Option Racing Cat Back Exhaust

[davehuff]

Hi, I am trying to find a good exhaust for cheap and I was wondering if anyone could tell me if the Option Racing cat back exhaust was a decent buy or not. I really just want something that adds a little hp and doesn't sound like a dying cat. I like the deep, growling exhausts. The link is http://www.optionracing.com/2007-sci...m-p-30653.html or you can just google it. Thanks!

[Money_pit]

idk man 144 for a cat back sounds crazy i got a megan drift spec catback and i love it deep growl sounds great but its around 400 shipped i really didint think 400 was bad specially since the really good ones are around 600 shipped id search youtube to see if someone posted a video about this exhaust

[CadenceScion]

If your looking for a decent sounding exhaust w/o the rasp/ricey sound, give TRD a look. You could also look into Borla and Magnaflow exhausts, just stay away from Megan, they have a very well known reputation of selling/manufacturing less than quality products.

[Money_pit]

had my megan a year no problems here!

[navylife59]

Stay away from anything that states "JDM" for the tC. This car, though produced 100% in Japan, it is not sold in any market except the US/US Territories markets. The use of "JDM" is a misnomer, therefore, a good indication that it is some cheap Chinese junk. Also, the adage, "too cheap to be good" still stands. Meagan products can be hit or miss. Some people have had good reviews and others have very negative comments so you may not get a good part. Any catback exhaust will need to have a sufficient resonator.

[davehuff]

Alright, really good inputs... I think I'm going to rethink this and look in to some other options first. Hey navylife, how do I know that an exhaust has a good resonator? Well actually I don't even know what a resonator is so maybe you can help me out there?

[CadenceScion]

Our Scion tC's come w/ a resonator, but if you are planning on adding a header for example, an after market one from Magnaflow or Moroso will help tremendously by absorbing and balancing out the sound and decreasing rasp. Think of a resonator as another muffler per say.

[navylife59]

HowStuffWorks "How Mufflers Work"

A resonator needs to be sized for that particular exhaust and tuned to dampen the standing waves in the exhaust at the frequencies that is the loudest and most annoying.

[Money_pit]

I would search youtube to find the one u like thats what I did

[xlxhockeyxlx]

agree 100% with navy

[navylife59]

Thanks for the vote of confidence. Yeah me! (Ok, I have kids that watch too much Disney) . I think I may have all of the algebraic equations to properly size a resonator. Have to do some arithmetic and report back.

[xlxhockeyxlx]

Shouldnt the resonator just depend on the wavelength you want, and then a corespondent frequency. so if you want a 10kHz you would need a smaller resonator than 1kHz, since the later would have a larger wavelength? , so a resonator should be on the order of 20-30 cm?

[navylife59]

You have the right concept but it is not as simple as distance to wavelength. The exhaust gas stream is full of pulses from the exhaust valves opening/closing and reflections. There is no single frequency even if you held the engine at an exact and unchanging RPM. Further, you would have to calculate for a median frequency at a given RPM level where you want the most attenuation and figure in either the next octave up or 1/2 octave. I am not good at Algebra.

[CadenceScion]

I was reading on several forums that the longer the resonator, the less rasp and a smoother tone, others have said that doing two smaller resonators will also be beneficial. The only question I have is where in the exhaust should the resonator(s) be placed for proper sound/rasp cancellation.

[xlxhockeyxlx]

navy i like operating in the imaginary "ideal" word where there is only 1 wavelength and no fluctuation

[navylife59]

Gotcha. It would be the easiest like designing a port tuned subwoofer enclosure. Unfortunately, just as Cadence has discovered, there is not one simple, definitive answer. Fluid dynamics is tricky enough by itself, but now you are adding acoustical theory which is a subset of fluid dynamics. I know from personal experience with my custom exhaust that you do NOT want to run 2 resonators of the same size as it creates a second order harmonic standing wave that sounds nasty when conditions are right. My condition is caused by excessive cam and spark timing retard. I have two 12" Topspeed resonators inline with each other. These are bullet style. That means they have very little absorption material (glass/metal fibers). It is my edumacated guesstimation that as the the range of frequencies being reflected in the first resonator creates a standing resonance wave in the second resonator. I surmise with my little eye that if I had went with one 24-36" resonator, two resonators of different lengths, or even spacing the two further apart; would have prevented or even altered the original resonance wave preventing the standing wave Of course, I could be totally off key base on my supposition. Like I said, I suck at Algebra.

[xlxhockeyxlx]

i want better cams and get to mess with timings, more power = more fun as long as you can stop and turn

[navylife59]

Brian Crower has staged cams, upgraded valvetrain and even a 2.6L stroker kit.