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  #1  
Old 01-20-2021, 10:21 PM
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rockitdoc rockitdoc is offline
 
Join Date: May 2020
Location: Fort COllins, CO
Posts: 208
Default Replace Plain Mag with E-Mag Option

On the Thunderbolt order form there are lots of option choices for mags, impulse mags, e-mags, etc.

Std layout is one plain mag and one impulse mag.

One option is replacing the plain mag with an e-mag. This would leave an impulse mag and an e-mag.

I have searched a bit and am still somewhat confused. I understand the E-mag is electronic, so the engine has one conventional magneto and one electronic. What I don't understand is the difference between the 'plain' magneto and the 'impulse' mag. and why there is no option for a plain mag and an e-mag.
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Begun 07-23-20
Emp Completed 11-12-20
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Thunderbolt EXP119 expected 7-21
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  #2  
Old 01-21-2021, 07:22 AM
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rockitdoc rockitdoc is offline
 
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Location: Fort COllins, CO
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Default

Quote:
Originally Posted by rockitdoc View Post
On the Thunderbolt order form there are lots of option choices for mags, impulse mags, e-mags, etc.

Std layout is one plain mag and one impulse mag.

One option is replacing the plain mag with an e-mag. This would leave an impulse mag and an e-mag.

I have searched a bit and am still somewhat confused. I understand the E-mag is electronic, so the engine has one conventional magneto and one electronic. What I don't understand is the difference between the 'plain' magneto and the 'impulse' mag. and why there is no option for a plain mag and an e-mag.
Figured it out. Impulse mag has a different drive gear. Replacing it is more complex.
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14A
Begun 07-23-20
Emp Completed 11-12-20
Slo Fuse Completed 3-2-21
QB Wings delayed until ?
Finish Kit expected 5-21
Thunderbolt EXP119 expected 7-21
2021 Dues Paid
Reserved: N52XL
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  #3  
Old 01-21-2021, 07:31 AM
Maxrate Maxrate is offline
 
Join Date: Dec 2008
Location: League city, TX
Posts: 593
Default

I have a friend running one Slick and one pmag on his Glasair. He has around 1200 hrs on his setup and has only sent the pmag in for overhaul once, and the slick twice. I called emag and they said basically the slick is along for the ride and there as a backup.

I installed dual pmags on a friends skybolt. Youíll need the non impulse gear if you ever decide to change to dual pmags. I would call to get that mag changed to a non impulse on your order.
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  #4  
Old 01-21-2021, 07:55 AM
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jcarne jcarne is online now
 
Join Date: Jul 2016
Location: Worland, Wyoming
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Default

This is certainly rare but see this thread I started awhile back. Those impulse couplers have had multiple AD's over the years and I am certainly not the only person that has had one fail and cause damage to other parts of the engine. I won't ever put an impulse coupler back into any of my engines.
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  #5  
Old 01-21-2021, 08:37 AM
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wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 4,292
Default Impulse to Pmag

Quote:
Originally Posted by rockitdoc View Post
Figured it out. Impulse mag has a different drive gear. Replacing it is more complex.
I just swapped mine. The Impulse mag comes out just like the non impulse.
Difference is there is a spacer that comes off and the two studs have to be removed and replaced with shorter studs.
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I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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  #6  
Old 01-21-2021, 08:46 AM
pa38112 pa38112 is offline
 
Join Date: Mar 2008
Location: Clarksboro, NJ
Posts: 923
Default

An impulse coupling is for starting your plane. Without it, the mag does not produce as much current at the low speed of cranking your engine with the starter. The impulse is a spring-loaded mechanism that speeds up the rotor just before it is time to fire. Once the engine is running there is a centrifugal force that disengages it. They are usually only installed on one magneto. Your ignition switch is wired to ground out the non impulse magneto during cranking. P-mags use battery power co create the spark. If you have one p-mag you do not need an impulse coupling on the magneto. The p-mag will start the engine and then the magneto will come up to speed.
When you run a P-mag, it advances the spark timing based on RMP and manifold pressure. Once it starts to advance it, it is then firing before the magneto (which is always firing at 25 degrees before top dead center). In that case, the fuel is already burning by the time the magneto fires. The magneto is not really helping your combustion, so it only there as a back-up incase the P-mag fails. It is better to have the fuel/air mixture begin to burn from both plugs for more complete and efficient combustion.
I run two P-mags. I feel that there is sufficient redundancy since each has a separate internal back-up power supply.
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  #7  
Old 01-21-2021, 08:56 AM
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rockitdoc rockitdoc is offline
 
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Ive decided to go full monty. Ordered engine with one emag and none on other side. I told lycoming the plan is to put on a second emag. Lycoming cant put second emag on at factory cuz of lawyers. So, they will prep engine for second emag. Btw, i emailed both emag and lycoming re this plan and they both got back to me immediately. Impressive.
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Begun 07-23-20
Emp Completed 11-12-20
Slo Fuse Completed 3-2-21
QB Wings delayed until ?
Finish Kit expected 5-21
Thunderbolt EXP119 expected 7-21
2021 Dues Paid
Reserved: N52XL
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  #8  
Old 01-23-2021, 12:15 PM
msmst25 msmst25 is offline
 
Join Date: May 2020
Location: West Linn, OR
Posts: 125
Default Reference

Iím wondering if anybody can recommend a good book or other reference source that describes these things. I donít know much about engines, and Iíd like to learn, but find it difficult to piece the information together from multiple posts on forums. Is there a book about aircraft systems that anybody recommends which would include things like differences between ignition systems?
Thanks for the help.
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  #9  
Old 02-13-2021, 04:32 PM
klh1507 klh1507 is offline
 
Join Date: Jun 2017
Location: Meridian, Idaho
Posts: 6
Default Another good book

"Powering Your Plane" by David Prizio. Available on EAA's website.
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  #10  
Old 02-14-2021, 01:52 PM
Scott Hersha Scott Hersha is offline
 
Join Date: Jan 2005
Location: Cincinnati, OH
Posts: 1,790
Default

I replaced my impulse mag (left side) with a SureFly SIM, as recommended by SureFly because of impulse coupling issues and ADís. I start the engine on the SureFly. This setup is the same price as the non-impulse replacement, keeping the impulse mag spacer on the accessory case. If my right side Slick goes TU, Iíll install a second SureFly on the right, and then I could use either/both SIMís for engine start.
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