Cold-air intake systems?

In this thread I tell the saga of buying a new Scion XB. My second question is going to sound inordinately stupid, but hey - here goes:

When they mentioned a cold-air intake system, I thought it had something to do with the air conditioning. I had no idea it was a performance enhancement. So what I want to know is, how effective are these things (it’s an AEM, for whatever that’s worth) in terms of acceleration and/or mileage? I couldn’t really find any website that even explained to me what they were or how they work, let alone give me any kind of real opinion.

Also, if I did want to get one, does it make sense to get it from the dealer at $335, or would I be likely to do better going to a shop and having one installed? Last question - do they show on the outside, and if so, where on the car? They talk about colors on some of the websites, which seems pretty pointless if it’s under the hood.

A cold air intake can be something as simple as re-routing the air intake away from the engine parts (that are hot). A cowl induction hood or a ram-air intake are cheap and common variations of a cold air intake. All this means is that the intake air is about the same temp as the outside air, not the engine compartment air. Colder air is more dense than warmer air so you get the benefit of having a better combustion mix in the piston chamber. Thats about it. Unless you get some extremely expensive setup you arent going to be doing anything exotic with the intake air (like using liquid nitrogen, alcohol, or the AC to cool it).
I dont think youll be able to notice the difference, unless you take the car to the track and make some before and after passes. You might knock off a couple tenths. Shop around for similar packages like the dealer is willing to install. Usually, these are pretty simple to install and come pre-fitted for your exact car. I would only recommend this to someone who is going to be doing other mods as well, like a chip swap, exhaust work or some other bolt on mods.
I dont think youll be noticing a performance difference with just the cold air intake alone. You might get a slight bump in your gas mileage though, if you drive the car the same.

Thanks, Uncommon.

$355 for a CAI? Holy cow. Just wait until the xB aftermarket stuff catches up and pick up a Injen or Cosmic CAI for a third of that price.

The Injen in my Matrix did some good but as Uncommon Sensep mentioned, you might not notice it. Mine on a dyno ran 165 WHP (180 HP offically). If you estimate a 15% loss that puts me at ~189 HP. Not bad for $200 CAN (stock Matrix ran about 158 WHP).

If you can get one specifically for your car, and can turn a screwdriver, attempt that first! :slight_smile:

It’s usually the case that accessories ordered through a new car dealer are noticeably more expensive than when bought aftermarket. They’re banking on the idea that having spent thousands for the car, you’re in a mood to dismiss hundreds as unimportant.

A cold air intake is usually a metal tube that replaces the stock plastic airbox and tubeing. They are routed to someplace where they can pick up cold air for the engine. In the case of my car you drilled a hole for the tube and the filter went inside the fenderwell, but there are different designs that do not require cutting or drilling.

This is a hotly debated topic on many message boards but I would not expect more than 10 HP gain depending on how well the stock intake system works. badmana’s 7 HP gain is probably fairly typical although some cars with well designed stock intakes may not make any gains. I can’t find the exact number but an engine typical gains ~1% HP per 10 degrees cooler air and there are also some gains from a less restrictive intake path.

A CAI will make a fairly loud roaring, sucking sound under heavy throttle (The stock plastic intake tubing usually has some sort of resonator (IE muffler)built in that you remove when you install a CAI) . Some consider this a benifit while others hate it.

If you do decide to go with a CAI you should be able to find an aftermarket one for much less than $355. However since it is a new car under warranty the extra money may be worth it to avoid any issues if a warranty problem comes up.

I used to hear all these stories about how people installed CAI’s and then accidentally drove through a big puddle, doing untold damage to their cars. Were these stories exaggerated, were those improperly installed, or are modern CAI systems designed so that that’s no longer an issue? I guess if you can get them as an option from the dealer, they can’t expect you to be avoiding puddles.

Murphy’s law of puddles: You cannot accurately determine the depth of a puddle before driving into it.
Yes, you can wipe out an engine by driving into a “puddle”. However you have to drive into a big enough puddle to fill the airbox with water, and have the engine suck in enough to do damage. You also have to have enough engine speed that a large enough volume of water is sucked down the intake to cause damage. This does not happen from going through a 2" deep puddle. I would venture a swag that for the cars I teach on a “puddle” of at least 24" and a fair amount of speed is required to hydro lock an engine.

Just to clarify what Hydro Lock is.

Air compresses in the cylinder just fine. Water does not. That leads to spun bearings, bent connecting rods, broken crankshafts, mangled heads, and other uncool engine mis-haps.

I originallly worried a little about hydro-lock but after measuring the height of my intake, it isn’t a concern anymore. If I run through a puddle deep enough to cover my intake (20" off the ground) I have other problems to worry about! :smiley:

I have a Miata and have used or investigated several of these. A 10 hp gain is probably optimistic. The power gain comes both from cooler intake air and a less restrictive intake path. Depending on the stock layout and where its air inlet is, the CAI may not really be much cooler. In any case, almost all of the power increase will be at high RPMs. Given what you’ve said about your shifting habits, I don’t think you’ll feel the increased power at all.

The CAI may actually have a negative affect on the performance as well. On the Miata, for example, the stock air intake system is tuned, using resonance chambers and so on, to increase low RPM torque.

Some of the CAIs look kind of cool, but unless your in the habit of propping up the hood and staring into your engine compartment for hours at a time, the value of the aesthetic enhancement is probably minimal.

Thanks for all your input.

In fact, the car is plenty peppy at high RPMs. But, while I vastly prefer small, economical cars, I must say that you can never have *too much * pep in a car! That being said, this doesn’t sound like a worthwhile investment, at least now, while the car is new, everything is tight and working at optimum. Maybe when it gets older and tireder.

I continue to love the xB - I get a little giggle everytime I see it - that bright yellow and bizarre shape mean I’ll *never * lose it in a parking lot! But mostly I love its pragmatism - the roomy interior, excellent handling, spirited acceleration, and just all-around driving-enjoyability, as well as the excellent mileage and quality (neither of which I’ve experienced first hand yet, since I have yet to put in my first tank of gas).