what is this extension on the air intake pipe?

[raj55]

On the black air intake pipe of both citigo and Up we see a bulb like extension that leads no where. What is it,? Is it an air intake silencer?? Here is a photo showing that.

http://www.autoblog..../#photo-4696119

Edited 3 November, 2012 by raj55

[pedroxy]

This is a bell-mouth air entry. It has a number of flow advantages, but also reduces airflow noise. ( It is a shape commonly used in public water supply systems, but works with air and fluids).

[raj55]

I was not referring to the entry "mouth" which is bell shaped, but to the blind tube attached to the side of the air intake pipe distal to the mouth (i.e. after the mouth). Can you see it?

[skomaz]

My guess is it'll be a Helmholtz resonance chamber - helps smooth out torque curves by matching the air intake resonance (ie the pulses in the air in the intake tract) to those of the engine.

Edited 5 November, 2012 by skomaz

[pedroxy]

My guess is it'll be a Helmholtz resonance chamber - helps smooth out torque curves by matching the air intake resonance (ie the pulses in the air in the intake tract) to those of the engine.

I guess you're right ...I am more used to seeing them for exhaust tuning.

In this case it's probably more for induction noise control (some owners report weird induction type wheezes and whines) , and providing a small amount of optimum rpm range assistance.

Edited 5 November, 2012 by pedroxy

[raj55]

Thank you. Next question, what is inside that cavity/resonance chamber, a piece of humble foam?

[Jim H]

My first thought is it would be a pipe that sucks hot air from around the exhaust manifold helping the engine warm up quicker. However as you said, it doesn't lead anywhere and no other pipes around it then, so as it could only be a resonance chamber of some sort. Like you I've never seen them on the intake, only exhaust of cars. I have a feeling some motorbikes have them though.

[CortinaGT]

Thank you. Next question, what is inside that cavity/resonance chamber, a piece of humble foam?

Who knows, but there does seem to be a small grill, or drip hole like molding under the rear end.

[Crista]

It's an accumulator so that air supply is maintained when reversing up a hill. Sorry just kidding - it's a resonance chamber - just does its job as designed. A lot of cars have this fitting. Doesn't need maintenance or any fiddling with.

[raj55]

Thank you and,

now the last question (answers in simple english please without the scientific jargon), what does it do here in the Up?

1. low rev sound reduction?

2. just for show, so that you can compare Up to Porsche and Miata and others who have it.

3 some other valid reason?

[Crista]

2. just for show, so that you can compare Up to Porsche and Miata and others who have it.

??

[raj55]

??

Apparently, these cars have a Hemholtz resonator attached to their air intake or super charger or exhaust. I still haven't understood if they reduce sound, change sound character or increase power (exhaust hemholtz). Why would VW include in a low power little car beats me.

[skomaz]

Thank you. Next question, what is inside that cavity/resonance chamber, a piece of humble foam?

Usually nothing but fresh air - they act as an extra air chamber, thus affecting the mass of air in the intake tract and therefore the resonant frequency of the air in the tract.

[skomaz]

Thank you and,

now the last question (answers in simple english please without the scientific jargon), what does it do here in the Up?

1. low rev sound reduction?

2. just for show, so that you can compare Up to Porsche and Miata and others who have it.

3 some other valid reason?

I don't know for definite but probably both 1 and 3...

I'd expect that as it will change the resonant frequency of the air in the intake tract (and this is the primary cause of induction noise) it may lead to a quieter car. It is also likely that in changing the resonant frequency it means that vibrations induced in other components (sch as bodywork) are also reduced - again making for a quieter car.

However, I'd expect the real reason is to flatten out the torque curve of the engine. Usually they are added not for noise purposes but to either increase torque at low revs or to smooth out peaks in the torque curves of the engine that are a result of the resonances within the intake tract.

Both of the above have been my experience on my MX5, which, being an early 1.8 has a similar appendage in one section of the intake as well as a widening or 'silencer box' type resonator in another part of the intake. The former is for torque enhancement (as proven by others through dyno plots with the section replaced by a straight pipe of the same length and diameter) and the latter is for quietening the intake (personal experience of replacing this section with a non-resonated part shows it works).

Cheers

[RobMurrant]

Old topic but still..

They're also called Phlenum Chambers.
My understanding is they help when going from Wide Open Throttle to Closed Throttle.

High flow = low pressure (WOT)

Low flow = high pressure (CT)

 

Without it, if the throttle is suddenly closed and the pressure builds up quick, the pressure can force the throttle body open again. The extra volume in the Phlenum Chamber helps keep the pressure change down. It's not only large displacement noisy cars that need them!

 

[Emil]

There's no turbo so I find it hard to believe that pressure could force the throttle flap or butterfly open again. Or could even turbo do that? First time I hear this kind of theory though. 

[Breezy_Pete]

Throttle valves are hinged around their centreline, so I can't see how pressure (which would act both sides of the hinge) could open it?

[ronime]

It is a Helmholtz resonator. It is there to reduce unwanted surges and drops in intake flow caused by odd resonances. As already stated, it helps to smooth out the torque curve and prevent annoying intake noise/booming at resonant frequencies.