Posted for "George Braly" <gwbraly@gami.com>:

Wow... Almost everybody is "right" in their comments on this ...  and yet the
important stuff is being missed.

Right now,  we don't have enough data from Scott Kruegar to know for
sure what is or isn't important.

He says ...  "Lasar ignition will lower EGTs by  70-90degrees."

Somebody else says it doesn't matter, because it is "relative"

Please...let's back up.

70-90 degree change in EGT in   relation to "what" ?   1)   What the engine EGTs   WOULD be if it had two properly timed
standard magnetos?

2)       What the engine EGTs are on ONE magneto ?  Compared to ONE
Lasar System operating?

3)       What the engine EGTs are on both of the standard backup mags in
the Lasar system operating without Lasar  doing its electronic thing?   4)   And is this  70-90 degee drop observed at  full power ?  Or only in
cruise?   Or both?

So,  Scott,  help us a bit please?    Data, please?


If I take off in my engine at book  300 turbonormalized Hp, 22d magneto
spark timing, and book fuel flow,   the  EGTs will be operating around
1250 to 1300F.

At 50dF   LOP in high power cruise,  the EGTs will be about 1450F.

IF .... IF ...  I advance the timing about 4degrees,  and keep
everything else the same,  I will DROP those EGT temps by somewhere
between 60 to 90d  F.  If I am at takeoff power,  that will be a VERY bad thing.    VERY VERY
bad thing.    That will make the peak internal cylinder pressures go up
from about 950 PSI up to something like 1050 or 1100 PSI.  That is very
close to the  "drop off the cliff" kinds of bad changes.
 

If I am at 225 Hp,  LOP in cruise,  it *might* be just fine,  although
the CHTs will rise considerably (about 25F or so).

In this instance,  the change in EGTs - - would not be "relative" at
all,  it would be meaningful to know what the absolute value of the EGTs
was before invoking  LASAR and afterwords.

On the other hand,  normally,  all EGT readings are only referenced to
peak EGT (or TIT) and in that sense,  their absolute value is much less
important.

So...Scott,  can you get us a more robust description?

 Regards,  George