It was 35°F this morning when I left for work today. To permit lean burn in temperatures like these, and to widen the lean-burn window during warmer weather, I installed a warm air intake.
I bought a 36" length of 2" pre-heater hose for $10 at NAPA. It's basically a flexible, foil-lined paper tube. I ran it from the factory airbox, under the battery tray, over to the cat. It actually ends about 1.5" away from the cat.
This WAI is good for +20-30°F above ambient, once the cat gets hot. IAT's start to rise after about two miles, and it takes about five miles (of my ten mile commute) for IAT to reach its maximum.
It works. Despite the cold, I was able to lean burn quite a bit on the way to work, and I got 66.0mpg, which is 5mpg better than my average commute thus far. On the way home, I had IAT=75°F and lots of lean burn. I managed 59.9mpg despite bad traffic.
As an added bonus, the new intake is about 900g (2lbs) lighter than the old one. In a car that started at 1837lbs, that matters.
I need to reduce airflow through my engine bay even further. This engine barely produces enough heat to run the defroster anyway, and now I want to make sure my cat stays toasty, for the sake of emissions and intake temperature.
To do: An undertray, complete from the bumper to the firewall. The front half will be easy, but the back half has to deal with the cat and the suspension.