Today's Message Index:
----------------------
1. 09:11 AM - Re: Re: Electronic Ignition (Rhonda Bewley)
2. 10:28 AM - Re: Re: Electronic Ignition (Neal George)
3. 10:41 AM - Re: Re: Electronic Ignition (Linn)
4. 10:45 AM - Re: Re: Electronic Ignition (Dj Merrill)
5. 11:59 AM - Re: Re: Electronic Ignition (Danny Riggs)
6. 12:48 PM - Re: Re: Electronic Ignition (Neal George)
7. 12:48 PM - Re: Re: Electronic Ignition (Kelly McMullen)
8. 03:16 PM - Re: Re: Electronic Ignition (John Dunne)
9. 05:45 PM - Re: Re: Electronic Ignition (Dj Merrill)
10. 06:03 PM - Re: Re: Electronic Ignition (Kelly McMullen)
11. 06:14 PM - Re: Re: Electronic Ignition (Dj Merrill)
12. 06:26 PM - Re: Re: Electronic Ignition (Linn)
Message 1
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| Subject: | Re: 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.
Rhonda Barrett-Bewley
Barrett Precision Engines
2870-B N. Sheridan Rd.
Tulsa, OK 74115
(918) 835-1089 phone
(918) 835-1754 fax
www.barrettprecisionengines.com
________________________________
From: owner-rv10-list-server@matronics.com
[mailto:owner-rv10-list-server@matronics.com] On Behalf Of John Cox
Sent: Wednesday, May 22, 2013 6:36 PM
Subject: Re: RV10-List: 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@alum.rpi.edu>
wrote:
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
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| Subject: | Re: Electronic Ignition |
Linn -
I'm not suggesting that one plug stops firing, but that one plug becomes ine
ffective.
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 sin
gle electronic ignition to replace one mag. "Went out and ran it up and got 1
00-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 BT
DC. For all intents and purposes, the mag is not contributing.
Neal George
Sent from my iPhone
On May 22, 2013, at 4:44 PM, Linn <flying-nut@cfl.rr.com> wrote:
> On 5/20/2013 9:35 PM, Neal George wrote:
>>
>> 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 nee
ds to have the flame lit in multiple locations to achieve reasonable combust
ion in the time allotted per power stroke.
>>
>> If you're running one mag and one EI, you're only running on one plug abo
ve 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
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| Subject: | Re: Electronic Ignition |
I'm a little slow but I'm catching up. ;-)
Since our engines are dinosaurs, maybe we should go back and install
another engine control .... like the early cars .... that changed the
timing mechanically.
NOT!!!
Thanks for the note.
Linn
On 5/23/2013 1:28 PM, Neal George wrote:
> 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 George
> Sent from my iPhone
>
> On May 22, 2013, at 4:44 PM, Linn <flying-nut@cfl.rr.com
> <mailto:flying-nut@cfl.rr.com>> wrote:
>
>> On 5/20/2013 9:35 PM, Neal George wrote:
>>>
>>> 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
> *
>
>
> *
>
> No virus found in this message.
> Checked by AVG - www.avg.com <http://www.avg.com>
>
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| Subject: | Re: Electronic Ignition |
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/
Message 5
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| Subject: | Re: Electronic Ignition |
I think D.J. summed it up nicely with this paragraph:
"With one EI and one mag=2C 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."
If you do the research on this subject you will find that one EI system wil
l 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 argu
e that it's probably more important as a backup but it does contribute to f
lame propagation.
It seems like that every EIS company has a different way of getting spark t
o the cylinders. One is CDI based=2C another develops the spark via an indu
ction method and another has its built in alternator to fire the plugs. It'
s been an interesting discussion!!
> Date: Thu=2C 23 May 2013 13:45:31 -0400
> To: rv10-list@matronics.com
> Subject: Re: RV10-List: Re: Electronic Ignition
> From: deej@deej.net
>
>
> On 05/23/2013 01:28 PM=2C Neal George wrote:
> > For all intents and purposes=2C the mag is not
> > contributing.
>
> You are absolutely correct=2C but I think there is a fair argument to be
> made that it doesn't need to. The hotter=2C longer spark from the EI is
> not only adequate to run the engine=2C 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=2C 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=2C 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/
>
===========
===========
===========
===========
>
>
>
Message 6
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| Subject: | Re: 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@deej.net> wrote:
>
> 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/
>
>
>
>
Message 7
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| Subject: | Re: 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:
> -
> 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
Message 8
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| Subject: | Re: 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@gmail.com> wrote:
>
> 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@deej.net> wrote:
>
> >
> > 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/
> >
> >
> >
> >
>
>
Message 9
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| Subject: | Re: Electronic Ignition |
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
--
Dj Merrill - N1JOV - VP EAA Chapter 87
Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/
Glastar Flyer N866RH - http://deej.net/glastar/
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| Subject: | Re: 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:
>
> 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
Message 11
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| Subject: | Re: Electronic Ignition |
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
--
Dj Merrill - N1JOV - VP EAA Chapter 87
Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/
Glastar Flyer N866RH - http://deej.net/glastar/
Message 12
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| Subject: | Re: 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:
>
> 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
>
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