SOHC (Single Overhead Camshaft) and DOHC (Dual Overhead Camshaft) are two types of engine valvetrain designs. Both place the camshaft(s) above the cylinder head to control valve operation, but SOHC uses one camshaft per head, while DOHC uses two—one for intake and one for exhaust valves.
DOHC engines typically offer better performance, efficiency, and support for more valves, while SOHC engines are simpler, lighter, and more cost-effective.
What is the difference between SOHC and DOHC? 1. Basic Definitions:
SOHC (Single Overhead Camshaft) :
Has one camshaft per cylinder head , which operates both intake and exhaust valves.
DOHC (Dual Overhead Camshaft) :
Has two camshafts per cylinder head :
One controls intake valves
The other controls exhaust valves
Also Read: What is a camshaft?
Also Read: Why is a DOHC engine better than a SOHC engine?
2. Technical Comparison:
Feature SOHC DOHC Camshaft Count 1 per cylinder head 2 per cylinder head Valves per Cylinder Typically 2 (1 intake, 1 exhaust) Often 4 (2 intake, 2 exhaust) Valve Timing Limited control More precise and flexible Support for VVT Basic support Excellent compatibility
3. Performance:
Performance Aspect SOHC DOHC Power Output Moderate, good for low-mid RPM Higher power, especially at high RPM Airflow Efficiency Less efficient Better airflow = more efficient combustion High-RPM Operation Less suitable Designed for high-performance engines
4. Maintenance & Cost
Aspect SOHC DOHC Complexity Simpler design More complex valvetrain Cost Lower manufacturing & repair cost Higher production & service cost Weight Lighter engine head Heavier due to extra camshaft & valves Timing Setup Simpler timing belt/chain layout More intricate timing configuration
5. Real-World Application:
Usage Scenario SOHC DOHC Small Cars Widely used due to cost-effectiveness Used for balance of performance & efficiency Motorcycles Common in mid-range models Preferred in high-performance bikes Sports Cars Rare Standard setup
6. Advantages & Disadvantages:
SOHC Pros:
Simpler and cheaper
Easier to maintain
Adequate for economy and basic performance
SOHC Cons:
Limited power potential
Less efficient at higher RPM
DOHC Pros:
Higher performance and RPM range
Better valve control and breathing
Supports advanced tech like VVT (Variable Valve Timing)
DOHC Cons:
More expensive to manufacture and maintain
Heavier and more complex
7. Manufacturing Cost:
Aspect SOHC DOHC Parts Count Fewer components (1 camshaft) More components (2 camshafts, more valves) Design Complexity Simpler head design More complex cylinder head and valvetrain Production Cost Lower Higher due to extra parts and machiningEngine Size More compact Bulkier cylinder head assembly
✅ SOHC is cheaper and simpler to manufacture. DOHC requires more materials, machining, and precision.
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