Finally, an answer to what the OEM intake does

[KSXNSX]

I am not sure if it has been answered before, but many people on this board have questioned what that extra piping on the OEM intake scoop does--the piping that extends from the air scoop behind the driver's side fender lining and terminates in itself.

The answer is: it is a Helmholtz resonator used to decrease induction noise.

http://www.popularmechanics.com/how_to_central/automotive/1888037.html

This probably explains the increase in sound amplitude when you remove it.


"That empty piece of plastic is called a Helmholtz resonator. Really. And it's just empty. Actually not: It's full of air. It's attached to the ducting between your air cleaner and the intake manifold. And although it looks like it can't have any real purpose, it does. It's there to reduce the noise your engine intake duct makes. Huh? It has an interior volume with a very specific resonant frequency, like an organ pipe. Pressure pulses traveling back and forth in the duct have a resonant frequency as well. A pressure pulse whipping past the entrance to the resonator (at the speed of sound) partially enters its cavity. The pulse then bounces off the far end of the resonator, and returns back to the duct a very short time later. By now the pressure pulse has traveled a half-wavelength farther along the duct. The pressure pulse re-entering will cancel out at least part of the negative pulse at that point. The net result is reduced noise, at least at or near the resonant frequency of the resonator. Many car manufacturers use this technique to reduce intake-tract noise. Some vehicles have several of these devices in different places along the duct.

Why do you care? This device should have no effect whatsoever on the performance of your engine"

 

[jmp]

Would the -- even slight -- disruption in airflow created by the arrows of air (as appearing in the diagram) exiting and entering the primary flow path create any loss in power? Small changes to exhaust flow, cylinder head flow, etc. can have a measurable impact, would this not as well?

I am DEFINITELY no flow expert, or for that matter expert of any kind when udnerstanding the dynamics of internal combustion engines. Curious to get feedback on what my plain sensibility suggests???

 

[KSXNSX]

Would the -- even slight -- disruption in airflow created by the arrows of air (as appearing in the diagram) exiting and entering the primary flow path create any loss in power? Small changes to exhaust flow, cylinder head flow, etc. can have a measurable impact, would this not as well?

I am DEFINITELY no flow expert, or for that matter expert of any kind when udnerstanding the dynamics of internal combustion engines. Curious to get feedback on what my plain sensibility suggests???

There's probably nothing that would organically perterb the setup enough to cause any major changes in flow/power. The cylinder is filled with air, and once a dynamic equilibrium is established, things should flow nominally.

 

[heySkippy]

used to decrease induction noise.

That's crazy talk! Why would anyone want to do that?

 

[KSXNSX]

That's crazy talk! Why would anyone want to do that?

Manufacturers are always trying to decrease noise (intake, exhaust, etc.) I don't know why they do it with sports cars too. It makes sense for a camry, but not an NSX.

 

[davidf]

Check out the pic on post 32. Those canisters serve the same function. The piping is pretty much straight through but the canisters somehow do muffle sound.

 

[davidf]

Check out the pic on post 32. Those canisters serve the same function. The piping is pretty much straight through but the canisters somehow do muffle sound. http://www.nsxprime.com/forums/showthread.php?t=103575

 

[Hugh]

The thing is curved at the bottom to prevent the entry of rain water into the system. It's plenty wide to not impede airflow. When you're zipping along at high speeds the air is forced in there at high pressure anyway.

Those largemouth bass looking aftermarket scoops are useless. You can't increase the size of the intake on the throttle body so all you're ending up doing is creating back pressure and a possible loss of performance. Honda used supercomputers and an army of highly trained engineers to design the car. I realize that a lot of improvements can be made using aftermarket pieces but screwing with the intake is a waste of time and money.

 

[Briank]

It's kind of like an appendix, no one knows exactly why its there and you can live without it but it does serve a purpose.

 

[TNT NSX]

The thing is curved at the bottom to prevent the entry of rain water into the system. It's plenty wide to not impede airflow. When you're zipping along at high speeds the air is forced in there at high pressure anyway.

Those largemouth bass looking aftermarket scoops are useless. You can't increase the size of the intake on the throttle body so all you're ending up doing is creating back pressure and a possible loss of performance. Honda used supercomputers and an army of highly trained engineers to design the car. I realize that a lot of improvements can be made using aftermarket pieces but screwing with the intake is a waste of time and money.

if the largemouth bass looking after market scoops are useless, how do you explain the increased hp shown on the dyno charts? are the advertisements misleading us?

 

[heySkippy]

if the largemouth bass looking after market scoops are useless, how do you explain the increased hp shown on the dyno charts? are the advertisements misleading us?

Here we go...




Actually, I'm the proud owner of one of those big mouth bass intakes *and* I drive in OMGXBOXHUEG rainstorms. I can at least testify that this isn't a recipe for instant hydrolock.

 

[docjohn]

It's kind of like an appendix, no one knows exactly why its there and you can live without it but it does serve a purpose.

Funny,maybe the aftermarket intake is the Bursa of Fabricius!:wink:

 

[ExCfive]

So why in the picture is this "appendix" thing shown after the air filter whereas on the NSX it is before the air filter??? Is it still the same thing?? Not that it matters much (to me) as I have the DF intake scoop and love the sound, but just curious.....

 

[NSXFRIEND]

Key word pressurized, if any vapors go back into this thing and there is a spark

 

[ChopsJazz]

It's kind of like an appendix, no one knows exactly why its there and you can live without it but it does serve a purpose.

Appendix. Funny. But I removed my resonator a long time ago and I'm not dead. Yet. Divorced again, but not dead. :wink:

 

[mc-ca]

I asked my brother in law about this a couple of years ago. He designs these intakes for a living. They are there for two reasons: 1. lower the noise from the engine and 2. prevent water from getting into the engine.

All new cars need to be tested to have noise lower than some federal spec or they can't sell them. The intake noise is the first place they go as it's higher frequency than the exhaust and easier to control (not as hot or fast moving). The test weighs high frequency higher than low as people are more sensivite to high frequencys (A weighting). The resonators are a great way to block the noise but they do induce turbulance into the airflow and lower horse power. He thought than replacing the factory intake with a one without resonators would add about 5hp.

The water issue is a big one as it will wreck the engine. He called it something like "hydrolock" where the engine just seizes because water does not compress like air. They test by driving the car through standing water at a certain speed. All the cars he has worked on are front engine with a top mounted intake. They worry about splashing getting into the intake as it's so high. He saw where our intakes are located and was amazed we don't have a lot of problems - Honda has obviously solved it in their design. This is what kept me from going for the extra hp.

 

[KSXNSX]

So why in the picture is this "appendix" thing shown after the air filter whereas on the NSX it is before the air filter??? Is it still the same thing?? Not that it matters much (to me) as I have the DF intake scoop and love the sound, but just curious.....

It doesn't matter if it is placed before or after the intake.

The article explicitly mentions different cars place it in different places.

This particular car used for the picture and diagram just happens to have it after the filter.

 

[tosugrad]

So no consensus on this? I want to remove my PURELY for sound enhancement.

 

[GreyHoundSteve]

So no consensus on this? I want to remove my PURELY for sound enhancement.

I think the consensus on this is that its just like the OEM vs UNI air filter debate; One is proven and the safest, the other is louder and might add a couple hp at a greater risk of potential problems. If you want or need the extra noise and maybe a few hp then it might be worth the risk to you, if you value safety of your engine more and prefer the intake quieter then nothing beats OEM.

Thats how it appears to me anyway.

 

[docjohn]

So no consensus on this? I want to remove my PURELY for sound enhancement.

Depends on what you expect as sound enhancement.I have the resonator and oem pipng removed and with the uni heard more woosh/wistle.with the paper element less woosh and wistle.What is absent though and what is still cool anytime I drive someone elses stock car with stock exhaust is the induction honk at wot.That methodical bellow sound that some would say is more exciting than the blaring exhaust blat I hear with my gtlw and intake mods.

 

[evel333]

I remember my stock S2000 exhaust had one. Was like night and day when I put on an aftermarket one that lacked a resonator.

 

[RYU]

So is there a definitive answer to any HP gains/losses by removing the OEM snorkel and just leaving the inlet of the intake box sucking from the fender? I know it will be louder and could potentially introduce water etc...

I'm sorry if this OT a bit. On the fence about posting a new thread considering the direction this is going. Also researched a few threads including the ones below but no real answer.

http://www.nsxprime.com/forums/showthread.php?t=104024&highlight=remove+oem+scoop&page=2
http://www.nsxprime.com/forums/showthread.php?t=114184&highlight=remove+oem+scoop