Horsepower is a function of torque. So the more torque you have the more horsepower you will have if you can spin the engine faster. Bigger engines make more torque due to displacements and compression ratios. For example diesels are torque monsters but don't make much horsepower as compared to a gas engine due to their lower RPM limits. My wifes 2.0 liter VW TDI only makes 140 horsepower but 235 ft.lb of torque due to the high compression ratios of diesel engines. Gas engines depend on higher RPM's to make Hp due to the lower torque they provide with their lower compression ratios.Quote:
Originally Posted by Hoopskier
For a given torque and speed, the power may be calculated; the relationship between torque in foot-pounds, rotational speed in RPM and horsepower is:
P(hp)= (T[ft.-lb])(ω[RPM])/5252 or Hp = T x RPM / 5252
Where P is power, Τ is torque, and ω is rotations per minute. The constant 5252 comes from (33,000 ft·lbf/min)/(2π rad./rev.).
The fact that most big diesel engines redline at less than 3000rpm illustrates the vast amount of torque they make at lower RPMs. This pretty much explains why Large boats and Trains use diesel engines, they need torque at lower RPM's to get the large Mass moving. This also helps by not having to have a lot of gear reduction in a big gearbox that would be needed with a Gas engine turning high RPM's to generate sufficient torque to move a heavy object. But in a skiboat you need both torque and RPM, if the RPM is limited you will not be able to go fast as you don't have a gear box to help spin the prop faster. So a bigblock gas engine would be the WAY to go if you want torque and speed in a skiboat! Check out the old MasterCraft Barefoot boat. They all said 454 cu in on the back of them!
