Dual P-MAG Reliability in 2017

[Toobuilder]

Originally Posted by DanH

....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...

...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...

Thanks Dan for clinically articulating the engineering challenge P-mag faces.

It seems clear after all these years that the P-mag has battled 3 main issues:

1. Physical alignment and security of the timing magnet.
2. Software driven magnet position (easy to set, vulnerable to random reset)
3. Electronics vulnerable to the operating environment (heat and chemical intrusion)

All of the above could easily be fixed by using an external crank trigger and moving the brains into the cockpit. Add complete adjustability of the curve and you'd have a real winner.

OTOH, add an SD-8 to CPI and you are already there.

[spatsch]

Originally Posted by DanH

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 was applauding your approach of trying to bring logic to this until you made above unsubstantiated claim.

What data do you have to back this up in any way?

You seem to imply that physical TDC alignment in general (not specific to P-Mags) is more reliable then a software/electronics based approach. Having written highly reliable software myself which has run for many years at this point (in other areas) I totally disagree with this broad statement. An electronic/software based TDC setting can be made at least as reliable as a mechanical one if done properly (mechanical once do fail too as you stated yourself).

Now I have no knowledge if P-Mag did it properly or if they fixed it properly after they had those faults. So the one advantage of a mechanical approach is that all of us can look at it and see if we think it's a proper approach whereas with software and most integrated electronics we can not. Only thing we can do on software/electronics is trust the manufacturer and look at overall statistics. If the manufacturer provides no data we are stuck speculating. Openness generates more trust which some manufactures seem to have learned whereas others haven't.

Also just because TDC is set properly doesn't mean the ignition will not fire at random times. There are other possible electronic/software faults which could cause random ignition under a byzantine fault scenario (you mentioned at least one in your thread). So again as soon as you go to ANY electronic ignition you trust the manufacturer to have done the proper fault analysis and use the proper technique. If you actually want to "see" what's going on you really need to stick with the old mags.

Maybe we should have an open source electronic mag project as other communities have for similar things (e.g. drone software/control). That way everybody could look at the code and help the manufacturers to find bugs and fix them. I would doubt that anybody is that open in our community yet though ... .

Oliver

[rv6ejguy]

"Lost Timing" events would certainly worry me.

You can do all the analysis you want but in the end, the system either works properly all the time or it doesn't which means it's either well designed and tested or it isn't.

Nigel's independent testing uncovered several things about the product that people may not have known before. Information is good.

We don't worry about lost timing events or programming changes which don't take hold with SDS because they never happen. Change the timing on CPI and it's instant and accurate to within 1 degree. Shut off the unit or lose power while the engine is turning and it re-initializes and verifies crank position before starting the spark train again when power is restored. Anything else is not acceptable in our view.

[N363RV]

Originally Posted by Ironflight

You know folks, there is a huge amount of useful (and some not so useful - you can sort that out...) data in this thread, but very little of it has to do with "PMAG Reliability in 2017". So most of the really good info will be lost because people aren't going to be able to search for it (let's all admit that the search function is pretty basic here), and they won't look under this title to find info on SDS equipment (for instance).

And there is absolutely no way a Moderator can (or will) sort this mess out.

Think about that folks - if you have presented good, new information here - think about going and starting a new thread. Or it is all lost for posterity.

Paul... this thread has been maddening to read. At this present time I think there over 135 responses.... very few of them actually answer the OP question. I honestly didn't believe there was a moderator reading this thread at all. This thread is so far off the rails it provides very little tangible information regarding the original topic. Paul...you are very respected in this community and I thank you for your comments regarding the thread creep.

[Snowflake]

It would actually be easier for a moderator to remove the posts that *are* on topic, and put them in a new thread... Then rename this one to "SDS Reliability in 2017."

[Dbro172]

They were reliable for us today; dual Pmags since August 2017, one for Easton, one for me

[Flyyak]

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

[erich weaver]

Originally Posted by Flyyak

I understand that others with 0360 A1A engines have had similar issues especially with shaft and bearing problems.

What is the source of this information?

Thanks,
Erich

[Chkaharyer99]

Originally Posted by Flyyak

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.

[N363RV]

Originally Posted by Flyyak

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