Malesbaca.com – The performance of a 4-stroke engine is heavily influenced by the design and characteristics of the camshaft. To improve engine performance—especially in racing applications—modifying the camshaft’s duration and maximum lift is essential. This article explains how to calculate camshaft duration and calculate camshaft lift practically, complete with formulas and examples.
By understanding these fundamentals, you can determine the right camshaft specifications for daily use or racing purposes.
Daftar Isi:
Importance of Modifying Camshaft Duration and Lift
Duration and lift are two key aspects that determine how long and how wide a valve remains open. Without proper adjustment of these two parameters, engine modifications may be ineffective, as the air-fuel flow won’t be optimized.
This modification can be done by:
- Redesigning the stock camshaft
- Using aftermarket (racing) camshafts that meet your needs
How to Calculate Camshaft Duration
Duration is the number of crankshaft degrees during which the valve remains open. To calculate camshaft duration, you need to understand the LC (Lobe Center) value, which is the peak point of the camshaft relative to BDC (Bottom Dead Center).
1. Determining the Lobe Center (LC)
LC is typically measured after installing the camshaft in the engine using a degree wheel mounted on the magnet (left side of the crankshaft). This measurement reveals the center point of the intake valve opening.
Example:
- LC on Jupiter Z = 103
If you want a duration of 310°, you need to calculate the intake opening (In Open) and intake closing (In Close).
2. Formula to Calculate In Open and In Close
Use the following formula:
in close = duration - 180 - in open
Example calculation:
- Target duration = 310°
- in open = 52°
- then:
In close = 310 - 180 - 52 = 78How to Calculate Maximum Camshaft Lift
Maximum lift indicates how far the valve opens, measured from the camshaft base circle to its peak.
1. Lift Max for Stock Engines
For daily use:
- Lift Max = 23% of intake valve diameter
Example:
- Intake valve diameter = 25 mm
- Lift Max = 0.23 × 25 = 5.75 mm
2. Lift Max for Racing (Short and Long Circuits)
- Short circuit (drag or road race):
- Lift Max = 29%–31% of intake valve diameter
- Long circuit:
- Lift Max can reach up to 35%
Illustration: Camshaft & Measurement
Calculating Camshaft Duration and Lift
Conclusion
Calculating camshaft duration and lift requires precision and accurate measuring tools. However, with the basic understanding provided in this article, you can better determine the camshaft specs that match your engine’s needs.
For daily use, purchasing a ready-to-use racing camshaft might be sufficient. But for maximum performance on the track, calculations like these are key.
