Engine torque: simple about complex things

What is torque and why is it more important than horsepower?

When it comes to engine performance, most drivers immediately look at horsepower. But experienced mechanics and racers know: the real “strength” of the car lies in another parameter - torque. This is the same invisible energy that makes the wheels spin, climb hills and accelerate sharply at traffic lights. Without it, even a motor with 500 hp. It will be useless, like a sports car without wheels.

Torque is measure of rotational force, which the engine transmits to the crankshaft, and then through the transmission to the wheels. Imagine that you are unscrewing a nut with a wrench: the longer the wrench or the stronger your force, the easier it is to move the rusted threads. The same principle works here: moment = force × leverage. In a car, “leverage” is the radius of the crankshaft crank, and “force” is the pressure of the burning fuel on the piston.

But why then are horsepower so often mentioned in car advertising? The point is in marketing: power (hp) is easier to think of as “the speed at which work is done,” and torque as “the ability to do this work.” For example, diesel engine usually has high torque at low revs, so it pulls trucks well, while a gasoline engine with peak torque at high revs is better suited for sports cars.

Physics of the process: how torque is generated

To understand where torque comes from, let’s look at the operation of a four-stroke engine:

1. Intake: The piston moves down, the air-fuel mixture enters the cylinder.
2. Compression: the piston goes up, compressing the mixture (at this moment almost no torque is generated).
3. Working stroke: the spark plug ignites the mixture, the expanding gases push the piston down - This is where up to 70% of the cycle torque is created.
4. Issue: The piston pushes out the exhaust gases (torque is again minimal).

Key nuance: the torque depends not only on the gas pressure, but also on crank angle. At low speeds (for example, when starting off), the cylinders are filled less well with the mixture, so the torque is weaker. As the engine spins up, the filling of the cylinders improves, and the torque increases - up to a certain limit, after which it begins to fall due to mechanical losses and air resistance.

Why are diesel engines more powerful than gasoline engines?

Diesel engines do not have a throttle valve, so at low speeds the cylinders are filled with air more efficiently. In addition, a high compression ratio (14:1–20:1 versus 9:1–12:1 for gasoline engines) provides greater pressure during fuel combustion. That is why diesel engines produce maximum torque already from 1500–2000 rpm, and gasoline engines only from 3500–4500 rpm.

Units: Nm vs kgfm vs hp

Torque is measured in newton meters (Nm) is a standard unit in the SI system. But in old technical documents (especially for domestic cars) you can find kilogram-force per meter (kgf m). To convert kgf m to Nm, multiply the value by 9.81 (gravitational acceleration). For example, 10 kgf m ≈ 98.1 Nm.

How is torque related to horsepower? Power (hp) is the product of torque and engine speed, divided by a factor of 7027 (to convert to metric hp):

Power (hp) = (Torque (Nm) × Revolutions (rpm)) / 7027

Example: if the engine produces 200 Nm at 4000 rpm, its power will be (200 × 4000) / 7027 ≈ 114 hp. This explains why diesel engines with a “modest” 150–200 hp. easily outpaces gasoline engines with 250+ hp. in load capacity or acceleration from low speeds.

Parameter	Gasoline engine	Diesel engine
Peak torque (Nm)	150–300	250–600
Peak torque speed	3500–5000	1500–2500
Maximum power (hp)	120–500+	100–400
Efficiency at low speeds	Weak	High

How to Read a Torque Graph

In the technical characteristics of a car, graphs of the dependence of torque and power on engine speed are often given. Here's how to interpret them:

• 📈 Peak moment: The point where the curve reaches its maximum. The lower the speed at this point, the more “elastic” the engine is (it pulls better without changing gears).
• 🔄 "Shelf" moment: a flat section of the graph where the torque hardly changes. Ideal for overtaking - there is no need to rev the engine.
• 🚗 Intersection with power: Typically occurs around 5000-6000 rpm. After this point, the torque drops, and the power still increases (but this is already a “red zone”, harmful for the engine).

Example: y Toyota Land Cruiser 200 with diesel 1VD-FTV moment 650 Nm is already achieved with 1600–2600 rpm. This means that the SUV can overcome off-road conditions at low speeds without the risk of stalling. And for sports Honda Civic Type R moment 400 Nm appears only when 2500–4500 rpm - but at high speeds it gives diesel engines a head start in dynamics.

Practical Application: How Torque Affects Driving

Knowing the characteristics of torque will help you:

• 🚛 Select a car for the task: to tow a trailer you need a diesel engine with a torque of 400 Nm, and for city trips a gasoline engine with 150–200 Nm.
• 🔧 Save fuel: keep the speed in the maximum torque zone (usually this is 2000–3000 rpm for diesel engines and 3000–4500 for gasoline engines).
• 🏁 Accelerate faster: change gears at the moment the torque drops (and not according to the tachometer!). For example, if the moment falls after 4000 rpm, change gear before the needle reaches the red zone.

Experienced truck and SUV drivers often use the technique "engine braking", relying on a high moment. For example, when descending a mountain, you can engage a lower gear - the engine will hold the car back without the risk of the brakes overheating. This works due to the fact that the crankshaft “pulls” the wheels back through the transmission, and the high torque enhances this effect.

Keep the speed in the zone of 70–80% of peak torque

Avoid sudden accelerations (they push the engine into an inefficient zone)

Change gears smoothly, without “failures”

Use the highest gear on the highway (if the torque allows you to maintain speed) -->

⚠️ Attention: if your car is equipped turbocharged, be careful with sudden gas pressure at low speeds. Turbo lag (delay in the turbine reaction) can lead to jerking when the torque suddenly “picks up” the wheels. This is dangerous on slippery surfaces!

How to increase torque: tuning and misleading myths

Many car owners dream of “pumping up” the torque of their engine. Here's what really works:

• 🔥 Chip tuning: flashing the ECU can increase the torque by 10–20% by optimizing the ignition timing and fuel maps. But this is only relevant for turbocharged engines!
• 🌀 Turbine installation: a naturally aspirated engine after turbocharging can increase 30–50% torque, but will require strengthening the piston group.
• 🔧 Exhaust manifold replacement on the “spider” improves gas removal and adds 5–15 Nm at high speeds.

Now let's look at the myths:

• ❌ "Zero" air filter: gives an increase in power only on racing cars with forced engines. On production cars the effect is - ±0 Nm.
• ❌ "Magnet for fuel line": has no effect on the moment. This is pure quackery.
• ❌ "Sports candles": can improve ignition, but the increase in torque will be no more 1–3%.

⚠️ Attention: if after tuning the torque increased by more than 25% from the factory value, be sure to strengthen gearbox and clutch. Standard units are not designed for such loads and may fail!

FAQ: Frequently asked questions about torque

Can high torque damage the transmission?

Yes, if the torque exceeds the calculated loads for the gearbox or axles. For example, Nissan Patrol with the moment 600 Nm requires a reinforced automatic transmission, otherwise it will “burn out” after 50–80 thousand km. When tuning, always check the safety margin of the transmission.

Why do electric motors have torque from 0 rpm?

Electric motors generate maximum torque (200–600 Nm) immediately at start, since they do not depend on the speed and fuel combustion process. Therefore Tesla Model S accelerates to 100 km/h in 2.5 seconds without “dips” - unlike an internal combustion engine, which needs to rev up.

How is torque related to towing?

For towing a trailer, it is not so much the peak torque that is important, but its Availability at low speeds. For example, Ford F-150 with the moment 500 Nm at 1750 rpm will pull a 5 ton trailer easier than BMW M5 with 750 Nm at 4000 rpm - despite the lower number.

Is it possible to feel the moment during a test drive?

Yes! Please note:

• How quickly the car responds to the gas pedal at the “lower” range (1500–2500 rpm).
• Is it necessary to change gears frequently when overtaking (if so, the moment is “narrow”).
• How smoothly does the car accelerate without “dips”.

For example, Skoda Octavia with 2.0 TDI (340 Nm) pulls from any speed without switching, and Mazda 3 with 1.5 Skyactiv (150 Nm) requires you to “turn” the motor.