VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #1  
Old 10-19-2019, 08:28 PM
svyolo svyolo is offline
 
Join Date: Oct 2017
Location: bellingham, wa
Posts: 150
Default EFI wiring question/philosophy

I am wiring up my SDS fuel injection. I was planning on using some automotive style (Delphi) multi-pin connectors on the cold side of the firewall to connect everything to the engine. I could just unplug them if I wanted to remove the engine. Lots of cars do it similarly where they have plugs mounted on the engine so the engine can be replaced as a complete assembly, wiring intact.

I am wondering how practical or necessary this is on an airplane. Is the value this adds worth the additional failure points induced?

I have a lot of experience with DC wiring. I can crimp, and I can solder. I have done very large amounts of both. But I have never owned an airplane.

I ask this here instead of the electrical section because it is specific to EFI.

Thanks for any answers/opinions.
Reply With Quote
  #2  
Old 10-20-2019, 08:49 AM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
 
Join Date: Jul 2009
Location: Mojave
Posts: 4,372
Default

In my opinion the only way this would be useful is if you planned to change engines quickly for some reason. This would also require that you had a second engine (and harness) built up and ready to install at a moment's notice.

In reality, the engine harness is a "lifetime" install. I hard wired mine from the engine components to the ECU. As long as the engine side harness can be separated from the engine without cutting wire or metal I think you have as much engine change/maintenance utility as you need.
__________________
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.

Michael Robinson
______________
Harmon Rocket II -SDS EFI - Flying
RV-8 - Flying
1940 Taylorcraft BL-65 -flying
1984 L39C - flyable, available for sale
Reply With Quote
  #3  
Old 10-22-2019, 09:01 PM
svyolo svyolo is offline
 
Join Date: Oct 2017
Location: bellingham, wa
Posts: 150
Default

I was also considering putting a fuel pressure switch on the pressure side, and if fuel pressure drops below a specific level, lets call it 30 psi, the second pump automatically turns on. Has anybody else done this?
Reply With Quote
  #4  
Old 10-22-2019, 09:26 PM
Mike S's Avatar
Mike S Mike S is offline
Senior Curmudgeon
 
Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 14,831
Default

Quote:
Originally Posted by svyolo View Post
I was also considering putting a fuel pressure switch on the pressure side, and if fuel pressure drops below a specific level, lets call it 30 psi, the second pump automatically turns on.
Consider if the low pressure was due to a leak in the engine compartment.

Consider if there was a fire from that leak.
__________________
Mike Starkey
VAF 909

Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

Sold after 240+ wonderful hours of flight.

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
Reply With Quote
  #5  
Old 10-23-2019, 05:46 AM
emsvitil's Avatar
emsvitil emsvitil is online now
 
Join Date: Oct 2019
Location: SoCal
Posts: 75
Default

Quote:
Originally Posted by Mike S View Post
Consider if the low pressure was due to a leak in the engine compartment.

Consider if there was a fire from that leak.

A compromise would be to have the low pressure switch on a toggle so that you could have the 'automatic' feature only be on during takeoff and landing.

You'd also want a warning light if the 'automatic' feature has been activated.

You would need to use a latching relay so that the backup stays on until you turn it off.
__________________
Ed
Reply With Quote
  #6  
Old 10-23-2019, 08:43 AM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
 
Join Date: Jul 2009
Location: Mojave
Posts: 4,372
Default

Quote:
Originally Posted by svyolo View Post
I was also considering putting a fuel pressure switch on the pressure side, and if fuel pressure drops below a specific level, lets call it 30 psi, the second pump automatically turns on. Has anybody else done this?
My second pump is wired to and labeled to my former "boost pump" switch. No harm running both pumps at the same time, and more importantly, no need to unlearn decades of muscle memory and training.
__________________
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.

Michael Robinson
______________
Harmon Rocket II -SDS EFI - Flying
RV-8 - Flying
1940 Taylorcraft BL-65 -flying
1984 L39C - flyable, available for sale
Reply With Quote
  #7  
Old 10-23-2019, 09:04 AM
airguy's Avatar
airguy airguy is offline
 
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 4,743
Default

Quote:
Originally Posted by emsvitil View Post
A compromise would be to have the low pressure switch on a toggle so that you could have the 'automatic' feature only be on during takeoff and landing.

You'd also want a warning light if the 'automatic' feature has been activated.

You would need to use a latching relay so that the backup stays on until you turn it off.
And there goes the way of Boeing - overengineering a simple task.

If the fuel pressure drops, you'll know it by the engine coughing, no lights needed. Flip the switch and move on. No need to add more points of failure.
__________________
Greg Niehues - PPSEL, IFR, Repairman Cert.
Garden City, TX VAF 2019 dues paid
N16GN flying 500 hrs and counting! Built an off-plan 9A with too much fuel and too much HP. Should drop dead any minute now.
Reply With Quote
  #8  
Old 10-23-2019, 10:09 AM
Ralph Inkster Ralph Inkster is offline
 
Join Date: Feb 2008
Location: Calgary, Alberta
Posts: 556
Default

Thoughts on installing the wire harnesses on the engine & having reasonable serviceability later. Consider not using grommets to pass the harnesses thru the baffling, instead create a plate/grommet affair large enough that the full harness & connectors (coil connectors, injector plugs for example) could pull thru if you ever have to take the engine off.
Others may help here with description failure symptoms of hi press/hi volume electric pumps they have experienced.
What we experienced in the one unit (not sold by SDS) that went bad on us is no loss of pressure but caught a lot of brass debris in the down line filter(gascolator). We caught this one before catastrophic failure and because of the down line filter didn’t experience any injector issues. Our 45 psi fuel didn’t drop & if it did, say to 30, we feel the engine would have told us we had an issue much before it degraded to that level, with power loss in progressing lean running. First item on our check list for power loss is second fuel pump than change tank, as mentioned above, a long learned response. I wouldn’t automate this for reasons mentioned by other posters.
__________________
Ralph
Maintain lots, upgraded - repaired - & modified more, rebuild a few, & built some too.

Last edited by Ralph Inkster : 10-23-2019 at 10:13 AM.
Reply With Quote
  #9  
Old 10-23-2019, 04:14 PM
svyolo svyolo is offline
 
Join Date: Oct 2017
Location: bellingham, wa
Posts: 150
Default

I will just put it on a switch. And no big connectors on the wiring harness. Thanks for all the input.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 11:16 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.