Sender: "Marvin Kaye" <marv@lancaironline.net>
To: lml@lancaironline.net
Date: Wed, 05 Jan 2005 20:40:58 -0500
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From: "George/Shirley Shattuck" <kloop@plantationcable.net>
Subject: Engine performance
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I have not closely followed the recent posts about engine performance with a
reduction of 1" of MAP etc.  But since I was out on a post maintenance
flight this week I decided to record some numbers to throw in the mix for
those of you who know about things like this.

Seems to me that our airplanes are all different so getting meaningful data
might be hard.  That is, the spread of data points is going to be wide, and
the performance is going to vary quite a bit as a result of intake design
differences, airfoil inconsistencies and other drag here and there.   I
designed my induction airbox, for example, to be a fairly large plenum,
thinking that the air comes in at X velocity then slows down in the space
behind the inlet, but the pressure builds in front of the entrance to the
injector body.  Seems to work.  That plenum between the cowling intake (same
diameter as the injector body inlet) and the injector I formed out of about
three BID's of glasscloth.

January 3, 2005 over middle Georgia
Altitude: 8500 ft.
MAP: 23.1 (full throttle)
RPM: 2350
KIAS: 176
KTAS: 204
OAT: 13 deg C
Gr. Wt: 1440 lbs. +/-
EGT: 50 deg. ROP
FF est: 9.3 gph

I carefully reduced power 1" MAP to 22.1 MAP without touching the mixture or
prop control.

The FF came back to an estimated 8.2 gph, the egt rose to 25 deg. ROP and
the airspeed slowed to 166 KIAS.  After this stabilized, I went back to full
throttle and things returned to their previous state.

All of the above must be taken with a grain of salt and a SWAG taking into
account all the variances of an airplane built in the garage, in the
mountains at 7000 ft. with a glass of wine nearby and a yellow lab dog to
consult with.  Dog's name was Lance, by the way.

The maintenance I was doing was the replacement of the brake lines.  Prior
to start one cold morning as I checked the brakes before cranking, the left
brake line failed.  The old nylaflow line that came with the kit in 1989
split in the left wheel well where it went between ribs.  I had left it
unsupported and uncovered and apparently the vibration of many take offs and
landings fatigue failed the line.  I would recommend supporting and/or
covering the brake lines with something in those areas where they are
subjected to wind blast buffeting.  Removing and replacing the lines meant
removing the header tank and all its associated connections, which was a big
pain.

George Shattuck
N320GS