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Old 09-24-2015, 05:21 PM   #1
Justin100
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Default Difference in a cheap versus expensive exhaust system

So I saw a video online and I noticed that there was a 350z that sounded extremely raspy and cheap like weedwacker sound.

My momentum exhaust system does not sound like that. It has a nice deep tone even after 4k rpm.

What makes a cheap exhaust system sound like that? Is it because the material is really thin? Something inside the pipe?

Here is the video I saw

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Old 09-24-2015, 06:27 PM   #2
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Im not sure exactly why cheap ones sound like that but ew
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Old 09-24-2015, 06:44 PM   #3
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Because resonators and exhaust leaks.
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Old 09-24-2015, 08:20 PM   #4
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Well I have a full Motordyne including the art pipes and it definitely has some rasp. So even expensive c as nt get away from rasp
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Old 09-24-2015, 10:55 PM   #5
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Is it just me or does it sound like something is wrong with that car. Sounds horrible!
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Old 09-25-2015, 03:16 AM   #6
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That is the sound I wanted to stay miles away from whenever I bought my exhaust. My Invidia Gemini has resonators built - in and I went with HFCs to avoid rasp. But that video is a whole new level
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Old 09-25-2015, 03:51 AM   #7
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Quote:
Originally Posted by HRMoneyPit View Post
Well I have a full Motordyne including the art pipes and it definitely has some rasp. So even expensive c as nt get away from rasp
because you have wide open exhaust.... its gonna happen, but it was usually at higher rpm's on mine.

that car sounds like a sick honda
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Old 09-25-2015, 04:42 AM   #8
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Haha that sounds terrible, any chance it just has straight pipes? It will sound like crap without decent resonators in place. I do believe pipe quality and the engineering that goes into the exhaust flow makes a big difference too.
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Old 09-25-2015, 06:57 AM   #9
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Rasp is - to severely oversimplify - sound waves crashing into one another inside the pipes and exiting as that annoying metallic sound we call rasp. As you reduce the backpressure (and/or change the velocity of the exhaust pulses), the sound waves (represented as a sine wave) tend to steepen due to what's called "wave steepening phenomena".

If there's no resonator or tailpipe EXIT (in both cases, a "larger chamber in which to reduce the 'angle of the sine wave'") as it travels down the pipe, the first sine waves get crunched by the exhaust pulse behind it and creates a seeming "echo" due to the crashing wave forms.

In English, it comes down to the acoustic properties of the pulses exiting the car.

In real life and again, in its most simplistic form, stock exhaust systems and well engineered/tested systems can be created/built to take the rasp out (or minimize it) through extensive R&D + tuning of the pipes (shape, length, size, etc). Lower end manufacturers simply don't have the resources to do this type of testing and tweaking. They take some piping and bend it up ***** nilly to fit or as "best as they can copy the 'real thing'...", not necessarily perform. This is done to meet a price point not an acoustic curve.

With this said, the way to reduce or eliminate (hopefully) rasp from an inexpensive system is to essentially turn it into an expensive system by adding H or X pipes - X-preferred - on a dual system or mid-pipe resonator(s) of specific volume - chamber displacement, not loudness (Vibrant or Magnaflow or.....). Moral of the story: If you don't like/want rasp, figure on spending the dollars up front for an engineered exhaust OR adding to a less expensive one.

Side note (history lesson of the day ): In the development of the Z33 (the "comeback" Z, as it were), Nissan engineers specifically tuned the exhaust to mimic - as closely as possible - the original S30 exhaust. If you listen to them side-by-side, you can hear the familiar tone. Fascinating.

Cheers,

Mic

Last edited by MicVelo; 09-25-2015 at 07:00 AM. Reason: spelling
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Old 09-25-2015, 07:06 AM   #10
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Im Telling You guys. It's not dollar amount, Motordyne is not cheap and still rasp at 3k-4k
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Old 09-25-2015, 07:29 AM   #11
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Quote:
Originally Posted by HRMoneyPit View Post
Im Telling You guys. It's not dollar amount, Motordyne is not cheap and still rasp at 3k-4k
I should have stated/disclaimed that it's "not always about the price". In your case, the ART pipes are "most likely" what causes the rasp due to the straight piping nature of such. Would be willing to bet that with real cats (even HFCs) providing some of the initial chamber volume needed to straighten the acoustic wave, you'd have less or possibly no rasp.

Motordyne is up there with the cream of the crop aftermarket suppliers and their exhaust systems are very well built but unless you're Nissan (or Toyota or GM or....), even then the R&D going into such an exhaust system are not up there with manufacturers who HAVE to produce cars (and components) that meet the 99% of the consumer public that would object to "that funny noise".

You should hear the tinny note of my Volvo's exhaust - particularly when cold! UGGGH. Sounds like the sardines in the can are still alive and trying to get out!

Last edited by MicVelo; 09-25-2015 at 07:30 AM.
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Old 09-25-2015, 07:58 AM   #12
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Quote:
Originally Posted by MicVelo View Post
Rasp is - to severely oversimplify - sound waves crashing into one another inside the pipes and exiting as that annoying metallic sound we call rasp. As you reduce the backpressure (and/or change the velocity of the exhaust pulses), the sound waves (represented as a sine wave) tend to steepen due to what's called "wave steepening phenomena".

If there's no resonator or tailpipe EXIT (in both cases, a "larger chamber in which to reduce the 'angle of the sine wave'") as it travels down the pipe, the first sine waves get crunched by the exhaust pulse behind it and creates a seeming "echo" due to the crashing wave forms.

In English, it comes down to the acoustic properties of the pulses exiting the car.

In real life and again, in its most simplistic form, stock exhaust systems and well engineered/tested systems can be created/built to take the rasp out (or minimize it) through extensive R&D + tuning of the pipes (shape, length, size, etc). Lower end manufacturers simply don't have the resources to do this type of testing and tweaking. They take some piping and bend it up ***** nilly to fit or as "best as they can copy the 'real thing'...", not necessarily perform. This is done to meet a price point not an acoustic curve.

With this said, the way to reduce or eliminate (hopefully) rasp from an inexpensive system is to essentially turn it into an expensive system by adding H or X pipes - X-preferred - on a dual system or mid-pipe resonator(s) of specific volume - chamber displacement, not loudness (Vibrant or Magnaflow or.....). Moral of the story: If you don't like/want rasp, figure on spending the dollars up front for an engineered exhaust OR adding to a less expensive one.

Side note (history lesson of the day ): In the development of the Z33 (the "comeback" Z, as it were), Nissan engineers specifically tuned the exhaust to mimic - as closely as possible - the original S30 exhaust. If you listen to them side-by-side, you can hear the familiar tone. Fascinating.

Cheers,

Mic
Well said. Also, awesome tidbit of information at the end... never knew about the exhaust tone between the Z33 and S30. That's cool as hell.

Also, would you expect anything less out of that Z in the video? Looks like it drove through a swarm of late 90's/early 2000's Civics.
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Old 09-25-2015, 02:38 PM   #13
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I know it's the test pipes. Part of me hates the rasp, and not really hearing the VQ sound I always wanted. But then I don't DD the Z, so I like it loud as it. Idk guys :/
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Old 09-25-2015, 03:18 PM   #14
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I've heard a couple of nice sounding cheap exhausts at local car meets, they did however take it to a shop that knows how to properly line them up and stuff, they usually don't line up as easy as an expensive kit. Also longevity, maybe? I mean a cheap one would probably fall apart after a couple of years.
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Old 10-14-2015, 02:20 AM   #15
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Remember, you get what you pay for. Cheap exhaust may sound good though you can't be sure how long it will last.
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Old 10-15-2015, 11:16 PM   #16
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Omg that sounds like someone installed weedwackers underneath it :/
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Old 10-16-2015, 10:43 AM   #17
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My ears! (x_x) The rasp is real...
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Old 10-16-2015, 02:22 PM   #18
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Quote:
Originally Posted by bboypuertoroc View Post
Well said. Also, awesome tidbit of information at the end... never knew about the exhaust tone between the Z33 and S30. That's cool as hell.
Quote:
Originally Posted by MicVelo View Post

Side note (history lesson of the day ): In the development of the Z33 (the "comeback" Z, as it were), Nissan engineers specifically tuned the exhaust to mimic - as closely as possible - the original S30 exhaust. If you listen to them side-by-side, you can hear the familiar tone. Fascinating.
That is almost identical to the Z33.
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Old 10-16-2015, 02:42 PM   #19
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That sounds like my car with a Motordyne exhaust and ART pipes
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Old 10-16-2015, 02:47 PM   #20
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My exhaust is rasptastic above 4k rpm below it sounds fine... I have a pretty small resonator that I blame.
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