DOHC, SOHC, OHV, VVT and so on. We see them being advertised all the time when a new vehicles come out but what do these acronyms mean? Here’s a brief explanation for the most common ones.

OHV – Overhead Valves

Back in the day, the timing of an engine was done by a single camshaft situated just above the crankshaft. When the camshaft turned it pushed against pushrods which in turn actuated rockers in the engine head which in turn pushed open the valves. This type of timing configuration is almost phased out in favor of more efficient systems but you will still find it in some vehicles. The Corvette is the last sports car to have such valvetrain but even that will be phased out in favor of newer technology.

SOHC – Single Overhead Camshaft

As the name suggests, the is a single camshaft controlling the timing of the valves. But it’s a single camshaft over each cylinder head so if it’s an engine with a “V” configuration, there would be one camshaft for each of the cylinder heads. The purpose for this type of configuration is to allow the use of more valves for each cylinder which in turn improves performance and fuel efficiency.

DOHC – Dual Overhead Cams

Like SOHC, DOHC also utilizes a camshaft over the vales but instead of one, two are used for better timing control. It also allows for different camshaft profiles for the intake and exhaust valves which benefits performance and fuel economy.

VVT – Variable Valve Timing

A VVT actuator is a device that attaches to the end of a camshaft and using oil pressure, it rotates the camshaft by a few degrees. The reason for this is to control when to open and close the valves of the engine. By controlling this, it allows for more torque at lower engine speeds or more horsepower at higher engine speeds. This technology is so successful that almost all manufacturers utilize it across all of their engine options.

TCS – Traction Control System

Traction Control is a program in a vehicle’s main computer that limits the amount of wheel spin in certain conditions. When a road is wet or when a vehicle has more power than the tires can cope with, the traction control system prevents the wheels from losing traction with the pavement. It can be done in two ways. The most common is by applying light brake pressure to the drive wheels until wheel slip stops. The other method is by limiting the engine’s power; done either by reducing fuel supply to the engine or suppressing a spark in the combustion chamber.

ABS – Anti-lock Braking System

ABS is a technology that was invented by the Air Force in an attempt to prevent planes from skidding on a runway when landing. The technology eventually trickled down to vehicles and is now available on almost all new models. When braking with a lot of force, the wheels will lock up which will increase the braking distance of the vehicle and potentially end up in an accident. ABS modulates the braking force by applying and releasing the brakes very rapidly to prevent the wheels from locking when braking. By doing this, the braking distance remains short and it also allows the driver to steer the vehicle in an emergency.

ESC – Electronic Stability Control

Arguably the most important development in vehicle safety has been ESC. Like traction control, it is a program that utilizes the ABS system to automatically brake certain wheels when the vehicle begins to slide in a direction other than straight. When swerving in an emergency to avoid an obstacle on the road, a vehicle has the tendency to spin around or (if it’s a tall SUV) to flip over. This system prevents the vehicle from spinning and it allows the driver to remain in control. This system is so effective that it has become a law that new vehicles be outfitted with this program.