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Big Turbo exhaust advice? Looking for minimum drone with GTX2554 (MRX)

Messages
19
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1
Location
Metro Detroit
#1
Hey guys, I just installed the Mountune MRX turbo kit, and its great so far (working through the tune revision process). My car has a stock downpipe and a Tsudo 2.75" exhaust. The Tsudo, with stock turbo, is...droney. Pretty gnarly drone from 3k rpm to about 4500 rpm, where it entirely disappears. I installed some sound dampening in the trunk/spare tire area, but it didn't help much.

I was hoping that maybe the change in turbo might take the savage drone beast, but the opposite occurs. The car is even dronier with the MRX . I daily this car, drive my 5-year old son in it and drive it on the freeway a lot. Drone in that rev range isnt something I can live with. I have some sensitive ears apparently, which makes sense...I wasnt kind to my ears as a kid, going to lots of concerts and race events without ear protection. At age 37 I just cant handle drone. My kid doesn't like it either :)

Any suggestions on what to do, as far as an exhaust? I don't want to go any smaller than 2.5". I considered swapping mufflers or having a helmholtz resonator or "drone pipe" installed by a shop, but locally I cant seem to find anyone confident that they can figure out the math and cancel the drone properly. Also swapping mufflers is a pain because of the unusual 2.75" exhaust size.
 
Messages
185
Likes
55
Location
Dayton
#2
Maybe the Mountune turboback to match with the MRX? I have their turbo back on the stock turbo and it's pretty good about being growly under acceleration and pretty quiet otherwise.
 
Messages
397
Likes
99
Location
YYC
#5
OT: Shouldn't you have an aftermarket downpipe?

What you need

Upgraded intercooler such as mountune PN 2364 IC BA1
Cobb Accessport - Mountune supplies a base tune for your Accessport
mountune Intake or suitable option PN 2364-CAIS-AA
Upgraded High Flow Down Pipe
Replacement Blow Off Valve such as our PN 2364-BOV-KIT
You could try extending the tips a bit further out from the bumper - that helps with the in cabin noise
 

re-rx7

1000 Post Club
Messages
1,619
Likes
198
Location
Ardmore
#7
Stock. Nothing to gain with exhaust even with this turbo. Multiple tuners have input. If you must have 2.5" FS Werks
 
Messages
443
Likes
119
Location
Chicago
#9
Kinda surprised it's droning with the stock cat still in. There should be a lot of catback-only options work little to no drone.
 
Messages
185
Likes
55
Location
Dayton
#14
Hmmm, I noticed better spool times with the stock turbo (MP215 tune at the time) after adding the MT turbo back. Maybe you can still hit peak power but you're losing some room under the curve on the low end?
 
Messages
275
Likes
103
Location
Calgary
#17

koozy

2000 Post Club
Messages
2,962
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1,540
Location
Los Angeles, CA, USA
#18
yes and similar to those running cat less downpipes. the conversation has been focused about the cat back being restrictive. This topic has come over so many times that people forget what the stock cat back has proven to be capable of.
 
Messages
94
Likes
6
Location
Alexandria
#20
I just got a CP-E. I have the depo catless and had just the stock muffler before this. It is louder in every sense from what I had before. It is louder inside than what you would expect with how relatively quiet it is outside the car. (Read this as, you won't get in trouble with the cops but people will know) you can tell that the resonator does its job. It has a little low end growl as you move up in rpm (not under load) and when you get above about 1.8k rpm till about 3k rpm there is almost no exhaust noise when cruising. Above that it can be completely down out with the radio at half volume. It is loud but not unbearable over 75mph. Like I said for a form of reference if your radio is at or above the middle marker you won't hear it even at 80.
 

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