A Simpler Explanation Of The Measurement Of ONE HORSE POWER

valhalla360 wrote:

pnichols wrote:

I'm NOT trying to start once again that infamous RV/truck owners' timeless discussion ... BUT: Isn't all horsepower the same? And also don't modern rotating machines merely convert their available horsepower into the required rotating torque at the required location using various gears and driveshafts?

Now here's what I'd sure like to have explained ... why a 300 horsepower diesel RV engine can "tow better" than a 300 hrosepower gas RV engine? That has never made sense to me. :h

Two engines putting out equal HP will tow equally well...this assumes you mean will they be able to exert the same pulling power.

There are a few caviots:
- HP = Torque x RPM, since diesels make higher torque but peak at lower RPM, they sound quieter when producing peak HP due to the lower RPM, whereas the gas engine is fine but it sounds like it's screaming up at 4000-4500 RPM.
- This assumes there is a gear ratio that lets the motor reach peak HP. In the old days of 2...3...4 speed automatics, you often wound up in a gear that didn't let the engine reach peak HP. Modern 6-10 speed automatics largely eliminate this issue.
- Exhaust brakes are an add on that make a diesel more controllable on a downgrade...it can't pull more because of it but it does improve the towing experience.
- It's changed with modern gas engines putting out similar HP to the diesels but in the past, the diesel was typically a HP jump compared to the base 5L gas V8.

Mike ... very well stated ... and about what I thought!

I've always thought that the diesel owners thought that their rigs pulled better because they didn't have to rev the engine very high to tap the engine's horsepower. Kindof a preference thing, not really based on engineering facts.

The V10 in our small motorhome will paste me back into the seatback if I punch it, but it takes 4000-5000 RPM to do it.