This is one debate that car enthusiasts have all the time; “My car has more horsepower, so it’s better. Nope, mine has more torque, so it’s better.” Today, we’ll explain what Horsepower and Torque are, what’s more important, and who needs what.
First of all, let’s define power in simple terms. Power is what takes you to a high top speed. It’s essentially the measure of the rate of work that an engine can do. So, if the engine can do a lot of work quickly, it’s termed as very powerful. That’s what fast cars have powerful engines. Power is denoted by Bhp/Kw/Ps/Hp.
Torque is what sets something in motion. It’s the turning force that the engine generates to get the car moving. It’s essentially the measure of work done by the engine. So, if the engine can do a lot of work, it can pull a lot of weight around. That’s why trucks have diesel engines that produce high torque. Torque is denoted by Nm/Kg-m/Lb-Ft.
How are power and torque related?
Horsepower = (RPM * Torque)/5252
Here rpm stands for revolutions per minute, or the number of times a crankshaft of the vehicle rotates per minute.
What this means is, torque will always be higher than the horsepower until 5,252 rpm. After this rpm, horsepower will become greater than torque. This is also the reason why high revving engines (rpm>5,252) makes more horsepower while low revving engines (rpm<5,252) make less horsepower.
So, what’s more important, horsepower or torque?
Both of them, and this varies from task to task. Here are a bunch of real-life scenarios that will help you understand how horsepower and torque work in the real world.
You live in the hills, and need a vehicle that needs to pull you, your family and luggage up some very steep inclines
You need to buy something like the Mahindra Bolero DI. The Bolero DI has a 2.5 liter turbo diesel engine that produces a lot of torque at low rpm (63 Bhp at 3,200 rpm and 182.5 Nm at 1,440-1,500 rpm). It also has low gearing, which makes sure that most of the engine’s torque goes to the wheels at low rpms. So, this is an ideal vehicle for such an application.
On the other hand, a Mahindra Scorpio 2.2 mHawk produces much more power (120 Bhp at 4,000 rpm and 280 Nm between 1,800-2,800 rpm) but this vehicle will need to be revved heavily to climb steep inclines. This will also result in lower fuel efficiency in hilly regions. However, the same Scorpio will be much faster than the Bolero on the highway as it produces power at a higher rpm and is geared to utilize that power.
Key takeaway: Diesel engines can be used for both high speeds as well as heavy load carrying. The key difference here is gearing.
You want a fast accelerating car to win traffic light GPs
The Honda City has a high revving 1.5 liter petrol engine, and well matched gear ratios that help it accelerate very quickly. The City’s VTEC motor makes 117 Bhp at 6,600 rpm and 145 Nm at 4,600 rpm.
The Ford Figo Diesel has a powerful 1.5 liter diesel engine and well matched gear ratios. Result: Great acceleration that’s even faster than the Honda City’s 10 second timing. So, the Figo Diesel will beat the City Petrol in a drag race, but when it comes to top speed, petrol power will still rule.
Takeaway: Petrols generally have higher top speed while diesels can accelerate very quickly. The City will be a faster car than the Figo despite the torque deficit. This is because the power (which is required to maintain a high top speed) is higher on the City, and is produced at a higher rpm.
You want a very fast highway car
Here, you can buy either a petrol or a diesel. Go for a petrol car such as the Skoda Octavia TSi if your highway runs aren’t too many. On the other hand, a diesel such as the Chevrolet Cruze will do if you want a fast highway car that’s quite fuel efficient too.
Takeaway: Powerful petrol and diesel cars that have engines tuned to make a lot of power can do big highway speeds. Again, it boils down to gearing.
You want a highly efficient city car that’s easy to drive
Here a diesel car with ample low end torque means that you can putter around town at low rpm, without having to shift gears too many times. For instance, the Ford Figo Diesel is a much better bet for city commutes in terms of fuel efficiency and ease of driving. A similar petrol car, say for example the Maruti Swift will need much more gear shifts.
Takeaway: If you do big monthly distances in the city, a diesel car with good low end torque is the best bet.
These are just some of the real-life scenarios we’ve laid out for you, to show how power and torque work in the real world. But remember, it finally boils down to the engine and gearing that will make a car suitable for a particular application. One size clearly does not fit all.