Significance of valves in an engine?


I’m a noob car guy, learning more every day.

I’ve had I think 14 cars in my 7 years of being licensed, and in that time I’ve heard a lot of people mention something like “oh the 12v is better than the 16v” when talking about two models of the same car.

What’s the significance, what does it do?

I have a basic understanding of how a combustion engine works, if that helps.

In: 1

Your basic engine needs 2 valves per cylinder, one to let the air/fuel in and one to let the exhaust out.

Adding additional valves can increase the total area of the valves so you can move the air/exhaust through faster/easier and generate more power.

Changing from 1 intake valve to 2 can also result in smaller valves which instead of being a hefty piece of metal with a strong spring to pull it back, you instead have to much smaller lighter pieces which you can move faster meaning the engine can reliably rev up much higher.

You don’t really care about the valve count on the engine, you care about the horsepower and torque figures and the valves help influence that. The 16V version of an engine is likely more powerful than the 12V version even though they have the same displacement (volume inside the cylinders) which means its a bit more efficient.

With additional pistons the crankshaft has to work differently. That’s why a V12 is more balanced than a V16. [This]( is helpful

Mmmmmmmbacon basically told you what the valves do, so I’ll answer the other part of your question.

When someone says “the 12 valve is better than the 24 valve” or whatever, it’s not necessarily the number of valves that is what makes the engine “better” or “worse.” It’s just a reference to the specific engine, followed by an opinion on it. The reasoning behind the opinion may or may not actually have anything to do with the valves themselves. Often the higher valve number engines have other added complexity for performance, which could impact reliability. Or a lower number simply isn’t as powerful an engine, if that’s what you are looking for.

For example, Cummins diesel engines, like those in Dodge Ram pickups used to be twelve valve, then went to twenty four. Some people swear by the old twelve valve ones due to less complexity of both the engine and the fuel system.

Edit: not awake yet.

Four valves per cylinder allows for larger intake/exhaust ports, lighter valves, and softer valve springs. Larger ports means less pumping losses; power from the engine goes to the wheels instead of being wasted trying to force air in and out. Lighter valves can reverse direction between opening and closing easier, which allows the engine to rev higher. Lighter valve springs are more reliable/durable since there’s less force to cause metal fatigue.

As others have mentioned the valves are what the the fuel and air in and the exhaust out of the engine. A base level is 2 valves per cylinder but more can be added, up to 5 o believe. This adds complexity to the engine and often is done for more power output. Because of the power increase auto makers advertise often will advertise the number of valves as a way to promote their engines and to distinguishing versions from eachother. Usually more valves is more better but sometimes this isn’t the case, usually this is notable since the engine with more valves should be the better option.