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)