- The Response - Power losses associated with
the driveline (transmission, primary gears, clutch, oils
sprockets and chains) is normally considered to be 14% to
17% for a modern 250 cc motocross bike. Therefore 53.3 HP
@8300 RPM at the rear wheel translates into 62.3 HP at
the crankshaft if using the 17% factor and 60.7 if using
the 14% number. Using this information it is
- easy to calculate the BMEP (brake mean effective
pressure) of this engine.
-
- 53.3 * 17% = 62.3 at the crankshaft.
- 62.3 / 8300 * 5252 = 39.45 Torque.
- 39.45 * 1236 / 250 cc = 195.08 psi BMEP.
-
- Aren't you glad you don't have a snowmobile that
loses as much as 50% of its power between the crank and
the track?!?
-
- Rick
-
-
-
-
-
- Ok , Thanks
I do have a 540cc Yamaha
snowmobile... about 50% ouch that's a lot... 62.3 HP is a
respectable number coming from 250cc. I would be happy to
get 62.3 hp and 39.45 Torque out of my 400cc Pilot motor
( stock its rated at 37hp).
-
- Thanks again
- hoser :)
-
-
-
-
-
- The TRX250R was rated at 36 HP from the factory.
Figuring in the normal 50% over design factor necessary
to satisfy most engineers and a few more percent than
that because this is real life - there is plenty of room
to work within most engines. The only thing that's a
little questionable with that engine is the long stroke
which prevents it from stratospheric rev levels.
-
- Considering you have a 400 cc modern high output
engine, I would think that if it were blueprinted and
optimized to run race fuel, horsepower numbers like you
want are not impossible. However if you want to have your
cake and eat it too you will have troubles. Engines
designed for ultimate power eat and drink expensive, high
quality parts and fluids and require frequent
maintenance. Tuning into this sweet-zone is a one way
street - once you experience the thrill you'll never
enjoy riding the Pilot the old way again. Letting kids,
wives, friends and just about anyone else drive it
becomes something that will just never happen again.
-
- Rick
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