Matronics Email Lists :: View topic

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Electronic Ignition
Goto page Previous 1, 2, 3, 4

Matronics Email Lists Forum Index -> RV10-List

View previous topic :: View next topic

Author Message

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Wed May 22, 2013 6:50 pm Post subject: Electronic Ignition

I seem to recall G3i using the term "wasted spark".  I chose to get two 

Bendix S-1200 mags, which is the best mag Bendix ever made(same charge 

freshly overhaul as new Slick). Sure, some of the benefits of 

electronics would be nice, but I don't want to do dual bus, dual 

alternator or dual batteries. If 5% fuel savings is true, I save 1 gal 

every 20 hours. Gonna take a lot of hours to pay for the extra expense 

of EI and whatever electrical changes are needed. If Pmag ever shows up 

and gets a few years of development fixing bugs after they are in the 

field, I'll revisit. A friend in RV-7 with E mag and a Pmag had total 

ignition loss a few hundred feet in air, just barely enough to get back 

to runway. A high voltage event had damaged electronics in both mags. Be 

careful with your choices, especially with dual EI.



On 5/22/2013 4:36 PM, John Cox wrote:

 	  Quote: 	
		   This seems the point at which the positives of EI need to be clearly 

 stated  - balanced against their negatives.  Then compared directly 

 with the clear positives of a magneto and its negatives.  When a 

 reader understands the trade-offs they can better understand the 

 frustration with the always coming into the near future Pmag for 6 

 cylinders which was going to solve everything (comes to mind).



 Mr. Barrett (or the lovely Ms Rhonda) could weigh in on why the high 

 performance engines he builds use what they do and why power output 

 diminishes on their dyno with one EI and one magneto. Note: a most 

 popular blend with the RV-10 crowd.  Another question is what do S.D. 

 Tucker, K. Chambliss and M.Goulian bet their lives on??



 Tim's input had something to do with that isolated manufacturing 

 incident with Slick mags a few years ago.  Two Slicks with bad carbon 

 made for a bad day.  Two EI have their own Achilles heal.  As of 

 today, there is still no single right answer.



 Lycoming has made such an advanced engine in their iE2 with knock 

 sensors, variable timing and redundant FADEC wiring for the Lancair 

 Evolution TEO-540-A1A.  The additional price knocked a few willing 

 participants out of the evaluation and they opt for turbine.



 Know your mission, choose wisely, land safely Every Time.



 John Cox

 On Wed, May 22, 2013 at 3:51 PM, Bob Turner <bobturner(at)alum.rpi.edu 

 <mailto:bobturner(at)alum.rpi.edu>> wrote:



     

     <bobturner(at)alum.rpi.edu <mailto:bobturner(at)alum.rpi.edu>>



     Linn,

     Your error is in assuming that a post that starts out "we gotta

     talk" is going to be rational.

     The poster said, correctly, that having two ignition sources and

     two propagating flame fronts helps the fuel burn more completely

     within the alloted time (especially true for fixed timing mags),

     and hence improves engine power and efficiency. (which is why

     there is an rpm drop on runup when operating on one mag).

     He also said, correctly, that if you have an EI plug with advanced

     timing, that its flame front may have propagated past the second,

     mag fired plug, before the mag has fired, and thus the mag is

     "doing no work", to use his words.

     But then he says that this is "bad". If it was bad, then the EI

     guys just wouldn't advance the timing. But they do, because the

     engine runs more efficiently with advanced timing under typical

     cruise conditions. Even if it's only one plug that's advanced. His

     arguement makes no sense. I thought maybe it was an IQ test, to

     see how many people responded.



     --------

     Bob Turner

     RV-10 QB





     Read this topic online here:



     http://forums.matronics.com/viewtopic.php?p=401148#401148



     ===========

     arget="_blank">http://www.matronics.com/Navigator?RV10-List

     ===========

     http://forums.matronics.com

     ===========

     le, List Admin.

     ="_blank">http://www.matronics.com/contribution

     ===========





 *

 *


	


-----

No virus found in this message.

Checked by AVG - www.avg.com

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

Rhonda(at)bpaengines.com
Guest

Posted: Thu May 23, 2013 8:11 am Post subject: Electronic Ignition

Here is Monty’s feedback on the issue….  

   

EI can be “tailored” to a specific ignition advance curve whereas a magneto cannot.   EI can also incorporate a retarded position for improved starting whereas a magneto requires either an impulse coupling OR some type of auxiliary spark creating device.  EI can also be constructed for redundancy necessary for aircraft engines which is a requirement of certification.  

   

Having said all of this magnetos are a very reliable ignition source.  They more or less generate their own power, and if one malfunctions in West Fence Post, Wyoming on a Sunday afternoon, most local mechanics can repair it.  However, with EI you will have to wait on the Brown truck.    

   

There are other inherent problems with EI that is currently marketed.  One of the biggies is that as soon as the engine is started the ignition goes to the fixed advance position which does nothing but increase the CHT.  Another problem with the current crop of EIs is that for every setting of an engine there is a finite point at which peak efficiency is obtained.  It is a function of where the ignition point occurs relative to crank angle in each cylinder.  The requirement for proper ignition “mapping” is a good dynamometer test cell or cylinder pressure measuring equipment, which is very expensive.  The proper ignition point varies with manifold pressure, RPM, mixture strength and inlet temperature.  It is a very complex set of circumstances.   

   

To further explore this subject I need to explain why the M14 EI came into life.  The Russian magnetos are quite heavy, are somewhat troublesome, and parts are extremely difficult to obtain plus there is no overhaul data available.  During the development of the M14 electronic ignition it was decided that no parts of the Russian ignition system were to be used.  We started with a clean sheet of paper.  It was also decided to thoroughly “map” the engine under all possible operating conditions for optimum ignition points.  We have a test cell with that capability.  All this mapping was done on a mule engine that the shop owns.  The M14 electronic ignition is a dual system, i.e. it should not be operated as a one and one system.  There are certain design differences that inhibit this choice.  It is also a coil near plug system (18 individual coils, 1 for each sparkplug), so that a coil loss has minimal effect on the ignition system.  Each controller has a built in alternator which provides power to run that specific system at engine speeds above about 450 RPM.  Once the engine has been started using battery power for the ignition source the engine will keep running normally, even with the master off.  During the “start mode” there are multiple sparks to ensure better starting even with cold weather starts and flooded induction system.  

   

As far as I know Tucker, Chambliss and Goulian all use magnetos: not a bad choice when you consider the logistics  involved.  

   

Monty Barrett  

BPE, Inc.  

   

     

[b]Rhonda Barrett-Bewley[/b]  

[i]Barrett Precision Engines[/i]  

2870-B N. Sheridan Rd.  

Tulsa, OK  74115  

(918) 835-1089 phone  

(918) 835-1754 fax  

www.barrettprecisionengines.com  

        

  

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of John Cox

 Sent: Wednesday, May 22, 2013 6:36 PM

 To: rv10-list(at)matronics.com

 Subject: Re: Re: Electronic Ignition  

  

     

This seems the point at which the positives of EI need to be clearly stated  - balanced against their negatives.  Then compared directly with the clear positives of a magneto and its negatives.  When a reader understands the trade-offs they can better understand the frustration with the always coming into the near future Pmag for 6 cylinders which was going to solve everything (comes to mind).    

   

    

Mr. Barrett (or the lovely Ms Rhonda) could weigh in on why the high performance engines he builds use what they do and why power output diminishes on their dyno with one EI and one magneto. Note: a most popular blend with the RV-10 crowd.  Another question is what do S.D. Tucker, K. Chambliss and M.Goulian bet their lives on??  

    

   

    

Tim's input had something to do with that isolated manufacturing incident with Slick mags a few years ago.  Two Slicks with bad carbon made for a bad day.  Two EI have their own Achilles heal.  As of today, there is still no single right answer.  

    

   

    

Lycoming has made such an advanced engine in their iE2 with knock sensors, variable timing and redundant FADEC wiring for the Lancair Evolution TEO-540-A1A.  The additional price knocked a few willing participants out of the evaluation and they opt for turbine.  

    

   

    

Know your mission, choose wisely, land safely Every Time.  

    

   

    

John Cox  

  

    

     

On Wed, May 22, 2013 at 3:51 PM, Bob Turner <bobturner(at)alum.rpi.edu (bobturner(at)alum.rpi.edu)> wrote:  

--> RV10-List message posted by: "Bob Turner" <bobturner(at)alum.rpi.edu (bobturner(at)alum.rpi.edu)>

 

 Linn,

 Your error is in assuming that a post that starts out "we gotta talk" is going to be rational.

 The poster said, correctly, that having two ignition sources and two propagating flame fronts helps the fuel burn more completely within the alloted time (especially true for fixed timing mags), and hence improves engine power and efficiency. (which is why there is an rpm drop on runup when operating on one mag).

 He also said, correctly, that if you have an EI plug with advanced timing, that its flame front may have propagated past the second, mag fired plug, before the mag has fired, and thus the mag is "doing no work", to use his words.

 But then he says that this is "bad". If it was bad, then the EI guys just wouldn't advance the timing. But they do, because the engine runs more efficiently with advanced timing under typical cruise conditions. Even if it's only one plug that's advanced. His arguement makes no sense. I thought maybe it was an IQ test, to see how many people responded.

 

 --------

 Bob Turner

 RV-10 QB

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=401148#401148

 

 

 

 

 

 

 

 ===========

 arget="_blank">http://www.matronics.com/Navigator?RV10-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

 ===========

 

 

   

  

   

   	  Quote: 	
		    http://www.matronics.com/Navigator?RV10-List 	
0 	  Quote: 	
		   	
1 	  Quote: 	
		   	
2 	  Quote: 	
		   	
3 	  Quote: 	
		   	
4 	  Quote: 	
		   	
5 	  Quote: 	
		   	
6 	  Quote: 	
		   	
7 	  Quote: 	
		   	
8 	  Quote: 	
		   	
9

      [quote][b]

neal.george(at)gmail.com
Guest

Posted: Thu May 23, 2013 9:28 am Post subject: Electronic Ignition

Linn - 

I'm not suggesting that one plug stops firing, but that one plug becomes ineffective. 

Most electronic ignition systems advance spark timing with MAP, RPM or both. Since the magneto doesn't advance, it's spark occurs late in the combustion cycle and therefore doesn't contribute appreciably to the combustion event. 

Recall all the glowing reports you've read from folks after installing a single electronic ignition to replace one mag. "Went out and ran it up and got 100-RPM drop on the mag and zero drop on the EI ". Well... No kidding. The EI fires at 32- or 34-deg BTDC and the mag doesn't fire until 25- or 20-deg BTDC. For all intents and purposes, the mag is not contributing. 



Neal GeorgeSent from my iPhone

On May 22, 2013, at 4:44 PM, Linn <flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com)> wrote:

[quote]                   On 5/20/2013 9:35 PM, Neal George       wrote:

     

      	  Quote: 	
		          	  Quote: 	
		  --> RV10-List message posted by: Neal George <neal.george(at)gmail.com> (neal.george(at)gmail.com)



Tim / Robin (et al) - 



We gotta talk.



Our aircraft engines DO NOT have two ignition sources for redundancy. It's required for best operation. 



The combustion chamber in our opposed air-cooled engines is so big it needs to have the flame lit in multiple locations to achieve reasonable combustion in the time allotted per power stroke. 



If you're running one mag and one EI, you're only running on one plug above idle. 	
     	
     Pardon my ignorance and I'm a little slow so       bear with me.  What you infer is that one plug/cylinder quits       firing???  Why???  Which one quits .... the mag or the EI???

       Well, the mag doesn't quit so that leaves the EI .... which       (AFAIK) doesn't quit ...... so where did you get derailed???

       Linn



[b]

flying-nut(at)cfl.rr.com
Guest

Posted: Thu May 23, 2013 9:41 am Post subject: Electronic Ignition

I'm a little slow but I'm catching up.Â          

       Since our engines are dinosaurs, maybe we should go back and       install another engine control .... like the early cars .... that       changed the timing mechanically.Â  

       NOT!!!

       Thanks for the note.

       Linn

       

       On 5/23/2013 1:28 PM, Neal George wrote:

     

     [quote]              Linn -Â 

       

       

       I'm not suggesting that one plug stops firing, but that one         plug becomes ineffective.Â 

       

       

       Most electronic ignition systems advance spark timing with         MAP, RPM or both. Since the magneto doesn't advance, it's spark         occurs late in the combustion cycle and therefore doesn't         contribute appreciably to the combustion event.Â 

       

       

       Recall all the glowing reports you've read from folks after         installing a single electronic ignition to replace one mag.         "Went out and ran it up and got 100-RPM drop on the mag and zero         drop on the EI ". Well... No kidding. The EI fires at 32- or         34-deg BTDC and the mag doesn't fire until 25- or 20-deg BTDC.         For all intents and purposes, the mag is not contributing.Â 

         

         Neal George         Sent from my iPhone

       

       

         On May 22, 2013, at 4:44 PM, Linn <flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com)>         wrote:

         

       

        	  Quote: 	
		                                 On 5/20/2013 9:35 PM, Neal George             wrote:

           

            	  Quote: 	
		                	  Quote: 	
		  --> RV10-List message posted by: Neal George <neal.george(at)gmail.com> (neal.george(at)gmail.com)



Tim / Robin (et al) - 



We gotta talk.



Our aircraft engines DO NOT have two ignition sources for redundancy. It's required for best operation. 



The combustion chamber in our opposed air-cooled engines is so big it needs to have the flame lit in multiple locations to achieve reasonable combustion in the time allotted per power stroke. 



If you're running one mag and one EI, you're only running on one plug above idle. 	
           	
           Pardon my ignorance and I'm a little             slow so bear with me.Â  What you infer is that one             plug/cylinder quits firing???Â  Why???Â  Which one quits ....             the mag or the EI???

             Well, the mag doesn't quit so that leaves the EI .... which             (AFAIK) doesn't quit ...... so where did you get derailed???

             Linn

           

       



om/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List

s.com">http://forums.matronics.com

om/contribution">http://www.matronics.com/contribution



	
       

No virus         found in this message.

         Checked by AVG - www.avg.com

         05/23/13     [b]

deej(at)deej.net
Guest

Posted: Thu May 23, 2013 9:45 am Post subject: Electronic Ignition

On 05/23/2013 01:28 PM, Neal George wrote:

 	  Quote: 	
		   For all intents and purposes, the mag is not

 contributing. 


	


	You are absolutely correct, but I think there is a fair argument to be

made that it doesn't need to.  The hotter, longer spark from the EI is

not only adequate to run the engine, it does so far more efficiently

than the mag that it replaces.  There are many reports of fuel savings

from replacing just one mag with an EI, which clearly implies that the

engine is performing more efficiently running off the one EI than it did

before running off two mags.



	With one EI and one mag, the mag truly is relegated to the "redundant

backup" category rather than the "necessary to have two mag-fired plugs

in order to burn all of the fuel in the cylinder head" category.



-Dj

-- 

Dj Merrill - N1JOV - VP EAA Chapter 87

Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Glastar Flyer N866RH - http://deej.net/glastar/

jdriggs49(at)msn.com
Guest

Posted: Thu May 23, 2013 10:59 am Post subject: Electronic Ignition

 	  Quote: 	
		  I think D.J. summed it up nicely with this paragraph:"With one EI and one mag, the mag truly is relegated to the "redundantbackup" category rather than the "necessary to have two mag-fired plugsin order to burn all of the fuel in the cylinder head" category."If you do the research on this subject you will find that one EI system will give at least 90% of the claimed gains in fuel and power efficiency. The one mag (in a one mag one EIS system) isn't going to contribute much but it IS adding it's flame within the firing dwell time of the EIS. I would argue that it's probably more important as a backup but it does contribute to flame propagation. It seems like that every EIS company has a different way of getting spark to the cylinders. One is CDI based, another develops the spark via an induction method and another has its built in alternator to fire the plugs. It's been an interesting discussion!!  	




 	  Quote: 	
		   Date: Thu, 23 May 2013 13:45:31 -0400

 To: rv10-list(at)matronics.com

 Subject: Re: RV10-List: Re: Electronic Ignition

 From: deej(at)deej.net

 

 --> RV10-List message posted by: Dj Merrill <deej(at)deej.net>

 

 On 05/23/2013 01:28 PM, Neal George wrote:

 > For all intents and purposes, the mag is not

 > contributing. 

 

 	You are absolutely correct, but I think there is a fair argument to be

 made that it doesn't need to.  The hotter, longer spark from the EI is

 not only adequate to run the engine, it does so far more efficiently

 than the mag that it replaces.  There are many reports of fuel savings

 from replacing just one mag with an EI, which clearly implies that the

 engine is performing more efficiently running off the one EI than it did

 before running off two mags.

 

 	With one EI and one mag, the mag truly is relegated to the "redundant

 backup" category rather than the "necessary to have two mag-fired plugs

 in order to burn all of the fuel in the cylinder head" category.

 

 -Dj

 

 

 -- 

 Dj Merrill - N1JOV - VP EAA Chapter 87

 Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

 Glastar Flyer N866RH - http://deej.ne======================

&gt================
	


 	  Quote: 	
		   

 

 


	


 		 	   		  

  [quote][b]

neal.george(at)gmail.com
Guest

Posted: Thu May 23, 2013 11:48 am Post subject: Electronic Ignition

Dj - Partial agreement. 

The reported efficiencies come from advancing the spark. 

The physics of the combustion chamber remain. The combustion chamber is so large and the stroke so short that two geographically separated sparks are necessary to extract maximum power from each combustion event. 

Not to hijack the thread or change focus, but here's another point to consider. Timing specifics notwithstanding, our engines were tested rigorously and  certificated using two synchronized sparks. (Yes, I understand that many of us are not operating in as-certificated configuration, but isn't that the basis of our safety and performance expectations?). Certification includes prop combinations and vibration analysis for structural integrity. 

Changing the characteristics of combustion initiation changes the characteristics of the power stroke, which changes the vibrations and harmonic response of the engine and its individual components.  Ever seen the result of a thrown counterweight?

Neal George

Sent from my iPhone

On May 23, 2013, at 12:45 PM, Dj Merrill <deej(at)deej.net> wrote:

 	  Quote: 	

 On 05/23/2013 01:28 PM, Neal George wrote:

> For all intents and purposes, the mag is not

> contributing. 

    You are absolutely correct, but I think there is a fair argument to be

 made that it doesn't need to.  The hotter, longer spark from the EI is

 not only adequate to run the engine, it does so far more efficiently

 than the mag that it replaces.  There are many reports of fuel savings

 from replacing just one mag with an EI, which clearly implies that the

 engine is performing more efficiently running off the one EI than it did

 before running off two mags.

    With one EI and one mag, the mag truly is relegated to the "redundant

 backup" category rather than the "necessary to have two mag-fired plugs

 in order to burn all of the fuel in the cylinder head" category.

 -Dj

 -- 

 Dj Merrill - N1JOV - VP EAA Chapter 87

 Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

 Glastar Flyer N866RH - http://deej.net/glastar/

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Thu May 23, 2013 11:48 am Post subject: Electronic Ignition

I'd like to see some actual test data, rather than anecdotal reports. 

Depending on the EI system the spark may be hotter, longer, maybe both, 

although that is less likely. That still is NOT going to create a second 

flame front, nor is the mag spark likely to create one with what little 

fuel remains by the time it fires 10-15 degrees after the first spark. I 

suspect most of the gain is from the advanced timing, not the quality of 

the spark.

Only sophisticated test cell is going to get the kind of data needed.

On 5/23/2013 10:45 AM, Dj Merrill wrote:

 	  Quote: 	
		   -

 	You are absolutely correct, but I think there is a fair argument to be

 made that it doesn't need to.  The hotter, longer spark from the EI is

 not only adequate to run the engine, it does so far more efficiently

 than the mag that it replaces.  There are many reports of fuel savings

 from replacing just one mag with an EI, which clearly implies that the

 engine is performing more efficiently running off the one EI than it did

 before running off two mags.

   




	


-----

No virus found in this message.

Checked by AVG - www.avg.com

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

acsjohn

Joined: 27 Jul 2009
Posts: 15
Location: Australia

Posted: Thu May 23, 2013 2:16 pm Post subject: Electronic Ignition

Just to highlight one of Neal's points, have a look at ATSB investigation 200005572 under factual information regarding propeller failure.

It promotes a lot of thought.

 John RV10 40315

http://www.atsb.gov.au/publications/investigation_reports/2000/aair/aair200005572.aspx

On Fri, May 24, 2013 at 5:47 AM, Neal George <neal.george(at)gmail.com (neal.george(at)gmail.com)> wrote:

[quote]  --> RV10-List message posted by: Neal George <neal.george(at)gmail.com (neal.george(at)gmail.com)>

 Dj - Partial agreement.

 The reported efficiencies come from advancing the spark.

 The physics of the combustion chamber remain. The combustion chamber is so large and the stroke so short that two geographically separated sparks are necessary to extract maximum power from each combustion event.

 Not to hijack the thread or change focus, but here's another point to consider. Timing specifics notwithstanding, our engines were tested rigorously and  certificated using two synchronized sparks. (Yes, I understand that many of us are not operating in as-certificated configuration, but isn't that the basis of our safety and performance expectations?). Certification includes prop combinations and vibration analysis for structural integrity.

 Changing the characteristics of combustion initiation changes the characteristics of the power stroke, which changes the vibrations and harmonic response of the engine and its individual components.  Ever seen the result of a thrown counterweight?

 Neal George

 Sent from my iPhone

 On May 23, 2013, at 12:45 PM, Dj Merrill <deej(at)deej.net (deej(at)deej.net)> wrote:

 > --> RV10-List message posted by: Dj Merrill <deej(at)deej.net (deej(at)deej.net)>

 >

 > On 05/23/2013 01:28 PM, Neal George wrote:

 >> For all intents and purposes, the mag is not

 >> contributing.

 >

 >    You are absolutely correct, but I think there is a fair argument to be

 > made that it doesn't need to.  The hotter, longer spark from the EI is

 > not only adequate to run the engine, it does so far more efficiently

 > than the mag that it replaces.  There are many reports of fuel savings

 > from replacing just one mag with an EI, which clearly implies that the

 > engine is performing more efficiently running off the one EI than it did

 > before running off two mags.

 >

 >    With one EI and one mag, the mag truly is relegated to the "redundant

 > backup" category rather than the "necessary to have two mag-fired plugs

 > in order to burn all of the fuel in the cylinder head" category.

 >

 > -Dj

 >

 >

 > --

 > Dj Merrill - N1JOV - VP EAA Chapter 87

 > Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

 > Glastar Flyer N866RH - http://deej.net/glastar/

 >

 >

 >

 >

 ===========

 arget="_blank">http://www.matronics.com/Navigator?RV10-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

 ===========

 [b]

deej(at)deej.net
Guest

Posted: Thu May 23, 2013 4:45 pm Post subject: Electronic Ignition

On 5/23/2013 3:47 PM, Neal George wrote:

 	  Quote: 	
		   The reported efficiencies come from advancing the spark.


	


     Yes, but advancing the spark also gives the fuel more time to burn, 

which allows for more complete combustion versus the pair of mags, which 

leads to the decrease in fuel consumption.  More power is extracted from 

the same amount of fuel using the EI compared to the pair of mags 

because more of the fuel is being burned at the proper time.



 	  Quote: 	
		   The physics of the combustion chamber remain. The combustion chamber is so large and the stroke so short that two geographically separated sparks are necessary to extract maximum power from each combustion event.


	


     Clearly a more complete combustion event happens from having one EI 

and a mag installed versus having two mags installed, otherwise we would 

not see a decrease in fuel burn at the same power level.



     I would agree that having two EIs firing at the same time produces 

the best, most efficient combustion event, followed by one EI and one 

mag that is only slightly less efficient (by about 10% from reports), 

followed by two mags which is the least efficient.



     Real World data clearly shows that one EI and one mag is indeed 

more efficient (ie, produces a more complete combustion event) than two 

mags, regardless of the difference in timing.

 	  Quote: 	
		   Not to hijack the thread or change focus, but here's another point to consider. Timing specifics notwithstanding, our engines were tested rigorously and  certificated using two synchronized sparks. (Yes, I understand that many of us are not operating in as-certificated configuration, but isn't that the basis of our safety and performance expectations?). Certification includes prop combinations and vibration analysis for structural integrity.


	


     To be fair, the only ignition system available at the time of 

certification was the mag.  I highly doubt any new engine being 

certificated today would use mags.



     Your point about prop combinations and vibration analysis is well 

taken, however.



-Dj

-- 

Dj Merrill - N1JOV - VP EAA Chapter 87

Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Glastar Flyer N866RH - http://deej.net/glastar/

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Thu May 23, 2013 5:03 pm Post subject: Electronic Ignition

You are misinterpreting your observations. Advanced timing does not 

increase the burn time. In fact it likely decreases it, because the burn 

starts while the mixture is still being compressed by the piston. More 

power is generated by the advanced timing, not by any more complete 

burning. If you advance the timing enough, you will get detonation, or 

extremely fast burning. The decrease in fuel burn is simply you getting 

more power for a given throttle setting, and reducing the throttle to 

achieve same airspeed as before. If you advance timing and use same 

throttle settings you will go slightly faster and not save any fuel. It 

is a function of the percent power. Yes, you gain some efficiency IF you 

throttle back, but there still is a price to pay in harmonic vibration 

and the fact that you will lose power if the EI fails from loss of 

battery power or any other reason, just as you lose power if one mag 

fails. Two EI units WILL do better than one plus a mag. Is it as big an 

improvement? Of course not. But it would be an improvement without 

question. Probably in the 10-15% range.

On 5/23/2013 5:45 PM, Dj Merrill wrote:

 	  Quote: 	

 On 5/23/2013 3:47 PM, Neal George wrote:

> The reported efficiencies come from advancing the spark.

     Yes, but advancing the spark also gives the fuel more time to 

 burn, which allows for more complete combustion versus the pair of 

 mags, which leads to the decrease in fuel consumption.  More power is 

 extracted from the same amount of fuel using the EI compared to the 

 pair of mags because more of the fuel is being burned at the proper time.

> The physics of the combustion chamber remain. The combustion chamber 

> is so large and the stroke so short that two geographically separated 

> sparks are necessary to extract maximum power from each combustion 

> event.

     Clearly a more complete combustion event happens from having one 

 EI and a mag installed versus having two mags installed, otherwise we 

 would not see a decrease in fuel burn at the same power level.

     I would agree that having two EIs firing at the same time produces 

 the best, most efficient combustion event, followed by one EI and one 

 mag that is only slightly less efficient (by about 10% from reports), 

 followed by two mags which is the least efficient.

     Real World data clearly shows that one EI and one mag is indeed 

 more efficient (ie, produces a more complete combustion event) than 

 two mags, regardless of the difference in timing.

> Not to hijack the thread or change focus, but here's another point to 

> consider. Timing specifics notwithstanding, our engines were tested 

> rigorously and certificated using two synchronized sparks. (Yes, I 

> understand that many of us are not operating in as-certificated 

> configuration, but isn't that the basis of our safety and performance 

> expectations?). Certification includes prop combinations and 

> vibration analysis for structural integrity.

     To be fair, the only ignition system available at the time of 

 certification was the mag.  I highly doubt any new engine being 

 certificated today would use mags.

     Your point about prop combinations and vibration analysis is well 

 taken, however.

 -Dj

-----

No virus found in this message.

Checked by AVG - www.avg.com

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

deej(at)deej.net
Guest

Posted: Thu May 23, 2013 5:14 pm Post subject: Electronic Ignition

On 5/23/2013 9:03 PM, Kelly McMullen wrote:

 	  Quote: 	
		   Advanced timing does not increase the burn time.


	


     That is correct, and not what I was trying to say.



     Because the spark happens earlier in the cycle compared to the mag, 

the fuel has more time to burn before the piston hits maximum 

compression with the EI than it does with the mag.  This is one reason 

why it doesn't really matter that only the one spark plug of the EI is 

firing versus the two simultaneous mag plugs firing.



-Dj



-- 

Dj Merrill - N1JOV - VP EAA Chapter 87

Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Glastar Flyer N866RH - http://deej.net/glastar/

flying-nut(at)cfl.rr.com
Guest

Posted: Thu May 23, 2013 5:26 pm Post subject: Electronic Ignition

Just thinking out loud .....

I wonder if the increase in burn time is significant since while the EI 

ignition occurs earlier the fuel is not compressed as much and the flame 

front is actually slower at that ignition point. The increased 

compression may cause secondary ignition by the mag ......

Just thinking ....

Linn



On 5/23/2013 9:13 PM, Dj Merrill wrote:

 	  Quote: 	
		   



 On 5/23/2013 9:03 PM, Kelly McMullen wrote:

> Advanced timing does not increase the burn time.



     That is correct, and not what I was trying to say.



     Because the spark happens earlier in the cycle compared to the 

 mag, the fuel has more time to burn before the piston hits maximum 

 compression with the EI than it does with the mag.  This is one reason 

 why it doesn't really matter that only the one spark plug of the EI is 

 firing versus the two simultaneous mag plugs firing.



 -Dj

Display posts from previous:

	Matronics Email Lists Forum Index -> RV10-List	All times are GMT - 8 Hours Goto page Previous 1, 2, 3, 4
Page 4 of 4

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum