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Bill supporting your statement - Mazda supplied P-Ported housings. I can't
remember why they did whether it was for competition racing or such - they idled
OK.
The secret is to identify that which works best for our needs (AVIATION)
and set it up for that.
Overlap causes inlet fuel contamination/ dilution, SURE, but so to do
most engines, which have up to 30 degrees overlap ( if I remember
correctly).
In radical cam reciprocating engines, the cam keeps the valves open longer
- hence overlap. Two strokes have overlap.
The mixing of gases can be minimized with timing and shape of the ports and
velocity of the incoming gases - this is what Jerry's doing.
It would be prudent to wait for his development outcomes.
I calculated velocity and timing as did Jerry and he had expert
advice, mine was a bit rudimentary but the outcomes agreed. This is supported by
the Powersport specifications, so I don't see Jerry being too far off the
mark.
George ( down under)
Group,
I really would like to know where the idea that the PP rotary won't
idle came from?
This is total baloney. Lynn Hanover has commented several times that
his PP 12A idles just fine. Some carburated engines with unusual
manifolds sometimes have problems. This is true for both PP and side port
engines. Many of the earlier rotary engines used P ports.
If and engine is radically ported in either port type, (just like a
radically cammed piston engine), it can be difficult to make idle. If you keep
the port timing reasonable the engine ?WILL IDLE FINE, especially a EFI
engine. The throttle plates being close to the housings makes things work
better. The MB C111 used various rotary configurations. Most of the
engines were peripheral ported. There was no problem with idle, but
the sealing problems of that era prevented a production version. If your
engine is set up carefully without radical timing idle won't be a
problem. The real problems encountered by many people are caused by large
ports and extended port timings.
Bill Jepson
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