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Mags: IRAN Or Exchange?


AlexLev

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On 7/12/2020 at 2:26 PM, MikeOH said:

 

I'm still waiting for a cogent argument about what benefits variable timing brings to a stationary engine.

 

I think I may have one.... Or maybe more...

1) Keeping status quo... won’t get us any improvements....

2) Our engines are not quite stationary...

3) We have a red box and the related detonation we are trying to avoid...

4) We avoid the red box and detonation using timing and mixture...

5) Once the heavy loads of departure, climb, and acceleration are relieved...

6) Things are back in a more stationary mode...

7) This is where we set mixture without fear of detonation...

8) But, this leaves additional benefits still on the table... stationary timing is OK.

9) Advanced timing at this point in the flight would have a small benefit...

10) Efficiency gains are always appreciated...

11) Of course, the gains should be large enough for everyone to be able to measure...

 

So let the early adopters enjoy the advances in technology...

Sit back and watch the results roll in...

If the results meet expectations...

 

One of the things I really liked about @Bob_Belville... his approach towards some new electronic tech...
 

He added things like...

1) an Electronic mag

2) Electronic gyros

3) Electronic engine monitor, the big one JPI930

4) Electronic AOAi


Bob was an EE from MIT WPI (Even better)... and liked to report about the things he was using, and why... :)

If there is one argument for variable timing... for our engines...

We have one phase of flight that would benefit from advanced timing... compared to the other phases of flight...
 

How was that?

PP thoughts only not a mechanic...

Best regards,

-a-

 

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I will grant you that you provided a cogent argument.  However, (you knew that was coming!):

1) Not really an argument; more of a philosophy. I have no issue with improvements.  I have an issue with using new technology just for new technology's sake.  Show me the data that really demonstrates this improvement. I just haven't seen it with E-mags.

2) Compared to a power plant prime mover, yeah, they're not stationary.  Pretty damn close, though.

3, 4, and 5) I have not seen the claim that E-mags will allow us to run in the red-box.  Did I miss something?  I suppose if you backed the timing way off, but why would you as the highly retarded timing would not provide the same power.

6, and 7) Agreed. Normal operation in cruise is stationary and where you want to reap benefits.

8 through 11) Ah, now we're talkin'! The gains I've heard about seem very small, if noticeable at all.  Which makes complete sense: the fixed timing is already set to a near optimal value for where the engine spends the majority of its operational time!

How was that? :)

 

FADECs I believe in: closed loop control of all operational engine regimes.  An electronic ignition system is an integral part of such a system.  This is where, IMHO, the advancements need to be made...but, I'm not sure the market (personal GA) is big enough to justify the development and certification costs.

Bottom line: as stand-alone product E-mags just doesn't make sense to me.  YMMV, naturally

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I was looking for this. Found it.

 

https://www.kitplanes.com/the-effects-of-ignition-advance-on-cylinder-head-temperature-speed-and-efficiency/

 

The money line,

The gains from varying just the ignition timing are real, but small. Most of the efficiency advantage of EI systems likely comes from a higher energy and longer duration spark that allows LOP mixtures to be ignited reliably at high altitude. Once you can ignite a LOP mixture, subsequently varying the timing only has a small impact.

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9 minutes ago, MikeOH said:

I will grant you that you provided a cogent argument.  However, (you knew that was coming!):

1) Not really an argument; more of a philosophy. I have no issue with improvements.  I have an issue with using new technology just for new technology's sake.  Show me the data that really demonstrates this improvement. I just haven't seen it with E-mags.

2) Compared to a power plant prime mover, yeah, they're not stationary.  Pretty damn close, though.

3, 4, and 5) I have not seen the claim that E-mags will allow us to run in the red-box.  Did I miss something?  I suppose if you backed the timing way off, but why would you as the highly retarded timing would not provide the same power.

6, and 7) Agreed. Normal operation in cruise is stationary and where you want to reap benefits.

8 through 11) Ah, now we're talkin'! The gains I've heard about seem very small, if noticeable at all.  Which makes complete sense: the fixed timing is already set to a near optimal value for where the engine spends the majority of its operational time!

How was that? :)

 

FADECs I believe in: closed loop control of all operational engine regimes.  An electronic ignition system is an integral part of such a system.  This is where, IMHO, the advancements need to be made...but, I'm not sure the market (personal GA) is big enough to justify the development and certification costs.

Bottom line: as stand-alone product E-mags just doesn't make sense to me.  YMMV, naturally

Actually I agree with you and can see only minimal, almost immeasurable gains in efficiency and/or LOP operation.  They are there but probably not worth installation on their own.  However, buying a new “mag” for $1200 that is supposed to last 2000hours maintenance free is a cost saver compared to the traditional mags cost, maintenance and overhaul over that same time.  It’s still backed up by a traditional mag if it doesn’t work out.

No way I would put two on right now, but the maintenance cost savings is nice if it pans out and I get the additional benefit of the admittedly small efficiency gain.

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51 minutes ago, Ragsf15e said:

Actually I agree with you and can see only minimal, almost immeasurable gains in efficiency and/or LOP operation.  They are there but probably not worth installation on their own.  However, buying a new “mag” for $1200 that is supposed to last 2000hours maintenance free is a cost saver compared to the traditional mags cost, maintenance and overhaul over that same time.  It’s still backed up by a traditional mag if it doesn’t work out.

No way I would put two on right now, but the maintenance cost savings is nice if it pans out and I get the additional benefit of the admittedly small efficiency gain.

Ok. I think that's the first compelling reason I've heard: Doesn't need maintenance for 2000 hours.

I am curious how they get the rotor to last that long without maintenance?

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1 hour ago, GeeBee said:

I was looking for this. Found it.

 

https://www.kitplanes.com/the-effects-of-ignition-advance-on-cylinder-head-temperature-speed-and-efficiency/

 

The money line,

The gains from varying just the ignition timing are real, but small. Most of the efficiency advantage of EI systems likely comes from a higher energy and longer duration spark that allows LOP mixtures to be ignited reliably at high altitude. Once you can ignite a LOP mixture, subsequently varying the timing only has a small impact.

Interesting.  Could be a second good reason.

However, for my NA Mooney M20F, I've never had any issue running as far LOP as I desire.  That is, once I'm down to 7 gph (10,000 DA, WOT, 65%) I'm going too slow!

Maybe for a turbo at much higher DAs it would provide a benefit when deep LOP.

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  • 2 weeks later...

Thought I'd close the loop...ended up going with Aircraft Magneto Service to do two overhauled exchange units. The timing on the engine was already a bit off and each mag was just around the 500hr mark, so I decided to bite the bullet and just do both.

Cost-wise: it was about $2,000 for the two mags with $300 going back after I send them the core (so 1700)

Labor wise: 11-hours to R&R both mags, convert from a harness to ring-style connector, change oil, manufacture new oil breather hose (exhaust ate into mine), clean+gap spark plugs + boroscope+ compression test each cylinder. Downtime was only 1-day.

My engine purrs now though and I'm really glad I did it.

Edited by AlexLev
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9 minutes ago, AlexLev said:

Thought I'd close the loop...ended up going with Aircraft Magneto Service to do two overhauled exchange units. The timing on the engine was already a bit off and each mag was just around the 500hr mark, so I decided to bite the bullet and just do both.

Cost-wise: it was about $2,000 for the two mags with $300 going back after I send them the core (so 1700)

Labor wise: 11-hours to R&R both mags, convert from a harness to ring-style connector, change oil, manufacture new oil breather hose (exhaust ate into mine), clean+gap spark plugs + boroscope+ compression test each cylinder. Downtime was only 1-day.

My engine purrs now though and I'm really glad I did it.

Were those Slick or Bendix mags?   $300 seems pretty skinny for a core charge.   I think I'd be tempted to keep them as spares for that much.

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1 hour ago, EricJ said:

Were those Slick or Bendix mags?   $300 seems pretty skinny for a core charge.   I think I'd be tempted to keep them as spares for that much.

I just put new slicks on the Cessna and it was $500 (2 cores)

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50 minutes ago, ArtVandelay said:


At that price I would replace them at 1000 hours. FFR, where did you get that price?

I think he's referring to the core charge being $500, Champion recently increased the core charge for new slick mags to $250ea - previously it was $150

Edited by Steve2
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9 hours ago, EricJ said:

Were those Slick or Bendix mags?   $300 seems pretty skinny for a core charge.   I think I'd be tempted to keep them as spares for that much.

Bendix. I’m tempted to keep them or send them in for overhaul or IRAN to keep on the shelf, but we converted from terminal style to ring style connection so not sure if it makes complete sense.
 

For those that have had mags replaced, how much labor does it usually take your mechanic? I have an older vintage Mooney without a ton of room, so I thought the 4-5 hrs per side or so was a reasonable amount of time.

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1 hour ago, AlexLev said:

For those that have had mags replaced, how much labor does it usually take your mechanic? I have an older vintage Mooney without a ton of room, so I thought the 4-5 hrs per side or so was a reasonable amount of time.

I (we) did both mags (6 cyl), new harness and clean the plugs in maybe 6 hrs (less than a days work), A&P checked in on me twice, in all fairness he did turn on the buzz box for me...;)

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On 7/11/2020 at 11:56 AM, toto said:

+1

A failed mag check for me has only ever been caused by a fouled plug. 

Same here. It was due to believing two IAs who said the old plugs were good and also not properly leaning and a too rich at idle carb.  All those things caused bad mag checks. 

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  • 2 years later...
On 7/9/2020 at 7:06 PM, M20Doc said:

Longevity and reliability of magnetos have a lot to do with who does the work.  This is what gets replaced by Aircraft Magneto Service in Montana, and what they look like when they’re finished with them.

Clarence

DA200B16-816B-456C-8023-095DB3D140B8.jpeg

B8D7BD42-A5A5-4DB6-BCC4-6248EDB76028.jpeg

Clarence appears my mag went in the dumper, I have a surefly the other mag which failed the mag test has 480 hours since reman, and 1200 based on GEE BEE he’d exchange for new 

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1 hour ago, Danb said:

Clarence appears my mag went in the dumper, I have a surefly the other mag which failed the mag test has 480 hours since reman, and 1200 based on GEE BEE he’d exchange for new 

On your Bravo aren’t you blessed with Champion/Slick magnetos?

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