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  #61  
Old 05-11-2018, 12:54 AM
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Hartstoc Hartstoc is offline
 
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Location: Sebastopol,CA
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Quote:
Originally Posted by rv6ejguy View Post
My post was only responding to the other post where it was believed that an FI engine would run without fuel pressure somehow. The backup boost pump would supply that pressure.
Yes, and I was confirming that your post was correct, but adding that engine driven pump failure modes can be complicated. You cannot simply say that the backup pump would supply pressure required to keep the engine running. Insuring that would require some very complicated valving that completely bypasses the engine driven pump.- Otis
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  #62  
Old 05-11-2018, 07:00 AM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by Hartstoc View Post
Yes, and I was confirming that your post was correct, but adding that engine driven pump failure modes can be complicated. You cannot simply say that the backup pump would supply pressure required to keep the engine running. Insuring that would require some very complicated valving that completely bypasses the engine driven pump.- Otis
Agreed. Several different failure modes as you pointed out. Twin electric pumps would mostly eliminate that possibility as long as you had electrical power.
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 445.2 hrs. on the Hobbs,
RV10 95% built- Sold 2016
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  #63  
Old 05-11-2018, 07:39 AM
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rv8ch rv8ch is offline
 
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Location: LSGY
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Default mechanical pump failure modes

Quote:
Originally Posted by Hartstoc View Post
Yes, and I was confirming that your post was correct, but adding that engine driven pump failure modes can be complicated. You cannot simply say that the backup pump would supply pressure required to keep the engine running. Insuring that would require some very complicated valving that completely bypasses the engine driven pump.- Otis
Hi Otis, do you have more info on these failure modes? I for one have an engine driven fuel pump that has a backup boost pump (andair) and while I can imagine some mechanical pump failures that would stop the fan from spinning, I've never heard of one happening. Thanks!
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  #64  
Old 05-12-2018, 08:26 PM
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mfleming mfleming is offline
 
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Location: Joseph, Oregon
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So I thought I would give an update since I started this thread.

In the end, I decided to return the Efii pump. Robert accepted the pump and refunded the purchase price. I thank him for that.

Yesterday I ordered a Airflow Performance pump form Don. I also ordered a set of lines and hoses for the pump from Tom at TS Flightlines. At the same time I ordered the install kit from Van's.

I'm very pleased with this new direction and am looking forward to installing the whole system.
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Last edited by mfleming : 05-12-2018 at 10:00 PM. Reason: fix typo
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  #65  
Old 05-12-2018, 09:20 PM
Mark C. Mark C. is offline
 
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Mike, I have this fuel pump in my 9A installation for the last 2 years of operation, in fact on their company web site has my mounting setup is the second pictures from the top. It runs very quiet so I added a bright green led when the switch is on. Never an issue many times I have even missed seeing the run light even after 5 minutes of running. Even with having the Boost Pump, If I lose the engine mechanical pump I'm looking for an airport to land.. Mark C. RV9A
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  #66  
Old 08-09-2018, 02:00 PM
Langt Langt is offline
 
Join Date: Apr 2018
Location: Lambertville, MI
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Default Boost Pump Operation

Looks like this is now a dead thread, but I'll still add my two cents anyway: The issue of pump heat for a "boost pump" without a return path is real, but proper operation and understanding has shown that it is not significant. If it were, the bypass design of the EFii, Airflow, and Andair would be different. For example, instead of a return to the tank, you could add a small heat exchanger loop (maybe just a tube coil) to the either of the first two. Or you could put fins on the Andair body. But why add complication, weight, and complexity when not needed?

We know these systems WORK, so what follows is painfully unnecessary, but just to show some numbers in English units:

Assume nominal current draw of 4 amps at 12 volts = 48 watts
48 watts x 3.412 btu-hr/w = 164 btu/hr energy input. We will conservatively assume all the input energy goes into the gasoline. (This is fairly accurate at low temperature rises, but more conservative as the system temperature is higher since in reality some of the heat would escape to ambient via the pump body and connected tubing.) The specific heat of gasoline is about 0.51 btu/lb-F. Let's assume a fuel flow of only 1 gph. That's about 6 lbs /hr.

So, the gasoline temperature rise, conservatvely, is about:
164 btu/hr / (6 lb/hr x 0.51 btu/lb-F) = 54 degrees F steady state. Note that in this case, 54F is a fairly high rise, so there would be some heat loss to the surrounding air and it wouldn't really be this hot. But it's a worst case, as if you (stupidly) insulated the pump. If you are burning say 2 gph, it would only be a 27 degrees F rise, or at 10 gph, only 5.4 degrees F. But.... Don't leave power on and boost pump on without the engine running and think you can go to lunch! For that you would certainly need a cooler or return to the tank. Not sure what would fail, but something would.

Sorry for the long wind. Engineers are like that.

BTW, the Andair pump is cheaper this week if you order from England due the very favorable dollar to pound exchange rate. Maybe a buy opportunity until prices adjust.

Ted

Last edited by Langt : 08-09-2018 at 02:08 PM. Reason: Grammar
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  #67  
Old 08-10-2018, 04:44 AM
Lars Lars is offline
 
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Location: Davis, CA
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FWIW... The electric pump in my Airflow Performance pump/filter assembly failed recently after about 650 hours on the meter. Normal takeoff/landing use (I fly a lot of short hops so it?s been on a lot) and occasional oops when I?ve forgotten to turn it off despite the annunciator light. It gave warning. I noticed the pump seemed noisy, and a couple of passengers commented on it. Then the fuse 10 amps) blew a couple of times. Then once in the ground it didn?t run when I turned on the switch. The light came on but no noise. Quickly cycled the switch and it did come on.

That was the last straw. Grounded, ordered new pump from AFP. The new one is so quiet I can?t hear it when the engine is running. Based on my automotive experience the failure seemed typical- they usually don?t fail while they are running. Instead they just don?t turn on and/or they blow the circuit protection. I had expected the pump to last longer than it did, but stuff happens. I don?t have a good sense of mean TBF for high pressure EFI-type pumps in aviation use. In any case I welcome the (slight) reduction in cockpit noise...
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  #68  
Old 08-10-2018, 06:10 AM
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rv6ejguy rv6ejguy is offline
 
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I had 5000 hours on a Walbro EFI type pump in our shop car. Still quiet and working fine when the car was sold in 2016.
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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- 445.2 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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  #69  
Old 08-10-2018, 07:34 AM
Timberwolf Timberwolf is offline
 
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I currently have a dukes but intend on replacing it with an AFP when this unit dies. When I initially turn on the pump for a cold start, or a hot start sitting on a hot ramp you can hear it cavitate at first as it gets its prime. I expect this will eventually kill it. I keep this in mind and always listen for a change in noise or pressure loss to signal when it?s time. I think it?s just a product of the design.
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  #70  
Old 08-10-2018, 07:37 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by Langt View Post
....but just to show some numbers in English units:
I love it when you talk dirty
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