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Valve Overlap Formula:
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Valve overlap refers to the period in an engine's cycle when both the intake and exhaust valves are open simultaneously. This occurs at the end of the exhaust stroke and beginning of the intake stroke, allowing for better scavenging of exhaust gases and improved cylinder filling.
The calculator uses the valve overlap formula:
Where:
Explanation: The total valve overlap is simply the sum of the intake valve opening and exhaust valve closing angles, measured in crankshaft degrees.
Details: Proper valve overlap is crucial for engine performance optimization. It affects engine breathing, torque characteristics, emissions, and overall efficiency. Different engine designs require specific overlap periods for optimal operation.
Tips: Enter both IVO and EVC values in degrees. These values are typically specified in camshaft timing specifications or can be measured using degree wheels during engine tuning.
Q1: What is a typical valve overlap range?
A: Overlap varies by engine design but typically ranges from 20-80 degrees for street engines, with performance engines often having more overlap.
Q2: How does overlap affect engine performance?
A: More overlap generally improves high-RPM power but can reduce low-RPM torque and idle quality. Less overlap improves low-end torque and idle stability.
Q3: Can overlap be adjusted?
A: Yes, through camshaft selection, adjustable cam gears, or variable valve timing systems in modern engines.
Q4: Does overlap affect emissions?
A: Yes, excessive overlap can increase hydrocarbon emissions as unburned fuel can escape through the exhaust during the overlap period.
Q5: How is overlap measured in practice?
A: Using a degree wheel and dial indicator to precisely measure the crankshaft angles when valves begin to open and completely close.