hi, group does anyone know of anyone documenting an RX8 conversion on the
web. : cliff
Sure Don Dunbar is installing an RX8 engine in his Mustang II. There may be
others.
Paul Lamar
Tracy Crook is already flying one.
Bulent
What else do you know about this Bulent?
I am surprised I havent heard anything from Tracy on this.
I guess he is pretty busy. Probably trying to fly off the 40 hours before
Sun & Fun. My guess is he is also using the 2.85 six pinion gear box.
I better bring the Everett Hatch Memorial Fund check book in case he
decides to enter the Sun 100 race and average more than 220 MPH.
Paul Lamar
"Lemings, Bob" wrote:
Paul (L that is),
Is it reasonable to expect 200 hp from a mid-nineties 13B, fuel injected, non-turbo, with intake and injector modifications and in the rpm range allowed (under 6000)? Even at 6000 rpm, the prop will still be spinning at 2765 rpms, if my math is correct. (2.17 : 1).
Based on what I think I've learned from all you guys, it would seem that a reduction of 2.50 : 1 would be more appropriate (6000 engine rpm, 2400 prop rpm, with possibly a cruise setting of arond 4500 rpm, 1800 prop rpm)?
Do you have the HP rating, takeoff rpms, PSRU ratio, cruise rpms for your RV that you'd care to share?
Bob Lemings
Perhaps if you went to a peripheral intake port but why keep it under 6000 RPM?.
A rotary is just starting to work well at 6000. The rotor bearing loads are
a minimum at 6000 RPM. The equivalent number for a piston engine is 3600 RPM.
That is where the inertia loads are partially canceled by the compression loads.
This number is moved up on the RX8 engine as the rotors are lighter in weight.
6000 RPM is a good cruise RPM for that reason alone. It is perhaps not
the best for BSFC. I don't really know at this point in time.
It's an entirely different animal than a piston engine. Rotary RPM's are in
a new frame of reference. You have to forget all you know about RPM's
ingrained in our brains having lived with piston engines all these years.
Ken Welter runs close to 3:1 in his PSRU and 7500 RPM for take off. 2.85:1 is
what you will get with a Tracy's latest Ford C6 based planetary gear ratio.
I don't have an RV and my Kis Cruiser is not flying yet. Perhaps
some of the RV guys will chime in.
Paul Lamar
"Lemings, Bob" wrote:
Thanks, Paul,
I got the impression from reading web-site info that you had an RV with a rotary (that's what I get from reading too much-- it all gets jumbled together). After I rechecked, it turns out I was reading about your visit to Tracy with the water manometer, working on his RV.
I understand the rotary and high rpm's, but I also know that you can only spin a prop so fast. I was planning to use Tracy's 2:17 : 1 drive and I was worried about not developing enough horses at 6000 rpm and/or overspeeding the prop. I'm not up on power curves and maybe with the prop load and all the fuel dumped in for take-off, the horsepower may be there-- I just don't know. Obviously, the engine develops enough, since quite a few are flying. Tracy estimates the hp in his RV4 at 180. I'm planning to visit him sometime next month to get a bird's eye view of what he has done with the engine.
Anyway, as I've said before, I'm a rookie at this and I want to get all the facts straight before I jump in with both feet. I have access to an extremely capable rotary mechanic, but he builds engines for cars, not planes. He is very good at it though. We have one RX7 that used to be a twin turbo. He changed this to a single huge turbo with about 4 or 5 inch plumbing which develops an awesome amount of horsepower-- it is the most powerful machine I've ever driven, and I grew up on Chrysler Hemi's and 440 magnums in the late sixties. But, he hasn't worked on packing all that stuff under a cowling.
Bob
Jerry Bass wrote:
I have a RV6A with a Ross 2.85 reduction and a 68"dia by 78" pitch prop. I get 1500 vertical and 150nm/hr at 6500. I have run it at 7500 rpm and get about
165nm/hr single, with low gas. I suspect I could use more pitch. I will talk to Tracy at SNF about his 2.85 with a 74"x 88" prop. My gas milage is not what i
should get though.
Jerry Bass
540-932 3125
Cell 241-2675
It does sound like you are under pitched?
Ian is getting over 200 MPH or 173 kts with his RV6A and a 2.85:1.
How are you leaning your engine Jerry?
Paul Lamar
Thanks to all for the input.
The end performance I'm looking for is shown in the table below (factory specs for the MII) with a 200 HP Lycoming mill. I guess what I'm asking is can I get this performance from a 13B NA, and roughly what it takes to get there. Not sure how this table will transmit, but here it is. Lots of builders have achieved the numbers shown and often exceed them. One guy at S & F last year averaged about 250 mph in the 100, taking 2nd place overall (photo attached). Note the super-slick openings in the cowl.
O-320 IO-360
160 H.P. 200 H.P.
TOP SPEED (sea level) 210 mph 230 mph
CRUISE SPEED (true airspeed, 75% power @ 8000 ft.) 195 mph 220 mph
RANGE @ 75% POWER (37 gal. version) 780 miles 770 miles
RANGE @ 75% POWER (48 gal w/ wet wing) 1000 miles 990 miles
RATE OF CLIMB 1500 fpm 1900 fpm
SERVICE CEILING 17,000 ft 20,000 ft
STALL SPEED (clean) 62 mph 62 mph
STALL SPEED (full flap) 58 mph 58 mph
TAKE OFF DISTANCE 570 ft 470 ft
LANDING DISTANCE 680 ft 680 ft
ROLL RATE 190/sec 190/sec
Bob
Nice picture Bob.
Paul Lamar
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