COLD AIR INTAKE vs. STILLEN INTAKE

Since a few months ago, there has been a debate about the CAI and the SI. While there seems to be no argument that either modification would help make a car go "vroom", it was generally believed that the CAI produced more horsepower than the SI. Some members of the Yahoo Maxima club, however, questioned this assumption and the debate ensued.

THE QUESTION OF DYNOs
The most recent evidence we have is when Nabil and Cheston went to UPRD to test out their ECUs for the Maxima. Nabil had the SI in his Maxima and Cheston represented the CAI community with his GoHan Max. The two Maximas were dynoed, and the SI came out on top, showing more horsepower at the top end.

The arguments against the dyno results lie in how the tests are conducted. First, the comparison was done on different cars, which is a big "no-no" since its harder to determine an effective baseline. This is further compounded by the fact that we are looking for small power differences (about 5 Hp). Second, the hoods were up, negating any advantage the CAI has over the SI since no heat can collect under the hood.

The rebuttal from the SI team, however, is that underhood temps would not be an issue when the car is at speed. And, in a stop light race, the main limitation at takeoff is not the hot air under the hood, but tire traction. Also from the graph, the top end difference was more like 10 HP. So if the CAI was supposedly better, then the CAI would need to overcome this deficit, and then exceed the SI dyno run by 5 more hp. To counter the hood argument, Cheston's GXE did not have fog lights, so it is argued that the fan is providing positive pressure to the CAI and not the SI.

UNDERHOOD TEMPS

To see exactly what kind of temperature differences we are dealing with, I did an experiment with two thermocouples measuring the temperature simultaneously where the SI and CAI are situated.

This test was run by moving the car in a straight line at a given speed until a stable reading was achieved. A positive temperature difference indicates that temperatures under the hood were higher than the fenderwell temperature. At the time of the test, traffic conditions and sudden arrival of local law prevented me from achieving higher speeds. But the test does show that underhood temperatures do start out initially high, and remains so even with 30 mph air.

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