Hey all,



How many degrees above the top of the exhaust port is a peripheral port placed? This is for a 10a engine. Any help appreciated.



Thanks,



Jim

 

as many as you want. the timing of the ports can be varied to move the powerband around

 

I'm using the Rx-3 twin dizzy 10a housings which have the 3 exhaust-port holes. these have been all joined up, and raised about 2mm. I think this is as far as it goes with the old twin dizzy housings. I Want to know where would be the most suitable place to place a peripheral port in the housing. I have a pair of old MFR 12a PP housings, but am usure of copying them due to the exhaust ports being placed in a different place. any suggestions?



Thanks in advance,



Jim

 

The most important feature for drivability will be intake closing point. So I would copy the 12A port open point and side distance, but leave the closing point a little early. Smaller displacement engines tend to be more sensitive to port timing. So leave a little room for changes if the power is lower than you need up around 9,000 RPM. Then if required, you can go back in and move the closing point a few degrees later.



The interaction between exhaust port closing and intake port opening will be more appearant at lower RPM than at higher.



Just back from Sun&Fun looking at rotary powered airplanes.



Lynn E. Hanover

 

I havent been able to go the past few years, so lets hear some details from your trip

 

Thanks for the tips lynn. Has anyone else here built a 10a PP? I know of one other guy here in NZ that has one, goes by the name of RE10 on forums. He states that he uses 46mm ports? opinions? too large? I was opting for a 40mm ID. Anyone?



Thanks in advance,



Jim

 

I conversed with that fellow over using his manifold pictures on an aviation website. Very nice guy. But I have exploded two computers since then and all is lost.



He has both Pport and side ports in his 10A RX-3. Each manifold blocks off the unused ports. He said it is totally streetable. I have no idea what his choke size is. Where you need the big choke size is at wide open throttle at high revs. The tuning problem is the transition between off idle and enough flow to get the booster going full blast (assuming a caburetter). Could be longer accellerator pump stroke with smaller nozzles, light flywheel and so on. A street car is more fun if can just drop the hammer on it from a roll.



That 46MM is more than enough for the top end. A 12A can do 280 HP with 44MM chokes. The smaller the engine, the more difficult the transition tuning.





Lynn E. Hanover

 

Well, first...........



If you get a chance to see the flight demo of the new F-22 Raptor, go see it. It has thrust vectoring, so at lower speeds control inputs move the exhaust nozzles.



This allows for such things as hovering nose high, and doing a back flip in its own length and returning to hover.



This thing could turn iside an Extra 300 (very high performance stunt plane).



He can leave a hover and track forward at very low speeds. Stop in a hover. Power down and pitch forward to a level attitude and descend straight down (as in a flat spin) with no forward speed, for several thousand feet, then add power and shoot off at a 90 degree angle.



And the best part is that it is way louder than the F-15. Shakes your chest so hard it makes you cough. Most

folks have fingers in their ears, but since I left the hearing on a flight deck in my youth, I enjoyed it at full volume.



In the engines tent there were the usual suspects. The VW guy did a god job. VW down and up in 2 hours, explaining each item. Paul Lamar had a novice do a 12A down and up in 35 minutes. He did not build up the rotors of course, but to the untrained eye it was impressive, and got more guys and some girls interested in the rotary.



Tracy Crook had his plane (Renisis powered RV-4) and his demo stuff set up and running. He brings a partial 13B so people can turn the crank and watch the rotor going around. Since he is at the plane talking to people I took a turn in the tent explaining the rotary to many interested folks. I was hawking the "Nopistons" list for the unwashed as well.



Met some great people. Hooked up with old aviation friends and people that have been reading my stuff for years and so on. There was a real aircraft engine builder there and they did a 0360 from parts each day.



There was a "Flight Sciences III composit canard 4 place that is supposed to be powered by a Mistral rotary engine and reduction system.



http://flightsciences.net/



The plane design looks a bit shakey to me,(needs more wing area for a 4 place) And (the forward sweep needs a bunch of deep stress analisis) but it is getting done. The engine choice is correct.



Rode down from CMH in my friends old Bonanza with the new 0550. The extra power is cheaper on gas $3.30 per gallon than was the old 0470. The 0470 would not run lean of peak due to the low compression and poor distribution. On the 550 it is a piece of cake. So where the 470 was using 13.5 GPH and going 185 MPH, the 550 is lean of peak EGT and using 11.9 GPH with Gami injectors, and going over 200MPH.



Plus the cylinder head temps were 318 peak instead of 380 peak. So faster with less fuel and less wear on the engine. The rotary airplane engine can run at 200 degrees lean of peak if you were thinking ahead of me. So a rotary can have good mileage in special conditions.



We visited a young man who has, maybe 250 airplane engines in his shop. He builds them for air boats.

He has one that is a 550 (Continental 550 cubic inches) case with Lycoming jugs inverted to get well over

600 cubic inches, with a reground cam profile. Said the boats are faster (over 80 MPH) on grass than on water. Not my cup of tea.



Lynn E. Hanover

 

Yeah I thought so too, thats why I opted for smaller ports (40mm) to bring the power range down a touch. Am I closer to the money? this car is not for street purposes so I don't mind it being a bit of a pig to drive.



Thanks



Jim

 

That pair of 40MM will be plenty. My 12As are 250 HP at 9,400RPM with two 38MM chokes.



My Pport does about 280HP with two 44MM chokes. Some builders were claiming 300 plus with 44MM chokes.

But tyhey were over 10,000 PM all of the time.





Lynn E. Hanover