Warm air intake did not help
 

Several years ago, I tested a warm air intake on my Canyon, and saw no improvement. I had also sort of noticed that gas mileage improved with temperature up to about 75-80 deg F, but did not improve at higher temperatures. I assumed that the air conditioner was the reason. I recently noticed that power dropped off more at high outside air temperatures than I would have expected.

So I set the ScanGauge to display intake air temperature (IAT) and ignition timing (IGN). I do most of my driving in 55 MPH speed limits at an average speed of 57 to 58 MPH (1900 RPM), and a common throttle setting at that speed is 10" Hg vacuum. Some results are listed below (outside air temperature is OAT):

OAT IAT IGN
75 82 26
84 91 22
83 92 22

The above tests were all at 1900 RPM and 10" Hg vacuum. On one test at about 80 deg F OAT, the timing was jumping around from 21 to 25 degrees.

It appears to me that the knock sensor is retarding timing at higher intake air temperatures. Normal engine temperature is 184 to 188 deg F. I wonder if a colder thermostat would help gas mileage at OAT's over about 80 deg F by allowing more ignition timing advance.

Thoughts, anybody?

I didn’t get a detectable improvement from a HAI on my saturn. The scangauge was showing gains, but apparently the hai was throwing things off, and readjusting the trims on the SG basically made it a wash.

I wouldn’t try a colder thermostat, if anything dump the hai, and try a hotter thermostat.

My thought is that an exhaust heated hai probably helps you warm up faster, but doesn’t have a significant impact after that. If there was significant gains to be had I don’t think manufacturers would have stopped using them.

Retry in winter.