CAI vs. Pop Charger vs. OSCAI: Intake Temperature Test Results
I perused quite a few SAE articles regarding intake temperatures and their effect on different engine applications and found an interesting standard: By using the SAE correction factor "B" for temperature's effect on horsepower, we see that the correction factor for temperature is approximately 1% per ten degrees. That is, you get a 1% increase in horsepower for each 10 degrees you lower the temperature of the incoming air into your filter.
I am certain that many of you have personally felt the difference, on a cool, perhaps damp
(there is another correction for that) morning, when your car seemed to have more power than usual, and that those of you who have been lucky to participate in track days have posted lap times in the cool of the morning you could not equal on the warmer afternoon sessions.
This finding prompted me to swing by the local Radio Shack and purchase a digital thermometer with the sensor attached to its 10-foot wire. I attached it to my door.
I then routed the wire connected to the thermometer’s display out the window, under the hood and inside the cone filter to get the exact temperature of the air entering the throttle body.
Here is what I tested:
1) Intake Temperature at IDLE (8 minutes) with Pop Charger
2) Intake Temperature at IDLE (8 minutes) with CAI (I placed sensor in drainage hole in fender where the CAI would reside)
3) Intake Temperature with Pop Charger
4) Intake Temperature with CAI (I placed sensor in drainage hole in fender where the CAI would reside)
5) Intake Temperature with OSCAI (A 2” tube connected to a scoop under the car bringing cold-air to the filter. SEE
Outside Temperature: 34 degrees F
Test length: 2 Miles/Run
1) Intake Temperature at IDLE with Pop Charger: 95.8F and increasing
2) Intake Temperature at IDLE (8 minutes) with CAI (Sensor in hole in wheel well): 51.2 Steady
3) Intake Temperature with Pop Charger
Temp @ 40 mph: 47.6F
Temp @ 70 mph: 44.2F
Notes: The temperatures were volatile and increased when accelerated hard or came to a brief stop. Temperatures would not reach their low until the end of the run. When stopped for more than 2 minutes, the temperature would rise quickly to between 60-65 degrees.
4) Intake Temperature with CAI
Temp @ 40 mph: 45.1F
Temp @ 70 mph: 39.8F
Notes: Idle temps were already low, so low temperatures were achieved quickly. The temperature did not vary and stayed relatively constant when accelerating hard or stopping. Extended periods of idle would bring the temperature up, but not significantly. I suspect using the fender well as a heat shield aided in the temperature consistency.
5)Intake Temperature with OSCAI
Temp @ 40 mph: 45.0F
Temp @ 70 mph: 40.9F
Notes: The rate of change for the temperature was dependent on the speed I was going. The temperature increased when accelerating hard or coming to a stop, but quickly returned to it’s low under steady driving. Again, as the basic pop charger set-up did, momentary stops for 2 + minutes would send the temperature up to 60-65 degrees.
Conclusion/Serendipity
I was surprised that the Pop Charger by itself, without the CAI or OSCAI set-up was able to produce almost same temperature reading as the other two at speed. I guess, from what I gathered, the CAI benefits the most by creating a ceiling for temperature not to exceed (in this case 50 degrees) whereas the other two allow the intake temps to climb at the engines heated will. This 40 degree difference can be a factor in ¼ mile times where the car must idle for extended periods of time before launching. But as the outside temperatures increase, so will the air in the wheel well, thus making the differences slight. Additionally, I am not certain what adverse affects the longer tube combined with a bend may have on the intake airflow. Perhaps the tube may heat up thus warming the cooler air.
In the end, when comparing the extremes of winter and summer weather, say 10F vs. 100F (engine temps) and using the 10degree/1% power gain correction factor equation, in the Maxima’s case:
100-10 = 90 * .10 = 9% power increase for a 190 hp car which is somewhere around a 17 horsepower difference between the extreme summer and extreme winter case, then I guess cold air should be taken seriously. But when the difference between the ways of obtaining the cold air and inducing it into your engine yield almost the same results at speed, then what should you do? Who knows…
But maybe you could get a head start by using my write up! Enjoy and feel free to comment or add variables or conclusions that I have left out.
Linear Mode
