Project S2000: Part 20 – Stock Air Box Modifications And Not Going Faster

Project S2000: Part 20 – Stock Air Box Modifications And Not Going Faster

by Khiem Dinh

Khiem Dinh is an engineer for Honeywell Turbo Technologies at the time of this writing.  All statements and opinions expressed by Khiem Dinh are solely those of Khiem Dinh and not reflective of Honeywell Turbo Technologies.

After testing the ram air/cold air NACA duct in Part 19, I noticed a trend in the intake manifold pressure where it drops as the engine approaches redline. A member of one of the forums had commented on some of his own testing showing that removing the lid of the air box resulted in less pressure drop. He had used a pressure gauge attached to the intake tube common on off-road trucks to gauge when the air filter is dirty. So this got me looking into the guts of the stock air box. Was the 90 degree internal tube a flow restriction?


Using my practically non-existent Photoshop skills, this overlay shows just how much space the stock cone air filter takes up in the air box. Yeah, the Honda engineers took up all the space they could.
With the lid cracked open, you can see how the internal snorkel aligns with only a fraction of the air filter. Is there opportunity to better use all that air filter surface area?
I stuffed the camera in the air box, put on the timer and closed the lid. You can see how the snorkel does sit a fair amount away from the filter.
With the lid shut, it seals up the internal snorkel very well with the internal divider wall in the air box.


  1. “So, one lesson learned is Honda did a damn good job on optimizing the stock air box design and there’s nothing to be gained in power by hacking it up. Removing the air box lid will make your car much louder making everyone look at you. Removing the lid will also reduce your power significantly giving everyone more time to look at you. If you crave attention, I guess remove the lid. If you like more power and not drawing attention leave the lid on.”

    Can you please clarify, by gutting the airbox and leaving the lid on do you see a loss of power? I’m asking from the perspective of someone who likes intake sound and finds the OEM unmodified intake too quiet. I’m considering gutting it to increase sound instead of buying the K&N intake. However I will not do either of these if they will cause a loss in power.

    1. Gutting it does not effect power. To get some more noise, some people block off the port in the air box which goes to the resonator.

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