Mine is a 1974 P337 with Riley intercoolers and Horton STOL kit.
I run mine at the book RPM and MP settings, and apply a MP decrease of between 0" and 2", due to the Riley intercoolers. In cruise, I reduce my manifold pressure to achieve book fuel flows for whatever cruise power setting I have chosen. If temperatures are hotter than I want (we have a lot of hotter-than-standard days here in Southern California), I use cowl flaps to manage temperature. If cowl flaps aren't enough (as sometimes happens), I reduce MP further. It's a dance between MP, fuel flow, and temperature. Usually not too difficult.
For me, at gross weight, I am about 8 knots below book cruise speed while in the teens. Given that my plane has Riley air conditioning which I presume is not factored into the cruise performance numbers (extra air scoops, etc.), and also the STOL kit, I'm pretty happy with this.
At 16,000 feet, I'm often running about 192 knots in the summer, but winter allows more like 204 knots. That's if I choose the high power cruise settings and 160pph (total).
If I try to manage temperatures by enriching the mixture, while keeping the cowl flaps closed, I can achieve 200 knots in the summer too, but fuel flow grows from 160pph (about 27gph total) to 216pph (36gph total)! Not a good trade off.
I've generally found my P337 to be quiet at 2400 and 2450 RPM (which are recommended for high speed cruise, depending on altitude). I have tried it at lower RPMS, and also lower power settings. I haven't found that the lower RPM makes much of a noise difference, nor much of an efficiency difference. Lower power settings, of course, are more efficient per mile, in terms of fuel.
Dan
Quote:
Originally Posted by frank.oconnor19
I was just wondering if anyone routinely uses lower RPM settings, 2200 or 2300 when at cruise? Is it quieter? Endurance? Etc. Just wondering if I could take advantage of others experiments.
Thanks
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