Originally Posted by
killerbee
Jeff, I have done a little testing on this subject, so I'll chime in. The 2 openings stamped in the fender, are not sufficient for the d-max needs. If you use an intake that snuggles up to it, you will have a great deal of pressure drop across that transition, I measured a 10-12 iwc loss, which is about .5 psi, on stock airflow. nearly 1 psi on with 28 psi boost, from custom tuning. That is very significant. It is important because, as a result of the resultant suction, pre-heated air leaks in more readily around the openings and cracks. That reduces the "cold air" effectiveness by a small margin. Plus the turbo must work harder to produce the same plenum boost (1 psi harder), this creates more heat, bad for turbo longevity (higher rpm) and bad for power (hotter charge).
IMO, if you can get more opening, WITHOUT losing cold air effectiveness, do it. The intake I built is a box sealed to the fender, and also has a "normally closed" sprung relief door on the front face of the box. Shrouding that opening helps preserve cold air effectiveness under max performance conditions. The other really good reason for doing this, mostly overlooked, is weather freindliness. Too much suction force (pressure drop) on the fender, will draw in heavy contaminants, like water. This originally is why you and I need a cold air solution: GM used to have the intake snugged to the fender, until the element got loaded up from excess moisture. A larger opening, believe it or not, would create a lower vacuum effect.
I prefer the "through the front" sprung door approach for the vacuum relief.
Any pics of the setup?
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