What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Ignition question

bob888

Well Known Member
Started my engine for first time today and no leaks or flames, ran great (extremely relieved...). The question. I have relates to "mag drop" which really isn't. I have a magneto on the left and electroair ignition on right. At 1500 rpm I get. 150-200 rpm drop when I cut off the electroair ignition and a modest 50 rpm drop when I cut the magneto. Is this normal/acceptable? If not, any suggestions?
 
Congratulations!!

Started my engine for first time today and no leaks or flames, ran great (extremely relieved...).

Bob, congrats on breathing life into the beast:D

Normal to see what you experienced with a mag/EI combo,
 
The drop will be significantly more when you turn off the electronic ignition as it is much more efficient and its timing is variable. I am surprised at the magnitude of the drop. My rpm drops about 50 when I turn off the electronic ignition and only about 15-20 rpm when I turn off the mag. 200 rpm is excessive for any airplane I've ever flown and sounds like an issue with the mag.
 
My experience with two different combinations of EI systems in parallel with a mag is that the drops are roughly equal between a mag and an EI.

At different times, I've run the Electroair and eMag systems (about 7-8) years each.

I'd check the timing again on both systems.
 
Last edited:
I run a Slick mag and an Electroair EI; yours sound normal, but do double check the timing and idle mixture after first start.

For my run up, I use 1700 rpm, lean engine on both ignitions until it increases, then comes back down to 1700. This LOP setting gives 50 rpm drop on the EI, and a 100-125 rpm drop on the mag. If I use a ROP mag test, the EI shows no drop, and the Slick drops 50, just like my old Piper.

The lack of drop on the EI is from stronger spark, plus the advanced ignition timing it delivers at low MP settings
Jay
 
My experiences with Mag / EI setups are more in tune with Jay's description, larger rpm drop on Mag / minimal drop on EI, assuming 1700 rpm leaned run-up done.
Because you are experiencing higher drop on the EI, is it possible the 2 ignitions are wired backwards on the ignition switch (assuming you are using the common ACS dual switch) and getting fooled as to which ignition is actually live? Switch points on that switch are OFF RT LT BOTH START.
Way to check is to pull the EI breaker during run-up & see if switch position matches.
 
Last edited:
Bob,
I am curious how you have the Electroair wired to check your two ignitions. Are you using two switches, one for each ignition, or are you using the ACS key switch, and the wire they provide to do so. I am contemplating this system and still working through the wiring. They mention backfires are possible when doing the run up if you use the key switch option....
 
I can see backfire possibilities if the ACS switch is switched from
BOTH -> Left -> BOTH -> RIGHT than back to BOTH during ign checks.
I do BOTH -> LEFT -> RIGHT -> than back to BOTH during my run-ups, noting rpm each step, haven't experienced backfires...
 
Back
Top