Inlet design rationale

[ariZona28]

This is a 2 part question. 1st, can someone tell me why there are these large extra chambers on our V6 intakes? Curious as to what (if any) purpose they serve. 2ND, what is the best way to clean out oil residue from this chamber and its smaller companion on the other side? After 50K miles mine is well lubricated. Can only remove so much with rags, fingers and obscenities. I know the catch can discussion will come up. I have a dirty side can I installed 5K ago, may do clean side in near future.

[DSX_Camaro]

1. Resonators. Reduce intake noise.


2. I am quite partial to Simple Green.

['10CamaroDude]

There is only one large chamber. It's a resonator, so you don't hear the intake
growl. That's why people change to CAIs, they want to hear it. Why? I don't know,
but they do. It's not only a resonator, it's an expansion chamber.

The resonator in your intake is technically known as a Helmholz resonator, an acoustic
device used to control pressure wave harmonics. Air bouncing back out of your engine
and into the intake tube doesn't do it in a single pulse the way it would in a single
intake runner; the multiple pistons put out pressure waves at their own intervals, and
some of those are going to try to bounce back in while others are going out. The
result is a "clog" or high pressure area in your intake tube that ultimately limits airflow
through almost the entire rpm spectrum.

Air flowing into your cylinder head's intake port doesn't move in a straight line while
the valve is open, then politely stop in its tracks to await another valve opening.
When the valve closes, the moving column of air slams into it, then compresses and
bounces back like a spring. This pressure wave travels backward at the speed of
sound until the intake runner opens up or it hits something, and then it bounces back
toward the cylinder. This is the "first harmonic." The pressure wave actually bounces
back and forth two or three more times before the intake valve opens again.

Adding an expansion chamber to the intake tube forces air coming back out of the
engine to slow down to fill the cavity, thus expending a great deal of its energy and
slowing the pressure wave reversion. This slowdown allows fresh air to flow toward
the engine without fighting pressure reversion waves the entire way, thus aiding in
cylinder filling. Since these pressure waves are essentially sound, giving them a place
to expend their energy before exiting the air filter box ends up dampening the intake
noise and quieting the engine. Thus, the resonator helps to make the engine
paradoxically quieter and more powerful.

It's a tuned intake, believe it or not. I have actually gained one MPG when going
back to the stock intake from the CAI.

Of the two types, it's a side-branch resonator; a chamber that sit next to the tube
and is connected to it via a small duct or channel.

They increase air flow by dampening harmonic reflections due to air flow being
suddenly cut off (on the falling edge of each intake cycle), which cause the air mass
to bounce back and create back pressure that interferes with the next intake cycle.

They work in exhausts for eliminating drone by flipping the phase of the exhaust
pulse.


Back to the intake:
That smaller one, from the fresh air vent off the LH side valve cover is made
so that works properly. The problem is, if you have a 10-12, or early 13, your
PCV valve orifices are too small. There is an updated part, or a modification
procedure. You're not supposed to get oil and moisture in that fresh air
side, but the inadequate PCV on the earlier models causes pressure to go
out that side. That's why it's called the clean side. It also alleviated an oil
leak from the front main seal. IT also stopped a lot of venting through the
fresh air side, where I was getting oil.

[ariZona28]

Thanks DSX for reminding me about Simple Green. I use it around the house often. I recall I used it on some greasy Buick valve covers once with good results. Thanks '10 for a thorough explanation. I figured there was a purpose other than some engineers artistic creativity.