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  #21  
Old 10-11-2018, 09:49 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
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Quote:
Originally Posted by Mark33 View Post
Guess Iíve never really understood the purpose of that internal alternator on the 912ís.

Mark
I suspect the designers were looking at...
  • No external drive
  • Minimal add'l weight
  • Simple addition to existing CD ignition coils
  • No moving parts
  • Reliability
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Jim Stricker
Hinckley, Ohio
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PPL/ASEL 1970 - Sport Pilot since 2004
80 hrs Flying Aeronca Chief 11AC
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RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 402

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  #22  
Old 10-11-2018, 10:15 AM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by Piper J3 View Post
I suspect the designers were looking at...
  • No external drive
  • Minimal add'l weight
  • Simple addition to existing CD ignition coils
  • No moving parts
  • Reliability
Probably true. Unfortunately they used a Ducati regulator, not well regarded as far as reliability goes.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 424.4 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


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  #23  
Old 10-11-2018, 10:23 AM
Mark33 Mark33 is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
There are a few options for adding more amps to the 912 charging system already.
I know there's other options for adding additional charging power to the Rotax but what about ditching that entire setup and just going with a single modern external alternator that we're all familiar with. I guess "adding stuff on" goes against the grain for me and my need for clean, concise, and consolidated systems. I really hate to "patchwork" things together. Also, regarding full ignition ďandĒ injection system, is there any reason to keep the stock Rotax ignition systems? Couldnít the SDS ECU handle the both the ignition and injected side just like it does on the Lycoming based engines? I would think that it would be better to consolidate all engine operating parameters into one system instead of a hodgepodge of different components to control the ignition and injection. The bottom line is that if you loose one the othe one isnít going to do you any good. I think having the Rotax setup exactly like we now have our Lycoming based engines with both electronic ignition and injection in one system is the way to go. I've never personally owned or operated a Rotax but I've heard that the ignition system is basically off of a Ducati motorcycle and that it can be troublesome and expensive to fix or replace if needed. So once again, I go back to the question of why not have one consolidated ignition and injection system?? Am I missing something?

Mark
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  #24  
Old 10-11-2018, 10:40 AM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by Mark33 View Post
I know there's other options for adding additional charging power to the Rotax but what about ditching that entire setup and just going with a single modern external alternator that we're all familiar with. I guess "adding stuff on" goes against the grain for me and my need for clean, concise, and consolidated systems. I really hate to "patchwork" things together. Also, regarding full ignition ďandĒ injection system, is there any reason to keep the stock Rotax ignition systems? Couldnít the SDS ECU handle the both the ignition and injected side just like it does on the Lycoming based engines? I would think that it would be better to consolidate all engine operating parameters into one system instead of a hodgepodge of different components to control the ignition and injection. The bottom line is that if you loose one the othe one isnít going to do you any good. I think having the Rotax setup exactly like we now have our Lycoming based engines with both electronic ignition and injection in one system is the way to go. I've never personally owned or operated a Rotax but I've heard that the ignition system is basically off of a Ducati motorcycle and that it can be troublesome and expensive to fix or replace if needed. So once again, I go back to the question of why not have one consolidated ignition and injection system?? Am I missing something?

Mark
Yes, if you can add some more amps to the charging system, we can do fuel and spark control and eliminate the carbs and factory Rotax ignition. This would give bigger economy gains than just the EFI side. There would probably be some weight gain there. Our coil packs weigh around 2 pounds each, not sure what the factory coils, pickups and ignitors weigh.

The Rotax stator ring weighs about 3 pounds. I suppose that could be removed and put towards an external alternator.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 424.4 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


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  #25  
Old 10-12-2018, 07:43 AM
AJSWA AJSWA is offline
 
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Ross, out of interest, what are the additional 912 charging systems you eluded to?
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  #26  
Old 10-12-2018, 08:27 AM
Mark33 Mark33 is offline
 
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Quote:
Originally Posted by AJSWA View Post
Ross, out of interest, what are the additional 912 charging systems you eluded to?
I'm sure Ross will chime in but I think he was referring to a standing external alternator like we were discussing....but there may be other options. If that anemic Rotax charging system could be eliminated and replaced with a standard external alternator, than there would be plenty enough juice to power a complete electronic ignition and and electronic fuel injection system...just exactly like we now have for our Lycoming based engines. This setup would not only allow you to remove the carburetors and the problems that go with them but also allow you to eliminate that Ducati ignition system that comes stock on the Rotax.

Mark
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  #27  
Old 10-12-2018, 01:42 PM
philrisl philrisl is offline
 
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Location: Deltona, FL
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I run a B&C 26 amp alternator driven by the prop governor pad at the back of the gear box in my Rans S19. Works great, ultra reliable and well controlled voltage. I still have the Rotax charging system as a backup with a SH regulator but have never switched to it except at run up to verify its operation.
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  #28  
Old 10-12-2018, 02:05 PM
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rv6ejguy rv6ejguy is offline
 
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This position might limit the intake manifold design options unfortunately. Works fine with the carbs. Rotax does offer a belt driven option and it wasn't even too badly priced last time I looked.

On the RV-12, it looks like the easiest thing to do would be to stick with twin TBs and tap the MAP signal off the balance hose. Use a cross hex drive to activate both throttle plates simultaneously. We could retain the factory cast manifolds and weld injector bosses to those like we did with our earlier systems.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 424.4 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


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  #29  
Old 10-12-2018, 04:48 PM
alexe alexe is offline
 
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Ross,
Would utilizing twin Throttle Bodies lead to possible synchronization issues much like we have with carbs?
Alex
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  #30  
Old 10-12-2018, 05:51 PM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by alexe View Post
Ross,
Would utilizing twin Throttle Bodies lead to possible synchronization issues much like we have with carbs?
Alex
Not if it was designed properly with a stiff hex shaft driving both throttle plates with rigid, adjustable drive arms. Single cable activates the cross shaft. You'd still have to synch them but they would stay that way forever.

There just isn't much room for a single transverse plenum with single throttle body unless we designed a rather intricate custom fabrication, casting, 5 axis CNC'd part or additive manufactured one. In these small quantities, any of those processes= lotsa $ and few would be willing to pay, me thinks. You'd have to move the coolant bottle and ignitors as well. Would look something like the factory iS manifold shape at least.

For charging system upgrades:

https://www.silent-hektik.de/UL_912_LiMa.htm

http://www.ultralightnews.ca/rotax91...rnalAltKit.htm

https://www.cps-parts.com/catalog/rt...xternalalt.php
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 424.4 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


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