How much does the RPM increase when the pulley is enlarged by one centimeter?
3 Answers
Enlarging the pulley by one centimeter increases the RPM by 1480 per minute. Below is an introduction to the related content of the timing belt: Composition of the Timing Belt: The timing belt is an important component of the engine's valve system, consisting of the drive pulley, driven pulley, tension pulley, and the belt itself. Function of the Timing Belt: The timing belt ensures that during engine operation, the piston's stroke, the opening and closing of the valves, and the ignition sequence remain synchronized. The timing belt is a consumable part, and if it breaks, the camshaft will not operate in sync, which can lead to severe damage from valve and piston collision. Therefore, the timing belt must be replaced according to the mileage or time specified by the manufacturer.
I've been in auto repair for over a decade and often see people tinkering with pulley wheels. Increasing the pulley diameter by one centimeter usually decreases rather than increases the rotational speed. This happens because a larger wheel means the belt travels farther per revolution, but with the engine speed unchanged, the accessory speed slows down. Let's calculate the ratio: if the original diameter was 15 cm and increased to 16 cm, the new speed is the original speed multiplied by 15 divided by 16, roughly dropping to 94%. For example, an original speed of 3000 rpm would decrease to about 2820 rpm, a drop of nearly 200 rpm. This is a significant change. Slower water pump or AC compressor speeds might lead to cooling issues, making the car prone to overheating in summer. Friends who enjoy modifications should be cautious—measure the original pulley size before making changes. Don't cut corners recklessly to avoid breakdowns on the road.
I usually enjoy tinkering with car modification parts, and calculating these parameters is fundamental. Increasing the pulley diameter by one centimeter to raise the RPM? That's a misunderstanding—it actually decreases. To put it in formula terms, the new RPM divided by the old RPM equals the original diameter divided by the new diameter. Assuming the original diameter is 15 cm and you increase it by one centimeter to 16 cm, the ratio is 15/16 = 0.9375, so the RPM drops to 93.75% of the original speed. Converting the RPM value: if the old RPM was 2500, the new RPM would be around 2343, a drop of about 157 RPM. If you want to increase speed, you should reduce the pulley size, but shrinking it too much can cause slippage and reduce belt lifespan. In actual modifications, I've tried fine-tuning but recommend keeping changes within one centimeter—for major adjustments, it's best to use professional tools for testing.
