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  #1  
Old 06-24-2021, 05:45 AM
Larry DeCamp Larry DeCamp is offline
 
Join Date: Apr 2010
Location: Clinton, Indiana
Posts: 1,124
Default EFII reliability discussion ?

Rocketman1988 recently commented “ if you drill down far enough, you will find single point failures”. Yes, carbs have floats and orfices. Mechanical injection has one servo. EFII has one circuit board.

So my question is, under what assumption is a single board EFII system viable for an airplane ? You have 4or6 injectors controlled by a single brain. Not really any worse than a single fluid path to the cylinders ???

OK, then lets use two circuit boards to fire the injector coils. How is that managed if one board goes TU, or they simply disagree ?

Your comments would be appreciated.
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  #2  
Old 06-24-2021, 06:31 AM
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rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
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Quote:
Originally Posted by Larry DeCamp View Post
Rocketman1988 recently commented “ if you drill down far enough, you will find single point failures”. Yes, carbs have floats and orfices. Mechanical injection has one servo. EFII has one circuit board.

So my question is, under what assumption is a single board EFII system viable for an airplane ? You have 4or6 injectors controlled by a single brain. Not really any worse than a single fluid path to the cylinders ???

OK, then lets use two circuit boards to fire the injector coils. How is that managed if one board goes TU, or they simply disagree ?

Your comments would be appreciated.
I can only state from our experience in the field with around 1400 aircraft and 400,000+ flight hours over 26 years on single ECU aircraft. Zero ECU failures to our knowledge. With an additional 350,000+ hours on 700 dual board ECUs, we've heard of 2 actual hard ECU failures, one unknown cause, one traced to tie wrapping sensor cables to the spark plug wires (please don't do this).

Have had a few more where the engine ran badly on one ECU where there was a wiring issue like intermittent grounds.

In the case of SDS and dual ECUs, the pilot manually switches to the backup ECU if the engine were to run rough or actually stop.
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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- 449.1 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ



Last edited by rv6ejguy : 06-24-2021 at 07:47 AM.
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  #3  
Old 06-24-2021, 07:30 AM
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rv8ch rv8ch is offline
 
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Location: LSGY
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Default

Quote:
Originally Posted by rv6ejguy View Post
... In the case of SDS and dual ECUs, the pilot manually switches to the backup ECU if the engine were to run rough or actually stop.
I think this is a wise design choice, considering the application, the possible error modes, and the training of the user.
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  #4  
Old 06-24-2021, 07:44 AM
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rv6ejguy rv6ejguy is offline
 
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We looked at trying to automate ECU switch over years ago but after looking at how many different ways something COULD fail and permutations of those ways, it would be very hard to write software to cover all of them with certainty and without making the system more complicated and in fact maybe more likely to fail as a result.

We felt it best to leave ECU control in the hands of the pilot given the number of times the ECUs have actually failed. It's an extremely remote scenario if the system is wired correctly.

We've seen way more problems where things are not wired properly or with best practices or where there wasn't a well designed backup power system available when primary power went down.
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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- 449.1 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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  #5  
Old 06-24-2021, 11:04 AM
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vlittle vlittle is offline
 
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Location: Victoria, Canada
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Quote:
Originally Posted by rv6ejguy View Post
...
We've seen way more problems where things are not wired properly or with best practices or where there wasn't a well designed backup power system available when primary power went down.
Well put. Despite all of the resources available that try to teach best wiring practices and electrical architectures, electricity is still a mystery to many otherwise talented and dedicated builders.

I like it when manufacturers provide detailed wiring procedures. Even for us 'sparkies' it provides a baseline that prevents unintended consequences.

If we want to diverge from the recommendation, it forces us to understand the intent, do the FEMA and take the responsibility.

VV
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  #6  
Old 06-24-2021, 01:19 PM
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rv8ch rv8ch is offline
 
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You've probably already seen it, but here's a pretty interesting case of engine failure with EFII and the resulting crash.

https://www.youtube.com/watch?v=4PHTVTw_Y2A
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  #7  
Old 06-24-2021, 01:38 PM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by rv8ch View Post
You've probably already seen it, but here's a pretty interesting case of engine failure with EFII and the resulting crash.

https://www.youtube.com/watch?v=4PHTVTw_Y2A
Cause was the fuel pumps signed off when the single breaker they were fed from (both pumps plus the hydraulic pump!) tripped as the gear was cycled.

As I said, most failures are due to bad layout, bad wiring or no backup power. This one could not be said to follow best practice.

Whoever made the decision to wire like this simply wasn't thinking at all. Having twin pumps was wasted with this strategy.
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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- 449.1 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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  #8  
Old 06-24-2021, 06:45 PM
rocketman1988 rocketman1988 is offline
 
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Location: Sunman, IN
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Default really?

"...EFII has one circuit board..."

System 32 has two ECUs...
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  #9  
Old 06-24-2021, 07:38 PM
David Z David Z is offline
 
Join Date: Aug 2010
Location: Thunder Bay Ontario
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Just need 4 engines, each EFI powered by it's own electrical system, with two alternators per engine (8 total). That should cover all the redundancy concerns. Lose an EFI, well there's 3 other engines to take you along (sarcasm).

I wonder how the EFI systems (EFII and SDS) compare to FADEC on bigger planes in terms of single point failures and redundancy? Granted they have two engines, but those engines still aren't allowed to quit very often (ETOPS, etc.).
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  #10  
Old 06-24-2021, 07:48 PM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by David Z View Post

I wonder how the EFI systems (EFII and SDS) compare to FADEC on bigger planes in terms of single point failures and redundancy? Granted they have two engines, but those engines still aren't allowed to quit very often (ETOPS, etc.).
Most of our RV customers buy the dual ECU setup. All critical sensors are redundant with 2 fuel pumps as well. Only critical non-redundant part is the injectors and we have not seen one of those fail yet in 750,000+ flight hours. Mechanical FI and carbs also don't have redundant fuel delivery and that seems to be accepted.
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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- 449.1 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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