Hot data on cold air induction. Important.
Like many of you, I've been looking for some affordable horse power and cold air induction has been one of the areas of some interest to me. I've checked out several of the aftermarket CAI's and have not been impressed. My major concern is that they pull air from under the hood, usually the last place to look for cold air. Additionally, many of these units are not emissions approved and they strike me as a tad pricey!
So I checked out the stock system to see if it could be the basis of a CAI. What I found was mostly good news. The air box has a large, forward facing opening, a generally smooth interior, adequate volume above and below the filter element, and a large diameter discharge opening to the MAF. I would like a larger filter but a K&N type filter would probably provide sufficent flow for most applications in the 400 to 500 HP range. The plastic MAF to throttle body pipe (MAF pipe) is a bit of a disaster in my opinion, with a reduced diameter, ribbed walls and sloppy heat welded plastic seams all combining to compromise air flow.
Conclusion #1: The MAF pipe needs to be replaced with a unit that is resistant to heat soak (plastic) and has a smooth interior with a nice transition to the throttle body. Power gains? My guess is no more than 10 and more like 3 or 4 HP.
Conclusion #2: Replace the stock filter with a K&N type filter. Power gains? Again not much, perhaps 2 to 4 HP on a good day.
Next I looked at the intake of the stock air box. Its' large opening passes through the front bulkhead and draws air from behind the left headlight. After a through inspection I concluded that the stock air box was an effective cold air system in the factory configueratioin. To confrm that this was indeed the case I did a little test. I purchased two digital indoor/outdoor thermometers. I placed the sensor for one unit (the reference temperature) on the bottom of the front bumper cap, this is where you generally like to put a ram air intake if you have that option. This placement put the unit out of the sun and in the fresh air stream as the car moved forward. I then suspended the sensor of the second unit in the center of the stock air box opening. I placed the display heads for both units on the dash and hit the road.
My results: At 55 mph with an air temperature in the low 70's the difference in temperature on both displays was less than one degree F at all times, while moving forward. At rest both readouts would climb, the reference unit always maintaining a lower temperature by 5-7 degrees F. Once in motion it only took about a minute for both displays to return to near identical readouts. The delay in temperature drop can be attributed to the so-so response time of the thermometers.
Conclusion #3: Aftermarket CAI's have little to offer the GTO.
My opinion: Current CAI's are of little value. I know that dyno results may improve (Remember dyno results on a cold air system are generally of little value because the hood is almost always open and the air flow over the vehicle is not normal because they cooling is done by external fan. Under these conditions even a really good CAI or even Ram Air Intake will often show little or no gain but track times will improve) when they are installed but there is no reason to believe, at this time, that this has anything to do with a reduction in intake air temperature. Any gains are more likely due to improved airflow through the air filter element and MAF pipe. Additionlly, most units have an open element which means that when you close the hood you are feeding your engine nice tosty preheated air, the exact opposite of the desired condition. Some have suggested that these CAI's produce power by repositioning the IAT (intake air temperature) sensor to a more desirable location. This may be the case, but such a change has nothing to do with the CAI's primary goal of delivering cool air to the throttle body. If data are available that show that relocating the IAT produces more power sign me up! I just cant see spending $200.00-$300.00 for a complete CAI when relocationg the IAT may be all that is needed.
So my plans for now are to look for a high flow MAF pipe (anybody know who has them and how much they cost?), get a K&N filter and see if I can extend the air box intake to some exterior location to create a "ram air" intake for the stock air box.
Ok folks, let's hear what you think,
Last edited by wakarr; 11-14-2004 at 09:17 PM.