Point of a Resonator?


adblink182
06-07-2005, 12:52 AM
just checking it out on "howstuffworks" and they keep talking about sounds, and sound waves bouncing back etc etc....is that all they are for is sound?

I was offered to get a ubend delete and res removal for $100(canadian) and I'm thinking about taking it

will I notice any change? (I have an open cone setup right now)

but I just wanted to know whats hte point of the resonator and why remove it?

//edit oh ya, I have to go for a damn emissions test in the near future....will these 2 procedures affect me passing at all?

BNaylor
06-07-2005, 03:42 AM
Here's something that may be helpful.

Exhaust/Muffler Basics 101:

Exhaust gases leave the engine under extremely high pressure. If these gases escaped directly from the engine the noise would be tremendous. For this reason, the exhaust manifold sends the gases to a muffler, which is located between the catalytic converter (if present) or exhaust manifold and the tail pipe. The muffler quiets the noise of the exhaust by "muffling" the sound waves created by the opening and closing of the exhaust valves. When an exhaust valve opens, it discharges the burned gases at high pressures into the exhaust pipe, which is at low pressure. This type of action creates sound waves that travel through the flowing gas, moving much faster than the gas itself (up to 1400 m.p.h.), that the muffler must silence. It generally does this by converting the sound wave energy into heat by passing the exhaust gas and its accompanying wave pattern, through perforated chambers of varied sizes. Passing into the perforations and reflectors within the chamber forces the sound waves to dissipate their energy. The pressure of the gases is reduced when they pass through the muffler, so they go out of the tail pipe quietly.

There are two types of muffler design. A Reverse-Flow muffler is oval-shaped and has multiple pipes. Four chambers and a double jacket are used to accomplish muffling of the exhaust noise. Exhaust gases are directed to the third chamber, forced forward to the first chamber, from where they travel the length of the muffler and are exhausted into the tail pipe. A Straight Through Muffler has a central tube, perforated with several openings which lead into an outside chamber packed with a sound absorbing (or insulating) material. As the exhaust gases expand from the perforated inner pipe into the outer chamber, they come in contact with the insulator and escape to the atmosphere under constant pressure. Because of this, the expanding chamber tends to equalize or spread the pressure peaks throughout the exhaust from each individual cylinder of the engine. This type of muffler is designed for the purpose of reducing back pressure and, consequently, makes slightly more noise.

Since a muffler cannot reduce the noise of the engine by itself, some exhaust systems also have a resonator. Resonators are like little mufflers, and are usually the "straight through" type. They are added to the exhaust system to reduce noise.

Most "performance" mufflers provide some degree of quieting, all provide improved airflow, and many look good enough to display to bystanders! However, in order to obtain or maintain a reasonable market share, some makers make claims of "increased airflow", "flows better than a straight pipe", or "10% better flow than competitor X". We have conducted extensive testing of mufflers on actual strip performance and found that with a single 2-1/2" muffler on a 12.50 vehicle, there is very little performance difference between all brands of performance mufflers. When tested with a good dual system with some type of crossover, there is almost no measurable difference between brands, providing similar sizes are compared. Static airflow will be affected by test pressure and the methods in which air is directed into and out of the muffler. Accordingly we feel that bench tested airflow on mufflers is misleading and should carry very little weight when evaluating muffler performance.

There are distinct differences in pricing, noise levels, build quality, and packaging of "performance" mufflers. Here are some general observations about mufflers:

The larger the volume in a muffler case, the quieter the muffler.
Exhaust noise is the result of two factors - the noise escaping out the tailpipes, and the noise generated by the muffler case. Round or oval mufflers produce very little case noise because there are no flat sides (other than the ends which are typically reinforced), and thus no areas to vibrate in harmony with the exhaust noise passing within the muffler. Any vibration of a flat surface will generate noise. Rectangular mufflers can generate noise which will be heard inside the car as a resonance. The use of heavy metal cases, extensive welding of the flat metal to internal components, and internal insulation can help reduce the noise produced by the case in this style of muffler. The use of stainless steel will increase the expected life, add to the cost, and produce a better looking muffler. Larger pass tubes, or larger passageways within the muffler case will always make the exhaust noisier, and may reduce back-pressure. Excessive noise is not an indication of improved performance, and reasonably quiet mufflers are not necessarily restrictive.

To summarize, when a muffler of a given pass-through size produces reasonable flow capability, slight additional flow capability probably will not be recognized by our street/strip vehicles. When shopping for a performance muffler, determine how much noise and/or tone you want, how long you expect the muffler to last, the package size you can use, whether appearance is of significant value, and finally how much money you want to spend. We feel that the average street or street/strip vehicle will not be able to measure any performance differences between the top 8 or 10 mufflers available if similar sizes are used on a good dual system.

Unfortunately not all free flow performance exhaust systems are created equal. We regularly see aftermarket systems producing less power than the standard systems they replace. Some are unpleasantly noisy, and their gasflow potantial are dismal.


http://www.photobucket.com/albums/y186/lizzywiz/gtp.jpg
Thrasher CAI, DHP v1.0 ECU,
3.25 SC pulley, CAIT GMAF, Hi-Flow CAT,
u-bend delete, 160 TS,TB spacer,
MSD 8.5mm wires, Autolite 104 spark plugs,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

adblink182
06-07-2005, 07:37 AM
nice read

Resonators are like little mufflers, and are usually the "straight through" type. They are added to the exhaust system to reduce noise.


thats really the only thing they said about resonators, so basically I'm going to be getting a different sound out of it....is it a deeper tone? Cause if its anything like those stupid fart cans I'll leave it on

Berettaal391
06-11-2005, 03:48 PM
adblink182,

I had my u-bend and res. removed about a year and a half ago and noticed a nice gain on the "butt dyno"...the exhaust was a little louder outside the car but I noticed little change on the inside. The outside sound was more of a growl than a deep tone. It's a V6 so it was probably about as deep as it was gonna get without changing mufflers. I also assure you that there was no fart can sound at all. I actually ended up replacing the stock mufflers with Dynomax Super Turbos and love the sound although there is drone inside the car and if it was any louder I would put the res back on. Anyway, I don't think you'll be disappointed a bit with having the u-bend and res removed.

BNaylor
06-11-2005, 04:51 PM
There's nothing wrong with removing the resonator and it may help performance because of reduced backpressure. However, don't plan on taking a trip across country without the resonator installed. It will drive you nuts. :cool:


http://i5.photobucket.com/albums/y186/lizzywiz/gtp.jpg
Thrasher CAI, DHP v1.0 ECU,
3.25 SC pulley, CAIT GMAF, Hi-Flow CAT,
u-bend delete, 160 TS,TB spacer,
MSD 8.5mm wires, Autolite 104 spark plugs,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

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