exhaust question Options

[eldrewado]

So I made my own exhaust on my GT. After the stock resonator i upped the diameter of the pipe to 2.25 then it goes into a long glasspack muffler then a downpipe just before the rear axle. I seem to be getting better gas mileage, so i want to keep my flow through design, but its so LOUD. I ordered 2 vibrant resonators I heard one is good and two is better and they are flow through. The question is....Should I build the system resonator-resonator-glasspack,
resonator-glasspack-resonator, glasspack-resonator-resonator, or just leave the glasspack out?

[Galcobar]

One resonator is sufficient in an exhaust system.

The trouble is that people don't know what a resonator is -- and it's not helped by the marketing of exhaust component companies.

A resonator is something that comes stock on pretty much every factory car. It is not a muffler, and it's primary role is not to reduce the volume -- at least not the measured volume. A resonator is an echo chamber, in which soundwaves are bounced into each other. When they collide, the soundwaves cancel out, transforming the sound energy into a bit of heat.

This naturally lowers the decibel level, but the primary reason for installing a resonator is to smooth the tone of the exhaust. By being less annoying, it is perceived as quieter. The awful buzzy sound of a badly done exhaust (see idiot in a Civic) is usually due to the lack of a resonator. If your exhaust is a wind instrument, a resonator is what keeps it in tune.

Unfortunately, because it sounds good and is easier to write, exhaust companies like to label their cylindrical under-body mufflers as resonators. They're lying, but nobody seems to call them on it, probably because actual resonators aren't expensive and therefore are not subject to the competition and marketing. These false resonators can be obsolete designs or modern straight-through designs, but if they involve insulation of any form they're not actually a resonator.

A glasspack is a 1950s-era design. Typically they're packed with fibreglass, which aside from not being the best sound insulator is prone to breaking down and blowing out. The interior pipe, around which the fibreglass is wrapped, is usually louvered. While all these little scoops do direct exhaust flow into the insulation, they also create turbulence, slowing the exhaust flow and reducing the efficiency of the engine as power that could have gone to the wheels is instead spent on pushing exhaust gases through the turbulence.

Modern straight-through mufflers utilize better and more durable sound absorbent materials such as ceramic matting and ultrafine stainless steel wool, wrapped around a smooth perforated inner pipe. This design keeps the exhaust flowing quickly and efficiently. As a result you can use longer or more numerous mufflers without significantly impairing engine performance.

The stock design is resonator--baffled muffler. To improve exhaust efficiency while keeping sound levels at a decent volume, you'd want resonator--straight-through muffler--straight-through muffler. Happily there's room for the underbody muffler where the secondary catalytic converter would go on a California-spec car.