[dch921]

I have looked online and haven't been able to find an answer

Why are the air intakes on cars and trucks shaped the way they are.


Its not a straight shoot from the air filter to the throttle body. There are off shoots and dead space. This is just like my 2002 Tahoe and there is part of the air intake that just comes out and sits above the radiator and goes no where.

What purpose does this serve.

[gregb]

It's probably easier to design a molded plastic piece around the stuff that's on the engine, also, those offshoots and such are to dampen the noise.

[techinspector1]

At a manufacturing plant, the engineers don't have the final word, the bean counters do. If they can save 50 cents on 2 million cars, that's a million dollars.

[curtis73]

The dead air spaces are silencers. Take it off one time and floor it. The roar from the intake will be very loud.

[GunnerTHB]

I've got a K&N 57 Series intake on my 03 Silverado and I can't say I remember much of a noise difference.

[yknot]

The air isn't allowed to go from point A to point B because of Fluid Dynamics. The same way a Tunnel ram gives high RPM power. The intake runners are designed to boost performance. And I'm not just talking about tuning for the most HP. Many of todays cars have very elaborate intake manifolds, and all are designed to help the car, usually in it's sweet spot or most used RPM section. Because of the ever smaller engine compartments, engineers are forced to make manifolds more and more creatively. While it may not look like it, the air is routed in and around the intake to take advantage of a certain sweet spot. In general, the longer the intake runner, the higher the RPM band. And the shorter the intake runner the lower the band. By band, I mean the RPM band where the engine develops the most torque, or HP. If a certain engine produced a lot of HP, then the engineer's might be wanting to increase low end torque, to get that power down to a lower, more driver friendly RPM range. This is just one example, but when they go to the trouble of tuning the intake manifold, they do it for a particular reason, sometimes it's fuel economy, sometimes it's maximum power. There are even multiple runner manifolds, where the intake runners are short for low RPM grunt, and then at a certain RPM, a door or other mechanism opens and increases the runner volume, helping to make Higher RPM power or torque. The material the manifolds are made from isn't important, plastic is used because it is very easy to mold, mill and is very light. It also has various insulating properties, that aluminum doesn't have. In the older days, the intake had to be more structural then it has to be today, it doesn't have to hold up a carburetor, and many don't even have injectors in them. They simply route the air from one area to another, so strength isn't an issue. Non days, insulation, direction and length of runner are the challenges. The runner length is determined by the engines air flow requirements and the RPM range it operates in. Just like the exhaust, the intake has a frequency, this frequency is determined by RPM, stroke, bore, and air flow requirements . When a engine is operating at an RPM, there is a certain frequency that is generated by the intake valve opening and closing. This start and stopping of the air flow, produces a rhythmic wave, one that can be measured and tuned, just like they use the collector on a exhaust system to tune the exhaust gas frequency or wave length. Because booth processes, exhaust and intake, use mechanical openings set at a certain RPM, the resonance from these systems can be fine tuned, for power, torque or a combination of both.

[dch921]

what does the intake manifold have to do with the design of the air intake.

From what I have seen and heard there seems to be no sound difference from stock air intake and a cold air intake. You can sometimes hear the sucking of a cold air intake but I wouldn't go through all the trouble to add extra stuff to the stock intake to eliminate that.