DOHC Vs. SOHC – What’s The Difference Between Them?

If you are looking for a new car, you probably already found that there is often a mention of a SOHC or DOHC engine.

But what does these signs mean?

Both terms are used in regards to the camshaft. There are some significant differences between these two types of setups.

Before you decide which to choose, DOHC vs. SOHC, you need to understand what they mean and how they operate.

SOHC engine

SOHC stands for a single overhead cam. This type of engine comes with only one camshaft located in the engine head. With the SOHC engine, you do most often have one intake valve and one exhaust valve.

DOHC engine

DOHC is a synonym for dual overhead cam, and this means you have two cams operating the exhaust and intake valves. The engine has one header but with two cam rods. Unlike the SOHC, the DOHC has one camshaft operating the intake valves and another camshaft operating the exhaust valves. The camshafts are often tied together by a short chain but sometimes, the timing belt wrap around both gears.

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SOHC VS DOHC – What is the difference?

The difference between SOHC vs. DOHC engine is the number of camshafts in the car engine. SOHC means that there is one single camshaft, and DOHC means that there are dual camshafts. SOHC = Single Overhead Camshaft and DOHC = Dual Overhead Camshafts.

The engine is most often run 2 intake valves and 2 exhaust valves per cylinder with DOHC engines, instead of 1 intake and 1 exhaust valve on the SOHC engine. This increases the performance.

There is also some difference between these when it is coming to the performance and other aspects; let’s find out:

Which should I choose – DOHC or SOHC?

So now, when you know the difference between a SOHC or DOHC engine, which one should you choose, and what are the pros and cons between these engines?

There are actually a lot of differences between these that you need to know about.

1. Performance

The main difference between the DOHC and SOHC engines is the performance. Dual camshafts do often produce more horsepower, and it is therefore often equipped in newer cars.

This is because DOHC engines often use 4 valves per cylinder instead of one intake and one exhaust like SOHC engines.

Older cars had not the same need for performance, and therefore, they were fine with a single camshaft.

2. Fuel Efficiency

Because of the number of valves per cylinder – a dual camshaft engine will often have better fuel efficiency than a single camshaft engine. More performance can actually often lead to lower fuel efficiency. This is because of the much more efficient engine when you let it breathe properly.

3. Repair Costs

The downside of the DOHC engine is that you have many more valves, camshafts, and parts that can break down. A single camshaft requires far fewer parts for the engine to function properly.

If you are looking for a reliable engine without too much performance, SOHC is probably the right choice for you!

4. Smoothness

Because the DOHC engine also gives greater performance, you will often find these much smoother without misfires. This is because of the efficiency and easiness to control valve timings.

If the smoothness of the engine is important to you – you should choose a DOHC engine.

SOHC & DOHC FAQ