I was speaking to the head mechanic at my dealer today and we were speaking about the design of the stillen cold air box versus the stock air box. He said that the "cone" design has a lot more flaws than the "flat" stock filter. Apparently the cone-design is worse???

 

He's a dealer mechanic, you can't believe everything (or maybe anything) he says.

 

Flaws? What does he mean? Consider two things, square inches of filter area, and does it block heated engine compartment air? The stock box is a good design. It gives air at ambient temperature and takes it from a high pressure area at the front grill.

 

Probably the biggest problem with a cone filter like the Stillen unit is that it creates air tubulence in the lower rpms. The air basically tumbles upon itself and isn't laminar. Many of the gripes with these "POP" style intakes is that it reduces low end power and throttle response. What causes the driveability issue is the air flow is turbulent and choppy as it goes past the MAF sensor which gives the sensor inconsistent reading. The turbulent air also hurts the intake pulses through the intake tract. Not until the higher rpms does the turbulent air become more laminar in it's flow. What you end up getting is lethragic power in the lower rpms and a slight turbo-like surge in power in the upper rpms.

Another problem with POP style intakes on late model cars is that they can cause MAF failure. The 02/03 Maximas are a prime example. Running an intake on the 02/03 Maxima is a recipe for a MAF failure.

 

Partial quote follows, "Another problem with POP style intakes on late model cars is that they can cause MAF failure."
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Very true with respect to aftermarkef air filters that use an oil wetted filter medium. They do not filter as well as the factory type treated paper filters. The MAF depends on clean air passing over the sensor.