can someone go in depth as to how the intake noise tube works?

[pr086]

maybe someone thats taken it apart? show the pieces of it, how it connects, how it functions. i heard if you remov it you lose a few hp, curious why that is.

with talk of a revised intake for 2014 do you think it will still have it?

[eriktherod]

Well.. it kind of goes like.... brrrrrruUUUUUHHUHHHHHHHH!

Seriously though, it is a tube that T's off the side of the main intake tubing (post-filter, before it goes into the intake manifold). The noise tubing goes through a set of resonators near the the passenger compartment near the firewall.

The controversy of removing it comes down to if the intake resonance/air pressure was designed with this tubing in mind. While it seems like dead weight (I can't see how it really could be beneficial to keep it personally), some say it has a slight negative impact by removing it. Others are saying it's no difference.. so I'm not sure it's solved yet.

I don't think they'd revise it within the next year, it's too minor.

[wbradley]

I'm thinking something to do with a Helmholz somthingorother.

The wavelength of the sound emitted from the intake travels down the tube where there will be specific length sections and or/other aperati that will amplify the sweet (preferred) frequency and then channel it into the cabin.

This, perhaps to enhance the sporty driving experience without bouncing the needle off or anywhere near the redline. I really like the sound when I slightly blip the throttle on a downshift. That is, assuming the sound tube is actually contributing to that particular sound.

[jschendel]

Was it confirmed that the purpose was just to make noise?

The situation kind of reminds me of the "moo" sound that my RX7 made after replacing the stock intake, except opposite lol.


It was a common problem and was fixed by either putting a bulb at the end of the hose to muffle the sound, or cap it.

see example here (not my video) : [ame="http://www.youtube.com/watch?v=R95GI6u9tFk"]HKS blow off valve - YouTube[/ame]

[camelflage]

does the fr-s use a maf or map sensor? either way, it should be able to adjust for the increased airflow by removing the extra tubing.

[xpicer]

I just took mine out, buy now that i think a bit more about it. Not only
Does it create noise but it also alows the engine to breathe cooler air from the cabin, if you look inside the tubes most have diaphrams/ one way valves that alow air to be sucked in. Now as we all know the temperatures in the engine compartment are usually high (200 f + ) and the position of the air box dosent really allow cool air to blast directly to it. So in with these factors in place i believe the manufacturer created the pipe to help the engine by allowing if to suck cooler air when a certain vaccum is reached at the air box. Also the plastic piece that goes on the bottom pf the hose is there to collect and retain debris so that if the air cleaner fails there is less chances for your engine to suck the debris. so now , tomorrow im putting things back

[Stryker Trailwood]

the way it was described to me by the guys at the fr-s drive tour made it sound like there isn't actually any intake air/charge traveling all the way through the tubing and into the cabin or vice versa.

the air travels from the intake, through the tube, where it actuates a diaphragm that acts sorta like a bass drum and then that sound continues through the tube/resonators and then into the cabin.

when looking at the tubing, this makes sense to me, actually having air from the intake pushed into the cabin or the other way around, doesn't seem like something that the NHTSA nannies would approve of.

[wheelhaus]

I believe Stryker has it correct according to the tech docs I've read. The diaphragm doesn't allow any air to pass through. Instead it's flexible diaphragm will resonate (vibrate) at higher cycles of the intake air pulses, allowing the sound to pass through at higher rpm. Lower rpm won't resonate the diaphragm, so you won't hear much from it.

Its feasible that the intake system could perform better if tuned for it since high rpm efficiency must take intake and exhaust pressure waves into account, but eh, I dunno, seems like a stretch to say it helps/hurts performance since it's just a sound doodad and isn't allowing any real airflow.

[xpicer]

Did any opened their yet? Is it a diaphragm or a one way check valve???

[Pscylo]

Its a car kazoo. Simple. It was dyno'd at 1whp loss, but I am calling shenanigans, as the part has no real function other than to resonate engine/intake noise to the firewall making it sound vroom vroom for the driver.

[Sideways?]

I think there are photos of someone removing it in one of the intake / airbox development threads on here but I don't know exactly which one as it was ages ago since I remember seeing it...

This is not very helpful, I'll try to find the thread I'm not talking very coherently about...

Edit:

This from Perrin might help...

http://www.ft86club.com/forums/showthread.php?t=8129

[450hp/tonne]

Originally Posted by xpicer

Is it a diaphragm or a one way check valve???

Diaphragm only, as a check valve would allow unfiltered air into the engine ...

[Hawaiian]

Originally Posted by Pscylo

Its a car kazoo. Simple. It was dyno'd at 1whp loss, but I am calling shenanigans, as the part has no real function other than to resonate engine/intake noise to the firewall making it sound vroom vroom for the driver.

think of it as a plastic drum that uses air to beat it. There is no air let through it, however if you remove it, you need to plug the hole in your passenger foot well that is there to let sound in, not air.

Furthermore, there is no hp loss or gain. You will get a 1-2 hp fluctuation on dyno runs, and the vehicle was probably suffering from heat soak/hot oil making the numbers go down after dynoing the frs back to back with and without the sound tube (see the perrin catback thread). Can we please put this hp loss nonsense to bed and never bring it up again?

[Chewie4299]

Originally Posted by xpicer

I just took mine out, buy now that i think a bit more about it. Not only
Does it create noise but it also alows the engine to breathe cooler air from the cabin, if you look inside the tubes most have diaphrams/ one way valves that alow air to be sucked in. Now as we all know the temperatures in the engine compartment are usually high (200 f + ) and the position of the air box dosent really allow cool air to blast directly to it. So in with these factors in place i believe the manufacturer created the pipe to help the engine by allowing if to suck cooler air when a certain vaccum is reached at the air box. Also the plastic piece that goes on the bottom pf the hose is there to collect and retain debris so that if the air cleaner fails there is less chances for your engine to suck the debris. so now , tomorrow im putting things back

This made me laugh a little. The stock airbox draws air via a snorkel from behind the front bumper. That is going to be very cool air compared to the engine bay. The sound tube does not allow air to pass through it at all from what I understand.

Also a 1whp loss is well within any dyno's margin of error I'm sure.