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Performance Down pipe with stock Exhaust

35K views 11 replies 7 participants last post by  arcticscythe 
#1 ·
Im not sure how to start this so I guess we can just dive right in. I am interested in the performance boost associated with a stage 2 tune. I am debating between a invidia and a Cobb catted down pipe. Leaning towards Cobb because I have an accessport V3 already and I like already having a tune I can trust until I take it by my tuner, that any something about brand loyalty blah blah blah. Ive done my homework but I've hit a roadblock. Ive searched a handful of forums and youtube for about an hour and im coming up with mixed responses and nothing about sound volume.

I am interested in a new down pipe/Stage 2 tune and keeping a stock exhaust note. I get up at 4am every morning and idle the car until its warm (about 10 minutes) while I mix my pre-workout. I don't want the neighbors to hate me, and I dont want to have to deal with the officer thats post up on our stop sign every day to have any other reason to scrutinize me more. I have looked into daddy SCP exhaust products and their whisper line is the closest I've seen to stock but its still quite a bit more rumble. Honestly Im in love with the boxer rumble but I know my neighbors and most importantly my fiance wont like it while they are trying to sleep at 4am.

All that said. Im looking for either a VERY QUIET turbo back or for experience anyone might have with a Cobb down-pipe and the stock exhaust kit. I cant find a straight answer as to how restrictive the stock catback unit is or how much is being left on the table if I just swap out the down pipe. Im also looking for info about how much louder the stock system would be with a performance down pipe.

//Sidenote// I am slo looking at intercoolers because the stock unit on the 13 has fiber reinforced plastic end tanks. and they are known to be leaky above 18 PSI. Its on my list. I figure I can have my tuner run a conservative tune until I get ahold of an intercooler I like, then eventually injectors, pump and plugs before I settle down...

Thanks in advance guys.
 
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#2 ·
I have ran 2 down pipes. The perrin with divorced bell mouth and the Cobb. The perrin was quieter but made this weird whistling noise when the waste gate opened. The Cobb added a little deepness to my perrin cat back, but over all its not any louder. Im pretty sure you can run the stock cat back with an over sized DP and still get the increased performance from it.
 
#3 ·
Thanks @Epictofer. Thats the kind of info I was looking for I found 1 thread on nasioc that said the stock 2.5 inch pipes were more than enough up to 300-350WHP but nothing noting the change in tone. Im ok with a bit deeper I just don't want to be the *expletive* waking everyone up in the morning.

I welcome a bit more deepness, Ill have to shoot cobb a call as well and see what they say about running the stage 2 tune without a catback ( catback is noted in the map notes)

Thanks again
 
#4 ·
I have an Invidia Bellmouth catless DP to the stock catback and running a cobb stage 2 map for approx a year now. I didn't it being significantly louder when I installed the DP, maybe a bit more rumble and I can hear the turbo more. All the information I read indicated that the catback portion at stage 2 power levels would not be restrictive.
 
#5 ·
I have the catless SRS Tuning TBE and it is a just slightly louder than stock on start up/idle and has great sound when WOT but still not overly loud. And I dont know if it is louder or just a little deeper toned. I live in a house an my 2 neighbor's house are 50ft each side an they say they can't hear my car until I go down the road and that's because I step on it. :)

I was told to watch out for these exhausts but install was about 20 mins and that was taking the old off and installing the new.

Oh and it almost looks like it came stock which is really nice as well!
 
#6 ·
the 02-07 WRX has larger piping. The 08-14 WRX has a peculiar piece of pipe in the front of it's cat-back that is more like 2.25" and is a restriction. Cobb maps specify clearly that their stage 2 for 08+ require replacement of the stock cat-back.

If you want the quietest stage 2 car you can, what you want is to lob off the stock mufflers and attach them to an axleback exhaust system.

If you had an 02-07 I'd tell you to get a borla hush. They're quiet at lower RPMs.
 
#7 ·
Thanks guys, I've got a support ticket out with cobb at the moment and it sounds like everyones had about the same results, add a DP and the volume doesn't change much at idle and low RPM but it has a nice rumble at WOT.

@mosc, about the 2.5/2.25 debate I found the same thing on an exhaust forum somewhere but im pretty sure it also mentioned that the stock CBE is not a point or restriction until 300-350WHP which I'm nowheres near, Thats why I am asking Cobb directly, their map note show * CBE required * but there are a million manufacturers of CBE systems and Im not sure to what degree the restriction of OEM vs any name brand CBE will limit me. On the flip side of that coin I also read that the hatchback has a less restrictive design than the sedan ( no Y pipe for quad tips like the sedan ) so I'm not sure if that is where the 2.25 diameter sits or if its further forward like the mid-pipe.

I might just end up dropping my intercooler money into a Cobb TBE kit and call it a day for now. I can always do the intercooler, plugs, pump, Cobb BPV and a more aggressive tune later.
 
#10 ·
I might just end up dropping my intercooler money into a Cobb TBE kit and call it a day for now. I can always do the intercooler, plugs, pump, Cobb BPV and a more aggressive tune later.
This is an approach that is well-Engineered, and seems consistent with your modest performance improvement path. :)
 
#11 ·
I say pull the trigger on the COBB TBE. I just had mine installed yesterday and I'm extremely happy with sound and performance gains. The exhaust is pretty quiet during idle and not too loud when cruising around in the lower rpms. When you get on it though you'll definitely hear it. Im running the COBB stage2+SF 91 on my V3 until I can get a pro tune. So far everything looks good on the logs.
 
#12 ·
Im making a bit a change to my approach, since starting this thread I have done a considerable amount of research. I ended up with a Torqued Performance E-Tune and Eric has done quite a bit to get me near the top of stage 1 performance ( at least on California 91 octane fuel )

At this point my priorities have changed a bit, We had to pull a bit of timing from the map thanks to a tiny bit of knock learning and feedback knock. For the foreseeable future I want to work on cooling the intake charge rather than trying to increase boost with a TBE. Im leaning more towards Thermal Reflective tapes, turbo wraps and a more efficient intercooler.

When the intake charge is cool enough that we can advance timing again then I might consider a TBE.
 
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