1. What is the Quarter Mile Speed Formula?

The quarter mile speed formula estimates a vehicle's speed at the end of a quarter mile drag strip based on its horsepower and weight. This calculation demonstrates the importance of power-to-weight ratio in acceleration performance.

2. How Does the Calculator Work?

The calculator uses the quarter mile speed formula:

Where:

• \( HP \) — Engine horsepower
• \( Weight \) — Vehicle weight in pounds
• 224 — Empirical constant
• 1/3 — Exponent representing the relationship

Explanation: The formula shows that speed increases with the cube root of the power-to-weight ratio, meaning doubling horsepower doesn't double speed.

3. Importance of Power-to-Weight Ratio

Details: The power-to-weight ratio is crucial in vehicle performance. A lighter car with the same horsepower will be faster, while adding power to a heavy vehicle has diminishing returns.

4. Using the Calculator

Tips: Enter horsepower in hp (typically measured at the crank) and vehicle weight in pounds (including driver and fuel). Both values must be greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: How accurate is this formula?
A: It provides a reasonable estimate for rear-wheel drive vehicles with good traction. Front-wheel drive and all-wheel drive may vary due to traction differences.

Q2: Does this account for transmission and gearing?
A: No, this is a simplified formula that assumes optimal gearing. Actual performance may vary based on transmission type and gear ratios.

Q3: What's a good quarter mile speed?
A: Street cars typically run 13-16 seconds at 90-110 mph. Performance cars can achieve 11-12 seconds at 120+ mph. Professional dragsters exceed 300 mph.

Q4: Why the cube root relationship?
A: The cube root accounts for the fact that aerodynamic drag increases with the square of speed while power needed increases with the cube of speed.

Q5: Can I use this for motorcycles?
A: Yes, but motorcycle aerodynamics and power delivery differ, so results may be less accurate than for cars.