Ram-air induction has been a part of hot rodding for decades. In the '60s and '70s, factories experimented with all types of ram-air or cold-air packages because providing fresh air to the engine, rather than hot air from under the hood, increased power (and it looked pretty cool, too). Some scoops just guided air toward the carburetor, while more elaborate systems were sealed to the air cleaner and carb assembly. Systems ranged from the under-the-bumper scoops found on '69 Oldsmobiles to cowl-induction and Shakers that stuck through the hoods of Mustangs and other popular models. Ford, GM, and Chrysler learned long ago that feeding cold air, or more accurately, fresh air, to the engine definitely works.

In the '80s, Ford used a fresh-air system on its V-8 Mustangs and a similar system on the '86-present injected Mustang, which drew air from the inner fender area. The aftermarket took this design a step further and offered kits that extended the entry point from the inner fender to a more advantageous location. This meant either a headlight was removed or the scoop went under the bumper.

Using the headlight la the '64 Thunderbolt worked great for the track, but it wasn't practical to ride around with a headlight missing (though many did just that). On the other hand, placing the scoop down low was also controversial because while it could feed the engine fresh air, a low scoop picked up water, leaves, and other road debris. No doubt, more than one engine was lost due to foreign matter getting to the cylinders.

Today, cold-air kits are still the rage, but there is controversy over just how effective these systems are, specifically on '05-'06 Mustangs. Do cold-air kits really work, and, if so, how much power can be gained from using them? Sure, we've seen many of the kits gain 10-15 hp on the dyno, but what does that mean on the track? Additionally, how hard are they to install, and is tuning required?

To learn more, we decided to skip the dyno, grab a few kits, and head to the track. Our tester was an '06 Mustang GT equipped with an automatic for consistency's sake. We got our hands on AEM's Brute Force kit, which simply bolts into place with no tuning and sports an open-element underhood filter and sweet-looking inlet tube. We also bolted up Steeda's easy-to-install kit, with tuning provided, and, lastly, a trick design from WMS that grabs fresh air from the grill rather than from underhood. Of course, there are many more kits on the market, some which work fabulously, but these represented what we wanted for this test.

Baseline NumbersFor the cold-air trials, we used the previously mentioned '06 Mustang GT generously handed over by the crew at JDM Engineering, the only change being the huge Weld Racing 20-inch rims wrapped in Pirelli rubber. The plan was simple: eliminate as many variables as possible and chart what happened when we strapped on each cold-air kit. After a few test hits at Old Bridge Township Raceway Park, it was determined that even with the street tires, there would be no tire spin at all. We had stickier tires just in case, but they weren't needed. Jim D'Amore from JDM handled the driving and launched at a consistent 1,800 rpm on every run. Thanks to a PerformAire weather station, weather conditions such as temperature, humidity, and barometric pressure were monitored before each set of passes. All of these factors were computed by the weather station to come up with the density altitude (DA), which we also monitored. Additionally, the transmission temperature was kept between 200 and 205 degrees, the water temperature between 194 and 198 degrees, and the oil temperature between 193 and 197 degrees. The air/fuel (A/F) ratio was monitored with a Horiba A/F meter. By keeping all of the perimeters in check, we could accurately gauge changes to the inlet air temperature (IAT) and the elapsed time and mph, which would be the hard evidence.

The first set of passes gave us our baseline numbers, as the Mustang was run with the stock airbox. With a DA of 1,434 feet above sea level, the Stang clicked off a 13.858 at 97.28 mph. The second pass was practically a carbon copy, resulting in a 13.842 at 97.13. Heat soak set in for the third pass as the car slowed down noticeably to a 13.939 at 97.25. The IAT was measured at 93 degrees, and the A/F stayed at 12.5 consistently. Sixty-foot times ranged from 2.09 to 2.10. With our baseline numbers gathered, it was time to break out the wrenches and get down and dirty.

AEM Brute ForceThe first kit we bolted on was the Brute Force cold-air unit supplied by AEM. It came complete with air filter, inlet tube, and throttle-body spacer. No modification was needed to install the kit, and it bolted on quite easily. The open-element filter was shielded from underneath and from the engine, unlike the stock filter, which is contained completely in the airbox. With the kit bolted on, we were set to let the Stang rip.

The first run was a touch quicker than the baseline runs as the car tripped the timers at 13.833 at 97.40. The second pass was within two-thousandths of a second of the first one, a 13.831, and the car picked up a tiny bit of speed as it was clocked at 97.62. The third pass fell off dramatically, as the Mustang ran only a 14.051 at 97.05. This was confusing because while the first two passes were two-hundredths of a second quicker than the previous baseline runs, respectively, the third run was more than a tenth of a second slower, and the speed was down. We popped the hood and had our answer. The air filter that was clamped to the inlet tube was, well, not attached. There was a slick film around the rubber mouth of the air filter, and the hose clamp that was meant to keep the filter attached to the inlet tube had slipped off the rubber, causing the filter to fall off. After cleaning off the film and reinstalling the filter, we made two more passes, knocking down a 13.916 at 97.79 mph, followed by a 13.880 at 97.96.

The DA for these runs was up to 1,640 feet, so the air was a bit worse. The A/F ratio stayed at 12.5:1, and the IAT dropped to 89 degrees. The lower inlet temperature showed that the AEM kit helped lower the incoming air by 4 degrees, and it showed in the trap speed as the car picked up almost half a mile per hour.

Steeda High VelocityThe Steeda High Velocity cold-air kit was next on our list. This kit is similar to the AEM except it uses the stock inlet tube. Additionally, the Steeda kit comes complete with an SCT XCalibrator tuner loaded with a tune-up specific for the kit. We learned that on kits that have an increased inlet size, a tune is required to keep the air/fuel ratio in the proper operating range. Without the tune, the engine will go dead lean. If the inlet size is not increased from stock, no tune is required. The Steeda kit was a direct bolt-on, though we did have to unbolt the stock inlet tube from the stock airbox that we removed earlier. When everything was bolted on and D'Amore loaded up the Steeda program, Round 2 of track testing began.

The DA went up another 300 feet, registering at 1,961 feet. In racer speak, this can equate to about 0.02-0.04 seconds in lost elapsed time from our baseline numbers. The first run down the track ended after 13.781 seconds at 97.65 mph. The second pass netted a 13.764 at 98.14, and the final run a 13.850 at 97.67. The A/F ratio for the first two passes came in at 12.7:1, while on the last pass, it was recorded at 11.5:1. In addition, D'Amore noticed that on the last pass, the car went into what he termed "catalyst protection," which prevents the cats from overheating during hard use.

The 60-foot times were similar to the ones recorded with the AEM kit, and with the vehicle temperatures remaining the same, the IAT was within a few degrees of the AEM kit's final readings. But the Steeda kit picked up a tiny bit of speed over the AEM kit, though not enough to be noticeable from inside the car. The interesting change was the Steeda's elapsed times. Even with the weather worsening, the Steeda kit was worth a bit more in the elapsed time department. With the Steeda getting the car closer to the century speed mark, would the final kit push the car over the threshold?

Western Motorsports High VelocityThe Western Motorsports High Velocity cold-air kit actually experienced a two-part test, as it is offered with two options. The first allows you to run the car with a stock-sized inlet tube, and the second is for running the car with a larger inlet tube that requires the computer to be flashed with the tune accompanying the kit in the form of the SCT XCalibrator. The installation of the WMS kit was more involved than the others. The stock radiator cover was replaced with the accompanying cover/airbox, and the coolant reservoir needed to be relocated to the left-front fenderwell. This involves draining and filling the system.


The restrictive stock air inlet certainly hurt incoming airflow. The cold-air kits we tested not only freed airflow into the engine, but also helped keep the incoming air cool.


D'Amore used a Horiba air-fuel meter to monitor the A/F ratio throughout the test. Monitoring the A/F ratio during the test was critical to preventing a lean condition that would have damaged the engine or caused the computer to go into failsafe mode.


To keep track of the appropriate engine functions and temperatures, D'Amore used a NGS+ Scantool. The NGS+ is a dedicated Ford scan tool designed to work with the Ford ECM.


With the airbox and inlet system removed, the throttle body is in plain view. Also, notice the amount of room available. The AEM and Steeda kits had no problem fitting into the space reserved for the air filter in the left-front fender area.


Included with the AEM kit was this throttle body spacer, which required D'Amore to unbolt the throttle body and then reinstall it with the spacer. According to Lawson Mollica of AEM, the spacer was a prototype included with the kit in an attempt to improve plenum velocity. Mollica said most of the time the spacers do not make more power.

After the install was complete, it was time to let the Mustang rip with the new kit and the stock tune. With an altitude of 1,941 feet (ASL), the air was nearly the same as it was when we tested the Steeda kit. The first run netted a 13.871 at 97.40. That pass was backed up with a 13.908 at 97.30, and the final run of the series was a 13.838 at 98.13. The kit, in stock form, lost e.t. on the first two runs, but the final e.t. was comparable to the e.t.'s from the other two kits. The trap speed was also comparable to that of the other two kits. The major change with the WMS kit was the IAT dropped significantly to 77 degrees. Obviously, because air enters from the grill, and the air filter is located above the radiator, the result significantly lowered the temperature of the incoming air charge. While that should have led to some increase in power, the track times showed the same numbers as the other two kits with higher IATs. So, with the stock tune not showing any difference from the other two kits, would the tuned version of the WMS kit wake up the stock S197 GT?

After taking a few minutes to load the accompanying tune-up and change to the larger inlet tube, the test mule was ready to take another stab at the Raceway Park quarter-mile. The DA skyrocketed to 2,366 feet, but the car ran its three best passes of the day with the tuned WMS version. The first run ended after 13.694 seconds, with a trap speed of 98.48 mph. The second run was 13.699 seconds at 98.68 mph, and the final run was over after 13.784 seconds with a terminal velocity of 98.48 mph.

The IAT was once again recorded at 77 degrees. Of interest, however, was the change in 60-foot times with the WMS tuned kit. The last three runs showed 60-foot times of 2.06, 2.07, and 2.09 seconds, respectively. These three short times were the best of the day, bettering the stock 60-foot times by a few hundredths and the 60-foot times seen with the other two kits by nearly a tenth of a second. With the WMS tuned kit, the A/F ratio hovered around 12.8-12.9 during the three runs.

ConclusionAfter all was said and done, the test results showed the importance of getting cooler, fresher air into the engine. Starting with a stock IAT of 93 degrees, each kit showed lower IATs, which directly related to the power gains seen on the track. Of note is the continual increase in the DA during the day. While the DA was lowest while testing the AEM kit, the Steeda kit ran under a DA almost 200 feet higher and the WMS kit ran with a DA that was almost 1,000 feet higher. With this increase in altitude, the air going into the engine was slightly worse, thus cutting down on the true power output. Every time the DA increases, the e.t.'s worsen and the speed is down correspond-ingly. Normally, for every 150-foot change in DA, a naturally aspirated car will lose about a hun-dredth of a second in elapsed time.

While these kits are good for at least 10 hp, is there a huge difference in how the car runs after the kit? While 10 hp may or may not seem to be a lot, it is normally good for about a tenth of a second and 1 or 2 mph at the track. The other thing we must discern is whether or not the kits work better with or without a tuning program. According to Sam Cory of Steeda, using a tuner with a cold-air kit can increase the productivity of the new parts.

"I've seen the other kits sometimes work without a tuner, but what it comes down to is when you put on a cold-air kit, the car is lean," Cory says. "If you are going to make any serious type of horsepower, the car will go into failsafe mode and not run."

"Whether the car needs a tune or not depends on the kit," says Shannon Wall from Western Motorsports. "Our 80mm kit doesn't have a tuner included with it and it runs well. With a programmer, however, the car can obviously make more power."


After taking out the two screws holding the MAF sensor in the inlet tube, D'Amore removed the sensor, which would soon find its way into the inlet tube of the other kits.


D'Amore used the appropriate-sized Torx-head socket to bolt the MAF into the AEM inlet tube. Before you cinch down the bolts, make sure the MAF is positioned correctly. The MAF is marked to show the direction in which the air is to flow.


The AEM Brute Force kit is bolted up and ready to go. The kit was worth two hundredths of a second in elapsed time over the stock inlet system. Those two hundredths would have been more were it not for the worsening air conditions.


After cleaning off the tires, D'Amore let it all hang out for three runs with each kit. He left the starting line each time at a consistent 1,800 rpm in the automatic transmission-equipped car.


Bowe finished up the Steeda cold-air kit install by tightening the hose clamp that attaches the inlet tube to the throttle body. Unlike the AEM kit, the Steeda kit reuses the stock inlet tube.

Steeda and WMS both offered tuners in their kits, and Cory feels that a tuner with a cold-air kit is needed. "We changed the spark tables, the fuel tables, and all the stuff you can change," Cory says. "The control of the variable cams is important. We changed the environmental things like high- and low-speed fan "on" time, the idle, shift points in an automatic transmission-equipped car, the rev limiter, and got rid of the speed limiter."

Wall agrees. "The tune we have is supplied to us by SCT, and it is an optimal tune developed on the dyno," he says. "It is not on the ragged edge, but a tuner will only find a few horsepower tweaking it. Most of the gains seen with a tuner come with changing the transmission shift points, rev limiters, and such."

"WMS sent us the kit, and we tested it on a car out here in Longwood," says SCT's Charlie Mahoney. Mahoney adds, "We checked the air/fuel ratio and the fuel trims, and made sure all of the numbers were set for a cold-air kit rather than just a tune itself. We didn't have any problems getting the tune into the computer. When the project was started, it was just like any other we had worked on before. Because the '05s and '06s are fly-by-wire, we had some issues concerning that, but we had no other problems other than the ones we had tuning computers in other models."

The other side of the coin is the AEM kit, which did not come with a tuner. "We developed the intake to work with the factory ECM and program out of the box," says AEM's Lawson Mollica. "The kit is a tuned inlet designed to work with the rest of the motor. All the kit does is move more air into the throttle body, though with a tuner, you can get the car to perform a bit better."

The AEM kit we tested was a prototype that included a spacer that bolted onto the intake manifold behind the throttle body. While our kit came with the spacer, Lawson says that less than 5 percent of the kits AEM produces come with the spacer. Designed to increase plenum velocity, there was no gain in power from using the spacer.

To really take advantage of the kits, even the ones that come with a tune, taking your Mustang to a proven tuning specialist may help in utilizing all of the power potential that one of these kits offers. Whether you get a kit with or without a tuner, the numbers and the track data don't lie. The colder the incoming air, the higher the horsepower.


he Steeda kit features gasket stripping that seals the filter box to the inlet tube and the airbox to the hood of the car when it is closed. Through the opening, you can see the MAF sensor protruding into the inlet tube.


Except for the fact that the Steeda kit uses the stock inlet tube, the overall design of the kit is similar to that of the AEM. To avoid making the same mistake we made by having the filter fall off with the AEM kit, we cleaned the slick film off the mouth of the filter before tightening the hose clamp that attaches it to the inlet tube.


Accompanying the Steeda kit was an SCT XCalibrator tuner with a supplied tune developed by Steeda. Hooking up the tuner is as simple as plugging it into the computer port under the left side of the dashboard.


Flashing the tune into the computer is straightforward, as the XCalibrator has easy-to-follow instructions that come up on the screen. D'Amore loaded the program in a few minutes, and when it was done, we were ready to rip off a few more passes.


We were monitoring the A/F ratio to make sure the car didn't go lean with any of the kits. We also monitored the fuel gauge to make sure the car's weight didn't vary too much over the course of the day.


The differences in the stock radiator cover (bottom) and the WMS replacement (top) are quite apparent. The fresh air comes through the slots and the rectangular hole on the WMS kit. The WMS cover is also larger and bolted right up.

To utilize the ram-air design of the WMS kit, the coolant reservoir needed to be relocated. WMS supplied all of the brackets and hardware needed to move the reservoir from the radiator support to the left-front inner fender. Coincidentally, the reservoir moves to the place where the stock airbox was previously located.


Bowe puts the finishing touches on the radiator cover/ram-air box. The new cover runs all the way up to the throttle body.


The route the air takes to the throttle body is considerably shorter with the WMS kit. Air enters from the grill, travels upward through the openings in the cover, goes through the filter (not bolted on in this photo), and into the throttle body.

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The difference in the WMS kits is in the size of the inlet tubes. The larger inlet tube (left) requires the tune that comes in the supplied SCT XCalibrator tuner, while the basic inlet tube (right) doesn't need a tune. Notice the size difference between the tuned version and the non-tuned version.


The WMS kit is bolted up and ready to go. Notice the shorter inlet tube as compared to the other two kits. The location of the filter was good for the lowest IAT of the test, measuring a low 77 degrees, which is cooler than the outside temperature of 82 degrees when the kit was tested.


The WMS kit gave us our best speed of the day at 98.68 and our lowest e.t. at 13.694 seconds. Both of those numbers came from the tuned version of the kit. The non-tuned version ran similarly to the other two, recording a 13.83 best at 98.13 mph


The hardest part of installing the WMS kit is relocating the coolant reservoir. Moving the reservoir required draining the coolant, so be sure to refill and check the coolant level after the kit is installed.


The two slat-like openings on the WMS radiator support bring fresh air in from the grille. The small openings help promote the velocity of the incoming air, adding to the ram-air effect of the kit.


As was the case with the stock setup and the other two cold-air kits, the MAF sensor was also bolted to the inlet tube. In the case of the WMS kit, there was not a whole lot of inlet tube


As he did with the Steeda kit, D'Amore loaded up the tune that came with the WMS kit. Using the SCT XCalibrator that came with the kit, it only took D'Amore a few minutes to load the tune, which was supplied directly to WMS by SCT.


Does a cold-air kit really help in the horsepower department? Each kit showed an improve-ment over the baseline num-bers of the stock GT. The numbers can be even better with better weather conditions, as the air worsened as the day went on. This certainly hurt the amount of power gained by the kit, but you should expect at least a 10hp increase by bolting on a cold-air kit.