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  #11  
Old 08-12-2022, 07:18 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by Toobuilder View Post
Are you building your airplane on consensus? Seriously, there is so much information out there and so much competition in the decades since the Emag product hit the scene that this is not the forum to make a decision.

What is the mission statement for your ignition? Figure that out and then you can see if the emag aligns. If not, find another product.

You want a quick and dirty? Pmags will often give better performance than magnetos, but have similar (or increased) maintenance requirements. But they have a fixed ignition curve which may or may not suit your engine or how you operate your engine. More modern ignitions offer far more flexibility and versatility which will almost certainly fit your mission.

But Homework is required.
+1

I did not choose Pmags based upon all of the information posted here. I chose a more reliable and more tunable solution similar to the SDS system. Another vote to do your homework first.

Larry
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N11LR - RV-10, Flying as of 12/2019
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  #12  
Old 08-12-2022, 07:20 AM
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rv8ch rv8ch is offline
 
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Location: LSGY
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Quote:
Originally Posted by Tankerpilot75 View Post
How much of a CHT increase should I expect?

...

Iím seeking VAF community insights to help me weight the pros and cons of this decision. Thanks!
If you time the pmag ignitions differently, the CHTs can be lower. It's up to you. Contrary to others, I strongly recommend having a way to see what's going on in the pmag ignitions - there are two products that do this, the enginebridge and the eicommander. I have the eicommander and it gives me real-time info about the timing, and how happy the pmag ignitions are. Not to mention the guy that created it, Bill, is very helpful with any questions about the pmag ignitions.

Timing the pmag ignitions is very easy, once you have read the book and understand what you are doing. Adjusting the timing is a bit more complex, but the documentation is there.

If you are looking for set and forget and never think about it, I recommend getting a regular mag. If you want to understand a bit more, then the pmag is great. If you want to dive in and really tune everything, and are comfortable with electrons, I'd talk to Ross or Robert.
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  #13  
Old 08-12-2022, 07:21 AM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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Originally Posted by Tankerpilot75 View Post
Magnetos are reliable but I’ve even heard Mike Bush suggest electronic ignition for aircraft engines is both modern and better.

I’m seeking VAF community insights to help me weight the pros and cons of this decision. Thanks!
I am not sure that Pmags are anymore reliable than mags. My hanger neighbor just had his Pmag die and had to send it in for repair at well less than 500 hours. Similar stories out there - search for bearing failures. Asking for opinions is not the same as searching for the stories that will paint a picture of reliability and other issues, such as the high CHTs caused by overly agressive timing maps that cannot be adjusted for the operating conditions.

If you are hooked on built in elec b/u then P mag is the only option. However, it has drawbacks too, such as losing that b/u if the RPMs fall below around 800 and won't re energize. Thank about pulling the throttle back on final and then needing to go around. Small SLA batteries cost $25 and are very easy to install. The SDS system even has built in circuitry for charging and using it; Just wire the small battery to their box. Couldn't be easier. You can also do one mag and one EI, then no worries about power source.

Not trying to push my bias here, just trying to drive you to do the research. You have many choices today, however, Caveat Emptor still applies.

Larry
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N11LR - RV-10, Flying as of 12/2019

Last edited by lr172 : 08-12-2022 at 07:36 AM.
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  #14  
Old 08-12-2022, 08:21 AM
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bkervaski bkervaski is offline
 
Join Date: Mar 2017
Location: Birmingham, Alabama
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Quote:
Originally Posted by lr172 View Post
I am not sure that Pmags are anymore reliable than mags.

Asking for opinions is not the same as searching for the stories that will paint a picture of reliability and other issues, such as the high CHTs caused by overly agressive timing maps that cannot be adjusted for the operating conditions.

Think about pulling the throttle back on final and then needing to go around.
A couple notes:

Regarding reliability; agree that PMags seem to be as reliable as dinosaur mags, with the added benefits mentioned

Haven't heard of any high CHT issues, sounds more like a cooling problem. I can climb at full power to 10,000 on a 105 degree F humid day here in Alabama and never hit 385. About the only time I can exceed 385 is if I'm dragging it around at 75kts trying to "keep up" with my buddies in cubs, etc. Will definitely heat up then due to the lack of airflow over the cylinders, I usually have to break off to get it cooled down. Not really a PMag specific thing.

Talking about the PMag generators only working above 800rpm, true, but your ship power happily picks up the slack. However, try getting your prop below 1000 rpm on final, not sure it's possible.
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Last edited by bkervaski : 08-12-2022 at 08:28 AM.
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  #15  
Old 08-12-2022, 08:47 AM
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jcarne jcarne is offline
 
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Quote:
Originally Posted by bkervaski View Post
A couple notes:

Regarding reliability; agree that PMags seem to be as reliable as dinosaur mags, with the added benefits mentioned

Haven't heard of any high CHT issues, sounds more like a cooling problem. I can climb at full power to 10,000 on a 105 degree F humid day here in Alabama and never hit 385. About the only time I can exceed 385 is if I'm dragging it around at 75kts trying to "keep up" with my buddies in cubs, etc. Will definitely heat up then due to the lack of airflow over the cylinders, I usually have to break off to get it cooled down. Not really a PMag specific thing.

Talking about the PMag generators only working above 800rpm, true, but your ship power happily picks up the slack. However, try getting your prop below 1000 rpm on final, not sure it's possible.
Bill aren't you also running an IO-390 timed to 20 degrees? I thought those engines naturally run a little cooler

I have a well done baffle system on my engine and if my Pmag is timed at TDC on my IO-360 in those conditions I will approach 400 easily in climb. I took out about 4 degrees of timing recently and my CHTs now top out around 385 in hot conditions on climb. I have even started climbing at a slightly slower speed too so the heat reduction was very noticeable indeed.
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Last edited by jcarne : 08-30-2022 at 09:45 PM.
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  #16  
Old 08-12-2022, 09:08 AM
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bkervaski bkervaski is offline
 
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Quote:
Originally Posted by jcarne View Post
Bill aren't you also running an IO-390 timed to 20 degrees? I thought those engines naturally run a little cooler

I have a well done baffle system on my engine and if my Pmag is timed at 25 degrees on my IO-360 in those conditions I will approach 400 easily. I took out about 4 degrees of timing recently and my CHTs now top out around 385 in hot conditions. I have even started climbing at a slightly slower speed too so the heat reduction was very noticeable indeed.
I am, and in fairness to the topic, most of the RV folks I talk on a regular basis to are 14 builders or flyers.
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  #17  
Old 08-12-2022, 09:16 AM
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Toobuilder Toobuilder is offline
 
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As I said before, there are hundreds of threads on this site debating this exact question. One even has a "comparison matrix" built in which lists features and price and other pertinent data.

Lets throw out some facts, most of which are gleaned from those threads:

The Pmag initial curve is more aggressive than required for most engines, especially the AV. It is that "over" advance that drives much of the newly dscovered CHT issues.

The Pmag is maintenance intensive. It has many moving parts which need to be inspected every annual. Per the user manual, that inspection requires removal from the airplane.

"Back up power" for any dedicated EI that I know of is very modest indeed. As an example, The SDS CPI pulls slightly over 1.5 amps for a 540 at max RPM. I have measured this in flight. It does not take much of a battery to provide that low current draw for many many hours. The existing ships battery would fly that for days. Your "back up power" plan could be as simple as wiring the ignition directly to the existing battery.

PMags work "fine" for most people (just like magnetos) but they are pretty old school and have been eclipsed in the decades since they came out. If you really, really HAVE to stick with the "self powered" feature, then my advice is to stick with a mag in one hole to satisfy the security blanket issue, and go with SDS CPI on the other side, wired direct to the battery. It's flexibility will overcome the limited curve offered by the Pmag or other ignitions, and allow pretty much the full benefit of the most capable ignition system out there. Just make sure to order the dual hall sensor pickup so you dont have to change it out when you decide to dump the mag for good.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

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  #18  
Old 08-12-2022, 10:00 AM
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Carl Froehlich Carl Froehlich is offline
 
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Location: Dogwood Airpark (VA42)
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Some thoughts:
- CHTs. Yep - get more power out of a cylinder and CHTs go up. Take the timing too far advanced and the CHTs goes up. PMags are close to base timing (whatever you set them at) on take off and full power - so results will be very close to a mag set at that same timing. My many years of flying behind pMags demonstrate no issue with CHTs compared with a mag. I run the pMags (parallel valve 180hp IO-360) at base timing of 25 degrees with the pMag jumper in.
- CHTs. In LOP cruise I routinely get CHTs below 350 degrees in summer. Following Mike Busch’s Lycoming stuck valve guidance, I tend to add fuel to get to closer to peak EGT to keep CHTs around 350 (this also provides an excuse to burn a little more fuel and go faster). Here is his article on the subject:
https://resources.savvyaviation.com/...lves-stick.pdf
- There is intrinsic value in having engines that run without excessive pilot interaction. While I’m sure there is a covey of pilots that want to tweak engine parameters on a real time basis, I suggest for most there is little practical benefits on engine power or efficiency compared to dual pMags and a balanced traditional fuel injection system. But shoot fire - build what you want, just take with a grain of salt the “this is required” opinions.
- I’ve read most of the ship power dependent electronic ignition install manuals. I have no doubt these systems work as advertised. Considering my experience “fixing” electrical stuff in other experimental builds I fear only a minority of builders using ship power dependent installs produce a redundant power distribution design to keep the fan running for at least a couple of hours (bare minimum for my mission needs) after any single component, wire, breaker, solenoid, switch, junction, etc. failure. I’ve found ship power dependent dual EI installs with the back up battery (installed per the EI manufacture’s guidance) below 2vdc terminal voltage. The list goes on.

So my strong recommendation is to view your ship as a system with components that interact. Adding something without careful study of the impact on the rest of the system is how bad things happen. This is especially true for our modern IFR avionics and ship power dependent engines.

Side note. My first build had dual ship dependent EIs. I found the backup power recommendations in the install manual not adequate, and designed my own system and then tested it for the most practical electrical system failures. It worked as designed. But, that system was removed and replaced with dual pMags after 300 hours. I experienced multiple problems with them - driving the move to pMags

Carl

Last edited by Carl Froehlich : 08-12-2022 at 11:00 AM.
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  #19  
Old 08-12-2022, 11:43 AM
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MacCool MacCool is offline
 
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Quote:
Originally Posted by Toobuilder View Post
Are you building your airplane on consensus?……But Homework is required.
Of course, one key component in doing one’s homework on a Van’s RV maintenance topic is a post on VAF asking for opinions from the many knowledgeable folks here. I wouldn’t view that as building my airplane on consensus, but rather using that consensus as a starting point in doing my homework.
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  #20  
Old 08-12-2022, 12:53 PM
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RWoodard RWoodard is offline
 
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Location: Brighton, Colorado
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Quote:
Originally Posted by MacCool View Post
Of course, one key component in doing oneís homework on a Vanís RV maintenance topic is a post on VAF asking for opinions from the many knowledgeable folks here. I wouldnít view that as building my airplane on consensus, but rather using that consensus as a starting point in doing my homework.
That's kinda what I was thinking when someone objected to the initial question.

I've got a single pMag and a Bendix mag on my RV-3. Works just fine as far as I'm concerned. I did experience hot CHTs on my new somewhat enhanced engine rebuild until I de-tuned the timing curve by about 3-4 degrees.

My theory is that the lower compression B-flat engines with zero mods that spend most of their time at sea level can probably get away with the stock pMag timing installation at 0 degrees. The higher your field elevation and the more modified your engine, the more you'll want to de-tune the timing curve by timing the mag at something after 0 degrees. My engine has slightly higher compression and a Stage III cam. My home airport is 5,000'MSL. When I researched this several years ago, I was told that the timing advance starts at 25" of manifold pressure. For most folks, this is well into the climb or maybe even a cruise altitude. For me, it's usually a couple hundred feet subterranean!

Yesterday, I climbed from 5,000 field elevation to 14,500'MSL and just barely hit 400 degrees CHT. This morning I climbed from 6,800 field elevation to 13,500'MSL and made it to 395 before leveling off.

At 14,500'MSL (about 15,750 density altitude) I was burning about 5.7gph truing out at 165 knots. Not too shabby for a little RV-3 with an IO-320!
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