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Hot Air Intake Modification
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Photo 1 is the overview. Note the removed air intake tube resting on the front bumper.

Photo 2 is the view from the driver's fender giving a better perspective of the mod from the air box. The first part of the hose is simply slipped over the existing stump of the air box with the intake tube removed (see photo 1). I used a thin foam tape for an air tight and firm fit.

Photo 3 shows the splice of the 2 required 36" sections. I also chose the 2 different styles of this hose. The first being the paper skin coated, the second being plain aluminum. When purchased these hoses come compressed and are stretchable up to the stated limit on the box. Its at this coupling that a short section of 2" o.d. exhaust pipe is used. Readily available as a repair splice at most auto part stores. The hoses are firmly connected using the exhaust pipe section and standard automotive hose clamps. The zip ties prevent the coupling from sagging too close to the drive belt.

Photo 4 is a close up of Photo 3. Note the orange dipstick for location.

Photo 5 is the final turn toward the CAT as viewed from the right fender. The CAT is visible in the upper center of the pic. Also installed is a piece of modified factory stock sheet metal that is used for a 1986 Ford F150 I6 pickup's hot air connection. The hose coupling is 2". This piece of sheet metal is originally mounted on the exhaust manifold and a hose connects to the hot air door on the air horn of the filter housing. Many other carburated and some newer throttle body injection cars use a similar setup. Their sheet metal could be adapted for the best Insight hot air mod connection at the CAT.

This next evolutionary step will need to be carefully monitored. It may provide too hot an intake air and the desired MPG improvement may not be there in warm weather. In cold weather there is the possibility of chilling the CAT too much and setting a P0420, CAT below efficiency code. Currently in 40F ambient conditions I can achieve a +45F IAT increase. This requires approximately 8 miles of drive time to warm up.

Photo above is the modified sheet metal piece before installation.

I had previously used a single 36" section of hose, which closely corresponds to the length of the removed tube. This requires routing the hose under the engine's beauty cover and some slight compression of the hose, which is easily damaged in doing so. After 6 months or so the chaffing of the hose in this location and the forming took its toll, hence the long route I have now chosen.

As far as a parts list its pretty much self explanatory. The trick part is the 2ea 2"x36" hose. And it is becoming more of a rarity. PepBoys discontinued the hose in the 36" length, although you could splice the available 18" lengths as required. The plain aluminum as pictured is their item. It is cheapest in both price and quality. The best is still available through NAPA and is PN 8131351, a 36" length about $25. It feels heavier and is definitely tougher.

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Last updated 12/7/04