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Old 11-01-2000, 11:06 PM   #1
Fred Fredburger
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Post Straightening air in intake/before throttle body?

Hey, all.

I remember seeing some program on TLC or something where they would "straighten" water when it was going thru a hose to make it go straighter (imagine that). It comes into play when you see those little water fountain-type things where they shoot water out of a hose, then it goes into another hole, then water shoots out to somewhere else. It's tough to explain without seeing it.

Basically it comes into play that if you turn your hose on full-blast, it sprays all over, but if you were to fill a portion (towards the end) of the hose with stirring straws (like at the bar), it'll come out much smoother because there isn't as much turbulence in the hose.

Does this have any sort of application in the intake of a car, or would the air filter box hork things up? Could it help things between the air filter and the throttle body?

This has been bugging me for a while so I thought I'd ask.

Geoff.
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Old 11-02-2000, 06:20 AM   #2
Scottie
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You are basically talking about laminar and turbulent flow. And the bunch of stirring straws would similar to honeycomb. Even the filter element provides some flow straightening. If you have the second air, then your getting a form of flow straightening before the throttle body. You could use honeycomb in place of the filter, but I'm not sure there would be that much of a benefit if at all.

It would take a pretty long post to cover this topic. In a nutshell, turbulent flow and turbulence has it uses. It can aid in the mixing of air and fuel. Also, the MY99 MAF has a screen at its opening for the purpose of assuring a bottle cap shaped velocity profile. Laminar flow tends to have a more bullet shaped velocity profile.

[This message has been edited by Scottie (edited November 02, 2000).]
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Old 11-02-2000, 06:24 AM   #3
RidinLow
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You want smooth airflow up until it enters the combustion chamber; then you want turbulence to mix it up with the gas.

The funny looking nightstick thing on the intake tract smoothens airflow as does the honeycomb filter on the pre MY00's.
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Old 11-02-2000, 06:47 AM   #4
Scottie
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"The funny looking nightstick thing on the intake..." is a quarter wave resonator tube. Its there to attenuate pressure waves with a wave length 4 times that of the center line length of the tube. If attenuating (reducing) such waves is your meaning of smoothing out the flow, then yes that's what is happening. However, a quarter wave resonator tube would have no effect on reducing tubulence. In all likelyhood, as air flows past the opening of that dead ended tube, some tubulence may be generated.
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Old 11-02-2000, 06:58 AM   #5
rjones
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Sounds like some smarty-pants has a degree in fluid-dynamics

I've been down the dark path of the convergence between fluid behavior and soundwave behavior in the throttle body design of a formula SAE car. Simply contributing to this thread gives me the willies....
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Old 11-02-2000, 07:15 AM   #6
Scottie
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Nope, just a plain jane BSME. No extra course work in Fluid Dynamics. It was hell just getting through Gas Dynamics class. I think I've learned more since college than I did in college. Unless of course you consider downing a brewsky a study in Fluid flow. In that case that was my concentration. hehehehe
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Old 11-03-2000, 03:37 AM   #7
S.Damery
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Scottie,
Pardon my ignorance, the resonator tube essentially "tunes out" any pressure waves that occur as a result of the length of the intake tube? Does that effect the airflow efficiency (volume etc.) Does it contribute to reduction of noise as well? Sorry for all the ?'s.
-Shawn
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Old 11-03-2000, 04:56 AM   #8
Scottie
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Shawn,
A quarter wave resonator tube attenuates ("tunes out") pressure waves as a result of it's length, not the intake tubes length. As a pressure wave travels past the opening of the resonator tube, a wave of the same wave length will head down the resonator tube. Once it reaches the end it will bounce back towards the opening. Now if the resonator tube is one quarter the length of the wave in question, then the wave that bounced back in the resonator tube will reach the opening 180 degrees out of phase with the main wave in the intake tube. This effectively cancels a portion of the wave (attenuation). The simplified equation for a quarter wave tube is f=C/4L. C is the approx. speed of sound in air at 20 degrees C. L is the center line length of the resonator tube. And f is the tuned frequency. Say the quarter wave tube was .2 meters long (approx. 8"). Then the tuned frequency would be f=340/(4*.2) or f=425Hz.

The impact of such a tube on airflow efficiency would be minimal. Especially considering all the other losses through out the intake system.

A sound wave is a pressure wave, so yes it reduces noise at the tuned frequency.
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