Whirlwind 200RV and PMAG

Hi Folks,

I am getting ready to do a first engine start and not able to figure out a question about timing the PMAGs.

- I have an IO-360, Whirlwind 200RV prop and dual PMAGs.
- Firmware on PMAGs *NOT* updated to V40.
- The plan is to run with with jumpers in (Curve A).

The installation manual says that for "light mass props you may want
additional margin to make sure start- up firing occurs after TDC". The recommended timing is 2-3 degrees After TDC in such cases.

Wondering if WW 200RV fits the definition of "light mass prop"? Any recommendations on how should I be timing them?
1) At TDC?
2) Or 2-3 degrees after TDC?

Thanks in advance,
Ashish

Yes, consider the WW 200RV prop to be light weight, and yes, if not using V40 firmware, retard timing a few degrees. You need to know how many teeth are on your ring gear and do the math. I have 149 teeth on my ring gear, so 149/360 degrees = 0.41 teeth/degree. So to retard by 3 degrees, its only 1.2 teeth past TDC.

Agreed, or if you have an EICommander you can program the advance curve even a bit more retarded than the A curve which will also cover the situation.

Check your PM's.

I run the same set up and have my Pmags timed at TDC. No issues for me

I have the same set up. There have been a few times that it will kick back on a hot start if timed at TDC. Never a problem if timed 2~3 after TDC.

Timed Past TDC

I have the same set up and run with the Pmags timed slightly past TDC.

When I did my first flight I had it timed this way and used the "B" curve per Brad's recommendation. The way Brad explained it to me is that you retard the timing when you do it past TDC so on the "A" curve it is like getting a double shift.

The "B" curve timed 2-3 degrees past TDC is the same as the "A" curve at TDC or nearly so. I flew for 100 or so hours like on the "B" curve. Then I decided to try the "A" curve, I liked my cylinder temps better on the "A" curve but still time the 2-3 degrees past TDC just in cast of kickback.

I must admit I find messing with the timing intimidating due to my lack of knowledge on the subject so I have not installed the ECI Commander and I only go with book settings. I am sure I must be missing some performance enhancement because of it but so far I have not been motivated to learn more, I am having fun just flying so far, 300 hours in less than 2 years!

Cheers

If your P-mags have firmware version 40 (September 2014) or greater, there is no need to time them past TDC. This version fires the plugs a few degrees past TDC when in starting mode.

Version 40 also fixes another issue, check the Emag site for details.

Contact Emag, if you have any questions.

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.

I have an IO-375 originally with a Hartzell BA Prop and dual P-Mags timed at TDC. Never a problem while starting. Then I changed to a WW200RV Prop and I got occasional kickbacks. So yes I would rate the 200RV a "light mass prop". I retarded the timing to 3 degrees after TDC and all is good.
However when the engine is hot during the startup procedure - running already - and I try to keep the engine alive with the boost pump when it wants to stop due to hot fuel or vapor, I get occasional kickback. The ignition shifts the timing over I think about 200 RPM, that?s why. I can avoid this letting the engine run with higher fuel flow (about 1500RPM) for a while til it gets colder fuel and is smoothing out.

Low Pass said:

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.

Click to expand...

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.

N941WR said:

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.

Click to expand...

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!

Low Pass said:

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!

Click to expand...

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.