Remember that post from long, long, long, long ago about air intakes? The one that was going to tell you everything you needed to know about them so you could make good decision when it comes to purchasing an aftermarket system for your car and not the $60 look – a – like from eBay? Well guess what, it’s back. Finally. We left off with getting into the basics of an intake system, and we’re going to continue with intake science. Yes, there actually is a lot of important smart stuff you should know. Plus you’ll get smarter.
Let’s explain the basic science before we get into the short ram “it’s $50 cheaper” versus “cold air “it gives me some more power and puddles ain’t sugar honey iced tea” debate. Your factory intake was designed with a bunch of things in mind. Cost cutting and cheap design (only in some cases, most higher end cars actually have very good ones.) and noise. Why is there a giant tank attached to my airbox? Why is it this shape? Why does it route this way in my engine? Firstly, the giant attachment, or in some cases the size and shape of the box, is there to serve as a resonator. We love the sound aftermarket systems make because they’re free of these things. Air goes in, expands and moves and cancels out sound waves of the induction charge in the chamber (like your exhaust muffler) and then goes in. The problem is, from a performance standpoint, an engine can rev more freely without them, rev quicker with less delay, save weight, and in general, makes a nicer noise. In some cases, the restriction caused by these can be so great it holds back significant horsepower gains (removing the resonator on my Mazda 6 V6 netted an increase of 5-10 hp, and those numbers have been dyno proven, no butt dyno here.)
So with the noise gone, what else is there? Besides the temperature and humidity of the air that is sucked in, which is taken care of by the mass air flow sensor that determines the air fuel ratio, the way how air flows is extremely important, and is the reason why for some aftermarket applications, other systems can actually produce less horsepower and/or less torque at certain rpm’s. An intake that was engineered properly should have the right size piping, bends, and flow (calculated with a flow bench and other extensive testing) to have a smooth flow of air in the pipe before reaching the throttle body. Everything from the length of the pipe to the diameter and inner surface can affect the frequency and harmonics of the air as it enters the combustion chamber. If you’ve ever wondered why aftermarket systems are polished and try to eliminate as many sharp bends as possible, this is why. This is also why you’re factory intake looks the way it does. Unfortunately, many times, even aftermarket companies don’t get this tuning right, or accurate enough, so you’ll notice at certain rev ranges, power actually drops slightly because of turbulence with the waves of air.
So, no, while you usually can remove resonators and some restrictions and see benefits, you probably shouldn’t just go find a pipe and stick an open element filter on the end. Even though it is tempting. Of course, you may be wondering why it works on race cars or heavily tuned street cars. Well, those cars that you see with filters stuck right onto the velocity stacks or right on a massive pipe over the turbo are fine, because those engines don’t mind. They’re trying to make as much power as possible, and the team can rebuild their engine if they feel like it or after each race. In those cases, at least having a filter on a pipe helps, but at the speeds those cars travel and the power they make, the point is for the intake so suck in so much air it could ingest a small child, so it doesn’t really matter that much.