George,

 

Let's start with some history.

 

I had a 400 hour Don George 1992 Cermichromed I/O 320 with 9:1 pistons and a Hartzell carved (thickness tapers at the end), 70 inch constant speed prop.  I replaced BOTH Slick mags with the LASAR system (O 320 Control Unit (CU)), all timed for 25* BTDC.  I immediately experienced energetic takeoff runs, better climb rates and better performance ROP at altitude.  The EGTs were about 70 degrees cooler than similar power settings achieved with the old mags - The CHTs were 15 to 20 degrees higher.  I have not retained data from that era.

 

About 1.5 years ago, the engine was rebuilt with better breathing ECI Titan Cerminil cylinders, 9:1 pistons, a heavier crank and new one-piece cams by Air Craftsman in Prescott, AZ.  The prop blades were replaced with a Hartzell specified 84 inch prop cut down to 70 inches - without the "carved taper", i.e. they are thick at the tips.  This work was done by Warner Prop in Tuscon, AZ.  The engine was hung by a totally incompetent A&P in Sedona, AZ.

 

After re-hanging the engine, baffle adjustments, vibration eliminations, balancing the air to the injectors, etc. engine performance issues were addressed.  Last year, I noted here that the LASAR system was not performing as it had on the prior incarnation of the engine. I finally installed a switch to shut off the LASAR CU thus allowing me to run with the backup magnetos for comparison purposes.  It was discovered that the engine ran better on mags only than with the CU engaged.  This was diagnosed as bad relays in the lump in the mag pigtails that controls switching betwixt mag or CU so that both were engaged when the LASAR was engerized leading to worse performance than the mags alone.

 

I installed new LASAR mags (they perform the timing and spark distribution for the electronic system) and could not get the "sensor" mag closer than 29* BTDC.  Unison provided a replacement sensor mag which can only reach 26.5-27* BTDC, well within Unison's spec for + or - 3*.  Both are timed the same.  The sprightly takeoff runs, improved climb rate and general cruise performance returned. However, switching between mags only and LASAR (ROP, cruise at less than 24" MAP) did not show a difference in HP (speed) or fuel consumption except for .1 to maybe .2 gph.

 

A Unison rep went for a ride with me to try to clarify this but his engineering computer would not let him get beyond the password.  Note that Unison's proprietary (they won't tell me) timing maps depend on MAP and RPM - more on MAP and no timing alteration above 75% power (whatever that is) which is why operation above 26" MAP has no timing change, just a better, more robust spark.  However, also note that while I have fine wire plugs, the gap cannot be widened because the failure mode requires the plugs be gapped for backup magneto operation.

 

A final note to put this in perspective.  I use the Vision Microsystems EPI 800 engine monitor system - while digital, it is outmoded and limited because EGT and CHT temperatures are stepped in 8* increments and displayed to the nearest 10 degrees (I understand octal, just like my transponder digits).  Precise it is not.  Plus, I can only read one cylinder's temps at any given moment - I have to rotate a switch to see the others.

 

This last January 20th I made a flight from Chicago to Tampa, nonstop, 9500 ft, 40-50 degrees LOP, 7.4 gph, 192 KTAS, 30 gallons of gas, 3.9 hours and, at times, reaching 241 Kts ground speed.  I did switch off the LASAR for a short time and saw the fuel consumption increase by .4 to .5 gph while not changing any other engine management controls.  I reported general engine charactistics here as: