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Ask Mike!
Owning an airplane can be the adventure of a lifetime. However, without proper preparation and forethought it can be a painful and sometimes terrifying experience. Applying over 30 years of practical experience, Mike Thompson presents his advice for making the ride just a little bit smoother.
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05/18/2009 Ask Mike! Question
IO-550 Magnetos
Hi, Mike,
In the latest issue of the ABS magazine, top of page 11302, there is a mention of "1200 series mags" as possibly increasing the power of an IO-550 engine. Do you know what sort of magnetos those are, and whether they would make a difference?
Take care,
Raymond
Hello, Raymond;
In context, the author discussed the cylinder work and the Ram cam, as well as the mags. The 550B is rated at 300 +5%/-0, so a well tuned one could be capable of 315.
I do not know what type of mags you have, but if recollection serves, the 550's seem to be split 50/50 between the 1200's and the Slick 6300's. If you can't see the data plates, you can look at the mags and tell the difference by the harness attach plate: 4 screws is a Bendix 20/200 series, 4 nuts is Bendix 1200 series or 3 screws is a Slick 6300 series.
The 1200 series is the largest Bendix (now TCM) mag made. If it actually has more available output voltage, I don't know. There is no listing I have ever found on that.
There are also no listings on the magnetism of the rotors or magnet poles in the various mags. By feel, I can tell you the magnetic pull after the null (negative magnet position) is about the same. But the coil secondary resistance values of the TCM 20/200 series, 1200 series and Slick 6300 series are 12K-16K, 20K-26K and 13K-20.5K, respectively. You can make of that what you desire, but that tells me the 1200's might be the strongest. Worth the change? I wouldn't think so.
Gear Green,
Mike