Either my writing is too obtuse or opaque or I left something out.

You responded to my historical setup:

<<<<I suspect the reason you did not see improvement in=20 performance after
the 9:1 pistons on the LASAR was because it was=20 timing much to early,
and that was corrected during the=20 subsequent magneto
replacement/shuffle.
>>>>>

I did see vast improvement on the original setup with 9:1 pistons. = ;=20 After my engine was rebuilt (again with 9:1 pistons), there was a clear prob= lem=20 with the LASAR system which was identified after I installed the switch that= =20 enabled me to run mags only or EI only. The new sensor mag could not b= e=20 set properly, resulting in initial timing of 29* BTDC (should be 25*). Thus,= any=20 advancement by the LASAR was on top of that. More recently, that senso= r=20 mag was replaced with another that could only be timed to 27* BTDC - still a= =20 little advanced before the EI adds its own - exactly why I am running t= he=20 advance-conservative O-360 CU. So, I agree with the technical commenta= ry=20 that too early timing can defeat the performance objective.

<<<<<<<At high power ... changing the spark timing= =20 over a range of plus/minus
3 or 4 degrees off of Max Br= ake=20 Torque (MBT) timing has remarkably
SMALL effects on Hp. Almost=20 unnoticeable to a pilot.
>>>>>>>>

I can buy that. What about torque? I remember that HP =3D (= Torque=20 x RPM)/5252, the reason that HP and Torque curves cross at 5252 RPM, somethi= ng I=20 hope to never see with my little engine that could. After all, the=20 constant speed prop sees torque for prop pitch management and the torque plo= t=20 for 1 revolution of a 4 cylinder engine is rather torturous - especiall= y=20 the dip during compression. Who knows what the "harmonic damper" does=20= to=20 the CS prop except that it is "better" because of reducing the impact of tha= t=20 dip. Hmmm, I must remember to switch the GPS to Km for better=20 accuracy.

Then:

<<<<<<This concept is almost universally mis-understo= od=20 by engine builders.
For example, most IO-520 and 550 TCM engines ar= e=20 OVER timed at full
power and would actually make a bit more Hp if the tim= ing=20 was retarded
slightly.
>>>>>>

Exactly. That is what led to my comment about a timing compromise= by=20 the manufacturer. This may be somewhat true for the 320 also. On= e=20 person has told me that the Lightspeed EI can be obtained with the ability t= o=20 alter the timing and he has seen increased takeoff (full power) performance=20= by=20 slightly retarding the spark to something like 22* BTDC for that=20 operation.

<<<<<At lower power settings, the engines are a bi= t=20 more sensitive to
optimal timing to achieve MBT, as compared to&nbs= p;=20 full power operation.
>>>>>

Yeah, right now I am just poking around in the dark since the timing ma= ps=20 are Unison "proprietary" information - as though someone would copy=20 them.....

<<<<<What do your EGTs run at full power on take off=20 ? At what fuel flow?
>>>>>>

As I said in the post you are responding to, 1280-1290 and 15.4 gph.&nb= sp;=20 Note that the fuel flow could be less than accurate. After a long flig= ht,=20 the EPI totalizer will claim I used about 5% more fuel than that measured by= =20 those very accurate fill-up trucks (this includes same truck at the same air= port=20 on the same day). Of course, that was not flown at WOT. However,= I=20 will record more environmental data (Baro, Palt, OAT) when I collect th= is=20 information next time, including WOT lo altitude runs with and w/o=20 LASAR.

Thanks for keeping at this,

Scott Krueger

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