SOHC vs DOHC Engine - Which One is Better for Bike?

Role of Camshaft in an Engine

The camshaft is a mechanical device an internal combustion engine uses to perform its opening and closing action in the exhaust and inlet valves. It is a rotating cylindrical rod with multiple oblong lobes protruding from the engine's internal combustion chamber.

Depending on the configuration, it can be oil, liquid, or air-cooled. The primary function is to convert rotations into linear motions to propel the vehicle forward. To make an IC engine work, the fuel should enter, and exhaust gases should leave the cylinder at the right time. A camshaft allows achieving this motion independently or with a crankshaft. The three main functions of a camshaft are:

• Promotes inlet valve opening during the suction stroke.
• Opens the exhaust valve during the exhaust stroke.
• Keeps both valves closed for the rest of the time.

These are the steps involved in the working of a camshaft:

• The piston enters the cylinder, where the open intake valve sucks the fuel-air mixture into the chamber.
• The valve closes, pushing the piston back again to compress the fuel-air mixture inside the chamber.
• After compressing the mixture, the spark plug makes a small explosion to push the piston down.
• Lastly, it moves back up again, pushing burning gases out of the cylinder through an open exhaust valve.

A Single Overhead Camshaft engine has only one camshaft that operates both the exhaust and intake valves. Conversely, a Dual Overhead Camshaft engine has two camshafts, one for operating the intake valve and the other for operating the exhaust valve.

When we compare SOHC and DOHC, SOHC has fewer parts involved, but the power it produces is also less. However, it is cheaper to buy, manufacture, and maintain. On the other hand, DOHC is more flexible and gives more accurate control over the valve opening and closing timing. 

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SOHC vs DOHC Engine - Overview

To better understand the SOHC DOHC difference, you must look at this overview of both engine setups. While both have different configurations, pros and cons, here is a brief look at their engine setup:

SOHC - Single Overhead Cam Setup

SOHC stands for Single Overhead Camshaft, which means an engine with only one camshaft rod operating both the intake and exhaust valves. It usually has 2-3 valve configurations where one set of valves acts as intake and another set handles exhaust gases.

However, with advancements, modern SOHC setups now have 4-valve configurations, allowing more air-fuel mixture to enter and escape the engine when the exhaust valve opens. 

Moreover, SOHCs are easier to manufacture, repair, and maintain due to fewer components involved. They also have the added advantage of better torque due to their lighter weight, making them ideal for city use where mileage and acceleration are more significant than speed.

• When running at low speeds, an SOHC engine produces more torque than a similar DOHC engine
• Simple structure due to fewer components.
• Fewer parts mean lower manufacturing costs, making the bike more affordable.
• Easy and cheaper to repair due to the common availability of experts and replacement parts.

• Less capacity due to only two valves per cylinder.
• Oddly placed sparkplugs reduce the engine’s performance.

DOHC (Dual Overhead Cam Setup)

With mechanical advancements, automobile makers introduced DOHC as a way to increase their engine efficiency without upsizing their displacement. In a Dual Overhead Camshaft engine design, intake valves open at larger angles compared to exhaust valves.

It allows more air-fuel mixture to enter the engine, increasing its power output. Another advantage is that it lets the engine turn quickly, increasing its top-end power. Since the camshafts are spread apart, many automakers place the sparkplug in the middle. It increases combustion efficiency and results in a cleaner fuel burn. 

DOHC engines produce more power than SOHC but at the cost of reduced fuel efficiency and higher maintenance needs. Since a DOHC system has several components in its design, its maintenance needs increase significantly. Besides, it becomes heavier to operate.

Pros:

• Improves volume efficiency of an internal combustion engine.
• Implements a 4-valve per cylinder configuration that improves airflow in the combustion chamber and increases its capacity.
• When running at a higher speed, the maximum power and torque are higher, improving the bike’s strength.
• Sparkplug’s placement in the middle improves the engine’s fuel combustion capacity.
• DOHC engines can apply variable valve technology to adjust the camshaft according to its operating mode.

Cons:

• Higher cost due to complicated engine structure.
• Difficult repair due to meticulous parts and lack of skilled mechanics.
• Expensive repair and maintenance costs.
• The bulky structure increases the bike's weight, partly affecting its operation and balance.

What is the Difference Between SOHC and DOHC?

While both SOHC and DOHC are suitable for different types of bike users, let’s understand the difference between them to make an informed decision: 

SOHC vs. DOHC – Which Is The Better Choice?

After understanding both mechanisms, the main question that comes to mind is – DOHC vs SOHC which is better? To make an informed decision, remember that a DOHC has double the number of valves than an SOHC, leading to better performance, lower noise, and increased airflow.

Moreover, DOHC has better valve timing, which can significantly affect the engine's performance. In an SOHC engine, only one camshaft runs both valves, usually disturbing the timing. Moreover, the spark plug has an easier location on the top of the cylinder. 

Overall, the performance of a Dual Overhead Cam engine is better than an engine with a Single Overhead Camshaft. However, the price difference is one major advantage of choosing an SOHC over DOHC.

When comparing SOHC vs DOHC, a bike with an SOHC engine is more affordable and requires less maintenance. Moreover, it is easy to repair in case of a failure, lighter in weight, and higher initial torque than DOHC. So, when deciding between DOHC or SOHC, your performance requirements and budgetary constraints matter the most.

Conclusion

Considering the motorcycle's camshaft setup is crucial when planning to buy a two-wheeler. Its torque and power output largely depend on the camshaft arrangement it uses. If you wish for a bike with ample horsepower at high revs, go for a bike with a DOHC engine configuration. Otherwise, opt for a standard SOHC setup for decent performance at lower prices and maintenance needs. 

When it comes to finance, fund up to 95% of the bike’s cost with a bike loan from Hero FinCorp. Here, you can find the most competitive bike loan interest rate with flexible repayment terms.

A two-wheeler loan lets you convert the bike’s cost into EMIs while keeping your savings intact. Easy online availability, competitive interest rates, easy repayment terms, and minimal documentation requirements are the best qualities of a bike loan. Use an EMI calculator to choose a loan term with budget-friendly EMIs and repay them on time to build a decent credit score.

Read Also: How to Choose the Right Type of Bike Engine for Your Use?

Frequently Asked Questions

1. Which is more reliable: SOHC or DOHC?

A DOHC setup is more reliable than a SOHC in many ways. Firstly, it provides more precise valve timing and achieves better valve fit.

A SOHC setup can also reach high efficiency with proper tuning, but the same is achievable with a DOHC setup.

2. Is SOHC more fuel-efficient than DOHC?

SOHC is generally more fuel-efficient than DOHC due to its simpler valve setup, but eco-friendly practices can improve DOHC efficiency.

3. Does DOHC consume more fuel?

DOHC engines offer more power but are less fuel-efficient due to increased fuel consumption for optimal valve timing.

4. Why is DOHC faster than SOHC?

DOHC engines have better airflow, more power, and higher speed than SOHC due to increased fuel-air mixture intake and release, resulting in greater horsepower.

5. Why do some bikes still have SOHC?

Bike makers offer both SOHC and DOHC engines. DOHC is pricier, so budget bikes usually have SOHC.