How to Determine the Proper RPM for Shifting

In a manual transmission, the driver rather than the engine shifts the gears of the car. A driver knows when to shift gears based on the RPM or revolutions per minute of the engine. Shifting at a higher RPM provides increases the acceleration of the car, but if the RPM gets too high it can damage the engine or blow up the car.

Difficulty: Easy

Instructions

1. Keep an eye on the tachometer which measures the RPM. Most tachometers have numbers from 1 to 7 or 1 to 9 that correspond to the RPM. Multiply the number by 1000 to get the RPM of the engine.

2. Shift gears between 2,000 and 2,500 RPM for optimal engine efficiency. Allowing the RPM to go up to 3,000 RPM or higher increases speed but makes the engine work harder, which reduces fuel economy.

3. Watch out for a red warning light or for numbers highlighted with red strips. If your RPM reaches a warning number or a warning light comes on, you need to up shift immediately. Over-revving the engine causes damages and may cause oil to leak onto a hot exhaust causing a fire.

4. Listen to the engine. As you drive a manual transmission, you naturally develop a RPM ear that helps you know when to shift. The faster the engine turns, or the more RPM, the louder your engine gets.

5. Calculate the best RPM for shifting using gear ratios and torque curve. The next highest gear ratio divided by the current gear ratio provides you with an optimal time to shift.

6. Check the car's manual for recommend guidelines. The optimal RPM level changes depending on the type of car you drive.

Resources

• Datsuns offers examples on using gear ratio and torque curves.