How does resonancem work?

[Willy Estrada]

Can anyone be more through as to how resonance through a CAI can add HP gains?

[Cue-Ball]

Disclaimer: I am not an engineer. However; i have read books on this subject and think i'm knowledgeable enough to answer this.

In a nutshell, resonance allows a soundwave to assist in moving air through the system. Resonance is used in both intake and exhaust systems precisely for this. Engineers tune their systems to "capture" a sound wave and redirect it to do what they want. So, the intake/exhaust is designed so that when the sound wave goes through the pipe, it is reflected in such a way as to "push" along the air in the pipe (into the engine on the intake side, away on the exhaust side). In effect, this works as a sort of small-scale forced induction when used on intakes. Not sure if i explained this very well, but i think you get the drift. Basically, resonant sound is used to help move air through the system. This is similar to what is applied to subwoofer enclosures. When you "tune the port" to a certain frequency, you're causing the sound waves to push themselves along, which increases the amount of sound you hear *at that given frequency*.

Confused enough?

-Grant

[thaa]

Ferrari uses that on their exhausts I believe...

[Cue-Ball]

Most auto and motorcycle manufacturers use it on their vehicles, to some extent. Exhuast and especially intake systems are designed to take advantage of the resonance effect. From what i've read, the problem with stock systems is the heavy noise restrictions. Without noise, you can't get resonance, so the effect in a stock system is very minimal.

-Grant

[T4 Primera]

Unfortunately in-line engines are generally limited to a fixed intake resonance system, whereas engines with two banks of cylinders are sometimes fitted with variable resonance intake systems.

Mazda's 2.5 V6 as found in the MX-6 has a three stage variable resonance system (VRIS). It uses butterfly 2 butterfly valves which are open and shut at various engine rpm to change the size of the plenum chamber. This has the effect of giving the engine 3 torque peaks instead of one and keeps the whole torque curve higher.

[howard_w13]

[quote]Originally posted by Cue-Ball
Confused enough?

Most definately. So what else other than a cold air intake will produce enough resonance to produce real HP gains?

:coolguy: :coolguy:

[Cue-Ball]

I don't think there's any aftermarket item you can buy which will use resonance to increase horsepower. The reason that a CAI increases horsepower is because it's less restrictive and intakes colder air, not because it resonates better. In fact, i'd be quite shocked if a CAI used resonance AT ALL. Also, while resonance can add power, it's not much. Especially compared to the gains you'll see using a header, cold air induction, different cams, etc. Put simply, without a CAD program and an engineering degree, you're not going to get any benefits from resonance (other than what's there stock).

-Grant

[nis.k.a.]

A lot of aftermarket headers are designed to utilize the scavenge effect. Mate that with mandrel bends and ceramic coating for exhaust velocity, you've got hp. Of course the merge is always the propritery part. Especially in 4-1 headers, take AEBS for example. It has tremendous low-end output for a 4-1, credit the collector.

[Cue-Ball]

Yes, that is true. Many headers take advantage of this but it's more of a secondary thing. The main advantage of headers is the fact that they flow better because they are less restrictive. When i said nothing was available, i was speaking about intake parts, not exhaust. I don't know of any CAI/POP which makes effective use of resonance to increase HP. I suppose there might be one out there, but i've never seen it if there is.

-Grant

[nis.k.a.]

Here's the proof. Mr. Mike Kojima himself.http://www.se-r.net/engine/cool_air_intake.html