2003_SVT_Cobra_Intake_Comparison.xls
Lisa Reffett is quite a competitor....
Lisa Reffett is quite a competitor. With the Johnny Lightning Ram Air kit in place and the headlight removed, the NMRA Factory Stock racer mimicked 100-mph air with a shop blower aimed right at the filter. This was the only kit for which the installation dictated the removal of the headlight for increased access to outside air. This technique would most certainly have aided the other underhood conical cold-air kits.
Horse Sense:Think cold-air intake systems are no big deal? Think again. Class racers can spend entire seasons testing and retesting to make sure the one they use gives them maximum performance-especially in the summer's heat.
It's a simple rule: The more air you can get into the engine, the more power that engine can make. In addition, if you can ease the path of air entry into said engine, it will make much more power. Cool, free-flowing intake air has been a cornerstone of hot rodding since hot rodding began. And, from Ram Air to Shaker hoods and everything in between, we've been trying to get more horsepower from efficiently processing the atmosphere at any chance we can get.
Enter the awesome '03 SVT Cobra and its extremely underrated 390hp/390-lb-ft blown and intercooled 4.6 DOHC masterpiece under the hood. One of the hidden beauties of this car is that the factory has "corked" up the intake and exhaust side of the engine. This keeps horsepower to a sensible level, passes federally mandated drive-by noise standards, and gives us something to play with after we plunk down $35,000 for one of these nasty creations.
In October 2002, we gathered as many cold-air intake kits as we could find-an amazing nine variations. Our goal in this study was to demonstrate what kind of performance these kits offer while objectively describing the quality of the kit as delivered by its manufacturer. What we ended up with is a comprehensive study of what cold-air kits can do for your '03 Cobra, as well as a good idea of how these systems work in general-so that you 5.0 and Two-Valve 4.6 guys can benefit from our hard work as well.
Lisa Reffett is quite a competitor. With the Johnny Lightning Ram Air kit in place and the headlight removed, the NMRA Factory Stock racer mimicked 100-mph air with a shop blower aimed right at the filter. This was the only kit for which the installation dictated the removal of the headlight for increased access to outside air. This technique would most certainly have aided the other underhood conical cold-air kits.
Test Methods
To put the theory to the test, we enlisted the help of Paul Faessler and his shop full of Ford experts at Paul's Automotive Engineering in Cincinnati. Of equal importance, we asked a collection of '03 SVT Cobra owners to join us on Paul's chassis dyno to help verify and record the effects of today's latest cold-air options. Besides quantifying horsepower effects with these aftermarket parts on a stock '03, we also brought along a couple of cars that had been pumped up even more than the original SVT version, with free-flowing exhaust systems, supercharger pulleys to increase boost, and computer chips to optimize the tune-up. We thought these hotter-than-stock Cobras would really test who has the good stuff, as well as give some insight on products you may be working your way toward as your project '03 Cobra comes to light. As a side note, the data collected here can certainly be extrapolated to fit your nonsupercharged Cobra or daily driven GT.
As for the study itself, it included a baseline of each car with the stock silencer/filter/housing in place. Once this was established for a car, we then installed one of our cold-air kits, and the process was repeated. It is important to note that all runs were done in duplicate, and all the data was repeatable within 1 rwhp and 1 lb-ft of rwtq thanks to the watchful eyes of Paul's Automotive Engineering technicians on engine temp and time between pulls. This entire study, which includes all nine cold-air systems, was performed in one day.
The stock system really isn't that bad. The air intake silencer of yore is gone, and in its place is a nifty air stack with no baffling. And it's big-able to flow a lot of air. The problem is the same, however, with the air inlet hole just too small to feed a supercharged DOHC 4.6 engine that revs past 6,500 rpm like a freight train. Still, it does a good job feeding a stocker to the 365-rwhp mark. We baselined at 360.6 rwhp/367.1 rwtq and 369.4 rwhp/369 rwtq for the two stock '03 Cobras in attendance, and 420.7 rwhp/ 436.5 rwtq and 430.6 rwhp/445.2 rwtq for the two modified '03 Cobras. We're still impressed with the stock offering, and we're flat blown away by what $2,000 worth of bolt-ons will do for one of these factory supercars.
In the End
Going into this cold-air intake shootout, we knew there were several theories at work, and it was interesting to see just how each designer tackled those problems. We felt that the huge, underhood conical filters would really shine on the chassis dyno where engine temperatures can be better regulated with cooling. On the street, we believed those more elaborate systems would come out on top, since they are constantly supplying the supercharged engine with a cool blast of fresh air from the inner fender area. Our data showed that on a stock '03 Cobra, the car really liked the Densecharger, the JDM conical filter, and the K&N FIPK. The JDM and K&N setups are similar, but the Densecharger is a whole other animal. On the modified cars, the data seems to even out a bit. The top power producer with a 25.6-rwhp gain was the consistent K&N FIPK, but three other kits (from Amazon, Johnny Lightning, and Unlimited Performance Racing) increased output a solid 23-plus rwhp.
2003_SVT_Cobra_Intake_Comparison.xls