George Lendich wrote:

Lynn,
I found TDC as you suggested and marked it, put in the rotor and had
a play around ( no degree wheel yet).

Had a guess-da -mate on your IO ( looks similar to the Leeman) and
your IC which (looks to be a good 5 degrees after the Leeman)  - 5
degrees before 90
degrees ABDC.

Question !!
As 90 degrees ABDC is the max volume have you elected to have the 5
degree safety margin so as to not have a problem with compressing
the mixture and having
some forced back into the intake tube???

Another question!!
The overlap with a PP is much greater - with a greater volume of
exhaust gas mixing with the intake, there is a greater chance of
decreased volume efficiency
( rough idle etc.)

OR

does the greater volume of intake compensate for the mixture of
intake and exhaust ( maintaining volume efficiency) ? with the
nearby butterfly giving only a
better degree of control at low RPM?

Now given all this wouldn't it be better to have a late IC ( such as
yours) and a later IO ( even later than Jerry's) to minimize mixing
and have a better
volume efficiency.

The more I read the more I'm confused!
George (down under))

George,

You are not alone in the confusion department!!  From what I've read,
PP's come with a whole set of problems except high rpm horsepower,
mainly because of the overlap.  Excerpt from one article on ports is:
 "Peripheral intake ports (not pictured above) are simply a big hole
in each rotor housing (similar to the exhaust ports), with no side
intake ports whatsoever. Contrary to side port designs, timing is
determined by the apex seal rather than the leading edge of the
rotor. This results in massive intake and exhaust overlap and
subsequently very little low-RPM power, but the direct intake path
permits incredible high-RPM power that typically peaks well over
9,000 RPM. A peripheral port (PP) engine can develop over 300 hp in a
non-turbo application, but is not what normal people would consider
"streetable" (but some do!). The water seals are not compromised,
though some of the coolant passages are blocked by the intake passage
(but to a lesser degree than Monster porting) -- the engine life is
reduced by virtue of stress from high-power and high-RPM operation,
but not so much by coolant leakage or hot spots around the intake
area."  It would seem that if one wanted maximum performance across
the entire rpm range, the original ports would be left in operation
and smaller peripheral ports added with no overlap to increase the
available mixture.  But, since I've never built one, I'm just
speculating.

Bob

 This may or may not be true for high rpm engines with big ports.  I
have not heard of them suffering reliability  problems but maybe they
have.  But for our 6000/7500 rpm aircraft  engines,  with smaller p
ports,  very little exhaust overlap  and the butterfly located at the
housing the engines will idle well and still deliver significant  hp.
There is no reason these engines should  take a reliability hit.
Jerry

Bob, unlike cars we don't need power over the entire RPM range.
The power absorbed by the prop is prop RPM cubed or some such.
We are not driving cars here that require a lot of power at low
speeds. The torque or HP available at speeds less than top prop RPM
is irrelevant. There is absolutely no way to absorb this useless 
potential HP short of a variable pitch prop. 

Nobody has worn out a rotary yet in aircraft service. Until I see 
that happening I won't buy the reduced life argument. We are not 
dealing with piston engines here. Rotaries do not explode in the 
hand grenade mode like a piston engine do at some brick wall RPM red line. 

Everything in a piston  engines is only a few hundred RPM over
the red line of exiting  the block. Valves rods pistons what 
have you.

Paul Lamar

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