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...
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It's hard to compare the efficiency of gas vs diesel because diesel fuel has more BTU's.
I have always found this to be the easiest way to explain it. Torque is how much work you can do, and hp is how fast you can do it. 400 hp and 400 ft/lbs can do the same work as 200 hp and 400 ft/lbs, but it will do it faster. That's why they are both important. My MY truck had a 325hp diesel or 375hp gasser. The diesel was better at towing because it has more torque and can get the load moving, but once a load was moving the gasser would be able to keep it moving the same or better (assuming running at rated rpm).
That's not true. Horsepower and Torque are reported at "x" rpm, and is the peak for each if the rpms are different, as they are in nearly all motors (can't think of any where hp/tq peaks are at the same rpm.
My motor OEM spec's where 325hp @ 2900 and 610 ft/lbs @ 1600.
Doing the math that's 185hp @ 1600 and 588 ft/lbs @ 2900, neither of those are my engine's peak ratings.
Quoted hp is just that, the highest hp obtained on the dyno. It's a combination of rpm and torque.
Why do you have to be in top gear to make peak hp? In factory form my motor made peak hp at 2900 rpms, I could hit those rpms in any gear and be wide open making full power. Now in lower gears there will be some torque management, but that goes away at approx 35 mph.
Unless the vehicle has some safety programming there is no reason you cannot hit rated rpms at full fueling in gears below OD.
Often times peak hp is not needed in lower gears because the gearing reduction increases the engine power to a point where acceleration occurs or the fuel is reduced to maintain speed. But I can tell you that when you put your foot on the floor from a stop you are making full power as the engine goes thru the gears or you manually shift (not talking torque management which is on most modern vehicles).
I have done dyno pulls in 5th and 6th gear, peak hp is the same.
I have always found this to be the easiest way to explain it. Torque is how much work you can do, and hp is how fast you can do it. 400 hp and 400 ft/lbs can do the same work as 200 hp and 400 ft/lbs, but it will do it faster. That's why they are both important. My MY truck had a 325hp diesel or 375hp gasser. The diesel was better at towing because it has more torque and can get the load moving, but once a load was moving the gasser would be able to keep it moving the same or better (assuming running at rated rpm).
holstein13 wrote:
The horsepower rating that you always see quoted by everyone is the horsepower at the maximum torque and RPM.
That's not true. Horsepower and Torque are reported at "x" rpm, and is the peak for each if the rpms are different, as they are in nearly all motors (can't think of any where hp/tq peaks are at the same rpm.
My motor OEM spec's where 325hp @ 2900 and 610 ft/lbs @ 1600.
Doing the math that's 185hp @ 1600 and 588 ft/lbs @ 2900, neither of those are my engine's peak ratings.
Quoted hp is just that, the highest hp obtained on the dyno. It's a combination of rpm and torque.
holstein13 wrote:
Meaning, you only get that maximum horsepower in top gear at top speed and depending on how your vehicle is geared, you may never be able to achieve that top gear at maximum RPM because your vehicle is too heavy or has too much wind resistance or has some other friction
Why do you have to be in top gear to make peak hp? In factory form my motor made peak hp at 2900 rpms, I could hit those rpms in any gear and be wide open making full power. Now in lower gears there will be some torque management, but that goes away at approx 35 mph.
Unless the vehicle has some safety programming there is no reason you cannot hit rated rpms at full fueling in gears below OD.
Often times peak hp is not needed in lower gears because the gearing reduction increases the engine power to a point where acceleration occurs or the fuel is reduced to maintain speed. But I can tell you that when you put your foot on the floor from a stop you are making full power as the engine goes thru the gears or you manually shift (not talking torque management which is on most modern vehicles).
I have done dyno pulls in 5th and 6th gear, peak hp is the same.
