I have been running at 2500 for the last six years.  Acceptable performance.

RPM 2400 is an experiment.

Observations:
At FL240 and 2500MAP, the WOT manifold pressure is ~31.5".  Reduce RPM to 2400 raised MAP to 34", giving the cabin more pressurization in the upper deck.  A nice bonus.

RPM 2400 is quieter that 2500.

RPM 2400 apparently yielded an observed 3 KIAS increase in airspeed.  Hartzell similar prop efficiency?

LOP fuel flow of 17.1 gph at RPM 2500 compared to 17.1 gph at RPM 2400 is still the same engine power output (LOP). Same endurance and distance.

The lower RPM 2400 has less reciprocating internal frictional events per hour than RPM 2500.  Maybe an engine benefit?

In conclusion: it was an experiment that seems to have some value.  I will explore this with a New Jersey to Oregon flight next week.

Jeff
LIVP




On Jul 24, 2012, at 7:41 AM, <bronnenmeier@GROBSYSTEMS.COM> <bronnenmeier@GROBSYSTEMS.COM> wrote:

Jeff,

Why do you run at 2400 RPM? - I usually run at 2500 RPM. This makes you
a little faster.

CHT 394 seems a little high - I try to keep them around 375 -385. What
is your TITmax and do you remember at what TIT did you run? I usually
stay 60 to 70 degree below TITmax on the lean side.

In cruise LOP my cylinder #1 and #2 are the warmest. Most of the times
#2 is slightly warmer.

If I want more fuel flow / speed without increasing TIT and CHT
increasing the MAP works for me - sometimes I go up to 34MAP - this way
I can get fuel flows of around 19 with CHT<385 and TIT  below 70 of
TITmax - this really makes the plane moving fast.

Ralf

-----Original Message-----
From: jeffrey liegner [mailto:liegner@ptd.net] Sent: Monday, July 23, 2012 8:31 AM
To: lml@lancaironline.net
Subject: LIVP Power and Flight parameters from today's flight test.

Power and Flight parameters from today's flight test.

Level FL240 west bound: 15*F (IAS+41F)

MAP 31.5
RPM 2400
Fuel 17.1 gph (LOP)  FP 30
TAS 257
LIAS 174
High CHT 394 (#2, of course)
Cabin Altitude 10,000' (PSID 5.0)

If Fuel 18.1 gph, speed increases TAS 264 but CHT increase.

http://flightaware.com/live/flight/N334P

Comments? Analysis?

Jeff