|
|
Lehanover@aol.com wrote:
In a message dated 6/22/2005 7:23:37 AM Pacific Daylight Time, 13brv3@bellsouth.net writes:
While Lynn seems to love PP for racing, I'm not sure I've seen him
state that he thinks it's the best way to go for aircraft. How
about it Lynn, for, or against PP for aircraft use?
Either side port (Bridgeport) or Pport will work just fine for aircraft use.
This is your lucky day. I have a tube frame with a first Gen body and a factory Pport engine. It has a Weaver Brothers external pressure pump, but the front iron is intact, so you could go back to the stock pump if you like. It has a trans but no rear end. Needs a Speedway or similar quickchange. A nice trailer is included.
The Pport has shorter intake timing than the "J" Bridgeport engine. It idles much slower than the Bridgeport engine and has power a bit lower in the RPM range than the Bridgeport.
It is not difficult to drive around the paddock with a tall first gear. The Bridgeport is a nasty mess to drive around, and has around 3 HP until it get wound up a bit.The Pport is also still making power right through 10,000 RPM if that ever comes up. This is a 12-A Pport with about 300 HP at 10,000.
The home built 13B Pport could be much better. It is just too easy to build. As I pointed out with the 12A data at 7,500 212 HP and that engine has the intake tuned to give best power at 9,400 RPM. Those are real Ohio HP. Not those little California HP used to sell race engines.
A well done 13B Pport with very mild exhaust work should have 230 to 250 continuous at 7,500 RPM. Plan fuel pickups for a 45 degree climb angle.
If you only need 220 HP then the side port is quick and easy also.
Lynn E. Hanover
It's fun to bat around the incredible numbers a rotary is capable of, but for most of us 160-200 hp at cruise is about the most our airframes are designed for & can haul fuel for. Even big 4 seaters or very fast glass can't use more than around 225 continuous hp efficiently (75% of 300 hp). The airframe drag going up means you just waste gas making more hp than the airframe design speed calls for.
The question I'd like answered is this: What configuration can be made the most fuel efficient while making hp in this range?
Should it be p-port & 2.1 redrive, p-port & 2.85, side-port & 2.85, etc etc?
My gut is betting on a small-diameter p-port & 2.85 drive, hoping for good takeoff performance with a big, fixed pitch prop & keeping fuel efficiency up turning whatever it takes to cruise at the above power range. My needs in an RV-7 would be in the 160-180hp (actual cruise power setting) & someone in an RV-10 would need 190-210 actual cruise hp.
Charlie
|
|