AIRBOX / INTAKE DIY - Helmholz resonator bypass
#61
06-21-2008, 10:56 PM
The 997 air filter box has a resonator built into it .
It's purpose is to alter the sound coming from the engine .
The outlet of the resonator connects to the main air intake hose to the engine ( see red arrow in picture )
As the outside air ,on it's way from the filter to the engine inlet , is drawn past the resonator , it creates a sound frequency which cancels out some of the engine noise ( since similar frequencies tend to cancel each other)
If you want to know how it works, blow over the top of a bottle .
Depending on the volume of the bottle and the velocity over the outlet , the frequency changes (the Helmholtz principle )
The resonator outlet has a vacuum activated butterfly valve in it which closes at high rpm's , thereby disabling the resonator effect , and is open at lower rpm's.
If you want your engine to sound a bit more aggressive at lower rpm's, all you need do is to disable the resonator .
It will not do anything for performance, but it sounds cool . A bit like a mild performance muffler .
Some do it by replacing the OEM air intake hose with a rubber elbow from a plumbing supply place, or as I have done, just put a plug into the resonator hose ( see previous threads )
If you go the hose replacement route , be sure to put a cap over the resonator outlet to prevent dirt from accumulating inside
Or, you can buy the Fabspeed "cold air kit " for a little over $200 .
You will receive a pretty red rubber elbow and , according to Fabspeed , get at least a 10 hp gain to boot . Lol
It's purpose is to alter the sound coming from the engine .
The outlet of the resonator connects to the main air intake hose to the engine ( see red arrow in picture )
As the outside air ,on it's way from the filter to the engine inlet , is drawn past the resonator , it creates a sound frequency which cancels out some of the engine noise ( since similar frequencies tend to cancel each other)
If you want to know how it works, blow over the top of a bottle .
Depending on the volume of the bottle and the velocity over the outlet , the frequency changes (the Helmholtz principle )
The resonator outlet has a vacuum activated butterfly valve in it which closes at high rpm's , thereby disabling the resonator effect , and is open at lower rpm's.
If you want your engine to sound a bit more aggressive at lower rpm's, all you need do is to disable the resonator .
It will not do anything for performance, but it sounds cool . A bit like a mild performance muffler .
Some do it by replacing the OEM air intake hose with a rubber elbow from a plumbing supply place, or as I have done, just put a plug into the resonator hose ( see previous threads )
If you go the hose replacement route , be sure to put a cap over the resonator outlet to prevent dirt from accumulating inside
Or, you can buy the Fabspeed "cold air kit " for a little over $200 .
You will receive a pretty red rubber elbow and , according to Fabspeed , get at least a 10 hp gain to boot . Lol
so just to confirm... this mod here.. increases the sound at lower rpms only?
Any idea the purpose of the resonator?.. i mean if it gives a better note.. why have it in the first place.. just wondering if theres a downside to it..
thank you
#62
06-22-2008, 02:14 PM
K & N cold air intake mod
Hey guys!
I'm thinking of getting the K&N cold air intake mod........anyone done this? Is this the same type mod that all of you are talking about?
Does this mess with the warranty? Thanks!
I'm thinking of getting the K&N cold air intake mod........anyone done this? Is this the same type mod that all of you are talking about?
Does this mess with the warranty? Thanks!
#64
06-23-2008, 11:57 AM
thanks JCS for explaining..
so just to confirm... this mod here.. increases the sound at lower rpms only?
Any idea the purpose of the resonator?.. i mean if it gives a better note.. why have it in the first place.. just wondering if theres a downside to it..
thank you
so just to confirm... this mod here.. increases the sound at lower rpms only?
Any idea the purpose of the resonator?.. i mean if it gives a better note.. why have it in the first place.. just wondering if theres a downside to it..
thank you
The intake system was further designed to provide less resistance. A Helmholtz resonator is used to enhance acoustics. This provides more than 18 cubic inches (0.3 liters) of additional resonance volume between the hot-film air mass meter and the throttle butterfly and is activated between 5,000 and 6,000rpm to reduce oscillations in intake sounds. Porsche has applied for a patent for this technology that provides a deep, throaty sound without aggressive peaks.
#65
06-23-2008, 12:04 PM
I produced a line of loudspeakers in the 70's based upon the Helmholtz resonator principle.
#67
06-23-2008, 02:37 PM
The K&N design looks like anything but a cold air intake. It is vented to the hot engine compartment. Check out the EVOMS cold air intake. The Koni Challenge series cars use these.
#68
06-24-2008, 07:19 AM
My dealership told me stay away from the K&N, and to go for the Evoms. I did, and I like the Evoms- adds a nice sound. Really screams at open throttle above 4500 RPM's.
Here's a link to a vid showing how sound changed when I added the Evoms:
[media]http://youtube.com/watch?v=RP5VnyiT3X0[/media]
Here's a link to a vid showing how sound changed when I added the Evoms:
[media]http://youtube.com/watch?v=RP5VnyiT3X0[/media]
#71
11-06-2008, 03:28 PM
Why not just disconnect the vacuum actuator so it remains in the closed position. Isnt that basically what the kit does anyway?
Just have to figure out if the valve is open or closed when disconnected.
Also, i seriously doubt the ridges on the oem tube make any difference in flow numbers. It is just too far upstream from the intake manifold and intake valves.
Just have to figure out if the valve is open or closed when disconnected.
Also, i seriously doubt the ridges on the oem tube make any difference in flow numbers. It is just too far upstream from the intake manifold and intake valves.
#72
11-12-2008, 06:24 AM
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#74
10-14-2009, 03:56 PM
One option I've not seen discussed, but which should work would be to unplug the vacuum tube that connects the Helmholz resonator to the vacuum solenoid, and plug the vacuum solenoid with a $.02 vacuum cap. I wasn't sure what size I needed so bought a multi-pack from Auto-zone for $.99.
Capping the vacuum solenoid is a necessary step when removing the OEM airbox and installing an EVOMS box, so I don't see why it wouldn't work to just stop the suction from activating the resonator if using the stock box.
Am I the winner of the cheapest solution contest?
Capping the vacuum solenoid is a necessary step when removing the OEM airbox and installing an EVOMS box, so I don't see why it wouldn't work to just stop the suction from activating the resonator if using the stock box.
Am I the winner of the cheapest solution contest?
do u have pics about this setup?
anyway whats the best method so far?
thx
#75
10-14-2009, 05:55 PM
If you unplug the vacuum line only, the valve in the resonator will remain OPEN, not closed, and you will get the opposite of the desired effect.
You can try another hack and it does appear to work just fine just to see if you like the sound - it's easy to do and will give you a preview so you can decide if you want to bypass it long term. It costs nothing and requires zero parts.
You can bypass the resonator vacuum distributor control solenoid and plug the incoming source vacuum line directly into the vacuum line running to the resonator valve itself. The easiest way to accomplish this is to unclip the distributor solenoid from the airbox (it's the small gray solenoid on the back of the airbox). Then, remove the rubber vacuum elbow where it connects to this gray valve. Gently remove the small hard line on the other side of the valve from the rubber vacuum connector (the larger rubber connector -the hard line is the small, thin hard vacuum line running horizontal behind the box to the actual resonator valve). Firmly install the hard line in the rubber elbow that supplies vacuum and voila.
For those who don't know, this vacuum source on our cars is constant, provided by a dedicated vacuum pump that works at all times to provide on demand vacuum for various applications including the PSE valves, the resonator valve and so forth. I've not seen an instance yet where this vacuum source is interrupted so this would keep the resonator valve closed at all times.
That all said, I'd only do this as a test to see if you liked the sound. I imagine over time that being closed 100% of the time could weaken the valve or it's seal within the airbox resonator chamber. The right way is to simply plug it off securely. But this way is easier and cleaner, just not the ideal long term solution.
Last edited by Nexus-6; 10-14-2009 at 10:50 PM.