The Definitive Torque vs. Horsepower post
Year after year, I keep seeing the same old debates about torque vs. horsepower. Everyone seems to have a general idea that we are referring to power, but most don't really understand the relationshi...
Forum Discussion
I prefer to rearrange the OP's equation (Torque x Revolutions Per Minute / 5252 = Horsepower) so as to more clearly show that engine torque depends directly upon how much power the engine can produce, as follows:
Torque = Horsepower X 5252 / Revolutions Per Minute
Notice from the above restructured equation that A) the relationship between torque and horsepower has nothing to do with whether it's a diesel engine or a gas engine producing the horsepower, and B) that the torque in the equation is engine crankshaft torque ... NOT the torque that counts ... that which winds up on the axle of the drive wheels.
What the above equation means is this - for example:
Given a specific vehicle weight, going up a specific grade, at a specific speed, starting at a specific altitude ... a 465 HP diesel engine will do no better or worse than a 465 HP gas engine ... ASSUMING that both engines are geared correctly and that both engines can produce the necessary horsepower at whatever RPM is required by the design and fuel type of the engine. "Can produce" is a very important consideration -> as one cannot and should not compare a turbo charged engine of given horsepower to a non-turbo charged engine of the same horsepower whenever altitude (density of air) is involved.
Since a diesel engine, by design and by it's fuel's energy per gallon and burn characteristics can only run at lower RPM with the required long crankshaft throw-lengths - it's output at any required horsepower results in higher crankshaft torque. With a gas engine running at higher RPM due to needing more explosions per minute from it's fuel's lower energy per gallon - it's output at any required horsepower results in lower crankshaft torque due to shorter crankshaft throw-lengths. High or low crankshaft torque is made irrelevant whenever the proper gearing is in place so horsepower can be converted into the required torque on the drive axle for any given vehicle situation.
The result from all this is that a properly set up diesel vehicle pulls "different" - not "better" - than a properly set up gas vehicle if the altitude (air density) turbo versus non-turbo issue is not involved. Of course "better" is a matter of preference because some folks like a low RPM (diesel) engine for pulling while others might not mind a higher RPM (gas) engine for pulling.
If one was to compare an X-horsepower properly geared turbo-charged diesel to an X-horsepower properly geared turbo-charged gasser, then the diesel-gas debate might not count for much whenever altitude is a consideration in RV travel.
Torque = Horsepower X 5252 / Revolutions Per Minute
Notice from the above restructured equation that A) the relationship between torque and horsepower has nothing to do with whether it's a diesel engine or a gas engine producing the horsepower, and B) that the torque in the equation is engine crankshaft torque ... NOT the torque that counts ... that which winds up on the axle of the drive wheels.
What the above equation means is this - for example:
Given a specific vehicle weight, going up a specific grade, at a specific speed, starting at a specific altitude ... a 465 HP diesel engine will do no better or worse than a 465 HP gas engine ... ASSUMING that both engines are geared correctly and that both engines can produce the necessary horsepower at whatever RPM is required by the design and fuel type of the engine. "Can produce" is a very important consideration -> as one cannot and should not compare a turbo charged engine of given horsepower to a non-turbo charged engine of the same horsepower whenever altitude (density of air) is involved.
Since a diesel engine, by design and by it's fuel's energy per gallon and burn characteristics can only run at lower RPM with the required long crankshaft throw-lengths - it's output at any required horsepower results in higher crankshaft torque. With a gas engine running at higher RPM due to needing more explosions per minute from it's fuel's lower energy per gallon - it's output at any required horsepower results in lower crankshaft torque due to shorter crankshaft throw-lengths. High or low crankshaft torque is made irrelevant whenever the proper gearing is in place so horsepower can be converted into the required torque on the drive axle for any given vehicle situation.
The result from all this is that a properly set up diesel vehicle pulls "different" - not "better" - than a properly set up gas vehicle if the altitude (air density) turbo versus non-turbo issue is not involved. Of course "better" is a matter of preference because some folks like a low RPM (diesel) engine for pulling while others might not mind a higher RPM (gas) engine for pulling.
If one was to compare an X-horsepower properly geared turbo-charged diesel to an X-horsepower properly geared turbo-charged gasser, then the diesel-gas debate might not count for much whenever altitude is a consideration in RV travel.
