From: Tracy

To: Rotary motors in aircraft

Sent: Monday, March 12, 2012 1:35 PM

Subject: [FlyRotary] Re: Failure of an LS-1 D-580 type ignition coil

Quite possible you are running WAY too much fuel at lower MP if you haven't checked the monitor  (ALWAYS check the monitor when in doubt).   I didn't even consider the possibility that you had it so rich that the excess is running up the EGT as Lynn suggested.  Auto tune is to be used after you rough it in manually,  definitely check the monitor before invoking auto tune.

Tracy

On Mon, Mar 12, 2012 at 12:14 PM, Rob <rob@mum.edu> wrote:

Thanks for you input Tracy.

 

I haven't checked my mixture monitor under this condition yet. I'll check that next time I fly but I do notice that the EM2 indicates that the fuel flow, GPH, starts to be reduced as the MP decreases and the EGT increases. I have been told that I should try to avoid EGT's above 1550 degrees and definatelly not above 1600. In spite of these high temps upon decent I look for overheated spark plugs and damage piston top and don't see any indication of over heating. I really have to richen the mixture a lot to keep the EGT under control so the question is am I just adding more fuel where it is not needed when I'm reducing power.

I have been meaning to use the auto mixture feature in the EM2 to fix this but I'm not sure it is necessary. Maybe I should just adjust the mixture so it at leased stays below 1600 degrees.

Does this sound reasonable.

 

Robert Bollinger

EC2 EM2 works great.

In Ford V6

 

----- Original Message -----

From: Tracy

To: Rotary motors in aircraft

Sent: Monday, March 12, 2012 7:19 AM

Subject: [FlyRotary] Re: Failure of an LS-1 D-580 type ignition coil

This is a different thing entirely.   My guess is that your mixture is changing at lower MP and raising the EGT.   Assuming the ignition timing is OK, this is probably what you want.  Higher EGT due to leaner mixture at low power wont hurt anything within limits.   I don't know the limits of this engine of course.   What does your mixture monitor tell you under these conditions compared to high throttle?

Tracy

On Sun, Mar 11, 2012 at 10:51 PM, Rob <rob@mum.edu> wrote:

Is this the same thing that happens when manifold pressure is reduced but RPM is increased, like when I reduce throttle to go to a lower altitude or for landing? When I do this my EGT starts to climb to 1600 or even 1700 degrees. This in on my Ford V6 with Tracy's EC2 and EM2.   It dosen't make cents in this case either so it must be the same phenomenon. Do I need to worry about this climbing EGT or not?

Thanks for any insights?

 

Robert Bollinger

----- Original Message -----

From: Tracy

To: Rotary motors in aircraft

Sent: Saturday, March 10, 2012 8:22 AM

Subject: [FlyRotary] Re: Failure of an LS-1 D-580 type ignition coil

The other guys pretty much nailed it.   Less burning in the chamber and more burning in the exhaust header.

Tracy

Sent from my iPad

On Mar 9, 2012, at 11:53 PM, Dave <david.staten@gmail.com> wrote:

On 3/9/2012 10:22 PM, DLOMHEIM@aol.com wrote:

Tracy wrote:  >As usual, the in-flight symptom was a rise in EGT on the affected rotor.

 

Can someone describe the science behind a "rise in EGT" when we lose a single coil.  I would have expected a drop in EGT due to less thorough burning of the mixture and therefore excess un-burnt fuel which I thought would provide cooler temps of the exhaust stream as it passes the EGT probe.

 

Must be missing something very basic here...

 

Thanks for any clarity!  :)

 

Doug Lomheim

RV-9A / 13B FWF

The rotor combustion space is long and narrow at TDC. If you ignite the fuel air charge in a rotary at tdc from only one end, the flame front progresses slowly from one end of the "combustion chamber" to the other. Two plugs (and coils) for each rotor are present in order to facilitate complete burning of the fuel-air charge from opposite ends, and to extract as much power from the charge as possible before the "power stroke" portion of rotor rotation uncovers an exhaust port and begins the "exhaust stroke"

So.. in an abnormal condition characterized by a single coil failure (out of 4 coils).. the affected plug is dead... and the affected rotor has incomplete and SLOWER burning of the charge than normal. This delayed burning persists after the exhaust port is uncovered. So instead of exhaust gases (which have already lost heat to the block) passing by the EGT probe, you have actual flame front (from the still burning fuel air charge) passing the probe and combustion continues in the tailpipe. That explains why EGT on the affected rotor would rise in a rotary with dual plugs/coils per rotor. A single dead plug from fouling or other causes could also provide the same result.

Make Sense?
Dave (a lingering former rotorhead)