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Old 06-01-2012, 10:05 AM   #45
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Location: Wrentham, MA, MA
What I Drive: 2012 Race Red Focus SE

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Another 2012 Airbox Mod

I already had a K&N drop in filter. Here's what I did:

I ordered a new air box lid, part # BV6Z9661A from for $5.52 + tax and picked it up at my local ford dealer.

I bored a 3" hole with a hole saw on the drivers side front facing the rear of the grill and radiator support where they meet with the hood and fender. There are gaps that line up with the hole I cut and it appears to allow airflow from outside.

I provided a further heat barrier by installing a diagonal swath of foam insulation strips with adhesive on 1 side between the hole and the engine side ($8.36). It seals against the hood, verified by slight impressions in the underhood insulation.

At low speed it's barely noticeable. When you get on it sounds good/louder but not ridiculous. The seat of the pants dyno indicates a throttle response improvement.

This is a variation on removing the whole lid but you don't get that ridiculous, loud boggy sound and you have a heat shield. I kept the original lid in tact for dealer visits & inspections. Even if you don't follow my design you can experiment with your own for $5.52.

Sorry, no photo but I'm a techno moron.
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