flyrotary@lancaironline.net Mailing List Archive

Re your analysis comparing side ports with p ports, I wonder if such an analysis is even possible as they are quite different.? Anyway, I doubt that a standard port can deliver 100 hp or a street port 130 hp. per rotor, certainly not when limited to 7500 rpm.? Of course I am only guessing.? No real knowledge or experience.??

From a Daryl Drummond dyno sheet for a 12A bridge ported running 36MM chokes. One per housing.

6,500 RPM 139.6 Torque 173.3 HP

7,000 RPM 147.6 Torque 196.9 HP

7,500 RPM 152.6 Torque 218.2 HP Front EGT 1518/ Rear EGT 1492/ BSFC .671 oil 164/ pressure 100.1

F/A 12.1

Main 210/ air .80. A Pport with a slightly larger choke would better. A 13B Pport would do still better.

A 13B Pport injected would do much better.

Lynn E. Hanover

Lynn,

Good stuff!

For comparison, using my trusty hand made degree wheel, I revisited the bridge port and found it really opens very early 115 BTDC and closes quite late 72 ABDC. These figures could be played with depending upon the length and placement of the bridge.

I saw one bridge made up of holes ( about 1/4" I suppose), these holes had a bridge between them, which I thought was a good idea. Who ever made the holes also ground in recessed flutes to the holes on the inside, at the time I wondered how well that worked. I also felt one could vary the timing with the number and placement of the holes.

Similar variations can be also done with the street port, by varying the length.

The distance between IO/IC in the bridge port is something like 62mm and would represent a P-P of 2.44" dia ( 4.98 sq") - if you could fit it in!!

Would need a monster inlet tube to feed that sucker! I say this tongue in cheek of course as you couldn't fit a round PP this large in the housing.

The Factory PP is large enough with an opening of 50mm x 43mm, about 3sq" ( 50mm dia), which is fed by a 43mm inlet tube, about a 16% reduction in diameter.

I can't for the life of me figure out why the port opening has to be so much larger than the inlet tube. It may be the duration of the open inlet they are looking for.

Do you know what sort of power they found with the 13B stock PP?

Any how for those interested, I've settled on a 44mm inlet straight tube with a late opening and late closing - same a stock PP IO 86 BTDC and 75 BBDC.

I can buy 41mm and 44mm tube and have opted for the 44mm ID inlet tube, only 2.35sq" area.

George ( down under)

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