‘Power is nothing without control’

A vehicle’s engine power is measured in either horsepower (hp) or kilowatts (kW). 1 kW is equal to 1.36 hp, and 1 hp is equal to 0.735 kW.

Engine power measures how much energy the engine can provide to perform a task over a certain period of time. The higher the engine power, the faster a vehicle can accelerate and the better it can maintain a high speed. The engine’s power therefore describes its ability to deliver energy for driving. It depends on the engine’s torque and speed (number of revolutions per minute).

Generally speaking, more power results in better acceleration and a higher top speed. On the other hand, less engine power reduces the vehicle’s fuel consumption.

How many horsepower can you expect, depending on the type of vehicle?

What is torque – an often-overlooked piece of information.

Torque is the force with which the engine turns the wheels. It is measured in newton metres (Nm) and directly affects the acceleration capacity and pulling power of the vehicle.

We can illustrate this with a spanner. The longer the spanner, the easier it is to loosen the nut. Torque works in the same way. The higher the torque, the more force the engine can transfer to the wheels. This is particularly useful for low-speed acceleration, high pulling power without downshifting, and towing or transporting heavy loads.

Power (expressed in horsepower or kilowatts) is a function of torque and speed (power = torque x speed). An engine can have high power but low torque. An example of this is a motorcycle engine, which can reach a high speed range. By contrast, a diesel engine, which turns less, has a high torque at low speeds, while the torque is immediately available in an electric vehicle.

• A turbo diesel engine offers high torque at low speeds and is therefore ideal for long distances at a fairly constant speed.
• A turbo petrol engine has moderate low-end torque for longer than a diesel engine. It is therefore suitable for driving in towns and suburbs.
• A naturally-aspirated petrol engine only reaches its maximum torque at a fairly high engine speed. To accelerate well, the engine must therefore be revved up higher.
• An electric motor can access its torque directly and is therefore impressively responsive.

While it is true that there is no single ideal torque for all types of engine, since the type of vehicle and its use are much more decisive, it is possible to define an optimal torque according to the requirements:

City car (small and light)

Optimal torque: 100 to 180 Nm
Example: Peugeot 208 PureTech 100 (205 Nm at 1,750 rpm)
A moderate torque, which quickly ensures a balanced driving style in the city, without putting too much strain on the transmission.

Compact car / family saloon (balanced performance and consumption)

Optimum torque: 200 to 350 Nm
Example: Volkswagen Golf 2.0 TDI (360 Nm at 1,600 rpm)
Good torque at low revs, which increases pulling power and driving comfort on the motorway without frequent downshifting.

SUV / all-wheel drive (higher weight, requires power to pull loads)

Optimum torque: 400 to 600 Nm
Example: BMW X5 xDrive30d (650 Nm at 1,500 rpm)
High torque that facilitates acceleration despite the weight and increases towing capacity.

Sports car / supercar (desire for maximum performance)

Optimum torque: from 500 Nm
Example: Porsche 911 Turbo S (800 Nm at 2,500 rpm)
A huge amount of torque combined with a high-revving engine that enables lightning-fast acceleration.

Electric vehicle (torque available immediately)

Optimal torque: very high, but well controlled electronically
Example: Tesla Model S Plaid (1,420 Nm!)
The electronics often limit the torque to avoid a loss of grip.

Some comparative data for torque/weight

Light vehicle (1,000–1,200 kg)

A torque of 150 to 250 Newton metres is sufficient for good performance.
Example: Mazda MX-5 (1,100 kg / 200 Nm) → very manoeuvrable despite moderate torque

Medium-sized saloon (1,300–1,600 kg)

A torque of 250 to 400 Newton metres enables pleasant acceleration.
Example: BMW 3 Series 320d (1,500 kg / 400 Nm) → good balance

SUV or all-wheel drive (from 1,800 kg)

Requires 400 to 600 Nm to avoid a feeling of sluggishness.
Example: Audi Q7 50 TDI (2,100 kg / 600 Nm) → dynamic despite its weight

Sports car

For this type of vehicle, the ratio between weight and power is more important than torque alone.
Example: Porsche 911 GT3 (1,450 kg / 470 Nm) → moderate torque, but rapid increase in speed

Electric vehicle

Torque is usually very high, but the electronic control and weight are crucial.
Example: Tesla Model S Plaid (2,160 kg / 1,420 Nm) → peak performance despite weight

Do you need 1 Nm per kilogram?

No, this rule doesn’t always apply. A vehicle weighing 1,500 kg with a torque of 1,500 Nm would be excessively powerful. Here are some trends:

• 0.1 to 0.2 Nm/kg → city car (e.g. Clio, Golf)
• 0.2 to 0.3 Nm/kg → saloon car / SUV
• 0.3 to 0.5 Nm/kg → sports car
• 0.6 Nm/kg and more → supercar / electric car