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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Sun, Dec-02-2018, 01:49:56 AM   #1
matty088
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Default Rasp

I am gonna take heat for this one!!!

What is rasp?

I think I know what it is. Itís a louder sound from the exhaust thatís present in certain rpms when u are wot or just getting on it a little ? Sounds kinda metalíish. Tinnny. Itís even present on stock exhaust correct? I get a noise thatís mostly there when itís not fully warmed up. Itís almost like an exhaust leak. But I think this is the rasp that you guys speak of. Sounds awful. Real bad. My car is completely stock

So do I have this right?

I guess my next question is. What causes it to get worse. Headers?
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Old Sun, Dec-02-2018, 02:10:13 AM   #2
KS Golfer
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Default Re: Rasp

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Old Sun, Dec-02-2018, 02:34:06 AM   #3
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Default Re: Rasp

But it’s present with stock exhaust too right. Just not sure if it’s a leak or how these cars sound
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Old Sun, Dec-02-2018, 02:39:26 AM   #4
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Default Re: Rasp

Quote:
Originally Posted by KS Golfer View Post

This shit had me literally laughing out loud. Perfect.
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Mods: Genuine OE CSL Bumper, Both Karbonius and Streamline CSL Airboxes, OE CSL Snorkel w/ working Flap, OE Map Sensor + OE Air Rail, Paul Claude Custom Tune, CSL Engine management with CSL converted DME, Supersprint V1 Stepped Headers w/ Oversized Catless section 1, SS 2.5" Twin-Piped Oversized section 2, Rogue Engineering Muffler (soon to be switched), WPC treated rod-bearings, VinceBar (weld) + Redish Plates, Full Beisan VANOS lockdown, BBS LMs w/ PSS, CSL style CF diffuser, Vorsteiner CF CSL Bootlid, CSL SMG Engine DME tune, CSL '255' SMG DME tune.
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Old Sun, Dec-02-2018, 02:39:33 AM   #5
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Default Re: Rasp

yes. seems like all cars have it to varying degrees. changing the muffler or headers just amplifies the kazoo.

the easiest way to fix it is add a resonator to section 1 or buy a "rasp pipe/rasp terminator."
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Old Sun, Dec-02-2018, 02:40:27 AM   #6
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Default Re: Rasp

Quote:
Originally Posted by Dr M3an M3 View Post

This shit had me literally laughing out loud. Perfect.
it's pretty funny because it's depressingly accurate. so glad i got rid of it on my car.
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Old Sun, Dec-02-2018, 02:45:22 AM   #7
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Default Re: Rasp

Gunna reference this video I posted last night regarding my CSL Intake, right at 23-24seconds you can here some rasp come in at that RPM as well as at 34-35 seconds in. At about 36 seconds the rasp disappears and airbox takes over the noise. Audio isn't the best quality, was recorded with my older iphone sitting in my lap, but if you pay attention to those transition points you can here it. That is with a resonated X-pipe as well (resonators tame/help tune out the rasp).

To reduce it/get rid of it, get a resonated section 2. If you still have rasp present at a certain RPM, then adding additional resonators to the section 1 usually does the trick. It's just something inherent with the S54 and the dual exhaust. You will usually only hear it at a certain rpm from the exhaust gasses reverberating at just the right frequency to produce that noise. You could probably tune it out with a J-pipe or helmholtz resonator pipe like you would drone, though I've never seen those applied to this platform. Most guys just add canister resonators.

Tinny, metallic, marbles in a can all describe the noise that is referred to as rasp. Usually worse when cold starting and all the pipes are cold...Can sound like marbles rattling in a can for those first few minutes of warming up, then usually quiets down and isolates itself to a certain RPM frequency once things are to temp.
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Active Group-Buys (PM if Interested): OE CSL Bootlids, Supersprint Headers/Exhaust MEGA thread, New Supersprint Oversized Twin-Piped Section 2 ...and more to come!
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Last edited by Dr M3an M3; Sun, Dec-02-2018 at 02:52:45 AM.
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Old Sun, Dec-02-2018, 02:58:42 AM   #8
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Default Re: Rasp

You guys are great. So it sounds like what I have is In fact rasp. It’s more apparent when the engine is cooler. Or when I turn off the engine for a short period of time to get gas then get back on it when I leave. When the car is fully warm and been running I don’t hear it. Go figure.

Anyways rasp sucks.

I want to make my car a bit quicker but judging from the YouTube vids I hear, adding headers and an exhaust don’t sound great at all. Sounds like a civic. I can’t be doing that. I been looking at euro headers and euro cats. But man that’s a lot of dough to spend for a tiny increase in power. I can’t imagine simply moving the cats from the headers to the mid section is going to offer much (going from USA spec to euro spec) power. What are people getting with euro headers and cats and stock exhaust ?
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Old Sun, Dec-02-2018, 02:59:17 AM   #9
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Default Re: Rasp

the stock exhaust already has a resonator in sect 2 if i remember correctly? but sect 1 only a single resonator on one side of the dual exhaust. you need resonators on both sides.

this is what you want. well...there are cheaper routes, but I have this (and a supersprint resonated sect 2, and supersprint sport muffler).
https://www.bimmerworld.com/Exhaust/...er-E46-M3.html

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Old Sun, Dec-02-2018, 03:00:34 AM   #10
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Default Re: Rasp

oh yes. If I add a tune but keep the exhaust system stock will it yield anything? Which tune would be good in this scenario.

Thanks
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Discussing Rasp in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)