1. What is the RWHP Equation?

The RWHP (Rear Wheel Horsepower) equation estimates the actual horsepower delivered to the wheels based on vehicle weight, speed through the 1/8 mile, elapsed time, and a constant factor. This provides a more accurate measure of real-world performance than engine horsepower ratings.

2. How Does the Calculator Work?

The calculator uses the RWHP equation:

Where:

• \( Weight \) — Vehicle weight including driver (lbs)
• \( Speed \) — Speed through the 1/8 mile (mph)
• \( ET \) — Elapsed time for 1/8 mile (seconds)
• \( Constant \) — Empirical constant (typically 234)

Explanation: The equation accounts for the cubic relationship between speed and power required to accelerate a given mass over a fixed distance.

3. Importance of RWHP Calculation

Details: RWHP provides a real-world measure of a vehicle's performance capability, accounting for drivetrain losses and actual vehicle weight. It's essential for performance tuning and drag racing analysis.

4. Using the Calculator

Tips: Enter accurate vehicle weight (including driver), speed through the 1/8 mile, elapsed time, and the appropriate constant (234 is typical). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between RWHP and engine horsepower?
A: RWHP is typically 15-20% lower than engine horsepower due to drivetrain losses through the transmission, differential, and wheels.

Q2: Why use 1/8 mile instead of 1/4 mile?
A: 1/8 mile times are more accessible for many vehicles and tracks, while still providing accurate power estimates.

Q3: What's a typical constant value?
A: 234 is commonly used, but this may vary slightly based on track conditions and measurement methods.

Q4: How accurate is this calculation?
A: It provides a good estimate (±5%) when using accurate input values from properly conducted runs.

Q5: Should I use race weight or curb weight?
A: Use the actual weight during the run, including driver, fuel, and any other load the vehicle carried.