[snoep]

WHAT MAKES YOUR CAR FAST? THE DYNAMICS OF TORQUE AND HORSEPOWER

In discussions about car performance, the terms horsepower (expressed in hp or kW) and torque (expressed in Nm) often come up. But what do these terms really mean for a car's driving behavior and driving experience? Why does a turbodiesel with lots of torque sometimes feel quick, yet underperform at higher speeds? And why do Formula 1 cars with relatively little torque still deliver incredible performance?

In this article, I’ll explain using power and torque curves, practical examples, and insights from both engine technology and modern engine tuning.

TORQUE AND HORSEPOWER: WHAT’S THE DIFFERENCE?

Torque (Nm) is the rotational force produced by an engine. This determines how "strong" a car feels at a given rpm. Think of it like a lever: the more force, the easier it is to move something.

Horsepower (hp or kW) is the result of torque combined with engine speed (rpm). Horsepower determines how quickly a car can accelerate or build speed.

The formula for horsepower is:
Horsepower (hp) = (Torque (Nm) × RPM) / 7023

In summary:

Torque indicates how strong the engine is at a given rpm.
Horsepower combines this torque with how fast the engine spins (rpm).


Example:

An engine with high torque at low rpm delivers strong-feeling acceleration from a standstill.
An engine that revs high can still produce a lot of horsepower, even if the torque is relatively low.


1. POWER/TORQUE CURVES OF DIESEL TURBO ENGINES

In diesel turbo engines, you often see:

Torque: High peak torque at low rpm (typically between 1,500-3,000 rpm).
Horsepower: Due to the rapid drop in torque at mid-rpm (often starting at 3,500 rpm), the power curve flattens out.
Example: BMW G21 M340d (B57D30T2) before and after tuning



The torque peaks early but quickly drops off, causing horsepower to decrease at higher rpm.

1.1 EFFECT OF CHIP TUNING ON DIESEL TURBO ENGINES

Chip tuning increases boost pressure and optimizes fuel injection, resulting in more torque at low rpm. However, due to limited air supply, power still falls off at higher rpm.

2. POWER/TORQUE CURVES OF GASOLINE TURBO ENGINES

In gasoline turbo engines, you often see:

Torque: High and broadly available (e.g., between 2,000-5,000 rpm).
Horsepower: Flattens out at higher rpm (typically above 6,000 rpm) due to turbo limitations.
Example: BMW G20 M340i (B58B30TU) before and after tuning



Torque increases significantly at low rpm but flattens out at higher rpm due to turbo limitations.

2.1 EFFECT OF CHIP TUNING ON GASOLINE TURBO ENGINES

Torque: After tuning, torque increases significantly at lower rpm (from 540 Nm to 790 Nm in the example above).
[]Turbo limit: After mid-rpm, the turbos "run out of breath," causing torque to drop and the power curve to flatten.


3. POWER/TORQUE CURVES OF HIGH-REVVING NATURALLY ASPIRATED ENGINES

In naturally aspirated (non-turbo) sports engines, you often see:

Torque: Lower peak torque, but consistent across a broad rpm range.
Horsepower: Increases linearly to high rpm (often up to 8,000 rpm or more).
Example: BMW E60 M5 (S85B50) before and after tuning



Torque is relatively low but increases with rpm, keeping the power curve steep up to the redline. This results in a dynamic driving experience, but to accelerate quickly, you need to rev the engine high.

3.1 EFFECT OF CHIP TUNING ON HIGH-REVVING NATURALLY ASPIRATED ENGINES

In naturally aspirated gasoline engines, chip tuning has a smaller effect than in turbo engines because there is no turbo or supercharger to increase airflow. However, adjustments to fuel injection and ignition timing can still yield benefits:

Power gain: A small increase in horsepower. In the example the was almost 50 hp.
RPM limit: The rev limiter can often be raised from 8,250 rpm to around 8,500-8,600 rpm.
Throttle response: Improved throttle response for sharper acceleration.
The shape of the torque curve remains mostly the same, but peak power shifts slightly higher in the rpm range.

CONCLUSION

1. Turbodiesels
Acceleration from a standstill: Quick and strong due to high torque at low rpm.

100-200 km/h: Moderate, as power drops off at higher rpm.
Top speed: Limited by low power at high rpm.

Driving experience: Feels powerful at low rpm but loses excitement as torque and power drop off at mid-to-high rpm.

Use: Ideal for daily driving, city traffic, and efficient highway cruising.

2. Gasoline turbo engines
Acceleration from a standstill: Strong and smooth due to broad torque peak.
100-200 km/h: Good, with power available over a wider rpm range.

Top speed: High, depending on turbo size and boost pressure.

Driving experience: Dynamic acceleration at low and mid rpm, but turbo limitations reduce power at very high rpm.

Use: Versatile for sporty street and track use. Similar to modern Formula 1 engines with high-boost turbo systems.

3. High-revving naturally aspirated engines
Acceleration from a standstill: Moderate at low rpm, strong at high rpm.

100-200 km/h: Excellent, due to high power at high rpm.

Top speed: Very high, with power continuing to rise up to the redline.
Driving experience: Linear power delivery and an exciting, dynamic experience as rpm increase.

Use: Perfect for track use, where linear power and high rpm are essential.

SUMMARY

Turbodiesels: Great for quick starts and strong low-rpm performance but lose steam at high rpm. A turbo upgrade can help sustain power.

Gasoline turbo engines: Versatile and powerful at low and mid rpm, but limited at very high rpm. Turbo upgrades can improve performance.

Why modern F1 cars are so fast: They combine gasoline turbo engines with extreme rpm (up to 15,000), hybrid systems for extra torque, and advanced aerodynamics for maximum performance.

High-revving naturally aspirated engines: Shine at high rpm with linear power delivery, perfect for track use and thrilling high-speed driving.

I hope this article gave you more insight into how torque and horsepower affect the driving behavior of different engine types. Whether you prefer turbodiesels, gasoline turbo engines, or high-revving naturally aspirated engines, each offers unique performance and driving experiences. Ultimately, the choice depends on your personal preference and intended use.

[needless rules]

Hello,
It's great to see some math and science on this website, instead of members concerned that their wheels and calipers don't match. Thanks

[No one]

Torque is how much dough you have. Revs is how much you want to spend. Power is how much you can buy. Turbo is a loan. Chip tuning is pure marketing.

[Mason Hatcher]

Originally Posted by snoep

WHAT MAKES YOUR CAR FAST? THE DYNAMICS OF TORQUE AND HORSEPOWER

Are you the author?

[snoep]

Originally Posted by Mason Hatcher

Are you the author?

Yes, I am.

[Mason Hatcher]

Originally Posted by snoep

Yes, I am.

Very well done!