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      07-28-2012, 11:44 AM   #1
Z4MHawk
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RPI Modification

Ok, even after reviewing that great summary for the after market exhaust modifications I decided to go for that tunnel reverberating, tooth aching, car alarm setting, and hyper droning RPI. No complaints on what I suspected was going to be an authenic track sounding exhaust, even after the initial 500 mile break in and one excesive noise warning citation(story for another thread w/ pictures).

However, I had a couple of thoughts that perhaps many of you have already considered. Could I modify this flow-thru exhaust system to deliver "slightly" lower db's?

I had always thought the small, second tail pipe was a filler for the OEM cut-out, but never really looked at it before installation. Since there is no carbon build-up on it, this is either true or its flow must be restricted. There is a mesh patch inside it as it splits off the larger diameter exhaust pipe

Has anyone removed this mesh patch to allow the smaller pipe to receive more air, or any air?

Thanks!
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Last edited by Z4MHawk; 07-28-2012 at 03:05 PM. Reason: further research
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      07-28-2012, 11:39 PM   #2
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Would also like to know. Considering replacing the rpis before I lose my hearing...
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      07-29-2012, 12:08 AM   #3
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are they that loud?

i have no primary cats or resonators + cans and it's still civil if i want it to be.
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      07-29-2012, 12:41 AM   #4
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Quote:
Originally Posted by zubydafa View Post
are they that loud?

i have no primary cats or resonators + cans and it's still civil if i want it to be.
thats because you're probably near deaf.
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      07-29-2012, 01:35 AM   #5
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i have no primary cats (AA headers) and RPis and im startin to think i want it a bit louder.... either i dont think its too loud as well or it has begun to deafen me
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      07-29-2012, 02:30 AM   #6
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i love it with my euro jot coated headers (lol) by I'm wondering how an x pipe will suit me.
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      07-29-2012, 02:42 AM   #7
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Quote:
Originally Posted by Roffle Waffle View Post
thats because you're probably near deaf.
what's that i can't hear you



but really, it's not loud unless i want it to be. it's got a bit of a loud cold start. nbd. if i let the revs climb slowly and shift, you'd think it's just a sporty sounding car.

when i get on it and let the revs climb it's an angry bat out of hell.

i live in a quiet neighborhood and manage to get home at odd hours of the night after partying without being too obnoxious.
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      07-29-2012, 03:12 AM   #8
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the rpi's are LOUD, but when you look at the exhaust, particularly with the euro headers in place, theirs literally no sound surpression anywhere, it looks like the stock setup completely relied on those huge cans to get the noise down, hence their bulk and weight, the rpi is basically a tuned straight pipe!!!

its LOUD!!
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      07-29-2012, 03:13 AM   #9
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i need to get my DKF hangers on my car to see how much they dull down the noise... villa sed they make a difference!!
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      07-29-2012, 03:45 AM   #10
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wow i wonder what RPI on my setup would be like.

got me verrrry curious...so if a used set happened to pop up at a reasonable cost i might have to pick them up for when i feel like getting a noise ticket.
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      07-29-2012, 09:13 AM   #11
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I was thinking of approaching this on 2 fronts.

I know that what ever I do with this mesh patch over the smaller tube will probably not effect the exhaust flow very much beacuse it is at a 35 degree angle off the main tube but it might change the tone.They put it there for a reason!

I was also thinking of welding a perforated funnel inside the flange ring that connects the RPI to the X-pipe. This will produce a little back pressure but not as much as stock.

I still need to dynamat to help reduce cabin noise.

I have to say that it is a awesome sound to hear the whine of the S.C. and the deep tone of the RPI's, just before the car alarms go off and building seismonitor registers the mag. 2 earthquake.
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      07-29-2012, 05:38 PM   #12
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Dynamat , a layer of closed cell foam, and the ///m trunk mat helped but the drone and resonance from 2-3k rpm is still crazy. My shop left me a set of earplugs in the ashtray when I picked the car up as a complimentary "sound mod"

My last m5 was cat-less and resonator-less and it was still quieter than this....
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      07-29-2012, 05:52 PM   #13
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Oh, I have some leftover Damplifier pro (Dynamat only thicker) I'm happy to donate to any fellow rpi owners in the name of saving eardrums across America.
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      07-29-2012, 07:57 PM   #14
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Quote:
Originally Posted by ajw45 View Post
Dynamat , a layer of closed cell foam, and the ///m trunk mat helped but the drone and resonance from 2-3k rpm is still crazy. My shop left me a set of earplugs in the ashtray when I picked the car up as a complimentary "sound mod"

My last m5 was cat-less and resonator-less and it was still quieter than this....


wow! there's a guy around town with an e60M5 with meistershaft and some other exhaust goodies. it is LOUDDDDD.

you guys have me so curious about the RPI's now. i may have to pick up a used set once i get a real daily driver and reserve the M for the track and small trips here and there.
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      07-30-2012, 12:15 PM   #15
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They don't seem to be that loud to me.......Maybe mine are just more broken in since they have a lot of miles on them........
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      07-30-2012, 07:12 PM   #16
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You guys are doing loud wrong. I'm gonna have electric bypass valves in the car soon. right before the mufflers. They arrive tomorrow, but I have some things to do for a week or 2 before I install
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      07-30-2012, 10:27 PM   #17
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To be fair, I think the drone actually makes it louder inside the car....
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      07-31-2012, 12:35 AM   #18
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Quote:
Originally Posted by Roffle Waffle View Post
You guys are doing loud wrong. I'm gonna have electric bypass valves in the car soon. right before the mufflers. They arrive tomorrow, but I have some things to do for a week or 2 before I install
please share details!

also i'll have to hear this thing in person.
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      07-31-2012, 12:44 AM   #19
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cut outs are gonna be nice
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      08-05-2012, 06:33 PM   #20
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Quote:
Originally Posted by zubydafa View Post
please share details!

also i'll have to hear this thing in person.
these are the ones I ordered. Sitting in a box until I get my next paycheck to get installed

http://marylandspeed.com/dmh-low-pro...ut-p-1313.html

won't hear it in person unless you go to my new home in Delray Beach, FL
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      08-05-2012, 07:05 PM   #21
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Quote:
Originally Posted by Roffle Waffle View Post
You guys are doing loud wrong. I'm gonna have electric bypass valves in the car soon. right before the mufflers. They arrive tomorrow, but I have some things to do for a week or 2 before I install
Where are going to install the bypass switch? BTW, I think it should have only two settings, "off" and "11".

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      08-05-2012, 09:08 PM   #22
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Quote:
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Where are going to install the bypass switch? BTW, I think it should have only two settings, "off" and "11".

In that little free panel where people usually relocate their 12v outlets to. Hidden under the dash area (above the seat heaters and ashtray)

it comes with a switch you hold for 4-5 seconds for the flaps to fully open. You can stop it anywhere in between, but I'm gonna treat it as an on-off switch.

Should sound very interesting, since some air will still hit the stock mufflers
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