Torque vs Horsepower: Clarifying the Difference

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In summary: Mazda Miata might be able to reach high speeds in 4th or 5th gear, but the engine doesn't produce any power until around 4000 rpm. This is because the engine has a close ratio gearbox, which allows it to shift quickly between gears. Sport bikes also have close ratio gearboxes, which allows them to reach high speeds quickly.
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jmnew51
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I had a dispute with a fellow on the subject of automobiles.
He insisted that torque is the force that gets you across the finish line in a race.
I insisted that torque is only part of the equation and that horsepower is what does the work, as horsepower or kilowatts, etc. is a fuction of torque and r.p.m. Torque is basically a static force, right? I would just like some clarification on this.

I may be totally wrong, but please let me know either way.

Thanx for listening.

Jim
 
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You're correct. Torque is almost meaningless, since as you mention, you can have a static torque where nothing is moving. The key factors for a car engine are peak power and the torque versus rpm curve. The flatter the torque versus rpm curve, the wider the power band. In the case of race cars with very fast shifters and lots of gears, such as a Formula 1 car, the power band doesn't need to be that wide, so there's more focus on maximum power at the cost of a wider powerband.

Rear wheel torque is related to the rate of acceleration, but being fast from 0 to 15mph isn't the same as fast from 0 to 60mph, so again, it's torque times rpm which is power that counts. Converting this into lateral components, force times speed equal power, for example, force in lbs times speed in mph divided by 375 (conversion factor) = power/horsepower.
 
  • #3
Thank you Jeff for the clarification.
Maybe having more torque over a wider rpm is what he was referring to.

All in all, it's like saying that the amps is what lights the light bulb, but we know that we need the volts to push the amps through a given resistance.

I know what you mean by close ratio, quick change gearbox. My girlfreinds Mazda Miata tachs out at about 7000 rpm, and gears 1 to 5 wil take you to about 100+-mph before redline, but the engine does not develop any power till around 4000 rpm, hence the close ratio necessary. Same with sport bikes. Try accelerating in 4th or 5th gear at 2 or 3 thousand rpm.

Jim
 

What is the difference between torque and horsepower?

Torque and horsepower are two different measurements of an engine's power output. Torque is the measure of an engine's rotational force, or its ability to rotate an object around an axis. It is typically measured in pound-feet (lb-ft) or Newton-meters (Nm). Horsepower, on the other hand, is a measure of an engine's work rate, or how quickly it can perform a certain amount of work. It is typically measured in units of horsepower (hp).

How are torque and horsepower related?

Torque and horsepower are mathematically related. In fact, horsepower is calculated from torque and engine speed using the formula: horsepower = (torque x engine speed) / 5252. This means that a higher torque output at a given engine speed will result in a higher horsepower output.

Which is more important, torque or horsepower?

Neither torque nor horsepower is more important, as they both play crucial roles in an engine's performance. Torque is important for tasks that require more force, such as towing or accelerating from a stop. Horsepower is important for tasks that require sustained power, such as high-speed driving or racing. Both torque and horsepower work together to provide a balanced and efficient engine performance.

Can a car have high horsepower but low torque, or vice versa?

Yes, it is possible for a car to have high horsepower but low torque, or vice versa. This depends on the design and purpose of the engine. For example, a high-performance sports car may have a high horsepower output for fast acceleration, but a lower torque output since it is not designed for heavy-duty tasks. On the other hand, a truck or SUV may have a high torque output for towing and hauling, but a lower horsepower output since it is not designed for high-speed driving.

How can I improve my car's torque and horsepower?

There are several ways to improve your car's torque and horsepower, such as installing performance parts like a cold air intake, exhaust system, or engine tuning software. Regular maintenance, such as changing the air filter and spark plugs, can also help improve engine performance. Additionally, driving techniques, such as shifting at higher RPMs, can also help improve torque and horsepower output.

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