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  #11  
Old 08-08-2017, 08:07 PM
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rv6ejguy rv6ejguy is offline
 
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Location: Calgary, Canada
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We recommend the pump module be mounted horizontally, as low as possible in the airframe on low winged aircraft like the RV with wing tanks. Minimize the use of 90 degree fittings on the inlet side of the pumps.

Tens of thousands of flight hours with this layout shows it to be the most reliable.

We don't recommend the pumps be mounted firewall forward.

Whatever you do, don't mount the module vertically with the inlet facing up. This has caused cavitation and short pump life in at least 2 instances.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW- 416.6 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


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  #12  
Old 08-08-2017, 08:50 PM
Norcalrv7 Norcalrv7 is offline
 
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Location: McKinleyville CA
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Sort of related:

Ross, are most people drilling a bypass orifice in their fuel pressure regulator? Mine is equipped with one that was about the smallest drill but I could find. I notice when I first turn on the pumps, they growl a little bit for a second or two while the system purges vapor through the returns, then they are fine. 700hrs on the airframe with this fuel pump setup without a single problem.

my pumps are mounted horizontally on the floor in my -7a.

For what its worth, my system has several -6 90's in the suction side, as well as a large area, prefilter.

Caleb
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Based at EKA, Northern CA
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  #13  
Old 08-08-2017, 09:06 PM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by Norcalrv7 View Post
Sort of related:

Ross, are most people drilling a bypass orifice in their fuel pressure regulator? Mine is equipped with one that was about the smallest drill but I could find. I notice when I first turn on the pumps, they growl a little bit for a second or two while the system purges vapor through the returns, then they are fine. 700hrs on the airframe with this fuel pump setup without a single problem.

my pumps are mounted horizontally on the floor in my -7a.

For what its worth, my system has several -6 90's in the suction side, as well as a large area, prefilter.

Caleb
There is no need for a bypass hole in the regulator as the valve already bypasses as much fuel as is required to control the pressure vs. engine demand. I never understood why Jan did this, it was not a fix for having the pumps in a hot place or poor orientation on some installations.

The recommendation to avoid 90s is best, safest possible practice. Many people have at least one 90 before the pump at the fuel selector. The idea is to reduce restriction to minimize the chance of pump cavitation to a minimum. We want the pump inlets flooded so they never need to pull fuel.

The problem is not with 100LL at sea level on a cold day, it's running winter blend mogas on a warm day at high altitude where even the slightest inlet restriction can cause the fuel to "gas".
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW- 416.6 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


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  #14  
Old 08-08-2017, 09:26 PM
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Toobuilder Toobuilder is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
...The problem is not with 100LL at sea level on a cold day, it's running winter blend mogas on a warm day at high altitude where even the slightest inlet restriction can cause the fuel to "gas".
Which explains the lengths I'm going through to minimize inlet restriction - summer in Mojave + big fuel flow + high altitude + "California blend" auto fuel = big potential for vaporization.

My attempt to run that foul car gas may not work out, but I'd hate to leave a 90 in the system and always wonder if that was the one tiny factor that tipped the scales out of my favor. At least now if it vaporizes, I know I did everything I could to prevent it.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

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Last edited by Toobuilder : 08-08-2017 at 09:37 PM.
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  #15  
Old 08-09-2017, 01:13 AM
Norcalrv7 Norcalrv7 is offline
 
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Do we know first hand of someone who has had vapor issues with a high pressure fuel system? I flew my plane to 115F+ Redding CA a few times while running 87 E10 in the Subaru. This was done while using the same fuel system as now. In my case the only difference I saw was maybe an extra second to prime the system when I first turned on the pumps. I'm certainly not saying it isn't of concern, Just curious.

Caleb
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  #16  
Old 08-09-2017, 07:35 AM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by Norcalrv7 View Post
Do we know first hand of someone who has had vapor issues with a high pressure fuel system? I flew my plane to 115F+ Redding CA a few times while running 87 E10 in the Subaru. This was done while using the same fuel system as now. In my case the only difference I saw was maybe an extra second to prime the system when I first turned on the pumps. I'm certainly not saying it isn't of concern, Just curious.

Caleb
Yes, we've seen this several times with poor pump placement on mogas in the summer. We find the engine often continues to run ok but the pumps can fail in a few hours time. They don't take kindly to sucking a vapor and fuel mixture.

Your installation seems to have plenty of margin. That's good that you've tested at the extreme temps. Yikes. You fly at 115F?!!!

The most important thing is to have the inlet as low as possible on an RV which you do.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW- 416.6 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm



Last edited by rv6ejguy : 08-09-2017 at 07:37 AM.
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  #17  
Old 08-09-2017, 10:02 AM
rlmccarter rlmccarter is offline
 
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Location: Charlotte, NC
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Hi Guys,

I'm aiming for a simple design with margin for worst case (mogas at high ambient temp and altitude) - may never do that, but I like margin.

In the -8 there is enough room for SDS' mounting recommendation (low, horizontal, straight inlet) with 90 degree outlet and a service loop to the firewall.

My tech counselor is dropping by tomorrow to put a second set of eyes on the design before I finalize. I'll post pictures in a few days in case it helps others.

Cheers,
Bob
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  #18  
Old 08-09-2017, 10:12 AM
rv8ch rv8ch is offline
 
Join Date: Feb 2005
Location: LSGG
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Default pump(s) in tank

One of you clever engineers/businessmen need to design a kit that puts the pump in the tanks where they belong. Either one in each tank, two in each tank, two in one tank plus a transfer pump. Come on, guys!
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  #19  
Old 08-09-2017, 10:15 AM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by rlmccarter View Post
Hi Guys,

I'm aiming for a simple design with margin for worst case (mogas at high ambient temp and altitude) - may never do that, but I like margin.

In the -8 there is enough room for SDS' mounting recommendation (low, horizontal, straight inlet) with 90 degree outlet and a service loop to the firewall.

My tech counselor is dropping by tomorrow to put a second set of eyes on the design before I finalize. I'll post pictures in a few days in case it helps others.

Cheers,
Bob
You might look at angling the pump module to give you more room for fittings in the diagonal. You can also discharge from one of the side fittings and plug the end fitting to gain more room on the inlet end. Don't fuss too much. One 90 on the inlet should be just fine with the pumps on the floor. Very few people get away with no 90s and they are all working fine.

We're only saying best practice is to avoid putting in multiple 90s on the inlet side.
__________________

Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW- 416.6 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


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  #20  
Old 08-09-2017, 10:18 AM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by rv8ch View Post
One of you clever engineers/businessmen need to design a kit that puts the pump in the tanks where they belong. Either one in each tank, two in each tank, two in one tank plus a transfer pump. Come on, guys!
More complexity with more chances for failure. The recommended setup is proven with tens of thousands of successful flight hours. No need to re-invent the wheel and experiment here IMO.
__________________

Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW- 416.6 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


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