K&N Fuel Injection Performance Kit (FIPK)

The cold air intake (CAI) is one of the most debated topics in the Mustang world. Some say CAI kits aren�t worth the money. Some say it�s one of the first mods a Mustang should get. Personally, I didn�t care if the gains were worth the money when I decided to get one. I wasn�t really concerned at the horsepower per dollar ratio of the CAI. My car was new and I had to devirginize it. I like how the CAI looks and it was within my budget and it was a really easy mod to do. The filter is easily accessible. I can't imagine having to lay on my back and reach up into the fender to get to the filter. That meant a lot for a desk jock like me.

The FIPK was an easy installation. Most of the kit can and should be assembled even before opening the hood of the car. I did most of this in the comfort of my living room. The assembly is really simple and the instructions are really easy to follow. Basically, you take the factory intake tube out and remove the MAF. Go back inside and assemble the K&N FIPK with your factory MAF. Go back outside and it's just a matter of bolting in the K&N assembly.

Some late model GT owners have problems with the lower bracket rubbing against the a/c line. One owner reported a/c line leaks and had to replace the hose. Thanks to message boards, I was able to avoid this by not installing the lower bracket. You'll see it going straight up in the picture below. The upper bracket is enough to hold the assembly in place.

ENGINE BAY VS. FENDER

I read thread after thread on different message boards comparing the different CAI kits available for the Mustang. I realized there were so many choices but it can be narrowed down to two general types. There are ones with the filter in the engine bay protected by a heat shield, and ones with the filter in the fender. The arguments around the filter location are all about the air temperature. The engine bay mounted filters are said to suck hot air, while the fender mounted filters suck cooler air. The popular engine bay mounted kits are the Steeda and K&N kits. C&L, MAC and Densecharger are popular fender mounted kits.

I�ve seen the air temperature argument so many times and thought to myself, this was something I could easily validate. I went to the hardware store and looked for indoor/outdoor thermometers. I found this digital thermometer with an outdoor sensor on a 10� wire for $10. Perfect! I bought two so I could take temperature readings in the engine bay and in the fender at the same time. I hurried home and opened up the hood. I attached one sensor along the front brace, just behind the passenger side headlight. The sensor was about two inches in front of the K&N filter in the engine bay. I attached the second sensor to some cable inside the fender. It was about 4 inches into the cavity for the air silencer. I ran both wires into the car and attached the two thermometers to an old CD. I rechecked all my connections and I was ready to start my data collection. The geek inside me was happy and I�m sure I got a few weird looks from the neighbors. It was time to drive around.

The data told me that once I am moving above 15 mph, the temperature difference averages around 3.5 degrees. With the a/c running, the engine bay was around 4-5 degrees warmer than the fender area. At speeds less than 15 mph, the difference goes above 10 degrees. The engine bay is definitely hotter but only by a few degrees when the car is moving.

Does the air temperature matter? I can�t answer that. I�ve seen some claims on the Internet about losing 1 hp per 10 degrees increase in the intake air temperature. If we assume that is true, then having the filter in the fender gives you 1/4 to 1/2 hp over the set up with the filter in the engine bay. BFD.

Do I miss that fraction of a horsepower because I got the K&N FIPK? No. If we assume the 1 hp per 10 degrees is accurate, then my car will produce 2-3 hp more in the early morning than my drive home at 5:30 pm only because of the weather. The 1/4 to 1/2 hp is negligible.

Does the extra half hp result in better mileage or performance? In a laboratory or on paper, Yes. But in the real world, a slight incline in the road, or a light wind, or having a passenger, or a little traffic will have so much more impact on mileage and performance that the 1/4 to 1/2 hp is again neglible.

My recommendation is to choose a CAI that has the larger filter for more surface area, and one that has the shortest path to the throttle body. Arguing about a fraction of a horsepower in a controlled environment is like a fat chick refusing to carry pocket change because it will add to her overall weight.

Follow up: Just for the fun of it, I removed the K&N FIPK and installed the stock air tube with an Airaid filter (K&N type). I went to a dyno special at the local speedshop and it measured 216/249, 224/273, 213/245. I wasn't happy with it so I put the K&N FIPK back on and got dyno'ed again. The second time, it measured 218/250, 231/271, 223/256. If you look at peak vs peak, there was a 7 rwhp gain. If you look at averages, there was a 6.3 rwhp gain.

Cost: $224.85

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