AirMods NW also sells one. Someone please provide more details.
Others?
He tells me that the prop WILL have to be repitched. What they propose is putting it on the dyno and setting the pitch to give me a reasonable static rpm. As Garner mentioned to me the only certified props are the 57" or 59" pitch. Possibly a field approval would be required to make a increase in pitch legal.
The simple increase of 10 HP at 2700 RPM is due to the increase in compression ratio allowing for increased thermal efficiency of the burnt mixture. The specific fuel consumption (SFC) (expressed as Lbs of fuel per HP per hour) would increase slightly. This means you could make the old HP at slightly less fuel burn/hour or conversly you could make the new HP at the old fuel flow. Assuming the mixture is at "best power" to get a 12 percent increase in HP (18 to 20 more) you have to burn 12 percent more fuel to supply that energy.
At the very low RPM that our engines operate at porting and polishing the intake and exhaust port areas might improve the total cylinder charge by 1 percent or less (certainly not 12- 14 percent). Far more effective would be an increase in intake valve opening duration (change in cam profile) which gives away some low end performance but does a better job of cylinder filling at 2700 RPM. (the IO-360 200 HP series engines get that extra 20 HP over the Tiger O-360s at the same RPM by using this approach (it does make for a lopy, jerky idle due to this long duration of valve timing). I have seen people cut down the big diameter bronze valve guides which tend to "plug up" the airflow inside the ports of both the intake and exhaust sides of parallel valve Lycomings but the heat transfer from valve to valve guide to cylinder head is marginal to begin with in these engines and except for racing or acro engines that are rebuilt every 25 hours, this is not the way to go.
As far as using the static runup method rather than the STC approved prop pitches, ask them if they will sign the engine logbook (and indicate that on the 337 they summit to show installation of the 160 HP change STC.)to that effect. Bet they wet their pants. To get the two pitches approved in testing for issuance of the STC the test plan had to include tests which insured climb/cooling compliance with FAR 23.1041 recorded data corrected to a 100 degrees F outside air temp and FAR 36, the dreaded Noise profile test. The FAA considers any power/prop change a "accoustial change" and each prop/pitch approval is a seperate test series. (the STC holder had to do these tests twice, Once with a 57" prop and once with a 59" prop). Could he have certified a bigger range? sure, but he didn't.
>We are getting our O320-E2G (150HP) rebuilt and STC'd for '160HP'. >Today, we got some papers from the STC holder and it included a section >stating that the engine would be de-rated to 150HP. Are we getting >nothing for our money here?
I know what you mean, my 160 HP STC limits me to 144 HP. Still it performs better than a 150 HP. You also cruise at 75% of 160 HP, which is greater than 75% of 150 HP. I think that such limiting statements are made to avoid tests, new performance charts, etc.