One of the most common questions among those who are very curious about the performance of motorbikes is whether a 2-valve engine is better or a 4-valve engine is better, and if the 4-valve engine is better, then why is it better? Why do companies offer only 2 valves on most budget-oriented bikes?
Let’s take a look inside the engine and find out how many valves are best for an engine. However, I will not go into more technical terms and details, so that you do not feel bored. So I am discussing it in simple language so that everyone can understand the main point quickly.
What is the valve thing to know at the beginning? And what is its function?
In simple words, the valve is the door of the engine, like the door of our house. The main function of a valve is to allow or restrict flow.
We know that in four-stroke engines, once the crankshaft rotates, there are a total of 4 strokes, and with each stroke, fuel and air enter the cylinder through the intake valve, and after the compression and combustion process is completed, the gas is released through the exhaust.
This is the valve that opens and closes the doors of air and oil entering the cylinder and allows the exhaust gas to come out after combustion.
Two-valve engines are seen, which have two valves. One is the intake valve, and the other is the exhaust valve.
4 valve engine has two intake valves and two exhaust valves.
Now the question comes: if 2 valves work, then what is the need for 4 valves? And if 4 valves are good, then why use 2 valve setup?
Here, actually, purpose and cost play a big role. Bike companies use 2-valve engine setups so that the price of entry-level bikes does not go up. Entry-level bikes are very price-sensitive, and the market cannot be captured if they are not offered at competitive and affordable prices.
2-valve engine is easy to design and
A 2-valve setup engine costs less to manufacture than a 4-valve engine.
Just 2 valves and a camshaft—that’s it.
Since 2 valve engines have a lower cost, a single camshaft is used to operate two valves. By doing this, the position of the camshaft has to be along the middle of the cylinder, as a result of which the spark plug cannot be placed in the middle. 2 valve engines are forced to use side-mounted spark plugs, or twin spark plugs are also used. Since the spark plug is on the side, the combustion process is not very perfect.
However, 2 valve engines have some advantages.
As the initial and midrange power of the 2-valve engine is good enough, good torque is available.
On the bad side, the top end power is less, when going to high rpm, the bike seems not able to take the load, the speed is increasing less than the rpm, it cannot take the stress, the engine is costing, etc.
The reason for this is that the frequency is reduced due to the mass weight of the big valve
But as I said, commuter bikes don’t really need that much power at high revs. So companies use more 2-valve engines in commuter bikes to keep the cost low and the mechanism simple. Moreover, the mileage of 2-valve engine is also very good
On the other hand, 4-valve engine design is more complex and more expensive to manufacture.
Again, single camshafts or dual camshafts can be used in 4-valve engines.
4 valve engines have about 50 percent more airflow. Due to the low mass weight, the frequency is high, as a result of which the engine can take more breath and deliver more power at high rpm. Double overhead camshafts are used in 4-valve engines, due to which the spark plug can be placed in the center of the cylinder, which makes the combustion process perfect.
Conclusion
I hope you have easily understood from the above discussion what the difference is between a 2-valve engine and a 4-valve engine, and at the same time, you have also understood why one type of engine is better.
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