PMag Questions

[jbDC9]

Originally Posted by GOFT

I am not to keen to try hand propping an O-390.
A C-65 perhaps.

Thread drift; I hand propped an IO-520 on a Baron 58 once. Just once. Was the easiest hand prop I’ve ever done, and I suspect that was all luck. I certainly wouldn’t want to try it again.

[Walt]

Don't get me wrong, I think Brad and the others at EMAG do a great job and provide excellent service, a model company in that regard.
I just think some of the touted advantages as compared to mags are somewhat exaggerated, lately I've sent back a number of units for bearing changes which ends up costing around a kilo buck (for 2 units) with service cost and labor for customers. I've also had to spend quite a bit of time correcting/repairing bad wiring/installations at the less-than-ideal connector they use.
Are the advantages worth it, for some folks perhaps it is, for me, not so much.

[jcarne]

Originally Posted by Bavafa

Carl is not alone, I often get it started in one blade as well when cold engine. About 2 seconds of the boost pump is the right amount to get it started that way.Over priming usually causes more cranking for me.

I talked to Carl on the phone and have a subtle change I’m going to try. I think I am getting too much fuel often times. Sorry for the thread drift guys.

[DCBrown198]

Away from home I had one 6-cylinder PMAG internal alternator fail at 45 hours. Unit still provided excellent ignition for start, and flight. Had I developed a dead electrical system then that one PMAG would have died. I have two...so the redundancy was acceptable for the flight home. Emag promptly repaired the unit at no charge.

RV-10 builders take note. If you have your aircraft battery(s) in the rear as the plans call for, and you pull your bus power from the battery side of the starter contactor at the firewall, as the Van's generic electrical system describes, you may have starting problems with the PMAGs.

This is rooted in the voltage drop seem at the starter contactor as the starter is pushing the engine thru each compression stroke. Turns out that the voltage drop at the upper stage of each cylinder compression (right before the PMAG fires during start) is just enough to affect the PMAG and it may not send a spark at TC. After much frustration and trying to figure out why my engine would not start I was informed of this RV-10 issue by Brad.

The solution was to run a new #6 wire from the battery contactor at the rear battery to the buses up front so as to avoid the voltage drop developing on the #2 wire at the starter contactor. This seems to have solved the problem.

Furthermore, Brad advised on building in the ability to "boot strap" an independent electrical power capability to the PMAG(s) in the event of a weak main battery. If you you have a weak battery you may get the engine to turn over...but that weak battery almost assuredly will be at a voltage during start that will prevent the PMAG(s) from firing.

My solution was to buy a cheap 8 AA cell battery pack with plug from Amazon. I keep it in one of the seat backs. Should I have a weak main battery I simply plug my AA cell pack into a receptacle behind the instrument panel. This receptacle is wired directly to the PMAG power (bypassing the normal power switch). Works like a champ. Using this setup with a weak battery, if the starter can get one of the cylinders to TC, my PMAG will throw a spark.

David

[Carl Froehlich]

David,

A weak battery is a weak battery. This is the root problem. Your running additional wires may mitigate but does not address this problem.

I can report that my dual PC-625 battery install in my old RV-10 never had this problem. The new RV-10 will be done the same.

Carl

[lr172]

Originally Posted by Walt

Don't get me wrong, I think Brad and the others at EMAG do a great job and provide excellent service, a model company in that regard.
I just think some of the touted advantages as compared to mags are somewhat exaggerated, lately I've sent back a number of units for bearing changes which ends up costing around a kilo buck (for 2 units) with service cost and labor for customers. I've also had to spend quite a bit of time correcting/repairing bad wiring/installations at the less-than-ideal connector they use.
Are the advantages worth it, for some folks perhaps it is, for me, not so much.

I am a believer in the fuel efficiency benefits of EI, with proper advance, in cruise. But just do not get the fascination with Pmags. 100 hour inspections, $500 bearing replacements, automatic timing changes, sub-par connectors, no warranty if over a certain unobtainable temperature, etc. My EI has magnets on the flywheel with 0 maintenance and electronics on the cold side of the firewall. A $200 inspection or a $500 bearing swap easily covers the cost of a $30 backup battery with biannual replacement, mitigating the benefits of the built in alternator. And the battery still works at 700 RPM.

Just one guy's opinion.

Larry

[lr172]

Originally Posted by DCBrown198

Away from home I had one 6-cylinder PMAG internal alternator fail at 45 hours. Unit still provided excellent ignition for start, and flight. Had I developed a dead electrical system then that one PMAG would have died. I have two...so the redundancy was acceptable for the flight home. Emag promptly repaired the unit at no charge.

RV-10 builders take note. If you have your aircraft battery(s) in the rear as the plans call for, and you pull your bus power from the battery side of the starter contactor at the firewall, as the Van's generic electrical system describes, you may have starting problems with the PMAGs.

This is rooted in the voltage drop seem at the starter contactor as the starter is pushing the engine thru each compression stroke. Turns out that the voltage drop at the upper stage of each cylinder compression (right before the PMAG fires during start) is just enough to affect the PMAG and it may not send a spark at TC. After much frustration and trying to figure out why my engine would not start I was informed of this RV-10 issue by Brad.

The solution was to run a new #6 wire from the battery contactor at the rear battery to the buses up front so as to avoid the voltage drop developing on the #2 wire at the starter contactor. This seems to have solved the problem.

Furthermore, Brad advised on building in the ability to "boot strap" an independent electrical power capability to the PMAG(s) in the event of a weak main battery. If you you have a weak battery you may get the engine to turn over...but that weak battery almost assuredly will be at a voltage during start that will prevent the PMAG(s) from firing.

My solution was to buy a cheap 8 AA cell battery pack with plug from Amazon. I keep it in one of the seat backs. Should I have a weak main battery I simply plug my AA cell pack into a receptacle behind the instrument panel. This receptacle is wired directly to the PMAG power (bypassing the normal power switch). Works like a champ. Using this setup with a weak battery, if the starter can get one of the cylinders to TC, my PMAG will throw a spark.

David

Sorry, but that is just poor design engineering. In the auto world all engine electronics work down to 8.5-9 volts in order to deal with starter draw on a weak battery. I remember SDS posting that there units don't drop out until 9 volts as well.

Larry

[Bavafa]

Originally Posted by lr172

Sorry, but that is just poor design engineering. In the auto world all engine electronics work down to 8.5-9 volts in order to deal with starter draw on a weak battery. I remember SDS posting that there units don't drop out until 9 volts as well.

Larry

With that in mind, one could say, in an aircraft any ignition that can not be self-sustaining for power is a poor design engineering.

Self sustaining and super easy of installation has been one of my primary attraction to PMAG. In three airplane that I have owned and installed PMAG, none failed or needed service by PMAG.

[Ironflight]

Originally Posted by lr172

Sorry, but that is just poor design engineering. In the auto world all engine electronics work down to 8.5-9 volts in order to deal with starter draw on a weak battery. I remember SDS posting that there units don't drop out until 9 volts as well.

Larry

Just so the record is clear, you can power a P-Mag with a 9 volt battery and get a good start….I’ve done it just to see if what Brad says works - and it does.