Installing and testing the K&N AirCharger Intake Kit for the 2007 Shelby GT500
Air filter specialists K&N launched its new AirCharger intake kit for the GT500 (part #63-2571) back in March of 2007. According to K&N, the kit eliminates air restriction caused by the stock intake and dramatically improves air flow to the engine. K&N’s performance kit manager Bert Heck stated that “the factory air box was restricted in size and restrictive in air flow especially at higher RPMs. We made a larger intake tube that fit nicely under the front stabilizer bar.” The kit also features K&N’s million mile warranty, a washable and reusable air filter, and compatability with the factory holes and mounting points. With a claimed horsepower gain of 53.71 at the rear wheels, we couldn’t wait to get our hands on one to test it out. Adam Montague at ST Motorsports in San Bernardino, CA graciously let us use his dyno for testing as well as provide a bone stock GT500 for the test.
The first step was to get some base horsepower numbers. Our first dyno run with the car netted 455.4 horsepower and 433.2 lb-ft torque. According to Adam, this falls right in line with several other tests he has done with stock GT500’s. Next up was installing the K&N kit. Installation was very simple, and the K&N intake bolts into the stock location and fits nicely under the strut tower brace as claimed. With the new intake installed, we put the car back on the dyno to get the new numbers. The result? 483.5 horsepower and 453.6 lb-ft torque, a gain of 28.1 horsepower and 20.4 lb-ft torque. In addition to gaining less horsepower than expected, the extra air had exceeded the MAF sensor’s ability to adjust was now running lean with an air/fuel ratio of 13.4:1 compared to 11.8:1 at stock. After a call to K&N’s tech department, we were told that the PCM did not need to be retuned after installing the intake, but a search on the internet revealed that nearly everyone who had installed the kit was running lean as well.
To find out what kind of horsepower gain the K&N would produce with a safe tune, Adam plugged in a DiabloSport Predator Flash Tuner and used his programming wizardry to add in 10% more fuel to the MAF curve. Another pull on the dyno test and the numbers had dropped down to 468.5 horsepower and 437.1 lb-ft torque, and increase of 13.1 horsepower and 3.9 lb-ft torque over stock. While these numbers weren’t what we were hoping for, the car was now running at a safe air/fuel ratio of 12.0:1.
Despite our disappointing findings, we wanted to see if there was more potential with K&N’s intake. Adam programmed in a 93 octane performance tune along with the additional fuel. Another dyno run later the car was running at 501.2 horsepower and 472.7 lb-ft torque, a gain of 45.8 horsepower and 39.2 lb-ft torque compared to stock. So how much of this gain was due to the new programming? Adam had a database of dyno runs for this particular car and pulled up the numbers for the stock car with the 93 octane tune. At 472.2 horsepower and 455.3 lb-ft torque, the K&N intake helped produce an extra 29 horsepower and 17.4 lb-ft alongside the tune.
Although being under what K&N claims, the gains from the AirCharger intake were still substantial and worked even better with a performance tune from a DiabloSport Predator. The disparity might be in K&N’s baseline horsepower used for their calculations. A dyno sheet provided with the intake kit showed horsepower going from 413.4 to 467.1. While our test car finished with 16.4 more horsepower, it also started with 42 more horsepower. Judging by most dyno results we’ve seen of the stock GT500, anything in the 440-455 range is pretty normal, and 413 seems unusually low for a baseline number.
Overall, the K&N AirCharger intake for the GT500 does provide extra power – 13.1 more than stock, and it especially works well in conjunction with a performance tune providing a combined gain of 45.8 horsepower. From our own as well as others’ findings we would also recommend having the car retuned to prevent the engine from running lean. For more information or to find a retailer visit www.knfilters.com.
 The stock intake system has some room for improvement |  The GT500 goes on the dyno to get the baseline numbers |  The crank case vent fitting is removed from the stock intake and reused |
 Mounting brackets are fitted over the new intake tube |  The new intake tube is fitted over the throttle body |  The K&N intake bolts right into the stock location |
 The K&N intake fits cleanly underneath the strut brace |  The rubber trim is fitted around the heat shield to help keep out hot air |  The air filter is bolted to the intake tube |
 The mass air sensor is reconnected to the intake |  A look at the K&N intake system completely installed |  The GT500 goes back on the dyno |
 Adam added an additional 10% fuel to the MAF curve to prevent the car from running lean |  A 93 octane performance tuning combined with the new intake produced an extra 45.8 horsepower and 39.2 lb-ft torque more than stock |  Dyno results for the stock GT500 |
 Dyno results for the GT500 with the K&N AirCharger Intake Kit |  A comparison between the dyno results for the stock GT500 and with the K&N intake installed |  Dyno results for the GT500 with the K&N AirCharger Intake Kit with 10% more fuel |
 Dyno results for the GT500 with a 93 octane performance tune from the DiabloSport Predator |  Dyno results for the GT500 with the K&N intake installed and a 93 octane performance tune plus 10% more fuel from the DiabloSport Predator |  A comparison between the stock GT500, with the K&N intake installed, and with the K&N intake installed plus the 93 octane performance tune with 10% more fuel |
