What Constitutes an Air Intake System?
In general terms, an air intake system is a system attached to the engine’s air intake manifold and is designed to allow air into the combustion chamber. How much air can the intake system pass through to the intake manifold? The system should be able to pass between 15 and 20 kilometers of air every hour. This is much more that the engine actually needs but the intake system is not designed to control the amount of air.
Airflow is key. The air intake system is designed to allow the engine to take in fresh air as efficiently as possible. The air enters the air filter box through the air inlet duct, the intake silencer or resonator , and the throttle housing. The air is then sucked down the right or left intake runner towards the cylinder head. The engine always draws air from only one of the two cylinder heads at a time. The purpose of the other runner is to pump air into the combustion chamber, an action called "battery air."
The action is analogous to breathing in and out. It is not just important that air flows but that the flow is as efficient as possible. The air needs to be clean and free of obstructions and the flow of air should not be restricted as it enters the combustion chamber. This is accomplished by the throttle body assembly throttle plate or butterfly. The throttle plate will be sacrificed long before any damage will occur to the engine.

Emission Standard in California Explained
California has some of the strictest and most specific regulations concerning emission standards in the United States. Under rule 1216, all buildings must maintain PM10 (particulate matter) emissions at or below 30 mg/m3. Rule 444 (unconfined dust rule) also requires limits of less than 15% opacity for visible fugitive dust and less than 20% continuous time opacity for abrasive blasting sources. These rules apply to many types of businesses, particularly in manufacturing and production that have emissions as a result of their processes.
Rule 412 clearly states that it is unlawful to discharge any air contaminant, or combination thereof, for longer than 3 minutes in any one hour period such that any single source or point in the area where the air contaminant is discharged is opaque in appearance. After the Chief Engineer has assigned a numeric opacity limit to any source, no person shall exceed the opacity limit or visible emissions limit during any single period unless exempted. Section 102 (iv) defines "opacity" in terms of the light obscuration, the term number of the smoke plume, and the range 0-100% that a reading can be assigned. These and other regulations provide the parameters for assessing the legal emissions from the air intakes from any location.
California Legal Air Intake Options
The heart of a 2002 – 2009 2.3L Ford Mustang, call it the "Ricer" years, is a plastic intake manifold that has a metal throttle body housing. These engine intakes are a well know pothole of failures for these cars because of a design flaw that as the manifold heat cycles it distorts and causes the attachment points for the throttle body to flex and grow larger. They also have webbing to save weight and plastic is not the strongest material. Over time the plastic will warp at the bolts and the metal castings will crack and eventually fail. The result is an air leak that will cause a lean condition resulting in a check engine light and limp mode. In our shop we are calling them "flex-mans" for how this happens to the intake manifold.
The only legal air intake in California is a cold air intake system that is installed by the manufacturer or has been given a CARB Executive Order (EO) number. The reason these intakes require an EO number is because CARB has approved the intake after extensive testing proving that the emissions have not changed from stock. If you install an intake from a manufacturer that does not have an EO number then there may be emissions changes, and when that happens you are subject to a fix-it ticket. If you put a device on your car and it removes, modifies, or over rides an OEM part that the state has verified for emissions you may be cited, even years later.
The issue with emissions on cold air intakes is that like turbochargers, nitrous oxide and superchargers that increase horsepower, manufacturers want to offer them as performance upgrades. Most of the time by increasing the air flow in and out of the engine the horsepower will increase. Now, one of the reasons the OEM’s can sell a car at a lower cost is because they don’t make the performance version available right away. To keep up with emissions they spend hundreds of man hours developing a "Legal for California" product with an EO. Once the air intakes meet the criteria and are tested and pass they receive their executive order for sales. Most of the performance shops will rally behind the CA legal status and only sell cold air intakes that have an EO number for your 2.3L Mustang or they simply will not sell you anything. Unless you go to a swap meet or online and purchase a "coming soon" or "Pending" Cold Air Intake that at the very bottom of the box might have a sticker that says "California Compliant Pending". This means that the manufacturer has not yet been given an EO but is anticipating it based on the lack of issues with emissions to date. If you purchase this style of intake and install it, you will NEVER be able to register your car again due to emissions issues! NEVER! Simple as that.
The best options for a legal cold air intake on the 2.3L Ford Mustang EcoBoost 4-Cylinder is the inThgen cold air intake system that is available in three designs. The first is the Stage 1 intakes that require the factory air filter and offers no performance value over the factory intake system. This style of system is designed for sound and the additional air flow is negligable over the factory system. The stage 2 systems will accept a larger aftermarket air filter and will offer a performance increase due to the increased flow. Both of these intakes have a CARB approved EO number. The final intakes are systems that come complete with a replacement turbocharger inlet pipe. By replacing the factory intake tube this system offers a greater reduction in turbo lag.
The second legal cold air intake available for California is made by AFE and is endorsed by TreSport Tuning. The AFE Takeover cold air intake system is 50 state legal and CARB approved with an EO number. This system also includes a tune with the intake that must be flashed using a SCT-Flash device onto the factory ECU. If you’re wanting a "bolt-on and go system" for your Ford Mustang EcoBoost then the AFE system is not for you. They want you to install an air intake and within two weeks the intake must be taken off and its settings erased. Why? Because of hammering down on the throttle for great sound and then checking all of the data in live mode with the Flash device. This method allows them to develop proper reference charts for future intake designs. We do not endorse or condone this style of intake system for California applicants. Do it at your own risk!
Advantages of Using Legal Air Intakes
Driving with the right California legal air intakes can offer a myriad of benefits, from improved performance to better gas mileage, all without the need to worry about breaking any laws. These air intakes can be easily found on various online retailers, such as the ones on SuncentAuto.com, for many different types of cars, and can be the perfect addition to your vehicle for the price and enhancement of your ride. The benefits of California legal air intakes include:
Improved Performance
One of the most important benefits of using California legal air intakes is that they can significantly improve your vehicle’s performance, making it much more enjoyable and comfortable to drive. If you experience low oxygen levels in your vehicle, getting a legal intake can improve your gas mileage, allowing you to save a significant amount of money on gas. You will have more power, and you will be able to accelerate much faster.
High Levels of Redirection
Using the best California approved air intakes will also help you to divert and redirect smog water from your vehicle, ensuring that you will not be getting hit with any unnecessary fines. Fines can be expensive, and the list of charges can add up quickly. Avoiding these costs can help you to save a lot of money so that you can spend it on more exciting things, like food or trips with the family.
OEM Quality
Many of the California legal air intakes today are OEM quality, so you won’t be sacrificing quality for legality. Being able to drive your vehicle without worrying about any issues or illegal parts can greatly enhance your overall driving experience because you will feel much safer out on the street.
Getting California legal air intakes is a great way to make sure that your vehicle performs at its best by providing you with the extra power that it needs. Make sure that you look for air intakes that come with an executive certificate to ensure that authorities will recognize that your car is legal.
How to Select the Right Air Intake System
In California, the quest to find a legal air intake system for your vehicle can be quite the journey. With a myriad of options available, how do you know which system will be a perfect fit? As with any performance upgrade, it is important to consider various factors before making a final decision.
Vehicle Compatibility
First and foremost, you want to make sure that your legal air intake system is compatible with your vehicle year, make, and model. Most manufacturers will provide a list of applications that are covered by a certain product, such as their aFe Takeda Air Intake System.
Listen to Your Engine
Secondly, tuning can help determine if your legal air intake system will be just the thing for your motor. Intake systems work by removing restrictive areas of the factory system to improve airflow and throttle response. So while stock airboxes may be quieter than aftermarket systems, they are also not designed to keep up with aftermarket tuning. The goal is to allow the engine to breathe better to produce extra power. However, if your motor doesn’t have increased performance levels, then your factory air intake would have been sufficient. When you notice a decrease in performance or fuel economy, your next step should be to install a performance air intake system.
Optimize Performance
If performance and power are your top goals, the aesthetic aspects still have to be researched. Legal air intake systems come in different colors, finishes, and two types of filter media: dry and oiled. With the right filter, the quality and filtration level of your filter is increased, granting you longer service intervals. A cone filter is easier to clean than a panel filter, as it requires a simple cleaning with a re-oiling after. A panel-type, on the other hand, is often replaced with a new unit altogether, as some require cutting or modification to fit.
For those who want to increase engine performance, you will want to look at using dual air intakes. This helps create truly satisfying airflow and filtration, allowing for direct access to power. Because of the larger size, however, quality and price also become factors in. While you may want the best air intake for your car, you also want it to be allowed by California law.
Legal air intakes are all about peace of mind. With the right knowledge, you can ensure that you choose the right air intake system for your car.
Myths and Realities of Air Intakes and California Regulations
The importance of understanding legal air intakes
Many people feel that as long as the air intake looks like a factory part, it will pass inspection. Unfortunately, that’s not necessarily true. And there are a lot of people who don’t even know they HAVE an air intake, when in fact, they do.
From the factory, automakers design air intakes to draw air into the engine for optimal performance and efficiency. But after market air intakes are very different. Anytime one part of your vehicle is changed from the factory, the manufacturer’s warranty for that part may be voided.
In terms of air intakes, if the vehicle has an OEM intake that utilizes ducts, hoses, MAF (mass airflow), and air box, and you replace ALL of those components with aftermarket parts, the vehicle may not perform as efficiently.
California Law for After Market Air Intakes
After market air intakes are legal for sale and installation in California, but only if they comply with California restrictions. These restrictions apply when an intake replaces the entire OEM intake; a partial replacement may be fine.
Because C.A.R.B. policy is constantly changing and evolving, it is your responsibility to determine whether or not an installed air intake complies with C.A.R.B. regulations , so it is wise to contact a professional to help determine that.
Unfortunately, some people are diligent about choosing the right after market part based on California laws, but others feel the same thrill of bending the law, and they know how to play word games and say the right things to production staff to get away with deceptive part installations.
C.A.R.B. has developed a "List of Approved Parts (Executive Orders)" that addresses air intakes. But if the air intake isn’t listed there, does that mean it’s illegal? That’s a common misconception. Just because something is illegal doesn’t mean it’s approved by C.A.R.B., which is where some people get confused.
Aftermarket air intake systems fall under Section 27156 of California Vehicle Code, which covers all exempt aftermarket parts. Air intake systems sold as exempt from EPA requirements are therefore considered exempt from California requirements as well.
Here’s another piece to consider: A C.A.R.B. approved air intake system may be OK, but you still need to look out for compliance with other restrictions, such as Federal EPA Restrictions, California Air Resources Board (C.A.R.B.) Restrictions, Local Air District (ARB) Restrictions, and other Regional Restrictions. So have your expert tell you about those, too.
Installing and Maintaining Legal Air Intakes
Installing a legal air intake is a relatively straightforward process, but there are certain best practices that should be followed to ensure optimal function. Part of the intake process is selecting an appropriate location for the components. For maximum efficiency, most legal air intakes should be placed in the factory air inlet location on the vehicle hood. The intake should be secured using quality clamps and rubber seals around each of the hoses leading to the intake. Installers should keep an eye out for any openings in the air system once the install is complete. If any holes lead directly into the vehicle’s intake system, hot engine air could contaminate the system and increase emissions.
It’s important to put time into making sure that legal air intake systems are functioning efficiently. Monitoring the setup and ensuring that every component is sealed properly can prevent wasted air intake and increased emissions. Unfortunately, many motorists don’t check their air intake systems, which can cause them to become noncompliant with California emissions standards if the parts are damaged or the system is leaking. Property maintenance doesn’t have to be difficult or time-consuming. The simplest solution is regularly monitoring the system for leaks, whether that’s through visual inspection of the hoses or checking for the sound of hissing in the cabin of the vehicle. If you notice a leak, replace the damaged part as soon as possible.
Maintenance requirements differ depending on the type of component. In general, however, hoses should be replaced every four months, gang valves every month and differential pressure indicators every six months. Keeping a record of regular maintenance checks and repairs is the best way to ensure that your legal air intake continues to function properly and to avoid issues with the legal air intake law.
Penalties for Non-Compliance
California has some of the strictest environmental regulations in the country, and those regulations can bite you if you’re not compliant. Automobile owners who wish to avoid problems with CARB or the EPA are wise to make sure that the parts they plan to run are CARB legal.
Though owning an illegal intake system will not get your car impounded by local law enforcement, it does carry hefty fines if you get caught. The same bill that imposes fines for illegal exhaust systems also applies to illegal air intake systems. Driving a car with illegal parts is a ticket and a fine.
There are a few exceptions to this. One potential out is for people who own farm vehicles. There are certain exemptions for agricultural vehicles as well as off-road vehicles.
Beyond fines, the effects of quotation marks around here doing the car wrong go further. If you have a non-compliant engine, when the day comes (and it does come), you will face fines from the EPA and CARB. You don’t want to be that guy.
Besides fines, another reason to comply is to avoid being stuck on the side of the road. Car manufacturers/warrantees require that you keep your car compliant or else your labor to fix the car will not be covered. In a situation where your vehicle goes into limp mode due to intake problems, you will be paying extra out of pocket.
We highly recommend seeking expert assistance for advice on your vehicle and the requirements of the law in your state before making any modifications or additions.
Resources to Ensure California Emission Compliance
Given the complexity of California’s laws and regulations for emissions control, this problem can be daunting to most vehicle owners. Moreover, these regulations constantly evolve in terms of both interpretation and enforcement. As a general rule, the easiest way to answer a general question about the lease on emissions compliance is by visiting the website of the California Bureau of Automotive Repair (CA BAR). Not only is a good general resource, its website contains contact information for each regional California BAR office , and many provide telephone services that allow you to register complaints about the emission testing process. In addition, the California Department of Motor Vehicles [link here: www.dmv.ca.gov] provides another useful link, but it does not cover all areas of the Bar’s enforcement effort.
As previously stated, the laws surrounding vehicle emissions compliance are highly variable and it is likely that you will have to contact either or both agencies and possibly an emissions specialist to fully resolve your inquiry.