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Discussion Starter #1 (Edited)
So I have been running SLP Loud Mouth II's and like the sound but really miss the loud aggressive idle and amazingly loud WOT sound loud mouth I's create...problem is I hate the sound they make from 2500-3500 rpms and again at 4500-5000 rpms under mid throttle. It's like a fart can and then it begins to rap like when you down shift but only in reverse as you accelerate and the noise gets insane...

My first attempt was to remove the tips, my logic was if bad noise is coming down the pipe, the 4" tips would only act like a megaphone! Well I was correct and the sound did improve but it was dirty and muddled so win under part throttle but idle now was...meh?

So under the advice of an axhaust shop I looked for a smaller tip with a resonator knowing the resonator would only do so much but what the hell!

I ended up with Pacesetter Monza style tips....They are 17" long an exact match to the ones I took off but they are only 3", second they are resonated.

Result, the idle is deeper and more pronounced. And all that damn noise I had before is gone!!! Sure is still gets crazy loud when the cam comes in but nothing I can do there. I haven't gone down the highway yet but I am sure its not loud enough for me....Ill report later on that
 

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thanks for this thread I am struggling with the same thing . I have just cats right now but I need some thing to tone down the drone . I have flow master 40's but haven't put them on . I don't want to lose the WOT sound but the drone is a bit much.

GEO
 

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Discussion Starter #3
THanks! One of my local exhaust shops gave me some advice and they recommended first to remove the tips and evaluate the sound. This will give you an indication of what you have to work with. The tips will either magnify or help cancel noise. If you like the sound with no tips then run same diameter all the way out, if you want more diameter, but be careful on how long that tip diameter is as it will amply all sounds and maybe not cancel out the ugly stuff. The local small shops can really help you tune the sound
 

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Not such an odd solution...;)

When I was at DuPont many years ago, we had and acoustics and vibration engineering unit and test lab. Things like this were exactly what they studied for clients.

Acoustics of exhaust tone and harmonic vibration (drone) are directly related to the acoustic chambers the sound waves move through.

The muffler reduces high and low frequency vibrations cancelling them out. The resonator only reduces low frequency vibration and harmonic vibration (over-lapping sound waves that create a secondary harmonic as a combining of partial wave lengths)

The final tip acts as a trap (short path wave cancellation) for the sound waves or a magnifier (megaphone effect) depending on the configuration.

Many good exhaust shops know from empirical experience which works best in different configurations...even if they can't explain the physics behind it.

Sound is like water, if all of the waves move together in unison they create a pounding sound on the beach. If they are directed it multiple directions, they cancel each other out resulting in a choppy sea that causes a steady washing sound on the beach.
 

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Discussion Starter #5
Not such an odd solution...;)

When I was at DuPont many years ago, we had and acoustics and vibration engineering unit and test lab. Things like this were exactly what they studied for clients.

Acoustics of exhaust tone and harmonic vibration (drone) are directly related to the acoustic chambers the sound waves move through.

The muffler reduces high and low frequency vibrations cancelling them out. The resonator only reduces low frequency vibration and harmonic vibration (over-lapping sound waves that create a secondary harmonic as a combining of partial wave lengths)

The final tip acts as a trap (short path wave cancellation) for the sound waves or a magnifier (megaphone effect) depending on the configuration.

Many good exhaust shops know from empirical experience which works best in different configurations...even if they can't explain the physics behind it.

Sound is like water, if all of the waves move together in unison they create a pounding sound on the beach. If they are directed it multiple directions, they cancel each other out resulting in a choppy sea that causes a steady washing sound on the beach.
Excellent explanation!:beerchug:
 

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Discussion Starter #6
Its all about AM vs FM.....sound and electricity can be a ton of fun to play with!
 

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Hey Dave do you know where to find those tips online? Possibly in different styles to work with the 11+ chargers? I love the no cats and lm 1 but that fart can noise does make the car sound cheap under mid-throttle.

I saw WFTO used resonated tips to cure his rasp earlier this year. It's just hard to find tips to work with the 11+ that don't involve cutting up the slp exhaust.


Sent from AutoGuide.com App
 

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Discussion Starter #8
Pm sent! let me know if you need anything else
 
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