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Ignition Basics & P-Mag timing

akarmy

Well Known Member
Webinar announcement!

Bill and I have worked out the details and would like to announce the webinar.

Subject : Ignition Basics & P-Mag timing
Host : Bill Repucci
When : Thursday Feb 1st at 7pm Pacific / 10pm Eastern
How : Webex online -
Recording : https://youtu.be/u-peJetS028

Here is the agenda from the presentation
  • Introductions
  • Timing Basics
  • Retard Timing
  • Advance Timing
  • Charge Density vs. Fuel-Air Burn
  • Where to set your timing
  • Fact or Fiction – Magnetos vs. Electronic Ignition
  • IECAD & EICommander

If it goes over an hour, I’m either talking too much or you are asking a lot of questions!

Bill Repucci
 
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Thanks for setting this up Andy!

As you can see by the agenda, most of the discussion will be about ignition timing and the latter part about the P-mags and setting their timing to match your engine.
 
recording?

Cool - glad you are doing this. It happens right in the middle of my beauty sleep, which I badly need, so will it be possible to view a recording?
 
Mickey,

And my beauty sleep but we figured with this timing, we would catch most of the US. Europe, AU, NZ, etc. are kind of left out in the cold on this one. Sorry about that.

We were talking about recording it. WebEx has a record feature, so if all goes well, we will post it. That or we might do a second one, over a weekend, date to be determined. If we do that, I'll try to schedule it so we can cover those in the old world and in AU & NZ.

(BTW, you have heard most of what we are going to talk about over the phone.)
 
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Thanks Bill - I'll keep my ears open for a recording, and if I do happen to wake up at 0400 for some reason that day, I'll hop on the call. Always happy to get another chance to digest some good information.
 
Thanks

to Bill and Andy for the presentation. I missed the first half, but it was well worth the visit for what I did hear and see.
 
Thanks for all of you that joined us this evening and brought out some good questions! We enjoyed Bill's presentation and had a good chat about some of the topics around electronic ignitions and PMAGs.

For those that didn't make it, here's a link to the recording.

https://youtu.be/u-peJetS028
 
Thanks Andy for hosting this discussion, posting the video, and for everyone who took time out of their evening to attend. If there is enough interest, we can do a second talk scheduled to cover Europe, AU, and NZ.

There were many good questions, which is always appreciated and helpful to everyone.

Feel free to contact me, if you have any additional questions.
 
Ignition

Just watched it on youtube. Great presentation and I learned a bunch! Thanks Bill and Andy.
 
Webinar

Bill, Andy. Thanks for a very informative webinar.
Is EI Commander working on a remote with EFIS interface? Hopefully Dynon.
Panel space is limited and this info could easily be presented on the Engine panel.
 
Bill, Andy. Thanks for a very informative webinar.
Is EI Commander working on a remote with EFIS interface? Hopefully Dynon.
Panel space is limited and this info could easily be presented on the Engine panel.

Glad you enjoyed it and found it informative.

Talk to Dynon. We would be more than happy to work with them or any other manufacturer.
 
I too, am out of space. Presenting data on glass from various manufacturers of EFIS would be a big seller. Enjoyed the webinar. Thank you for hosting that.
 
I have some minor comments (big shock, right)?

Disclaimer: I watched the first part where you discussed the basics in its entirety, and skipped quickly through the rest of it where you were P-mag and EIC specific, so excuse me if this was covered later.

I hope this post is accepted in the spirit of constructive feedback that is offered.

We are in general agreement on the need to achieve PCP at the optimum crank angle. However, I believe your audience would be better served if you went into more depth on the variables needed to marry up PCP and the 15 ATDC. Flame speed is not constant. The stated data that the normal flame speed of 16.5 m/s is fine to illustrate that there is a flame front that has to travel across the piston (time/distance relationship), but is misleading in that there is a subtle implication that the data plate timing values on the Lycoming will give you PCP@ 15 ATDC. The fact is, an engine needs what an engine needs and it has been my experience that even the data plate values for timing is too advanced/sub optimal for full rich, 100% power. Flight test data I’ve collected indicates that like a fixed pitch prop, factory magneto timing is a compromise at both ends – it works, but it’s still sub optimal at the edges of the envelope. I am completely on board with your message that “more advance does not always equal better”, but until you get some comprehensive flight test data, you might want to hold off on specific recommendation. I have done a lot of in situ flight test on this exact subject and still just scratched the surface. I do know enough to disagree with your base timing recommendations though.

Also, a minor nit – the Angle Valve head is an important part of the performance improvement (over the PV), but so too is the far superior induction system. The large plenum and tuned induction tubes are a radical advance over the standard updraft sump. And the ability to achieve intake resonance is a big influence in charge density. It is the combustion chamber shape and induction tuning that conspire to move the required timing back compared to the PV.

On the subject of angle valve timing, I am anticipating an ignition system change on the RV-8 which has an angle valve on the nose. This will be its 3rd ignition system, and I intend to do an inflight sweep of the timing to emulate the current and previous ignition systems, thereby providing a "near real time” comparison on the distinct timing schemes between them. Among the testing will be sustained 100% power with a test to see just how far the timing can be retarded before the power drops off. Recall I did this experiment on the (parallel valve) Rocket and found a 10 degree sweep to have zero change on the maximum speed, and this included a drop well below the data plate advance, but did not go all the way to the performance dip.

I’ll publish the results here, and I expect that much of your presentation material will be validated, but I think some will be in conflict. In any case, hard data is rare on this subject so we’ll pin it to the wall for future use.
 
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Mike, that is all good and accurate input. However, for a tutorial on "timing basics", it is too much information. (I did mention that efficiency of the intake system also impacts timing, as does the exhaust system. Although I didn't specifically mention the exhaust.)

Maybe we can do an advanced engine tuning WebEx because now you are into more than just timing.

Too bad Bob A. passed away, he could have done one on speed mods. The possibilities are endless.

I was hoping you and/or Ross would have joined the discussion at the end.

It wouldn't surprise me one bit if your "hard data" conflicts with some my presentation. I am talking theory for the most part and discussing middle of the pack timing for standard engines. Once the compression ratio or any of a number of other factors change, the comparison changes. For example, I have a custom FAB on my stock ECi O-360. Flying side-by-side with friend in his -7 with a Lycoming O-360, I was indicating less MAP. We have no idea if it was because I have a -9, my FAB is different, or if my MAP sensor isn't calibrated the same.

Good luck with your new ignition and your tests. Let me know, if I can help.
 
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I too, am out of space. Presenting data on glass from various manufacturers of EFIS would be a big seller. Enjoyed the webinar. Thank you for hosting that.

Please contact your EFIS manufacturer, if you want this feature.

We reached out to a number of them over the years and they were not interested. We will be more than happy to discuss the options with them.
 
Bill, et al.,

I really enjoyed the webinar...very informative. Thank you!

My panel is in the final stages at Aerotronics and the discussion on ignition switches piqued my interest.

My current planned (IO-390, dual PMAGS) setup is a keyed ignition switch [OFF/L/R/BOTH/START] AND two momentarily actuated TEST switches (L and R Ignitions). Is this the optimum set up to be able to control/test my PMAGS? Or would the use of those 3 way switches (discussed in the webinar) be a better set up? I think those were described as down for OFF, Middle for Run, and momentary up for TEST?

Thanks in advance for anyone's input,

Rick
RV-14
140347
FWF
 
Rick, I need to put together a graphic on this.

I'm not a fan of key switches because the swinging keys always scratch the panel. Besides, who in their right mind is going to steal an E-AB? A thief is more likely to empty your panel than take your plane.

Regarding the switchology, my point was that you do not want to pass through "off" when moving from "run" to "test" and back to "run".

The reason is that as you pass through "off" (grounded) with the engine running on one mag, it will pump raw fuel into your exhaust and when the ignition comes back on, it will ignite that raw fuel in the exhaust with a bang.

Andy has some cool spring loaded switches and I have no as cool three way switches.
Andy's are set up as follows :

Up: Test. (Spring loaded position - unpowered and ungrounded.)
Middle: Run (Powered and ungrounded)
Down: Off (Unpowered and grounded)

Mine are set up as follows:
Up: Run (Powered and ungrounded)
Middle: Test (Unpowered and ungrounded)
Down: Off (Unpowered and grounded)

Keep in mind, if you wire them as either of us did, you will have to provide a means to provide power while they are grounded so you can set the timing.
 
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...Maybe we can do an advanced engine tuning WebEx because now you are into more than just timing...

I'll consider that in the future, but there's a lot of data to collect (and avgas to be burned) between now and then.

But yes, I welcome the collaboration opportunity.
 
Three thoughts I wanted to bring to your attention.

1. If you install an EIC, you must send your desired configuration to the P-mags. If not, you will run off the B configuration.

2. If you adjust your configuration with the free EICAD program, you do not install the jumper as you want to run off the modified B configuration.

3. We have an extensive Q and A document that will help you solve a number of P-mag issues. If you would like a copy, email me at bill .at. repucci .dot. com.
 
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For those who will make OSH this year, I will be giving my Ignition Basics talk again.

It is scheduled for Thursday, July 26th at 1 PM in Classroom C.

I hope to see you there.
 
This talk is a basic conversation about how electronic ignitions work and is not necessarily ignition specific.

Come on by and introduce yourself.
 
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