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  #141  
Old 10-17-2017, 06:36 AM
Chkaharyer99 Chkaharyer99 is offline
 
Join Date: Oct 2011
Location: Pilot Hill, CA
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Quote:
Originally Posted by Flyyak View Post
I have an RV7 with an 0360 A1A which has been converted to Precision Airmotive FI and dual Pmags with firmware 36. At. 98.2 hours the R mag failed and L mag had lateral an axial play in the shaft. Brad at Pmag rebuilt the bearings in L mag and added firmware’ 41 in both. I just reinstalled and they appear to operate fine for first few hours.

The engine was overhauled at engine shop in Florida to zero time.

I understand that others with 0360 A1A engines have had similar issues especially with shaft and bearing problems. If so, please let me know. neilclay@bellsouth.net
Neil,You indicate, "The engine was overhauled at engine shop in Florida to zero time."

Was your engine "overhaul" a result of the problems you described, specifically, "At. 98.2 hours the R mag failed and L mag had lateral an axial play in the shaft. Brad at Pmag rebuilt the bearings in L mag and added firmware’ 41 in both."

Thanks for sharing your experience.
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  #142  
Old 10-17-2017, 06:55 AM
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N363RV N363RV is offline
 
Join Date: Nov 2009
Location: Arlington, tx
Posts: 199
Default Thanks for letting us know.

Quote:
Originally Posted by Flyyak View Post
I have an RV7 with an 0360 A1A which has been converted to Precision Airmotive FI and dual Pmags with firmware 36. At. 98.2 hours the R mag failed and L mag had lateral an axial play in the shaft. Brad at Pmag rebuilt the bearings in L mag and added firmware’ 41 in both. I just reinstalled and they appear to operate fine for first few hours.

The engine was overhauled at engine shop in Florida to zero time.

I understand that others with 0360 A1A engines have had similar issues especially with shaft and bearing problems. If so, please let me know. neilclay@bellsouth.net
Thanks for letting us know about your experience.

For those of you reporting failure modes, please include make and model of your propeller... in addition to your make / model and accessory version of your engine.

Thanks
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  #143  
Old 10-17-2017, 11:23 AM
Bill Boyd Bill Boyd is online now
 
Join Date: Sep 2006
Location: Landing field "12VA"
Posts: 898
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Quote:
Originally Posted by DanH View Post
Ok, discard Nigel's report, and consider timing loss with a known cause, the arcing alternator B-lead.

http://www.vansairforce.com/communit...d.php?t=144336

At first, it was claimed that V40 would have prevented the issue, but that was obvious nonsense, as noted by this gentleman...

http://www.vansairforce.com/communit...0&postcount=31

...and recognized by the manufacturer:

http://www.vansairforce.com/communit...5&postcount=49

So why is it relevant to this particular exercise? The P-mag is unique, in that it's the only ignition which allows the user to insert the body and mesh the drive gear at random, then write a TDC position reference electronically. It's a wonderful feature as it relates to installation and inspection, as it makes timing a P-mag dirt simple. However, all design is the art of compromise. The same feature is an Achilles heel; the easy-to-set TDC position can also be reset. V-40 (and I suspect other patches too) is a example of an attempt to prevent unintended reset given a specific condition. The case of the arcing B-lead is an example of timing reset caused by a less predictable input, so it's not likely to be fixed with a software patch.

All other ignitions physically reference crankshaft TDC to the ignition. As such, installation requires physical alignment of trigger and crankshaft position. Losing that reference requires outright mechanical failure. It is slightly more difficult to install, but more reliable in service.

I've attempted to run though some basic "what if" analysis, which as Mike pointed out, would be followed by an estimate of probability. It does not appear we're going to be able to complete that examination due to lack of information. Frankly, it makes no personal difference to me. I'm just trying to lead the conversation back toward a logical estimation of reliability.

I will say this, based on reported field experience. The major P-mag risk is random timing reset. The major risk with other systems is simply no spark. Random timing can take out an engine. No spark merely means soldiering on with the other ignition.

The architecture which allows random timing reset due to outside factors has nothing to do with the P-mag's significant benefit, its internal power supply. A system with a hard TDC reference and internal power generation would be a heck of an ignition...but that's not what we have here.



Two things, and I'm outta here. One, it is easy to make sparks. The issue is the timing of those sparks. Two, all waste spark systems use the other plug in the paired coil as the return path for the secondary; that's why there is a wasted spark. It is very unlikely that the high voltage secondary is part of the ground path for control electronics.
(I believe they call that a magneto, Dan )
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  #144  
Old 10-17-2017, 08:13 PM
RhinoDrvr RhinoDrvr is offline
 
Join Date: Jun 2014
Location: Lemoore (Fresno), CA
Posts: 47
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Well, here's the conclusion of this thread from my end.

1.) I ended up installing two P-114 P-Mag's in my airplane. Both have v40 software and cooling fins on the case. They were wired with the existing LASAR wiring and manifold pressure lines, as well as blast tubes.

2.) I timed the P-MAG's 2 degrees after TC, so they should fire at 23 degrees at high power, and limit their advance to 32 degrees. Probably limiting the advantage I gain from them, but I like the increase in detonation margins.

3.) During test flight my performance was identical to the LASAR ignition it replaced WRT fuel flows and airspeeds. EGT's were identical, and CHT's were right around 330 degrees on an 80 degree OAT day.

4.) Cruise at 10,500' density altitude 20" / 2400 RPM (60% power) was 8.0 gph yielding around 165kts true.

5.) Idle is smoother now on the P-MAG's than it was on the LASAR, and engine starts are similar to a car. First blade and the engine fires, hot or cold. It's impressive.

6.) I am not 100% sold on the P-MAG's yet. If I have any issues with the timing, or reliability of the unit they're done and will be replaced with a different system, but for the ease of install I felt they showed the most promise at this time. Hopefully I'm not responding to this thread in a few hundred hours saying that I'm installing CPI and a Magneto...
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Last edited by RhinoDrvr : 10-17-2017 at 08:16 PM.
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  #145  
Old 10-19-2017, 07:46 AM
Flyyak Flyyak is offline
 
Join Date: Jan 2012
Location: Birmingham alabama
Posts: 55
Default Pmag reliability

My engine was rebuilt at JB Aircraft in Sebring FL to zero time. I am not a mechanic but I was informed that they have a great history and it has performed great to this point. I have a new constant speed Hartzell blended airfoil prop from Vans.

My engine came with two new Slick mags and harnesses which I removed after reading much about Pmags here. I removed these before installation on the RV.

I have a G3X system so I have been able to monitor the engine functions since first test flight. I had difficulty with oil temps (up to 225-230) a few times in the heat of summer in Bham Al mainly after refueling, touch and goes or during ground times after flights. Also some issues with CHT on climb if not careful. These experiences were not much different than experiences I have followed here by many others.

After I switched from AeroShell mineral break end oil, to 15-50, re-checked and modified engine baffling and changed to Stewart Warner oil cooler, oil temps OK and CHT ok but I am careful on initial climb out.

The Pmags have operated as advertised until the issues previously described. I am a little shaken at the final flight as my passenger was my wife who is a white knuckle flier.

I have certainly enjoyed and learned a ton from this building experience and from this forum. I have the pleasure of flying several different planes and I flew in the Army both RW and FW for 20 years. The RV is one of the most fun and versatile planes I have had the pleasure to fly.

All of the other planes I have flown (except turbines) have magnetos and I have never experienced a failure. The simplicity of the Pmags were a draw for me and I hope my issue was isolated and will not be repeated. I have decided to reinstall a non impulse Slick on the L mag which is the side of the bearing failure.

One of the sources of others with failures is listed in this thread. I spoke with Tim Andres and he experienced 5 different events from bearing failure to general failure of the mag just quitting operations. Both of us have 0360 A1A lycomings. Tim has a fixed pitch prop and I added FI and constant speed prop. After I questioned Brad about the cause of the failure, especially bearing failure with less than 100 hours, he stated that certain engine and prop combos may create an issue with Pmags. I hope that is not the case with my engine but I share my experience with you not as a proponent for any ignition system but as a matter of safety. The failure may be an isolated event which I hope but I will be a great deal more alert with the rebuilt Pmags.

Still running two until the Slick and harnesses arrive. Thanks for this forum. It has been an invaluable help to me during and after construction. Be glad to speak to anyone who wishes more info.

Neil Clay 205-253-9595
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