Fox Body Air Induction Guide Part 1

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Freshen up that old 5.0 motor and install new intake components. Not only will you gain more horsepower and torque, you will also increase your Foxbody's fuel efficiency and could straighten out any annoying rough idle issues.
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The key to making power (or one crucial key, the engine must still be able to take advantage of it) is to flow air into the engine. The more air you can flow into the engine, the more fuel you can dump in as well and more power you can produce. More air plus more fuel gives a bigger boom, which results in increased horsepower and torque production to rocket your Foxbody forward. The air filter, air intake (tubing), mass air meter, throttle body and finally the intake manifold itself, are all key areas on a stock 5.0L engine that can be improved to allow more flow and thus create more power.
Labeled Foxbody Air Intake System

Fox Body Mustang Air Intake Parts

Ideally, when picking air inlet parts it is best to have each part slightly smaller than the other, to create a funnel effect and increase air velocity as the air approaches the intake manifold. Think of wind entering a canyon, it will speed up and become stronger as it passes through the channel between cliffs. Let’s begin by examining replacement performance options for your Fox Body's stock air intake.

Fox Body Air Induction - The Basics

  • • When picking air inlet parts, the parts should gradually decrease in size to create funnel effect

  • • An upgrade to a performance air intake (filter) is ideal for air flow to the engine because of special materials that flow more air and combat dirt/clogging

  • • Replacing the stock plastic air track with an aftermarket cold air track will increase air flow and horsepower

  • • When selecting a new Mass Air Flow Meter, sizing and calibration should be suited to your precise needs

Replacement Mustang Air Filters:

The air filter is where everything begins. A dirty, clogged or otherwise deteriorated air filter can impact engine performance severely. A quick scrub of the old air filter can improve suction and throttle response. Yet better, a performance air intake is the preferred method to insure sufficient amount of air flow to the engine. Performance filters from K&N, BBK and Stack Racing use special materials in their filters to reduce resistance, turbulence, maximize flow but not sacrifice filtering ability. Thus, all the harmful debris remains out of the combustion chamber while you’ll benefit from better throttle response and maybe even a few extra horses as well. Furthermore, many aftermarket performance filters are reusable, meaning you can clean them using a special cleaning agent and they will be as good as new. Buy once; use forever—definitely a worthwhile investment.

Foxbody Cold Air Intake

Cold Air Intakes & Fox Body Mustangs:

Another easy method to increase airflow and potentially horsepower is to replace the stock plastic air track with an aftermarket cold air version. Essentially, how a cold air intake works is by placing the air filter in a location where there the air is colder (typically the fender well). The chemistry behind this is why your Fox Body makes more power with colder, denser air. Cold air is denser than warm air, thus meaning there will be more O2 (oxygen) molecules per volumetric unit of air to react and combust with the gasoline. Therefore, there can be power made! Remember, bigger boom (combustion) is bigger power (High school chemistry can be useful! This surprised me too…). Another factor that is often unconsidered is what the actual inlet tubing is made of. The stock one is plastic, an aftermarket unit is usually metal. The difference is heat transfer and absorption properties of each material. The stock plastic one will absorb heat and transfer some of it to the air flowing through it, thus warming it up. Metal has a much higher heat capacity and will not transfer much, if any, heat to the air passing through the inlet tract. This is just another reason to consider upgrading to an aftermarket cold air intake.

Foxbody Mass Airflow Meter

Mass Air Flow Meters & Sensors:

This applies to Mustangs from 1989 and on. 1987-88 Mustangs (except California 88’s) utilized a different computer system called speed density. If you own a 87-88 Fox Body (not from California), do not fret. Mass air conversions (converting a speed density car to mass air) are very common and not too hard to do. However, this is another subject entirely.

In 1989, Ford introduced a new computer system for its Mustang – the mass air flow system (MAF). Without going into too much detail, the MAF system places a hot-wire and temperature sensor in the air inlet tract (immediately after the air filter) that measures the amount of air coming in. Depending on how much air is detected, the computer reacts accordingly and adjusts fuel, timing and the likes. The older speed density was a pre-programmed system where the computer had a set table of lookup volumes and resulting fuel and timing values. MAF systems are great because they can adapt to almost any change made within the engine. Speed density, on the other hand, is a lot fussier when modifying the engine, particularly when it comes to replacing the stock camshaft.

The stock MAF unit is a puny 55mm unit. When selecting a new mass air meter, it is important not to go too big. Rather, it is always best to pick a part that suits your needs precisely. BBK, C&L and SCT all make very high quality replacement meters for your Fox Body--they slot right in place of the stocker. When selecting a new MAF meter for your Mustang, you must be careful of the sizing and calibration. Each meter comes factory tuned to work with a specific size fuel injector. Thus if you are still running stock 19 lb injectors with no plans to upgrade, don’t pick a MAF unit calibrated for 24 lb injectors, it will not work well at all. Generally, MAF meters around 70-75mm are the norm for mild street cars. Units up to 90mm are available, but are generally run on very high performance engines or track cars only. If you’re seeking a stout street machine, any 70-75mm offering from C&L, BBK or SCT will definitely do the trick.

Air Intakes: Understanding Your Mustang's Entire System

Replacing the worn stock air filter, intake tract and mass air meter are a good start to increase the 5.0L’s breathing ability. Although you can’t expect changing these parts to produce a truckload of horsepower, they do add enough to make an instantly noticeable difference. You can also consider these parts to be supporting parts--they will support horsepower, but will not generate huge numbers simply on their own. More importantly, however, is they remove the bottleneck found within your Fox Body's stock parts and will support the engine as more serious modifications are made. Additionally, throttle response should experience a noticeable increase. Continue on to the next section, Air Induction Part II for an overview on intake manifolds, throttle bodies and a road map on using these foundation parts to create huge horsepower gains.

- CMC

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