Ran an interesting test. I taped down temperature probe on my air filter housing. I have a standard airbox with cover grills cut out on my 90'. I ran the probe lead into the car connected to a digital thermometer. I had a second thermometer to measure outside temperature. As I drove the car under various conditions, I noted the temperature differences between the two thermometers. Obviously, when the car was stopped and the engine was running the temperature was up to 50 degrees above the outside temperature. However, as soon as I started to move again, the temperature dropped fast. One of the limitations of the test is that the thermometer is slow to register the true temperature. What I discovered was that around 30 mph the temperature difference (outside vs filter) is 2 to 5 degrees. Anything above 30 mph, there is no difference in temperature.

My conclusion is that the claim that C4 cold air intake systems reduce air temperature with an associated HP increase is bogus. I am not making any statement the claim regarding the ram air effect improving HP. I would be interested to see the difference in pressure inside the air filter housing for cold air vs standard at various speeds.

Carl

90' 6 spd
3.45 rear
350 with hooker SC, random cat, Power Effect cat back, mini-ram, K&N, high output coil, underdrive pulleys, Accel 219 cam, AFR 190 heads (milled to 58cc), full rollers 1.5, 30# injectors, Taylor wires, Dynamod HEI module, Custom PROM by Shalin, BFG KD/TA tires (awesome).

 

Carl,

I posted about the same results here a few weeks ago. However I can't say anthing about the forced air feature. That may make the kit beneficial but I don't know.

Larry

 

Wow.. interesting results. I too would really like to see the pressure difference, as I have the AO eng. forced air kit (ram air), and I think it has to add at least a few ponies at the higher speeds because of the pressure.

Think about it.. when you have the top off or the window down, and you're crusing at 80mph... stick your hand out the window perpendicular to the ground and feel that pressure. That's gotta be doing something. I know the air filter limits it and slows it down a bit, but that's a lot of pressure, so that's gotta be doing something.





[Modified by Glock'94, 6:10 PM 8/14/2001]

 

Thats a great job, Thanks.

 

Hmmm,
Very interesting!
:seeya

 

A related aspect to this subject is the design of the car itself, or more specifically, how the car cuts throught the air. Did you ever wonder why GM engineered the car to suck air from under the bumper as opposed to a "forced air" or "ram air" type set-up? It is due to the C4 design, where there is a pressure boundary layer that forms under the front bumper which is greater than the air in front of the bumper. Therefore, you get more intake air pressure from under the bumper than straight through it. Same goes for the C5; the ZO6 intake screens are only a supplement to the main air intake from under the bumper. This is also related to the "cowl induction" during the 1960's, where the intake would suck air from a high pressure area that formed around where the hood met the windshield. Just because it appears that ramming air through the front bumper is the most efficient and effective method does not always mean it actually is.