Just found a nice article about intake resonators over at AutoSpeed (http://www.autospeed.com/) that I thought might be interesting to some people here, so I nicked the interesting bit :)


3. Cancellation

This uses resonators tuned to a particular frequency and connected to the intake system. (Ah, so here is a description of those funny things you can see tee'd into the system!) When the intake system produces the frequency of sound that the resonator is tuned to, the air within the resonator is excited. It in turn produces a sound of the same frequency and amplitude, but with exactly the opposite phase. That is, when the intake system's waveform is high, the resonator's waveform is low - and the two cancel each other out.

Two types of resonators are used - Helmholtz and quarter wavelength. Helmholtz resonators are like bottles, with their tuned frequency being the result of their volume, neck area and neck length. Quarter wavelength resonators are characterised by having a constant diameter. Their resonant frequencies are determined by their length - for example, a quarter-wavelength resonator with a centre frequency of 67Hz (the firing frequency of a four cylinder engine at 2000 rpm) is 1250mm long.

Reductions in noise output of 5 - 10+ dB are possible, although usually only over a narrow range of frequencies.

The disadvantage of cancellation volumes is that they again take up space. Additionally, a variety of sizes may be needed if cancellation is to occur over a wide range of frequencies.

Normally, a mixture of techniques is used. For example, as shown here, a quarter-wavelength resonator (yellow), a Helmholtz resonator (green) and an expansion chamber (blue).

Note that all of these devices are for noise reduction, rather than intake volumetric efficiency tuning. So if any of the volumes is likely to be causing a restriction to intake airflow (and that's especially the case with a series expansion chamber), you can delete it without too much concern.

Interesting. I found a second and third resonator over the last week.

My intake resonators have been gone for a while now, and there is a big difference with them on and off, I tried putting them back on but the engine is robbed of power every time I put them back on, so they stay off permanantly now. I also get better fuel economy with them off. ;)
And yeah it does sound more meaty with them off.

Mmmm - interesting. I would like to see Dyno on that.
How much difference (%) do you reckon in power and consumption?


My intake resonators have been gone for a while now, and there is a big difference with them on and off, I tried putting them back on but the engine is robbed of power every time I put them back on, so they stay off permanantly now. I also get better fuel economy with them off. ;)
And yeah it does sound more meaty with them off.

What did you use to stuff the holes?

I've heard of Milk bottle caps or Gaderade caps. how do you ensure that they don't fall inside? do you get any Whistles? What sort of improments? hmm Dyno could be expensive and troublesome, how bout just do some 0-100 times or 0-60 for that matter of speed fines.. HAHA... ta

I did this to my 2.4lt TE and it made big improves on throttle and low end torque.

Might have to give it a beal with my 3.0lt :)

With such a slight mod 0-100 time might only vary some 0.1 sec. And one wouldn't really know if that's due to other factors than power.
I guess this mod is quite interesting, but very difficult to prove.
I would use some hard plastic sheets (bucket, oil can etc) and use fuel resistant silicon or clue. And place them inside the box if possible and paint black.


What did you use to stuff the holes?

I've heard of Milk bottle caps or Gaderade caps. how do you ensure that they don't fall inside? do you get any Whistles? What sort of improments? hmm Dyno could be expensive and troublesome, how bout just do some 0-100 times or 0-60 for that matter of speed fines.. HAHA... ta

i didn't really notice any gain in power, but damn the exhaust definately has more of a roar and burble to it.

i used the lids from 2L orange juice bottles, they had to be pried in with a screw driver, and the inside is slighty smaller so theres no chance of getting sucked in, no noise, no problems!

With the resinator boxes off it and with a pod, the throttle sound is unreal!!!
If you are lucky enough to own an Astron II in your TR/TS, this mod is a must and grab a pod filter. you WILL scare every1

why not just do what im doing. get your rich uncle toolmaker to make you up a nice custom shiny aluminium intake pipe to go with your custom cai sealed pod unit.. :D

do i hear a new business about to be started up?

i think it's called : MAGWGN's cheap as hell pod adapters. soon 2 be sold all over aus?

hey guys i did this today,
took out the resonators,
my mate had these really weird things off a gearbox or somthing ???
but yeh ne ways they fit in perfect with a little hack saw off the edge,

and my tinny noise has gone from the exhaust now, stocked as, but its still there in 1st gear but the rest of the gears are gone :p :p :p :p

should be even better with cams in it next week

You may find that tinny noise is only apparent as the new headers may be thinner than the stock ones.

do i hear a new business about to be started up?

i think it's called : MAGWGN's cheap as hell pod adapters. soon 2 be sold all over aus?
haha. bite me! will see when im done and your wanting to buy one! lol.

Out of subject - but my RPWs create not tinny but very aggro roar past 3K RPM. The thin'nes (?) of material mainly makes it bit louder, does not effect the timbre of the sound much.
I think the tinny sound comes mainly with those cannon mufflers, those big single mouth cans??


You may find that tinny noise is only apparent as the new headers may be thinner than the stock ones.

Yeah - my 1st gear is the softest strangest sounding gear - 2nd and 3rd just roar!! anything about 75% throttle and 3K RPM - well lets just say it gets your attention!!

Manual

I forgot to mention that mine is the four banger model, so I dont know what happens on the v6??? But it definetly works for my four te.

Oh and I just taped up the holes with duct tape.

I forgot to mention that mine is the four banger model, so I dont know what happens on the v6??? But it definetly works for my four te.

Oh and I just taped up the holes with duct tape.

Just to be on the careful side, I don't think that's a good idea using duct tape.. but hey, if it works... :)

Never underestimate the power off tape.

I seems to work as well as bluetack...

Duct tape is like the Force. It's got a Light Side and a Dark Side and it holds the universe together.

Actually MagnaV6Sports13 it is about the only thing that does work and stops the air from entering past the point of the mas sensor. :)

Hey there
Removed mine on the weekend and since I removed them I notice a slight gain in power, not much but every little bit helps. well see if it realy made a diff when I take the car out on the track again!!
And there`s a slightly lager roar in the exhaust!!

When I did mine on my 4 cly I used Black garden plastic, put it over the hole and forced the resinator back into the hole, trimmed off the excess plastic and whamo, all done and it still looks factory.

can anybody post up their V6 models of the resonator removed so i can get a better idea what you did...

cheers

kev