What Intake Manifolds Do and How They Work

What Intake Manifolds Do and How They Work

Last Updated February 5, 2020 | Sam Padgett

Breathing is just as crucial for your Mustang as it is for you. Without proper air intake, your engine performance will suffer. There are plenty of engine components that manage the air and fuel heading into the engine, but one of the more important parts of an internal combustion engine is the intake manifold. Even though intake manifolds are essentially a glorified bunch of tubes, they have a significant effect on your engine’s performance and help several parts of your vehicle work together in harmony.

What is an Intake Manifold

An intake manifold is a series of tubes that sit atop the engine. As air enters the car, it travels through the throttle body, then into the intake manifold and then finally into the engine itself. Basically, the intake manifold is the last stop on the air's journey before it reaches the cylinder heads.

Simple Intake Manifold

One of the big tasks that the intake manifold accomplishes is distributing the air (or air-fuel mixture in a carbureted engine) evenly to each cylinder. This way, when the camshaft opens the cylinder valves, the same amount of gas enters each cylinder.

As air passes through the manifold, it is subjected to the scrutiny of a bunch of different sensors. These sensors measure a variety of variables, from temperature to pressure. The sensors are ultra-important for any modern vehicle. For example, if the engine is fuel injected, the air temperature sensor is key to healthy engine function. Without knowledge of the air temperature, the density of oxygen in the cylinder would be unknown, and the proper air-fuel ratio could not be realized. A faulty sensor can cause stalling, knocking, or it can ruin your catalytic converter by filling it with unburnt fuel.

Additionally, the intake manifold is where the Mustang's throttle is determined. The throttle body sits in the entrance to the intake manifold like a bouncer, only allowing the proper amount of air into the engine at any given time. While sensors and the throttle body are not the intake manifold itself, the manifold provides a way for all of these components to work in unison.

How an Intake Manifold Works

Although there doesn't seem to be too much going on in the intake manifold beside the transfer of air from one place to another, intake manifolds actually employ some rather complicated properties of physics to be more efficient. There are two basic parts to the intake manifold. There's the plenum, the large cavity at the top of the manifold, and the runners, the small tubes that run to each cylinder individually.

Here's where it gets complicated. There's this phenomenon called the Helmholtz resonance that's honestly too complicated to go into complete depth here. Basically, it has to do with the resonance of gases in sealed containers. A quick example of this effect is when you make a note from a bottle by blowing over its top. Intake manifolds use this for their benefit by being built to maximize this resonance and send what are essentially shock waves of denser air down into the cylinders.

Even though intake manifolds do just seem to be air tubes, they are precisely engineered to perform their job to the utmost degree.

Intake Manifold Leak Symptoms

Like any other engine component, intake manifolds can fail. Leaks can develop in the manifold gaskets and cause significant performance issues. Without the air being properly pressurized, the air-fuel ratio is thrown all out of whack, causing every dimension of engine performance to suffer. Misfires, stalling, abysmal efficiency and sluggish acceleration could all result from a leaky manifold gasket.

Some intake manifolds also contain coolant, which can spray all over your engine bay if the intake manifold springs a leak. While this can eventually affect your engine's performance, it's best to periodically check under your car for puddles of coolant. If your intake manifold is spewing coolant all over the place, then your engine could overheat, leading to problems much greater than a simple leak.

Performance Intake Manifolds: What Can They Do For Your Mustang?

Even if you weren’t familiar with an intake manifold's purpose, they are something that you’ve invariably noticed. Since they sit on top of the engine, they are often one of the first things seen under the hood. In fact, some intake manifolds look quite flashy. In particular, many of Ford’s engines have some interesting looking intake manifolds, like the one offered on the Boss 302 engine.

Shelby GT350 Intake Manifold

These flashy manifold aren’t just for looks though. Performance intake manifolds do pack quite a punch and can significantly improve the way your engine functions. Similar to performance exhaust systems, the key to performance intake manifolds is creating smooth laminar air flow. By reducing turbulence in the manifold itself, air can flow more efficiently into the engine. Additionally, the size of the air hole on the intake manifold needs to match the size of the air intake. If the airflow is either constricted or expanded in the intake manifold, the air pressure will fluctuate and either starve the engine of air or create unnecessary turbulence.

Variable Length Intake Manifolds

Intake manifolds can be quite advanced automotive components. Variable length intake manifolds allow the amount of air being sent into the engine to change depending on its needs. This is similar in effect to other technological advances like variable cam profiles and cylinder deactivation, both of which help maintain power and increase efficiency.

Carbon Fiber Intake Manifold

Variable length intake manifolds allow for power boosts across different RPM ranges. Inside the manifolds are multiple paths the air can take. At low RPM, a thinner chamber is used to transport the air. This allows for more power by causing the air to travel at a higher speed, both filling the cylinder with more air, and increasing its turbulence so that it mixes with the fuel better.

At high RPM, a second larger valve opens which allows for greater airflow. This way the engine isn’t starved for oxygen. Additionally, both of the runners can be engineered to maximize the boost received from the Helmholtz response.

The intake manifold is one of the unsung heroes in your engine bay. If you are looking to upgrade your engine's performance, a new performance intake manifold is certainly a good option. Along with a cold air intake , and a new exhaust, an intake manifold can surely take your Mustang to the next level.

Sources: How Stuff Works | AutoBlog | Engineering Explained | obd-codes.com Image Credit: MotorTrend | Wikimedia

What Intake Manifolds Do and How They Work

The intake manifold is a core component of your car's respiratory system. By ferrying air to the engine and ensuring that it's evenly distributed between each cylinder, the intake manifold is a rather unassuming part that serves a critical role on any internal combustion engine.

Related Resources

Tune vs No-Tune Cold Air IntakesTune vs No-Tune Cold Air Intakes

If you’re looking to boost the power output on your Mustang, one of the first mods usually is a Cold Air Intake. The idea is to free up air-flow coming into the engine which allows your Mustang to breathe easier equating to more power. Factory airboxes are typically restrictive and don’t allow sufficient airflow to the throttle body and intake manifold in the upper RPM range. Adding a cold air intake will increase that air-flow when the engine needs it most allowing for more power!

Superchargers vs TurbosSuperchargers vs Turbos

Knowing the basic differences between a supercharger and a turbo will allow you to dig deeper into which may better fit your lifestyle. If you’re looking for an all-out race car, then a turbo may be a better option for you when it comes to maximum power output. If you want streetable, instant power, then a twin screw supercharger would be the choice for you.

Single vs Dual ExhaustSingle vs Dual Exhaust

Single vs dual exhaust is an age-old debate when it comes to upgrading from your factory exhaust. You may already have a single exhaust and are thinking about converting to a dual exhaust system. Perhaps you may just want to keep your single exhaust setup but still upgrade to a better aftermarket exhaust for added performance benefits. Whether you are looking to update your current exhaust setup or looking at vehicles to purchase, there are pros and cons to both single and dual exhausts.

When To Replace Your Spark PlugsWhen To Replace Your Spark Plugs

Spark plugs provide the ignition that keeps an internal combustion engine functioning. Knowing when and how to change your spark plugs is an important step in keeping your engine running well.