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-   -   Whirlwind 200RV and PMAG (https://vansairforce.net/community/showthread.php?t=119828)

N941WR 11-21-2014 01:12 PM

Quote:

Originally Posted by Low Pass (Post 935184)
200RV, 9.2:1, dual p-mags (old software, A curve), IO-360. Retarded 3-5 degs. Start procedure involves energizing starter, allow 3-4 blades, right ign on, engine fires, left ign on. Otherwise, I have experienced significant kickback and ring gear damage.

Bryan, if your P-mags are wired per the manual, you run the risk of them losing the timing mark. This is one of the scenarios V40 is designed to fix.

If your P-mag is powered but grounded and you crank your engine over / start it on one ignition, the positive pulses in the MAP line can act like someone blowing in the tube. (Although the MAP is a suction, we found there are some high order positive pressure waves present possibly from the intake valve slamming shut.)

If you start on both ignitions (both P-mags ungrounded), you should not have an issue.

Low Pass 11-21-2014 01:44 PM

Quote:

Originally Posted by N941WR (Post 935192)
Bryan, if your P-mags are wired per the manual, you run the risk of them losing the timing mark. This is one of the scenarios V40 is designed to fix.

If your P-mag is powered but grounded and you crank your engine over / start it on one ignition, the positive pulses in the MAP line can act like someone blowing in the tube. (Although the MAP is a suction, we found there are some high order positive pressure waves present possibly from the intake valve slamming shut.)

If you start on both ignitions (both P-mags ungrounded), you should not have an issue.

Need to verify, but I "unground" at position 2 on the toggle. Position 3 applies power to and "ungrounds" the P-mag. Cannot get to pos 3 without going though pos 2. And, it's worked now for 50-60 start cycles and no problemo.

Appreciate the suggestion/concern, Bill!

N941WR 11-21-2014 01:53 PM

Quote:

Originally Posted by Low Pass (Post 935206)
Need to verify, but I "unground" at position 2 on the toggle. Position 3 applies power to and "ungrounds" the P-mag. Cannot get to pos 3 without going though pos 2. And, it's worked now for 30-40 start cycles and no problemo.

Appreciate the suggestion/concern, Bill!

You must be doing something right, because you haven't had a problem.

If you are wired like I am, off is grounded and NOT powered, you won't have an issue.

People with a key/mag switch don't have an issue, as long as the thing ungrounds both mags for starting.


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