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Cooley On Cars
Car Tech 101: Cold-air filtersCold-air filters are essential to the performance of your car, and CNET's Brian Cooley shows you how to install one.
-Now there are two main reasons you put an air intake kit in your car. The first one is to optimize air flow, that is to make sure the engine is never starve for the air it needs to combine with fuel. The second reason is to get a cooler temperature on that air. Let's start with the optimized air flow. You need to make sure that breathing is free because there is so little time for a cylinder to be filled, between .02 and .006 seconds depending on the engine's rpm. Anything impeding that air flow means it doesn't completely fill the cylinder with air and gas and that is reduced volumetric efficiency. When it comes to cooling the air, that is important too because if you recall from high school science class, cooler air is denser air, denser air has more oxygen molecules in a cubic inch. More oxygen combines better with the fuel to get more power out of every time you fill and fire the cylinder. This is what air intake kits are all about. Now, of course, I'd love to install an air intake kit or just about anything on an F40, but I don't think it needs the help. However, our photographer, Celso, has an '06 Tahoe with the big V8. It could use the help. Let's do it. Bring her in. Here we go. Don't lose a mirror. You got it. Boy, you just got it. Okay, looks good. Celso, this won't hurt a bit. Okay, we'll start by removing the factory air intake system which you can see is a whole lot of plastic wreck. Okay, first thing in the air flow is this air box right here. This is where the air filter lives. I'm gonna disconnect the mass air flow sensor and then if I lift this off and pull off the lid here, this is your traditional air filter which is the sort of pleated paper thing. You can't see through that, right, I mean you're gonna see a big difference when I put the new one in. This is rather dense and air gets through here rather slowly. And down here is the bottom where that thing sits and I want you to see this. These are the intake nozzles on the old air box and notice what they breathe through, a couple of holes punched in the sheet metal here on the inside fender well. It gets air from basically down the right side of the fender. It's a little bit occluded 'cause the air's got a tortured 90-degree path to make up a narrow channel here, so that's gonna improve our air flow right there by getting rid of this turn, this corner. Okay, now I pull off the electronic connector for what's called the mass air flow sensor-- it's this guy right here, let me try and remove that, because this part we're gonna keep, a mass air flow sensor, you can just see right through there. It's got a screen to bring down turbulence on the front and on the back it's got electronic veins that can measure the volume of air that is rushing across this thing. It's the first piece of electronics that tell the engine how much air is on its way to the throttle body which is where the real intake begins. We're gonna put this back in. Now, the last big piece we gotta get rid off is this big kind of duct to work this plastic plenum I've loosen it up from the throttle body right there. You can look in there and see the big butterfly valve which is the beginning of the fuel air mixture chain. We're not gonna screw with that. That's serious stuff. But this is a large, very convoluted thing that has all kinds of warming and cooling chambers and it--which we're gonna get rid of and this may change some of the cold weather behavior of the vehicle. Okay, so what we've done now is we've remove this big, kind of occluded air box with that pleated filter and we built up this heat shield. This is gonna be our new replacement for the air box and I've mounted the mass air flow sensor on it. This thing just sits down on some studs here. Notice how much more of a flee-breathing apparatus it is than what came out-- okay, it's good. And now from the heat shield and mass air flow sensor, we're gonna put on this little coupling that's getting us to the other key part of this, a great big pipe, big diameter, very gentle curve, and not a bunch of chambers off of it, where a turbulence can build up and impede the flow into the throttle box. So, all in, this will take you about an hour. It's not a difficult job. It's one that requires that you fit and pre-fit things to make sure that the clearances are all good and important two points, keep all your old parts just in case and secondly, don't leave anything inside this apparatus-- not a washer, not a nut, nothing, because after the filter, there's no other gatekeeper that keeps things from being sucked in to the engine. The fastest way to a $10,000 bad weekend is to suck a nut or a washer in to your head. Now parts like always have these hot rod stickers that come with them. I don't stick them on my car. Instead I use them as a contact gauge. Take a piece of it, put it upside down here with the sticky side up and pull your hood down if you wanna check clearance. If it doesn't stick to the top of the hood, you know you've got to loosen a little bit of an air space there when you're not rubbing on the under lane within the heat shield. Okay, now the last part which is putting in the only service element and the coolest looking part-- well maybe that pipe is-- and that is the air filter. Notice how different that is from what came out, completely different shape. This guy you can't see through. This guy, it's a little hard to tell, but if you look inside here, far more breathable. This is an oil impregnated material. So, it's not as thick because the oil helped to draw dirt out. You service this thing once in a blue moon. You wash it and re-oil, you should probably almost never. Put this guy in it and see how this thing runs. Okay, our filter is snug up, so let's see what we've have accomplished. We've nailed all of our goals by getting a much more cool and unobstructed air flow cooler here because we have a metal heat shield, little more air around it, it's not so obstructive because it's not coming out of this tortured little turn here on the fender well, graceful, large diameter pipe. So, overall, we should have a cooler, easier flowing intake that get to the throttle body and into the mechanicals of the engine. Let's see if it drives or sounds any different. We're on the freeway. You hear it all right. -This is different, wow. -What are you hearing, more [unk]-- yeah. -Yeah. -Yeah. Sounded good, right? -This is that big difference. -Yes. -Yes. -That's because you move that big tone filter we put in there. There's not just air going in to it, but there's also noise coming back through. So, engine noise that was normally trapped-- that's a good sound. -Yeah, very different. Yeah. -Here we are at 3,000 rpm, so if we get a chance-- -Yeah. -open up a little bit. See if you're feeling more power and more torque. -Okay. -So, it's right here in this kit that's guaranteed to create horsepower. So, this is what I think is the placebo effect. People built these things and they go, "Oh, yeah. This feels faster." 'Cause it's so right there, yeah. -[unk]. -I mean, you can also [unk] gas mileage, not dramatic. -Okay. -A 102 mpg maybe, if you're really monitoring your gas mileage experiences. -I guess, for a car this size is always-- -[unk] going-- -anything else, yeah. -Yeah. -Thank you very much. The whole stuff sounds good. -Pleasure's mine. You got my usual 30/30 guaranteed-- -Yeah. -30 yards or 30 minutes and you've actually pass both. So, you're out of warranty. Now, here's why Celso didn't find his Tahoe, his night and day different after putting in the intake kit. These are dyno results from a vehicle like his with a kit like that, here's horsepower going up from 249 to 257, that's not night and day. Here's the torque difference, 245 to 253 foot pounds, again a little over 8-foot pounds or so, but notice on both of these, the improvement is on the high-end of the rpm range, where factory intake systems tend to make the engine run out of air. That's very common. This helps to address that. This is really good for high rpm run. Oh, by the way, Celso grabbed me in the hallway the other day and said he's actually feeling the power and torque improvement since we put that air kit on, more and more as he drives the vehicle. So that's good news as is the fact that no parts have fallen off yet.