1. What is Torque vs Horsepower?

Torque Definition: Rotational force measured in pound-feet (lb-ft) or Newton-meters (Nm). It's the twisting force an engine produces.

Horsepower Definition: Rate of doing work (1 HP = 550 ft-lb/sec). It's how quickly torque is applied over time.

2. The Fundamental Relationship

The mathematical relationship between torque and horsepower:

Where:

• \( HP \) — Horsepower
• \( T \) — Torque (lb-ft)
• \( RPM \) — Revolutions per minute
• 5252 — Conversion constant (derived from HP definition)

Key Insight: At 5,252 RPM, torque and horsepower values are always equal numerically.

3. Practical Differences

Torque Characteristics:

• Determines pulling power and acceleration at low speeds
• Important for towing and heavy loads
• Diesel engines typically produce high torque at low RPM

Horsepower Characteristics:

• Determines top speed and high-RPM performance
• Important for racing and high-speed applications
• Gasoline engines often produce peak HP at higher RPM

4. Engine Performance Curves

Torque Curve: Shows how torque varies across the RPM range. Typically peaks at mid-range RPMs.

Horsepower Curve: Generally rises with RPM until friction losses dominate. Crosses torque curve at 5,252 RPM.

5. Frequently Asked Questions (FAQ)

Q1: Which is more important - torque or horsepower?
A: Depends on application. Torque for towing/hauling, HP for speed/acceleration.

Q2: Why do electric motors have instant torque?
A: They produce maximum torque at 0 RPM, unlike combustion engines that need to build RPM.

Q3: Can you have high torque but low horsepower?
A: Yes - if torque is high but RPM is low (like in heavy equipment).

Q4: What's the 5252 constant in the formula?
A: Comes from HP definition (1 HP = 550 ft-lb/sec) and unit conversions (60 sec/min, 2π rad/rev).

Q5: How do gear ratios affect torque and HP?
A: Gears multiply torque but reduce RPM proportionally - horsepower remains constant (minus losses).