K&N also offers a cold-air kit of its own. The FIPK tested ($163.95) is actually the unit designed for the '01 Cobra-when no one in their right minds outside the walls of Ford SVT thought there was a supercharger in the future of our favorite little musclecar. This system isolates a big, fat, conical K&N air filter in the engine compartment and is surrounded by plastic and rubber to avoid hot, underhood air while grabbing ambient air from the gaping hole in the fender vacated by the stock system. The K&N FIPK surprised us. It made great power on a stock '03 and made the most power on the modified cars-a whopping 25.6 rwhp. With that wide filter flowing into what looks like a velocity stack for the stock mass air, the engineers at K&N really showed us something. Fit and finish on this kit are what you would expect from this aftermarket giant.
Understanding which systems worked better will take a lot more than our simple comparison, but it would be easy to argue that the stock car needs cool air, thus the Densecharger wins out with its nifty design. The modified cars seemed to want more volume of air, and the K&N FIPK with its huge velocity stack and wide filter seemed to work slightly better. Close behind were three systems featuring big conical filters shielded from the engine compartment and getting air from the fender area in some manner.
Another point to consider is that many independent tests have argued that the underhood air is not a big factor with the blown '03 Cobra because the factory intercooler is so efficient. The more important point to recognize is that this is a chassis dyno test, not a drag test. Had we obtained the resources to test each one of these systems back-to-back on the dragstrip, things might have been different. Having a big conical under the hood may not be the ideal way to go in real-world testing, but that test will have to wait for another day.
The suppliers also had some suggestions when we discussed the final data set with them. Many of them asked if we had considered monitoring inlet temperature, boost-level changes, and air/fuel ratios since they all dictate the real horsepower that an engine is capable of delivering to the tire. Factory Stock racers Lisa and Shane Reffett also pointed out many of the systems locate the mass air in a different orientation than stock. We hadn't even considered this a variable until Lisa shared with us that the F/S racers spend a great deal of time setting up the ideal location of the mass air meter in the path of the incoming intake charge. Was this affecting our data? Other '03 Cobra owners pondered what the effect of running long tubing had on the velocity of the incoming air versus the short-and-sweet approach of just clamping a big conical to the end of the mass air meter. All these variables could have been addressed if we were testing only one cold-air kit, but we weren't.
The K&N drop-in, stock replacement ($46.95) is basically a standard after-market addition for anyone with a high-performance car (or truck). Better gas mileage goes right along with more power as the air gets to the blower more easily. In addition to pulling the silencer, this is the bare minimum you could (or should) do to your Cobra to pick up some power. The whole thing can be put back to stock in 10 minutes, with no one the wiser. Surprisingly, the old pull-the-silencer trick didn't always work with these cars. We actually lost as much as 5 rwhp on some back-to-back pulls. To pull the silencer or not will ultimately be decided by the end user on the track-not the dyno.
The most dramatic part about changing the air inlet on the supercharged '03 Cobra is the sound. Oh baby, does this car start sounding pissed off! It is the sound of horsepower being created, and it's immediately intoxicating. All our kits offered an audible increase in psychological horsepower as well as seat-of-the-pants pull. As for a suggestion on which one of these kits to buy for your Cobra, we'll hedge our bets and tell you to call the manufacturers of the cold-air kits that interest you. Have them describe their design and testing program so you can determine how their kit will work with your combination.
The bottom line is, it's easy to add more than 25 rwhp to your '03 Cobra with hand tools and less than an hour of your time. Whatever kit you choose, we hope you're now better prepared to know what you're getting and what the kit will do for you thanks to our little test. Enjoy the newfound power!
Rick Erdman of Amazon Racing loves '03 Cobra Mustangs, and it shows. This system isolates a huge, 9-inch conical AFE air filter under the hood with a small plastic shield. The big news here is that the air filter is not a K&N, and that the open-ended filter is enormous-making a clear path to the blower. This system is clean, simple, and it works. Rick also offers a C&L meter upgrade with this package. Unfortunately, we did not have enough time to test both versions of the Amazon Racing kit. However, Rick did pass along that the meter upgrade works best with stock or near-stock combinations. Amazon's base kit sells for $139, while the system featuring a C&L meter goes for $299.