Lots of us, me included, love vehicles however aren’t completely positive what the entire whacky nomenclature means, particularly when trying below the hood. Phrases like DOHC, SOHC and OHV can sound complicated and downright intimidating to of us who aren’t fully conversant in the mechanical workings of a automotive. Don’t fret, although. I am right here to assist.
We will take this step-by-step collectively, and by the top, you may know the entire variations between twin overhead camshafts, single overhead camshafts and overhead valve engines. Then, you’ll be able to unfold your newfound data to everybody else who is just too scared to ask somebody at a automotive present for worry of being made enjoyable of.
OHV: Overhead valve
It is a class that’s fairly quickly going away. You will be hard-pressed to search out an overhead valve — often known as a pushrod — engine in something outdoors of a Common Motors LS/LT V8 or one among Stellantis’ Hemi V8s. All the pieces else is part of our subsequent class, which we’ll get to in a minute.
Pushrod engines are principally recognized for placing out heaps of torque at decrease engine speeds, however they’re not likely capable of run at excessive engine speeds like SOHC or DOHC motors.
Here is how an overhead valve engine works, based on Vehicles.com:
[T]he valves, which open and near let the air-fuel combination out and in of the cylinders, are above the camshaft, which is within the engine block. The camshaft prompts pushrods that transfer up and all the way down to function rocker arms that open and shut the valves within the cylinder head.
SOHC: Single overhead camshaft
For essentially the most half, a single overhead cam motor is a way more trendy setup than its OHV counterpart. In fact, as a result of there are DOHC motors, that are extra advanced and environment friendly, single overhead cam motors are normally present in cheaper economic system vehicles. For essentially the most half, they have two valves per cylinder — one consumption and one exhaust. There’s nothing fallacious with them, although, and so they nonetheless produce much more horsepower for his or her measurement and get higher gas economic system than OHV engines. The one draw back is that they normally do not produce as a lot torque.
Here is how a SOHC motor works, based on Vehicles.com:
In an OHC engine, the camshaft is within the cylinder head, above the valves, and the camshaft acts immediately on the valves or on rocker arms that open and shut the valves. On a single OHC engine, one camshaft opens and closes each the consumption and exhaust valves.
SOHC engines typically can run at greater speeds than OHV engines[.]
DOHC: Twin overhead camshaft
For those who’re driving a contemporary automotive, chances are high you are driving one thing with a twin overhead cam engine. They’re essentially the most environment friendly sort you will get, and so they produce essentially the most energy for his or her measurement. Also called twin-cam engines, they principally have 4 valves per cylinder. Having all of this further componentry means the engines can function with higher air-fuel mixtures. They will additionally independently change the timing between every camshaft and the crankshaft. Within the biz, we name that variable worth timing. It is some fairly neat stuff if you happen to ask me.
Here is how a twin overhead cam engine works, based on Vehicles.com:
With twin camshafts, one operates the consumption valves and the opposite the exhaust valves. On a V-type, or horizontally opposed engine, every cylinder financial institution can have two camshafts, so there’s 4 complete.
DOHC designs additionally enable utilizing 4 valves per cylinder as an alternative of two, which improves air circulation and will increase energy and effectivity. A draw back of DOHC engines is that they’ve extra elements and are costlier to fabricate.
