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

 
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