"Rogers, Bob J." wrote:

Are there any special considerations in setting up and running a peripheral
port engine?  I know that they make almost no power at low rpm, which is no
big deal, but how about the idle?  As I recall, the Everett Hatch
/Powersport engine had to have some rather drastic modifications to get it
to idle.  At the 5,000 to 6,500 rpm range we are considering for aircraft
cruise conditions, do you think the peripheral port engine gives a
sufficient advantage over the stock intake ports to make the necessary
modification to peripheral?

None.

It is also a myth that peripheral port engines have no low speed
torque. Last year I drove an old  NSU RO80 car in Germany with
peripheral ports and a three speed manual transmission.
It would pull strongly in second and third gears from low RPMs
up hill or on the flat. I specifically tested the car for this 
characteristic. Of course it was set up for modest power at low RPM's. 
It was not a race engine. It was true that an early P Port race engine
designed for peak power at 8500 RPM or above had no torque
at 1500 RPM but the same thing could probably be said about a bridge
port engine. Mazda solved that problem in the Lemans engine by
going to a variable length tuned intake. If you have a P Port
engine and the timing and  intake is tuned for low RPM you
will get plenty of torque.

Everett discovered that putting the butterfly valve down by the 
rotor housing made a drastic improvement in the idle. Not what I would
call drastic modifications. You drill a large hole in the rotor housing and 
epoxy in the butterfly valve and tube. See the ACRE NL web site for a drawing.
Everett was using constant dribble mechanical fuel injection at the time.
Timed pulsed fuel injection is an improvement on that. 

If Mazda or NSU had discovered this and had available electronic timed
injection early on  we might still be driving peripheral port engines.

The side exhaust and intake port on the other hand has some subtle advantages
as far as smog and BSFC are concerned. Un burnt fuel is swept around
to be recycled instead of going out the exhaust port. If a apex seal
breaks it does not jam between the exhaust port and the rotor tearing up
the rotor housing chrome surface. It is contained within the rotor slot.

Paul Lamar
 
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