Adjustable warm air intake (WAI)
 

Everything I've done here is before the filter. This is important, especially if your car has a Mass Air Flow Sensor.

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This is my old setup which was the incoming air routed through the stock resonator of my 1995 civic VX. I was only able to increase the temperature about 20 degrees.

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This is my modified lower filter box. The original intake hole is plugged with sheet metal with a 1/8" hole for drainage. A hole was cut in the front of the box and a three inch diameter aluminum elbow, from an old CAI system, was installed and sealed with silicone.

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Stock resonator must be removed or the box can't be re-installed. On the VX I had to remove the inner fender well.
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This is the "cut-out" that I am using as a mixing valve, they are $68us at Jegs.com. The bottom is connected to the hose from my exhaust manifold. To be honest, my car came with the “cutout” already installed, so I don’t know if the cable bracket comes with it or my Dad made it.

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The modified box is now in place. The small wire runs from the temp sensor to the gage installed on the dash.
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The cutout is attached to the elbow with a spectre silicone hose adapter from AutoZone.
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Hot air hose attached to cutout
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Hose intake at manifold is ziptied to the radiator fan shroud. And the manifold is enclosed with a flexible heat shield material (not sure where he got it).
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The cable is run from the dash through a sheet metal plate. Whichever side of the cutout is routed to hot air will dictate whether cable in is hot or out is hot. Mine is labeled “IN/HOT”. Above the cable you can see my gage, it is battery operated so no wires except the sensor. These are available at Walmart for about $10.
I am already seeing around 50°f increase from ambient!

Good write up. Thanks. And 50 degrees above ambient would be about 20 better than I get. In summer you're going to run upwards of 150 IAT.

Hopefully. I think I can get a few more degrees with a grill block in place. Maybe this weekend.

three questions here...

What is the highest tolerated IAT for a typical engine?
What are people here successfully running at, positive impacts?
What negative impacts have been noticed? other than power loss....

I know at somepoint pinging, detonation and other metalic noise will be noticed, but likely for other reasons such as timing advance.

My dad has a VX with this setup. He said 130° -140°f is the sweet spot. At 150 he starts getting detonation and timing retard, thus great power-loss.

Thanks,

Those seem to correlate with some of the extreme temperatures found on this planet. Now to figure out a way to get the plumbing run within my cramped engine bay. I would love to figure out a way to heat that air with coolant. My car has a anti-ice coolant loop through the throttle body. For now I just have a snorkel that pulls in the air from just below the hood.

I have considered using a heater core or a motorcycle radiator as a "inter-heater" as opposed to an "intercooler". This would not be practical on a VX in the winter because it is already a challenge to keep the engine at operating temperature.

I bet that I can reach those temperatures! :)

A few updates. The Spectre brand silicone adapter is from Advance not AutoZone. The silver heat shield material is from one of my dad and uncle's race car projects, and is expensive. If I were doing this from scratch, I would probably use thin aluminum like what lines the transmission tunnels of most modern cars these days. I would think it would be fairly inexpensive at a wrecking yard. Also the elbow is fastened to the box with machine screws and nuts, the silicone is only used to seal the seam.

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Not my best work, but I got the grill blocked this weekend! Black coroplast and zip ties, price of mod: $0.00USD!

First test was this morning. Ambient temp 46f, intake temp after warm-up 150f! Yikes!! I had to adjust the cable for the first time. I got it at a steady 130 after a little fiddlin'.

MPGs look good on first stint, 60.5 on my 35 mile commute with a 55mph average speed. normally I see 51-58 depending on wind and temps. I’m pretty happy so far!

Next: Make the grill block adjustable and add a fan-on indicator.