Understanding Valve Spring Bounce in Motor Vehicle Engines

In summary, the discussion focused on valve bounce in a 4 stroke, 4 cylinder motor vehicle engine. It was determined that valve bounce occurs when the valve spring operates above its natural frequency, which was calculated to be 5500 rev/min. Pushing the engine speed to 8000 rpm may prevent valve bounce since the camshaft only runs at half the engine speed. However, most vehicles have red lines at 6500 rpm on the rev counter, suggesting a safety factor. Other factors such as rod stretch, valve closing impact, and ignition timing may also contribute to the rpm limit.
  • #1
enkiduz190
10
0
Hi guys, i am doing some calculations on the valve spring of a 4 stroke, 4 cylinder motor vehicle engine.

To my understanding, valve bounce will occur once the valve spring is operated at a speed over their natural frequency (which i calculated to be 5500 rev/min). If i were to push the engine speed to 8000 rpm, does it mean that the valve spring won't 'bounce' since the camshaft only runs at half the engine speed? But if that was the case, why do most vehicle have red lines at 6500rpm on the rev counter? Is it really necessary to have such large safety factor?

Thanks
 
Engineering news on Phys.org
  • #2
Valve float is not by any means the only factor determining rpm limits. You get into things like rod stretch, valve closing impact, ring wear, cam lobe wear, and the ever-popular exploding flywheel that cuts your legs off.
 
  • #3
Also I would think that things like volumetric efficiency, valve timing and ignition timing will do the limiting for you.
 

1. What is a valve spring?

A valve spring is a type of mechanical spring that is used to ensure that valves in an engine or other machinery open and close at the appropriate times. It is typically made of metal and provides the necessary force to keep the valve closed when the engine is not running and to open it when the engine is in operation.

2. Why are valve springs important?

Valve springs are an essential component in an engine's operation. They help to control the timing and duration of the intake and exhaust phases, ensuring that the engine operates smoothly and efficiently. Without valve springs, the valves would not be able to open and close properly, leading to a loss of power and potential engine damage.

3. What are the signs of a faulty valve spring?

Some common signs of a faulty valve spring include a loss of power, rough engine idle, and unusual noises coming from the engine. If a valve spring fails completely, it can cause the valve to remain open or closed, leading to engine misfires and potentially severe damage.

4. How often should valve springs be replaced?

The lifespan of a valve spring can vary depending on factors such as engine type, usage, and maintenance. In general, it is recommended to replace valve springs every 100,000 miles or sooner if you notice any signs of wear or damage. It is also important to follow the manufacturer's recommended maintenance schedule for your specific engine.

5. Can I replace a valve spring on my own?

Replacing a valve spring can be a complex and delicate process, and it is not recommended for those without experience or knowledge in engine mechanics. It is best to have a trained professional perform this task to ensure it is done correctly and safely.

Similar threads

  • Electrical Engineering
Replies
1
Views
612
Replies
2
Views
3K
  • Engineering and Comp Sci Homework Help
Replies
3
Views
3K
  • Science and Math Textbooks
Replies
7
Views
1K
Replies
3
Views
833
  • Mechanical Engineering
2
Replies
35
Views
3K
  • Mechanical Engineering
Replies
5
Views
1K
Replies
4
Views
4K
  • Mechanical Engineering
Replies
7
Views
3K
Back
Top