position yourself within an easy glide to a very good airport before beginning your descent and to be mentally prepared to make a deadstick landing. My personal(well practiced) descent strategy would be to fly well behind the power curve, dirty config, max rich and max power allowing for a modest rate of descent, but my airplane will be equipped with fuel return lines so this will never be an issue for me.

I believe it is irresponsible for vendors to suggest that you will be “just fine” if you use such a pump as emergency backup to the engine driven pump, or to claim that electric pumps with internal or short-loop recirculation are suitable for continuous duty. Ironically, the very low failure rates of engine driven pumps have deprived us a meaningful data base.


This is all my personal opinion based upon a fair amount of study- if my concerns don’t ring true to anyone, they are free to ignore them!- Otis
 
If you are using a boost pump as a boost pump, there is not any problem or limitation with any of it's intended uses.

If you are trying to use a boost pump as the primary engine fuel pump, then you have chosen the wrong type of pump.

They are, for the most part, the same type of inline pump, if not the exact same part number. The issue is the fuel circuit, as Otis describes; short (excess fuel returning directly to the pump inlet), or long (excess fuel returned to a tank).

Otis is concerned about fuel heating with the short circuit during low engine fuel demand. You have yet to state why you believe using one continuously makes it the "wrong kind of pump". As others note (and you recognize), we rely on our boost pump to continue flight should the primary fail.

So, take a position please. Can an EFII-brand boost pump be relied upon to continue flight, without issue, following an engine pump failure? If yes, why is that different from using one full time in any application?
 
pumps

Boost pumps (including ours) are designed to backup the mechanical engine driven pump for mechanical fuel injection. These are for use with Bendix, Airflow Performance, Precision Airmotive or ECI mechanical fuel injection.
https://www.flyefii.com/products/boost-pump/

This is not the pump we use for electronic fuel injection. For electronic fuel injection we use a dual electric pump module with a full return fuel system that establishes pressure regulation with the use of a fuel pressure regulator at the end of the engine fuel rail.
https://www.flyefii.com/products/accessories/dual-electric-fuel-pump/

These are very different applications and very different pumps.

Robert
 
Boost pumps (including ours) are designed to backup the mechanical engine driven pump for mechanical fuel injection. These are for use with Bendix, Airflow Performance, Precision Airmotive or ECI mechanical fuel injection.
https://www.flyefii.com/products/boost-pump/

Thank you, but for the record, you dodged the specific questions.

Interesting sales page. Are you aware that the AFP module in your illustration has been obsolete for some time? A current AFP module looks like this:

http://airflowperformance.com/wp-content/uploads/2015/12/Auxiliary-Pump-2090255.pdf

Photo on page 3, dimensions on 7. It's actually a little more compact, if measured apples to apples, i.e. without fittings. EFII dimensions here:

https://www.flyefii.com/products/boost-pump/installation-tips/

Is your suction loss claim also based on the obsolete AFP module?

BTW, Airflow Performance boost pumps are continuous duty (first line, page 3), the question you were asked. Does your module get hot and quit pumping when run for an extended period? That is the OP's concern.
 
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BTW, Airflow Performance boost pumps are continuous duty (first line, page 3), the question you were asked. Does your module get hot and quit pumping when run for an extended period? That is the OP's concern.

So are the Andair pumps. Says right on their documentation.
 
Looking at the Airflow Performance PDF Dan linked to tells me the Airflow pump operates in an identical fashion as the EFii pump.

It seems to me the EFii pump I bought would hold up for continuous use just like the Airflow pump unless the EFii pump has a much higher GPM capacity and bypasses significantly more fuel.

Airflow and EFii do not mention the GPM capacity of their pumps.

EFii pumps advertises their pumps are suitable for engines up to 600HP.
I found a fuel consumption chart for HP vs fuel flow. 600hp equates to 33.86 gph or .564 gpm.

Since both pumps draw roughly the same amount of current and bypass at roughly the same pressure. They must both have a similar pumping capacity.

I can't see how the Airflow pump would not produce roughly the same BTU's as the EFii pump.

BUT its listed as continuous duty.

I'm guessing that Airflow is just not worrying about the BTU build up or has done some testing and thinks it doesn't produce enough BTUs to interfere with the pump operation.

I'm going to keep the EFii pump and put a thermocouple on it for phase I testing. I just need to find someone with a Airflow pump and instrument it up for a comparison...but I don't see how it could be much different.

The other thing that drives me to keep the EFii pump is it's American made and just looks like a quality piece of equipment.
 
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Looking at the Airflow Performance PDF Dan linked to tells me the Airflow pump operates in an identical fashion as the EFii pump.

It seems to me the EFii pump I bought would hold up for continuous use just like the Airflow pump unless the EFii pump has a much higher GPM capacity and bypasses significantly more fuel.

Airflow and EFii do not mention the GPM capacity of their pumps.

EFii pumps advertises their pumps are suitable for engines up to 600HP.
I found a fuel consumption chart for HP vs fuel flow. 600hp equates to 33.86 gph or .564 gpm.

Since both pumps draw roughly the same amount of current and bypass at roughly the same pressure. They must both have a similar pumping capacity.

I can't see how the Airflow pump would not produce roughly the same BTU's as the EFii pump.

BUT its listed as continuous duty.

I'm guessing that Airflow is just not worrying about the BTU build up or has done some testing and thinks it doesn't produce enough BTUs to interfere with the pump operation.

I'm going to keep the pump and put a thermocouple on it for phase I testing. I just need to find someone with a Airflow pump and instrument it up for a comparison...but I don't see how it could be much different.

The other thing that drives me to keep the EFii pump is it's American made and just looks like a quality piece of equipment.

I would expect the Airtex pump used by AFP has a lower flow rating than the Walbro and therefore less return flow.

Either way, caution still needs to be exercised. I doubt that AFP and Andair pumps can be run continuously at ICO. I would hope that they tested at the lower flows present at idle. I suspect 1-2 GPH would probably create an adequate dilution level to avoid most problems. The previous posters test at Osh seems to confirm that.

Larry
 
I would expect the Airtex pump used by AFP has a lower flow rating than the Walbro and therefore less return flow.

Either way, caution still needs to be exercised. I doubt that AFP and Andair pumps can be run continuously at ICO. I would hope that they tested at the lower flows present at idle. I suspect 1-2 GPH would probably create an adequate dilution level to avoid most problems. The previous posters test at Osh seems to confirm that.

Larry

I can't see how the Airtex and Walbro pumps can be much different in pumping capacity. They both operate at 12volts and pull about 4.3amps so that equates to 51.5watts...looks like their both doing about the same amount of work to me.

But to your larger point, "caution needs to be exercised", I do agree.
Any pump that recycles fuel looks like some test data is needed.
 
I don't have the boost pump, but I do have the Full Dual EFII set up, I don't know if the pumps are the same or not but mine flows 45 GPH after the regulator set at 35 PSI measurement taken on the return to tank line. I don't see how the boost pump could overheat as there will still be fresh cool fuel coming into it and mixed along with what is being recirculated, could be as high as 8-14 GPH or what ever your fuel burn is. :rolleyes:
 
You have your answer from the vendor about the EFii. Why not ask AFP? I did, via PM, several years ago, and got a satisfactory answer describing how they actually tested their product. As part of the discussion, he also mentioned the characteristics of the certified Weldon boost pump, which has been in use for over half a century.

Charlie
(I need to go to the store for more popcorn.)
 
I don't have the boost pump, but I do have the Full Dual EFII set up, I don't know if the pumps are the same or not but mine flows 45 GPH after the regulator set at 35 PSI measurement taken on the return to tank line. I don't see how the boost pump could overheat as there will still be fresh cool fuel coming into it and mixed along with what is being recirculated, could be as high as 8-14 GPH or what ever your fuel burn is. :rolleyes:

The BPM-1 boost pumps is not the same pump that’s installed with the full dual EFii setup. On the boost pump setup, typically there’s no return line for cooling.
 
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FWIW...

If a builder is really concerned about re-circulation heating, order an old-style AFP boost pump, and plumb the pressure relief return back to the tank via a duplex valve. The short path re-circulation systems came about because marketing gave folks the idea that a compact module was "better". Truth is the old style AFP boost could be plumbed for a re-circulation path of any length, including tank return.

Here's an example, from Andre Burger's build log. The line leading to the tee fitting is the fuel inlet. The blue cylinder closest to the camera is the pressure relief valve. Excess fuel exits the assembly through that valve. Andre has it going back to the tank selector valve outlet, a medium length re-circ path, which I suspect offers more than enough cooling.

http://www.mykitlog.com/users/displ...er&project=328&category=3897&log=72641&row=85

As noted previously, EFII's comparison of suction loss at 15 GPH seems to be based on that old school AFP pump. The later modular pump has a different pressure relief valve. I don't know what the suction loss might be for the newer valve, but it hardly matters.

The stated values are 4.1" and 0.7" H20, which sounds like a big deal. Ok, so convert inches of water to conventional terms for liquid (psi or kilopascals), then pull up a chart of true vapor pressure vs temperature for gasoline with an RVP of 7 psi/50 kPa or less, the range for 100LL. The temperature advantage appears to be about 1.6 degrees F.

Any pump that recycles fuel looks like some test data is needed.

Go for it Mike.
 
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The BPM-1 boost pumps is not the same pump that?s installed with the full dual EFii setup. On the boost pump setup, typically there?s no return line for cooling.

Correct, but....the circuit is not dead headed running against the relief, there is some flow in and out allowing (some) heat to be carried away.
 
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