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  #1  
Old 02-15-2019, 09:55 AM
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Hartstoc Hartstoc is offline
 
Join Date: Aug 2017
Location: Sebastopol,CA
Posts: 368
Default Test Data!!!- Anatomy of a fuel pump, part 3-

Now that we are getting comfortable flying “electron-dependent” aircraft and have powerful, lightweight lithium batteries at our disposal, I’ve been thinking it is time to find a way to SAFELY eliminate one of the last vestiges of the magneto era- the engine driven mechanical fuel pump. There are a lot of really good reasons for doing this that I won’t go into here, but the challenge in making it possible is to find a reliable electric fuel pump properly matched to the task. This thread documents my successful search supported by real data, and I’ve generated accurate performance charts under real-world conditions for three pumps.

Thousands of airplanes already sport electric boost pumps that seem to work well, but on close examination few of them make any sense at all in this context.Two problems with most pumps currently in use is that they generate flow and consume power FAR IN EXCESS of our needs, and many feature continuous short-loop recirculation of the vast majority of their output back to the pump inlet. This is no big deal for backup pumps used intermittently, but wholly ill-suited to continuous operation in a twin-pump setup with no engine driven pump. Some are also quite heavy, bad news with two installed. For continuous operation, return lines to the tank in use become mandatory, and the pump must operate efficiently to minimize electrical demand in normal operation and maximize range on battery power should the alternator fail.

A plethora of choices exist in the 500-1,000 HP range for auto racing applications, but precious few really make sense in the context of typical RV’s. Also, I’ve discovered that published performance data for pumps is often not detailed, accurate, and reliable enough to allow intelligent selection, and these do not take into account system-wide resistance that must be subtracted from the performance of the unrestricted pump.

I decided to build this test rig, shown here collecting data for one of the Walbro pumps. It incorporates pre- and post-pump filters and enough lift, bends, turns, and manifold reversals to roughly mimic the aft-of-firewall dynamic flow restrictions of a typical RV installation. Here, the return line is closed off, and “engine” output, dialed-in at 30PSI resistance, is being shunted to the flow-measuring vessel.



Here you can see the right side valve shunting output to the measuring vessel. The black marks were established using a precision flask, and the flow would be fully stabilized by the time the stopwatch was started at the bottom mark.



I did thorough dynamic testing of three pumps and used the raw data to generate the three Excel performance charts below, testing each pump at 10PSI intervals from 0-60PSI(increased to 5PSI intervals within my operating range of 20-40PSI). The rig allows precise stopwatch timing of exactly one gallon of fluid at each pressure point. It features 3-way valves to shunt the output return line flow and/or “engine” flow into a measuring vessel or back to the source tank. The return line output was blocked completely for GPH vs. Pressure testing, but I also measured pressure and return-line GPH for each pump with the “engine” flow blocked completely to mimic pre-start operation of the pump.

My system will be Bendix-type FI from Airflow Performance, tolerant of wide swings in system pressure, so each pump on my RV will be equipped with simple external pressure-relief valves outputting to return lines(instead of a more sophisticated pressure regulators needed for EFI) and large external check valves, so the rig features those as well. I’ll say more about my experience with the very interesting dynamic behavior of these relief valves in a later post in this thread. Stoddard solvent, a form of mineral sprits, is generally used as a safer alternative to gasoline for these tests, but I went a step further and found an even safer soy-based solvent substitute. After Collecting complete data for all three pumps using this solvent, which has a similar viscosity to diesel fuel, did a carefully grounded calibration run with gasoline on the winning pump at 30PSI to validate my results. Somewhat shocked by the increased flows with gasoline, I ended up repeating the entire test series for the winning pump using gasoline(while constantly purging the airspace in both vessels with Argon!). You will see two output curves for each pump, the lower for the solvent tests, and the upper for gasoline. For the top chart, every data point on all curves was collected directly. For the bottom pump, I did three data points with Gasoline and saw the same relationship as with the first, and was able to derive correction criteria for the remaining points on the gasoline curve. For the middle chart, the entire gasoline curve was generated using correction criteria.

Finally, I decided to dismantle each pump tested to compare design and construction- some photos and discussion will follow in a later post in this thread.(edit note 2-17-19: I tried to add this info here but exceeded the allowable post word-count. Please see the post on page three of this thread where I’ve added photos and commentary- O.H.)

Happily, a very clear winner emerged for RV’s between 125 and 300HP, the Walbro GSL414, with results shown in the first graph. Note that it generates a reliable flow of more than 35GPH at all pressures below 40PSI, and consumes less than 2.5Amps@13.2V through the 25-35PSI range that my RV will operate within. Even this output is far in excess of our needs up to about 300HP, but power required is so low that ONE of my twin EarthX ETX900-VNT’s will operate one of these pumps and a LightSpeed PlasmaIII through an entire 40-gallon fuel load!

Compare that with the absurdly high output and consumption of the Delphi from AP depicted in the third graph. All that surplus output pumped back through the return lines is wasted energy. At 795grams, the all-steel Deplhi also weighs nearly twice as much as the 454gram aluminum-body Walbro GSL’s.

I already feel well rewarded for the effort and dollars invested in this study, and I hope some of you find it useful as well.- Otis
And the winner is!: the Walbro GSL414
This pump pushes 36GPH@31.5PSI through the return lines drawing 2.4Amps@13.3V sitting idle at pre-start!



The Walbro GSL395 was also tested, but proved less efficient.



Here are results from the Delphi pump obtained from AP:
Pushes fully 62GPH@33 PSI drawing 4.2Amps @13.2V sitting idle pre-start. The flow from this pump was actually frightening to witness with gasoline.



This is getting long, so I’ll save photos and discussion of the disassembled pumps for a later post in this thread.

Notes: the ammeter used was placed in series with my trusty Flukemeter, and reported parallel to #but 1/0th of an Amp lower than the Fluke across a 1-6Amp range. Voltage agrees perfectly.

Here iare links to parts one and two of this series:
http://www.vansairforce.com/communit...hlight=Anatomy
http://www.vansairforce.com/communit...hlight=Anatomy

Finally, I want to thank Ross Farnham at SDS for suggesting the GSL414 and for serving as my sounding board in many emails during this work-
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Otis Holt-
RV-7A (bought)
Built Monnett Moni
Frmr Test Pilot/Author CAFE APR's:
RV-8A, S-7C, Europa, Glastar.
-2021 VAF donation!!-
"RV-Fun is inversely proportional to RV-Weight!"

Last edited by Hartstoc : 02-17-2019 at 11:28 AM.
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  #2  
Old 02-15-2019, 10:03 AM
slngsht slngsht is offline
 
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Location: Purcellville, VA
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Otis, this is valuable work! Thank you.

Have you looked at reverse flow possibility in Walboro pumps? I am not familiar with their design. Is reverse flow a possible failure mode? Should an external check valve be installed or not needed?
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  #3  
Old 02-15-2019, 10:14 AM
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Hartstoc Hartstoc is offline
 
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Quote:
Originally Posted by slngsht View Post
Otis, this is valuable work! Thank you.

Have you looked at reverse flow possibility in Walboro pumps? I am not familiar with their design. Is reverse flow a possible failure mode? Should an external check valve be installed or not needed?
Nota problem, each pump has a tiny check valve at the outlet. My installation will include a big external check valve for each pump like the one just to the left of the pressure guage on my rig. My concern is that a pump failure could generate enough debris to block the tiny valve ooen, so this will be prevented by the external industrial duty check valve.
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Otis Holt-
RV-7A (bought)
Built Monnett Moni
Frmr Test Pilot/Author CAFE APR's:
RV-8A, S-7C, Europa, Glastar.
-2021 VAF donation!!-
"RV-Fun is inversely proportional to RV-Weight!"
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  #4  
Old 02-15-2019, 10:26 AM
Lars Lars is offline
 
Join Date: Nov 2005
Location: Davis, CA
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Thank you for your efforts. I'll confess to having been a bit skeptical about whether your efforts would be worth the trouble; clearly they were, to the benefit of many of us. I'm thinking about eventually dumping my mechanical pump as well, and though I have plenty of electrons available I might as well select for the most efficiency.

Question: where did you obtain the GSL414? A quick search makes it appear that they are somewhat rare. Amazon's site claims to have them but for some reason they claim that "this item cannot be shipped to your selected location." Also couldn't find anything on TI Automotive's website. I would be a little concerned about developing a fuel system around a part, or parts, that prove to be unicorns. Having been bitten by that in the best.
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  #5  
Old 02-15-2019, 10:47 AM
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Hartstoc Hartstoc is offline
 
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Quote:
Originally Posted by Lars View Post
Thank you for your efforts. I'll confess to having been a bit skeptical about whether your efforts would be worth the trouble; clearly they were, to the benefit of many of us. I'm thinking about eventually dumping my mechanical pump as well, and though I have plenty of electrons available I might as well select for the most efficiency.

Question: where did you obtain the GSL414? A quick search makes it appear that they are somewhat rare. Amazon's site claims to have them but for some reason they claim that "this item cannot be shipped to your selected location." Also couldn't find anything on TI Automotive's website. I would be a little concerned about developing a fuel system around a part, or parts, that prove to be unicorns. Having been bitten by that in the best.
Thanks for the compliment! True the 414 is a bit rarer and a bit more expensive than the others($100-130) but they are out there. I believe you can obtain one from SDS
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Otis Holt-
RV-7A (bought)
Built Monnett Moni
Frmr Test Pilot/Author CAFE APR's:
RV-8A, S-7C, Europa, Glastar.
-2021 VAF donation!!-
"RV-Fun is inversely proportional to RV-Weight!"
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  #6  
Old 02-15-2019, 11:14 AM
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rv6ejguy rv6ejguy is offline
 
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Very good work here Otis. This will be useful information for many contemplating electric pumps.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 450.6 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ


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  #7  
Old 02-15-2019, 11:48 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
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Default Bravo,

Yes, Bravo, Otis. First for your time and $ investment in understanding what you need, and second for validation of what the pumps will really do.

This kind of work when going off plan is needed to ensure the safety of the final product. Sharing it for others leverages the work for others to use.

Keep up the good work!
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RV-7
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  #8  
Old 02-15-2019, 02:08 PM
slngsht slngsht is offline
 
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Thanks Otis, what is the part number/ manufacturer of that check valve?
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  #9  
Old 02-15-2019, 02:37 PM
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Hartstoc Hartstoc is offline
 
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Quote:
Originally Posted by slngsht View Post
Thanks Otis, what is the part number/ manufacturer of that check valve?
I beieve they are made in house by Airflow Performance, ditto for the return valves and the nifty banjo-fitting manifold to which the relief valve in the photos is attached. Talk to Don Rivera there, everything they to is to the highest standard, yet generally light in weight. For full redundancy in a dual-pump system, each pump should ideally have its own external relief valve or regulator and its own external check valve. You don’t want the failure of one pump to be able to impact operation of the other one.- O
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Otis Holt-
RV-7A (bought)
Built Monnett Moni
Frmr Test Pilot/Author CAFE APR's:
RV-8A, S-7C, Europa, Glastar.
-2021 VAF donation!!-
"RV-Fun is inversely proportional to RV-Weight!"

Last edited by Hartstoc : 02-15-2019 at 02:40 PM.
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  #10  
Old 02-15-2019, 02:57 PM
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Hartstoc Hartstoc is offline
 
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Default A couple of notes-

1-Beware of counterfiet Walbro pumps- they are copied right down to the labels in China. Cyberspace Automotive Performance, one dealer offering them online has actually published an offer from a Chinese company to offer the fake pumps to their company! They supplied the Walbro’s I used for my testing, and are associated with TI Automotive.

You can also count on pumps offered by Ross Farnham at SDS being genuine products.

2- I’ll be keeping this test rig for a while, so if anyone has a pump that can be set up with an an-6 flaired inlet and a 12mm male banjo outlet is welcome to send it to me for flow testing- no charge just pay two-way shipping. I’d love to do the Walbro GSL392 and GSL393.- Otis
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Otis Holt-
RV-7A (bought)
Built Monnett Moni
Frmr Test Pilot/Author CAFE APR's:
RV-8A, S-7C, Europa, Glastar.
-2021 VAF donation!!-
"RV-Fun is inversely proportional to RV-Weight!"
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