What Does A Cold Air Intake Do

Do Cold Air Intakes Work? – Why It Does And Doesn’t

Any car enthusiast would know that a cold air intake is amongst the first few modifications you can make to any car. It doesn’t matter how new or vintage the car is, cold air intakes are almost universal with a bit of imagination. So then, why have some people wonder do cold air intakes work?

If your car has even a modicum of sporting credential, then chances are there will be manufacturers out there developing a cold air induction kit.

Take the mundane, but pragmatic Volkswagen Golf 1.4 TSI for example. Even so, you can still pick up a cold air induction kit for it.

Not to mention sports cars. One of the latest sports cars to release, the Toyota Yaris GR, already has an eclectic selection of cold air induction kits available. The GR 86 will undoubtedly receive one very soon.

The swift production process of those induction kits is courtesy of performance parts makers. They either receive a donor car or go out and buy one as a research and development platform.

But here’s the question that inevitably arises from this situation. If aftermarket parts sellers put a lot of work into making professional induction kits, why are there people telling you that they don’t work?

It’s a sentiment that most petrolheads have shared on the forum over the years. Nowadays, people are convinced that cold air intakes don’t actually contribute to any performance gain.

However, it’s likely that those people telling you that cold air intakes don’t provide tangible performance benefits also tell you that they have it fitted. And some cold air intakes can be rather pricey.

So, if a cold air intake kit doesn’t work, why do people still buy them? And why do I almost always recommend it as one of the first mods you should make across multiple different articles covering various makes and models?

What Are Intakes?

Let’s get one thing out of the way first, what are intakes? If we define it technically, it’s an opening or a duct that allows fluid to enter.

In the context of an engine, the intake is essentially the nose of the engine. The fluid in this case is air, and the intake is where the air is drawn in from the atmosphere into the engine.

Now, it’s fair to say that not every car nowadays has an intake. Only engines relying on combustion processes will need an air intake. Therefore, electric cars can omit any sort of air intake.

But they still have air intakes for various different components such as the coolant radiator and A/C system. But I digress, the intake that’s pertinent to our topic is the intake for a combustion engine.

Design Details

Now, obviously, manufacturers can’t just put the air intake anywhere they want. It would work, but it wouldn’t be optimal at all. A poorly designed intake can lead to an engine’s untimely demise.

One of the most critical design decisions is that the intake needs to be located as high as possible within the provided engine dimensions. This is to avoid potential water ingress. It also needs to be away from dirt and gravel.

Despite so, it’s inevitable that dirt will be pulled into the engine. An air filter serves as the line of defense preventing microscopic particles from entering the engine.

Other than that, it’d be ideal for the intake to be away from the stifling engine heat. Over time, the engine bay eventually gets heat soaked, meaning that the intake air temperature will rise gradually.

It’s undesirable for two big reasons. For one, it’ll compromise engine operating efficiency. Air is denser when it’s colder, so it takes more space to pack in the same amount of air into the combustion chamber.

For carmakers, that’s not terribly important. What matters for them is the fact that an engine operating at lower volumetric efficiency is worse at emissions. It takes more energy to produce the same amount of power, resulting in more waste.

Ideally, the manufacturer would have enough room to locate the air intake away from the engine bay entirely. But this isn’t really possible in most cases, typically because of limited space and cost considerations.

Cold Air Intakes

Hence, this brings us to the topic of cold air intakes. A cold air intake by its very definition is an intake that, overtly, delivers cold air to the engine.

This means that regardless of the operating condition and duration of the engine, a cold air intake should still be able to keep the intake air temperature low.

Ultimately, the perfect cold air intake will impart heat upon the air that’s entering the engine. But that’s obviously impossible. cold air intake manufacturers only design and make their induction kits to be isolated from engine heat.

That’s the primary aim of a cold air intake. The second point is to free up intake flow. The notion is that manufacturers often sacrifice intake air volume for noise compliance, compact size, or cost.

However, the aftermarket industry rarely needs to conform to those boundaries. Therefore, they have more breathing room to free up air intake volume.

The last point of a cold air intake isn’t particularly important, but owners often have the idea that a cold air intake looks sportier and cooler. Some owners just want the wow factor of a cold air intake, so looks are important when designing a cold air intake.

So, Do Cold Air Intakes Work?

The big question remains, do cold air intakes actually work? From what I’ve said, the reasoning and operating principle of a cold air intake are plain to understand. It’s also easy to see why cold air intakes can indeed increase engine output.

In general, there are two camps to the argument. The best answer I can give is that it really depends on the situation. It’s also heavily reliant on the cold air intake design itself, the car, and the conditions.

Sentiment 1: Cold Air Intakes Do Work!

Companies and air filter makers will tell you that cold air intakes do work, and they can provide a gain of 10 to 20% over your stock output. Some people also believe that cold air intakes work.

It’s simple, in some cars, it is definitely possible to make a proper cold air intake. This means an induction kit that completely isolates and moves the intake location far away from engine heat.

In these cases, cold air intakes do work. A properly engineered cold air intake will undoubtedly improve engine output due to two reasons.

Reason 1: It Avoids Heat Soak

One, a genuine cold air intake does not suffer from heat soaking or heavily negates the effects of heat soak. Heat soak occurs over an extended engine operation, especially during hard driving.

This means that for cars that are being tracked for an endurance run, cold air intakes are a necessity. It prevents the engine from losing power over time on the track.

The reason is that modern computers have a sensor that monitors intake air temperature. If it determines that the intake air temperature exceeds the norm, it’s going to reduce fueling to compensate for the thinner air.

Therefore, with less air and less fuel, there’s less mixture to combust. A ‘smaller’ mixture produces a smaller explosion, thus creating less power.

If you know that your car has an issue with heat soaking (prevalent for cars with thick hood insulation), or if you track your car often, then a cold air induction kit is worth the trouble.

Reason 2: It Smoothens And Improves Air Flow

Normally, in a stock car, manufacturers compromise intake flow to reduce noise. One way manufacturers do this is via dampening materials, such as rubber, silicone, and plastic.

Those materials tend to absorb and dampen sound better than metal. The other way that manufacturers quieten induction noise is through noise baffles, resonators, and expansion chambers.

However, manufacturers tune those for a very particular application and calculated constants. When you change something in your car, it alters the engine harmonics. Some noise dampening measures can restrict flow too.

Slowing and restricting airflow is a major factor in intake noise. Air traveling at a higher velocity imparts more sound energy since there’s less time for the energy to be lost. This is why sound travels further and louder underwater.

Therefore, most aftermarket cold air intake kits you see are made of smooth steel pipes. The air filter used is also less restrictive, and incoming air has a straight path to the throttle body.

This is why if you have a car with a particularly poorly thought out intake, changing to an aftermarket intake can improve engine output. Generally, you can expect to see mild gains (<5%) changing to an aftermarket cold air induction kit.

Reason 3: It Shifts The Powerband

Cold air intakes don’t need to increase power output dramatically. In fact, sometimes, all they do is shift the powerband, which can actually have a big impact on a vehicle’s driving dynamics.

This can simply happen due to the engine requiring different amounts of air throughout its operating range. You’ll commonly see an increase in the mid-range torque with some intakes.

It can happen because most engines are designed with mid to low-end torque in mind. Therefore, cold air intakes can bring in more air than the stock intake at lower RPMs, improving mid-end torque.

But once the engine revs out, it chokes out because of other restrictions such as the camshafts. You’ll see this as the power peaks out the same way with a cold air intake and a stock intake.

Sentiment 2: Cold Air Intakes Don’t Work

With online information becoming easily accessible nowadays, people eventually discovered that cold air intakes might not make as much power as the makers claim. Independent dyno tests reveal that manufacturers’ claims are typically too optimistic.

A few factors contributed to people alleging that manufacturers are falsely claiming massive 20 horsepower gains in their naturally aspirated 4-cylinders.

Issue 1: Cold Air Intake? More Like Warm Air Intake!

The biggest issue that most people have with cold air intakes is that most of the widely purchased kits aren’t cold air intakes at all. It’s more or less just a stainless steel tube with a pod filter stuck at one end. Those are popular because it’s very affordable.

It’s an issue with the dilution of the term ‘cold air intake’. Instead of an actual, properly engineered, and designed cold air intake, those are usually universal kits to adapt an aftermarket pod filter to the engine.

Realistically speaking, you don’t even need to buy one. You just need a pod filter and spare steel pipes lying around to make one.

As those ‘cold air intake’ kits become widely available on popular online buy and sell sites, people eventually refer to any aftermarket intake kits as cold air intakes.

The ubiquitous coining of the term ‘cold air intake’ has earned genuine cold air intake kits a bad rap amongst performance enthusiasts.

Since people selling those universal intake kits have also marketed it as such, it further muddles the term ‘cold air intake’. In fact, it’s fair to say that for some people, the iconic red pod filter is all you need to call it a cold air intake.

Short Ram Intakes

When you’re thinking of aftermarket intake kits bought off from eBay that includes a couple of hose clamps, silicone hoses, pipes, and a pod filter, it’s more likely that it’s a short ram intake.

There isn’t really an official term for it, but it’s fair to say that short ram intakes are based on ram-air intakes. Ram-air intakes were really first used by muscle cars and motorcycles (and jets).

One of the coolest muscle cars to really use and market the ram-air effect is probably the ’69 Pontiac GTO. The forward-facing hood scoop opens upon full throttle, ‘ramming’ fresh air through a shorter path directly to the carburetor.

The ram-air effect increases dramatically as the vehicle speed rises. This occurs due to the increased dynamic air pressure. In fact, on drag cars with forced induction, it’s common to see an increase in boost pressure at very high speeds (>200 mph).

Now, modern cars with short ram intakes don’t need you to cut open your hood of course. It’s just a stubby intake piping that provides a very short and direct route from the air inlet to the intake plenum.

The argument with the short ram intakes is that they are too short. It’s the entire point of course, but this means that these intakes are often located close to the engine, sometimes even to the exhausts.

Therefore, it’s easy to determine that short ram intakes are very susceptible to heat soak. This leads to people saying that these intakes often compromise engine performance.

However, there are genuinely performance benefits to be had from short ram intakes. These can bring air in quicker from the low end, improving low to mid-end torque. But again, it’s typically minor (~3% gains) and varies from vehicle to vehicle.

Heat Prevention

Obviously, manufacturers of such kits understand that heat soak is a genuine issue with short ram intakes. It worsens as you drive the car for longer periods, making it unfeasible for track driving.

One way to alleviate the effects of heat soak is through proper heat shielding. This is why you see pieces of shiny heat shields surrounding the pod filters, to repel heat.

Some manufacturers even make use of the stock airbox, modifying it so that a large pod filter can fit within. The stock airbox is generally good at keeping heat away from the incoming air.

But once again, heat shields are no use if they instead soak up the heat. It’ll just delay and worsen the effects of heat soak.

Issue 2: Your Engine Isn’t Intake Limited

The other argument is the fact that most engines, especially performance engines, aren’t limited in output due to the intake.

One thing you’ll notice with most performance cars is the fact that they already have a very well-sorted intake. It’s not just the aftermarket, car makers understand that intake flow is important too.

And carmakers have a generous budget to spare on developing a proper intake system for their sports cars. In fact, sports cars make use of pod filters too, and they can make power without generating more noise.

Therefore, for sports cars with only an intake mod, even a proper cold air intake, it’s safe to assume that you won’t be picking up any extra power.

In fact, manufacturers nowadays are pretty knowledgeable in making good compromises with their intake systems. Changing to a cold air intake will not result in measurable gains in this case.

It’s all dependent on your particular application of course. But be wary of those manufacturers that claim an extra 20 to 30 horsepower from a straightforward cold air intake install. Especially when you have a modest small capacity 3 or 4-cylinder engine.

Making Supporting Mods

Despite what I’ve said, it’s fair to assume that most people that want performance gains aren’t going to stop at just a cold air intake mod.

For them, the cold air intake is just a supporting mod, part of the first stage bolt-on modifications. Cold air intakes help when combined with further breathing mods like performance headers, full exhaust system, larger throttle body, etc.

Most importantly, a tune optimizing the car for performance rather than emissions will be able to make use of the improved engine flow.

This is especially true if you’ve decided on making bigger modifications in the future. For example, if you swap out the stock camshafts for a set of performance cams, then a cold air induction kit will definitely help.

However, it’s worth noting that in most cases, you don’t actually need to retune for a cold air intake. Your engine has ways to measure incoming airflow. If it detects that more air is flowing in, it’ll compensate with more fuel.

A tune will however optimize the engine’s mapping and thus fueling for more performance over emissions. At the factory, emissions are always the priority over performance and fuel efficiency.

Do Cold Air Intakes Work – Proper Cold Air Intakes

As long as you’re spending your money on an actual cold air intake, it’s safe to assume that they work. They might not necessarily introduce perceptible gains in torque and power, but they will keep intake temperatures down.

This means that you can drive harder for longer given that you have other cooling mods installed. Cold air intake can be particularly beneficial for turbocharged cars, as it also improves the intercooler’s efficiency.

Genuine cold air intakes will relocate the air inlet away from the engine bay. Cold air intakes commonly take in air from the fog lamps or even in front of the bumper. It’s important to ensure that there is actually sufficient airflow into the inlet.

In some cars, it’s even possible to make use of the space within the cowl. This is known as a cowl air intake. It also makes use of the high-pressure zone localized to the windshield base.

Cold Air Intake Alternatives

Other than the aforementioned short ram intakes, there are companies out there innovating and developing other intake systems for some cars.

While these systems mainly function on a different principle, they still make use of the notion behind cold air intakes. After all, colder air is still better than hot air for engines.

Venturi Intake

One of the most commonly applied intake principles. The Venturi effect basically states that fluid entering through a narrower section will decrease in static pressure but increase in velocity.

Eventuri is one of the most well-known companies to make induction kits based on this effect. From independent dyno tests, it’s apparent that they work.

The main difference is that Eventuri intakes generally have a longer, larger velocity stack. It improves the Venturi effect. It’s made possible within a limited space via a reversed cone-shape filter.

It’s important to note that Venturi intakes and velocity stacks are different. Velocity stacks minimize parasitic losses from air entering a system. Venturi intakes promote pressure loss to increase air velocity.

Thus, Venturi intakes work better with a turbocharger. While the turbocharger has to work harder to compress the lower pressure air, it offsets the pressure loss generated by the Venturi effect.

Expansion Chamber Intake

Manufacturers commonly use this to tune out intake noise while improving engine efficiency. You can spot one either protruding out of the intake tube or as a sudden increase in diameter in the piping.

An expansion chamber is just that, a larger diameter in the piping. The purpose of this is to counteract the effects of the high-pressure wave generated by the intake valves slamming shut.

This pressure wave will travel all the way up the intake tract, potentially causing turbulence and acting against incoming air. The expansion chamber provides space for the high-pressure wave to diffuse without disturbing the low-pressure air.

Do Cold Air Intakes Work – Verdict

The answer is yes, cold air intakes work. Even if they do not provide overt gains in torque, they keep intake temperature cool. It’s critical for cars people bring to a track-day.

And as an extra, aftermarket intakes, including cold air intakes, amplifies intake noise dramatically. It might be unnecessary for typical car owners, but for enthusiasts? That’s priceless.

Disclaimer

It’s important to state that when you switch over to an aftermarket pod filter, it’ll almost certainly be worse at filtering than the stock one. They are less restrictive after all.

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