1. What is the Pulley RPM Equation?

The pulley RPM equation calculates the rotational speed of a driven pulley based on the sizes of both pulleys and the speed of the drive pulley. This is essential for proper car accessory drive system design and performance tuning.

2. How Does the Calculator Work?

The calculator uses the pulley RPM equation:

Where:

• \( Size1 \) — Diameter of drive pulley (inches)
• \( Size2 \) — Diameter of driven pulley (inches)
• \( RPM1 \) — Rotational speed of drive pulley (rev/min)
• \( RPM2 \) — Calculated speed of driven pulley (rev/min)

Explanation: The equation shows an inverse relationship between pulley size and rotational speed - as the driven pulley gets larger, its rotational speed decreases proportionally.

3. Importance of Pulley RPM Calculation

Details: Accurate RPM calculation is crucial for proper accessory operation (alternator, water pump, supercharger), preventing overspeeding components, and achieving desired performance characteristics.

4. Using the Calculator

Tips: Enter all pulley sizes in inches and drive pulley RPM in revolutions per minute. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Does belt type affect the calculation?
A: The basic calculation remains valid, but belt slip can cause actual RPM to be slightly lower than calculated.

Q2: How precise do measurements need to be?
A: For most applications, measuring to 1/8" (0.125") is sufficient, but precision applications may require more accurate measurements.

Q3: Can I use this for multi-pulley systems?
A: This calculates for two pulleys only. For multiple pulleys, calculate each stage sequentially.

Q4: What if my pulleys are different types?
A: Measure the effective diameter where the belt rides. Some pulleys may need special measurement techniques.

Q5: How does this affect supercharger performance?
A: Supercharger speed directly affects boost pressure. This calculation helps determine proper pulley combinations for desired boost levels.