Restricted Airway
The heavily touted 4.6L 3V motor in the new Mustang GT comes with a big jawbreaker stuck deep in its throat. The factory has it choking on its' own air inlet system. Restrictive air boxes and silencers have become the Achilles heel of Mustangs. The previous generation had the rubber fender insert and the 5.0L era Mustangs had the funky looking plastic contraption. The practice of immediately removing these things has became so notorious it is classified as a "free horsepower mod". Even the most green of Mustang enthusiasts know to rip their silencers out the minute they turn the corner from the dealer's lot.

For the '05 the restriction comes in several areas. First and foremost is the 2" square opening from which air enters into the air-box. How the car can lay down over 250 horsepower to the wheels sucking air through this swizzle stick of an inlet is mind blowing. Once the air makes it past the filter and mass-air meter (integrated into the air-box lid) it encounters the most severe restriction we've seen to date on any Mustang, the carbon filter. This rigid plastic piece resembles a tightly rolled up piece of corrugated cardboard. It performs an emissions function of trapping gasoline fumes that might be in the intake system.

The final restriction is the harsh bend in the throttle body duct. Ford has always used the pre-formed accordion shaped bellows to connect between the mass-air meter and throttle body. In our experience there has always been some power to be found by straightening this out, and perhaps even increasing the diameter - especially once you start adding other mods.


What separates the new Mustang's breathing problems from that of past generations is that on the '05 you can't just pull out the silencer or slap on a big conical air filter for decent power gains. The mass air meter and computer in the new Mustang is so sensitive to airflow changes that even removing just the carbon trap from the inlet tube results in a significant leaning out of the air-fuel ratio. Do that and a K&N filter and the engine will go lean enough to throw a check-engine light and trouble code.

If this sounds like a nightmare just talk to Lee Bender, owner of C&L Performance, the mass-air meter and inlet specialists. Usually C&L's products bolt right on, yield impressive gains, and require no tuning of the engines PCM. However, early on in their R&D process and dyno testing they realized the '05 was a different beast. The slightest changes in the factory air intake system would change the air-fuel ratio significantly. To make matters more complicated, the first couple dyno pulls immediately after a change would show no ill effects. Subsequent pulls would however show undesirably lean conditions, as if the engine management system was picking up the airflow change and improperly adapting to it. It didn't matter how slight the change, the engine ultimately didn't like it and power gains were less than optimal- and keep in mind C&L is using the same diameter mass-air meter housing and the factory sensor.

After beating their head against the wall the C&L team realized the '05 required some computer re-tuning to go along with the hardware upgrade. They teamed up with Diablosport who had also been at work developing an '05 tune for their Predator tuner product. The Trueflow system consists of a cast aluminum inlet tube and mass-air meter, a big K&N conical air filter and heat shield, and is bundled with a Diablo Predator tuner with a specific C&L 2005 Mustang tune. We had the opportunity to play with this kit on the dyno and at the track, here is how it performed.


With the '05 Mustangs mass-air meter integrated into the air-box lid, removing the entire air-inlet system is merely a five minute process.

Using a 10mm socket, remove the single bolt securing the air filter housing to the fender.

Disconnect the mass-air sensor plug as shown.

Squeeze to release the PCV system hose connection.

Loosen the clamp securing the stock rubber inlet bellows to the throttle body.

The entire factory air-inlet system can be removed now as a unit.

Using the provided Torx security bit remove the screws securing the mass air sensor cartridge.

Carefully transfer the sensor into the new C&L mass air meter and secure with the factory Torx screws.

We prefer to pre-assemble the C&L system on the work bench, then simply connect it to the throttle body. The filter shield is secured to the fender using the same bolt removed in step 2. C&L includes a bracket to further secure the mass-air housing to the motor if desired. Reconnect the mass-air connector and PCV hose.

With the engine off connect the Diablo Predator to the vehicles OBD-II service port. On the '05 it is located directly under the driver side dash. Follow the on-screen instructions to program the vehicles computer with the C&L specific tune. Further enhancements to the tune can also be made, as we detail in this article.

Track Gains
The first opportunity to test the C&L system came at a Wednesday night Bracket event at our local track. We generally don't prefer testing at bracket events because you typically get very few runs before you are into elimination rounds. To make matters worse our plan to run the '05 on slicks fell through due to the 15" steel wheels not clearing the disc brake calipers. So we did the best we could on the stock radials.

2.5mph gains at the track gave quick confirmation the C&L/Diablo air intake and tune was for real.
With only a total of three runs to acquaint ourselves with the new car we managed a best run in bone stock form of 14.42 @ 99.68 mph. This came on an embarrassing sixty-foot time of 2.39. Disappointed that we didn't achieve the stock-13's-on radials that so many '05 owners around the country are reporting, we chalked it up to the poor traction and lack of seat time in the new platform. With elimination rounds looming we quickly installed the C&L kit and reprogrammed the computer with the Predator.

We only got one pass with the C&L system in place, however the results proved to be a clear indication this was no ordinary duct and filter kit. With a slightly better 2.10 sixty-foot time the '05 tripped the lights at 13.86 seconds and 102.54 mph. We were dying to make another all out pass to see if we could get the ET lower, however the announcement came that it was time to dial-in and begin bracket rounds. We played it safe and dialed in at 13.8, and managed to run a 14.0@102. At least we backed up the trap speed gains with the C&L. Continue
(Dyno Testing)

In This Article:
Ford has always put a choke hold on the Mustang via a restrictive air-inlet system. The 2005 Mustang is no different, except in that a free flowing air box is alone not sufficient. The computer must be re-tuned. The C&L Trueflow package addresses this by including a C&L specific Diablo Predator tune. We test its worthiness in this article.

Also See:
High Five
Sound Thinking

The C&L Truflow system (below) consists of a re-designed cast aluminum mass-air to throttle body pipe. A cast aluminum mass air sensor housing replaces the stock plastic unit integrated into the air-box cover. A big K&N conical filter is sealed off from the hot motor via the included sheild.
Diablo teamed up with C&L to create a specific Predator tune for the C&L Truflow air inlet system.

Shown is the restrictive carbon filter trap which resides in the factory air-intake duct. This corrugated piece serves to trap any raw fuel vapor from the intake manifold. Removing this piece is good for a several horsepower gain, however often yields to wacky air-fuel ratios.











































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