Charge Motion Control Valve: How Does it Work?

The hard work for Ford when they’re developing a new V8 isn’t making more power. And it’s not reducing emissions. It’s being able to do both of those using the same engine. Giving it wide-open power while maintaining nice clean emissions results when you’re just driving around normally is what brings home the engineering big bucks.

It’s because what works well for high power doesn’t always work well for low power. Try a turbocharged car with a turbo chosen for 1,000 hp dyno runs. It probably doesn’t drive very well on the street. Much in the same way that the engine in your base Focus doesn’t exactly like to live life on the redline.

The Charge Motion Control Valve is a cool way that Ford came up with to make V8s a little more fuel efficient and clean at lower speeds.

An engine is like a big pump. It pulls air in, blows it up, and pushes what’s left out. In the middle, it makes heat and horsepower.

An engine is also kinda lazy at lower throttle openings and low RPM. Not much air can get in, so that air isn’t moving very quickly through big fat openings that were designed for the 400 hp top end. It’s like exhaling lightly though your wide open mouth. Try that (we’ll wait) and feel the air. Not only do you look silly, you can barely feel anything on your hand.

That lazy air doesn’t mix as well with the fuel in the cylinder, which means that the fuel doesn’t burn as thoroughly or as cleanly as it could. That means wasted fuel.

So enter the Charge Motion Control Valve. They’re valves (actually flaps) that control the motion of the charge. Simple as pie, right? It actually is one of those times where the name is more complicated than the function.

They’re small metal flaps that sit at the cylinder head side of every intake runner. They have a smaller hole in them, so at low speeds, they block much of the intake passage.

Putting them in the way does a few things. 

First, it speeds up the airflow since the same amount of air has to go through a smaller space. Block most of your open mouth and feel the air when you exhale. It’s more turbulent and faster moving. And you look even sillier. It also directs most of the air to just one of the two intake valves in each cylinder. That makes the air swirl into the cylinder even more, which means the air and fuel mix more thoroughly. So it burns better. That means better emissions and less fuel consumption.

Ford Patent Drawing. CMCV marked as part 70

So that’s it. The flaps control the movement of the intake charge, making it better.

Of course, it’s not all sunshine, rainbows, and wheelspin. Blocking most of the intake port means you can’t make much power. So as the throttle opening and RPM increase, the flaps open. Now the engine has the full intake runner to let it gasp in cold air.

Except that the flap is still taking up some space in there. Like a wide open throttle plate blocking a little bit of the middle of the intake. That can be bad for peak flow. Of course, the new Mustang GT is making 435 hp and 400 lb-ft, so it can’t be hurting that much, can it? The 5.0L in the Ford F-150 isn’t sluggish either.

That doesn’t mean that people don’t want to get rid of it. After all, if it’s for emissions, it must be bad, right? Hint, no. And this flap’s been on Ford’s V8s since the early 2000s. Since this is probably the first time you’ve ever heard of it, it must be doing a good job.

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