I went out on a cross country from Everett, Washington to Walla Walla and back the
last few days. Cruising at WOT at 11, 500 feet I had a MAP of 19-20 and was making
about 140 mph true rpm was around 6200 with a catto 3 blade 74 x 88 pitch. I need
some aerodynamic cleanup on my cooling scoop, something I intend to work on this
winter. But I think that I'm probably only making about 150 hp or so- not bad, but
not what I could make. I think that the NA 13BREW with four ports and 9.1/1
compression would not be a match for a 13 b with p ports and 9.7/1 compression. I'm
thinking that I might be building such and engine for an engine swap in the future.

Oh, and by the way, it was a great day for flying.

Brian Trubee

Build another engine with a p-port Brian. It will really help up high.
A 4 port will never match a p-port. A good 4 port manifold is hard to make as well.
I assume you have a 2.17:1 gear box.

Paul Lamar

I don't know if I would get an appreciable increase in power if I were to use
premium, I am using regular mogas at the moment.

Brian Trubee

BTW power in a rotary is directly related to RPM in that range.

The best pay off is work on the cooling drag first.

Pressure on any surface facing forward is drag. Use a water manometer.
Get a Gopro camera to record the results.

Paul Lamar

Right now I'm happy to just be flying, I'll wait until the weather turns crappy out
here before I start doing aerodynamic cleanups and other refinements. Oh, and my
temps were pretty good- highest was 201 one the coolant, 208 on the oil, that was at
10500 feet at 21 inches MAP and 39 OAT and 6000 rpm. . A little less throttle and the
temps dropped down to the 180s-190s.  Exhaust is running high- about 1950 -2000- but
my EGT probes are 1 1/2 " from the exhaust flange. The lowest that the EGTs run
regularly are around 1800. I think that these alarmingly high egts are a function of
the close proximity of the probes to the exhaust ports. Must keep an eye on the
headers when doing maintainance/checks.
Brian Trubee
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