"If you could buy a 380HO that makes 57hp, would you Buy a 440F, 503F, 470LC for more Money?"
Would I buy a 57hp 38HO it if it was unreliable and broke down on the trail or race track ?? - NO
The Production 380HO was 47.6hp @ 7150rpm.
<--- 2004 Skidoo Race Manual says both 380F 9.6cr & 380HO 11.2cr rated at 7000rpm! Standard 380F is listed at 36hp, and the 380HO 48hp Stock.
Targeted at European Sno-cross racing it needed to be somewhat reliable for race track conditions.
That's likely why it was not given 50+ hp (Reliability)
And why it wasn't offered to the largest markets in Canada and the USA lower 48 for trail use. (Warranty)
Since this is about flying, the highest known "flying reliable HP" 377/447 is the 46.3hp R&D piped 447UL
R&D Piped Aircooled motors - Assumed reliable.
447- 437cc @ 46.3HP = 9.4cc/hp
277- 268cc @ 30.5hp = 8.8cc/hp
503- 497cc @
62.3hp = 8cc/hp
<--- Stock 503UL was 49.6hp + 25.6% (Mild) = 62.3hp! When Designing a Tuned Pipe you can do the 496.9cc/7cc=
70.9hp or use the Max 40% Rule for Aircraft use. 49.6hp + 40% = 69.44hp. Racers will go Higher than 40% and turn them higher rpm. The fellow on Youtube that Races a 277F turns it 9200rpm using 14.5cr. 70.9hp - 69.4hp = 1.5hp difference. -->
Would still like to see a Rotax air-cooled UL motor modified for 7cc/hp @ 6500
Then tested for 5 minutes @ 100% followed by 2 hours @75% with a prop. (Repeated a few times)
Swinging a prop, a 6500rpm motor will still be Turning about 5900rpm at 75% power. (Formula below)
View attachment 113792
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You know guys like you who have probably never built a 2 Stroke for plane use, or built a Tuned Pipe for one or do you even have any 2 stroke on a Plane, you seem to have a lot of opinions, but No Facts. You have no problem with a 248cc Polini turning 8000rpm making 36hp on planes, but a Rotax turning 6500rpm for a few minutes making 52-53hp is going to fall apart.
Also, it's
75% Power, not
75% rpm! Are these
75% Power Settings Max Continuous Power, NO! It's more for getting the best GPH use!
670
[email protected] = 92 x 75% = 69hp
618UL
[email protected] = 73.4 x 75% = 55.1hp
582UL
[email protected] = 65 x 75% = 48.75hp
462UL
[email protected] = 52 x 75% = 39.0hp
503UL
[email protected] = 50 x 75% = 37.5hp
447UL
[email protected] = 40 x 75% = 30.0hp
377UL
[email protected] = 35 x 75% = 26.3hp
277UL
[email protected] = 28 x 75% = 21.0hp
277UL
[email protected] = 26 x 75% = 19.5hp
With a mild R&D Aero Tuned Pipe: Using the 7cc Rule to make 1hp is for 6500rpm, using 11.5cr, and using the Proper Size Carb! Using your +/- 1.0cr = 1hp which was from a 4 Stroke Chart, but Hey I understand these Numbers are all Theoretical Ball Park.
277UL [email protected] 268.8cc/7cc=
[email protected]
503UL [email protected] 496.9cc/7cc=
[email protected]
670 [email protected] 669.2cc/7cc =
[email protected]
Simonini Victor 1 Super,
54hp, is about the most perfect Production Engine. Using
9.5cr,
36mm Carb, 6500rpm and
400.5cc/7cc=
57.2 - 2hp for the low 9.5cr =
55.2hp! Now we know for a FACT the 380HO
368.4cc made
[email protected] from the Dyno Sheet and was making
[email protected] Variance from 7cc Rule
1.2hp! Now, does it use the Proper Size Carb? Victor 1 Super
400.5cc, 36mm, vs the 277UL,
268.8cc, uses a
36mm Carb? My 1972 292 TNT Single came with a
38mm Carb rated
[email protected] using 10.5cr with a Can Muffler.
Kawasaki 440 (68mm x 60mm)
435.9cc vs Rotaxs 447UL (67.5mm x 61mm)
436.7cc.
Kawasaki Stock Tuned Pipe -
63hp at 6750rpms, made
61hp@
6500rpm! Kawaski 440 435.9cc/61hp =
7.1cc and they have been used on Planes. They also use a lower CR than the suggested 11.5cr, either 9.5cr or 9.6cr. Kawasaki 440 is 435.9cc/7cc = 62.2hp a 1.2hp difference from Stock Tuned Pipe and the 7cc Rule! Rotax's 447UL is 436.7cc/7cc = 62.3hp! So I suppose you want to argue about .1hp!
To my knowledge, R&D Aero never made a Tuned Pipe for the 377UL/380F or the 380HO which wasn't sold in the Continental USA, or Canada, only in Alaska. We don't know who made the 380HO aftermarket Tuned Pipe, but it did make
[email protected] as the 7cc Rule says it should.
I like how you assume an Engine is unreliable in your opinion, yet you have never used one, or built one, or used any of these Engine Coatings!
As the Engine & Tuned Pipe Builder, YOU, decide what hp you want to make. Most all Part 103 & Most Small Kitplanes All have an MTOW that falls between
450lbs and
660lbs. Which
660lbs requires
40.1hp using the Simple Power to Weight Ratio of 1kw for 10kg Rule, if you want it to Fly Well. The 377UL/380F with some minor tweaking, a CR Bump, some Cylinder & Case Porting, using Dual 34mm Carbs or a 38mm, and use a better less restrictive Muffler, the 377UL/380F could probably make that 40.1hp or more even without a Tuned Pipe.
Cylinder and Case Porting you can Gain 10-15% more power.
Going from a 36mm to a 38mm can Gain you 10% more power.
A CR Bump from 9.6 to 11.6 = 2hp.
Just a Standard 377UL/380F 35hp +15% = 40.25hp Porting.
35hp + 10% = 38.5hp Carb Change Single 36mm to a 38mm. 38mm is as Big as the Stock 277, 377, 447, 503 Intakes go without Machining and Welding.
Per Aaens Carb Book same Aaen of Tuned Pipe Fame, the Mikuni Flat Side Carb is as close to EFI you can get. A New Mikuni Flat Side 38mm on eBay $135.