Subject: P-port meets expectations
From: Rotary Engine
Date: 6/8/2005, 12:50 PM
To: AA-me



These are the pictures and numbers for the 28 inch runner
version. This would make a good engine for the 2.17:1 gear box.
Note the torque peak is 5600 to 5700 RPM which would make a
good cruise setting.

Paul Lamar


Any guestimates on how much the performance graphs would shift using the
stock (non p-port) 13B engine?  Would it be fair to presume that the lower
RPM portion of the graphs would be similar?

Del Johnson

I have some HP curves for tuned side port engines. Here are a few.

I don't think so. The P-port tuning is unique due to (among other things) high overlap between exhaust ports and intake ports.

BTW Note: that this carb engine is generating as much HP at 7000 RPM as the
RX8 EFI engine generates at 8500 RPM.

If tuned for 8500 RPM the HP would be well over 300 I suspect.
Some of this is due to the simple fact that two two inch diameter pipes
have much less skin friction drag than six pipes with the same
total cross sectional area. In other words the engine gets more air
as there is less skin friction drag in the pipes. The mass of the air
ingested in a given cycle is the bottom line when it comes to HP
generation. The air velocity in the pipe can range up
to mach .6 or so.

Note also one rarely sees more than about 160 foot pounds of torque
out of any side port rotary engine and that includes the RX8 engine.
When the math is done HP = RPM X TORQUE / 5252. You will find the p-port
engine is generating more torque and HP from 5000 RPM on up.
The exact torque peak location in terms of RPM  will be located
by the length of the 2 inch pipe. The higher the torque peak location
in RPM the higher the peak HP will be. Note that the max torque
around 200 foot pounds has not significantly changed by changing the length
of the pipe. It was merely moved from 5600 to 6300 or so.
Again doing the math HP = RPM X TORQUE / 5252 you wind
up with more HP. Airplanes fly on HP and not engine torque per se.

Paul Lamar

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