Helix Downpipe mated with Borla Hush Catback

[sonicblue]

Just finished putting this setup on my 2002 WRX wagon. Supa' props to Murray and Roamin' Coyote for lots of help (heck, wYlie did the whole catback!). This post will lay out my impressions of the hardware, install and results. BTW, I already have a Helix uppipe.

HARDWARE:
The Helix is a great-looking pipe. A bellmouth design which removes both post-turbo cats, it has solid flanges, clean welds and nice bends. This one is the V2 which, as I understand, just relocated the mounting bracket. I had new gaskets and DP/CB bolts from Gruppe-S as well as a CEL fix for the O2 sensor.

The Borla Hush catback is interesting. It comes in three pieces: the axleback/muffler, the resonator pipe and a third small adapter piece with the flange for the downpipe connection. The three pieces slip-fit together and tighten up with C-clamps.

INSTALL:
Lots of people were having fitment issues with the Helix downpipe, some specifically with the Borla Hush.

EDIT: It's been established that the Hush is designed specifically to fit the beveled/donut design of the stock 3rd cat pipe. Further, the slightly upward tilt of the Helix was present on my DP as well. Put these two together == leak. The Hush end is just a hair smaller than the DP opening. When they meet at that "off" angle, the lower edge fits inside the DP but the top edge won't meet at all. My local Midas came up with the following solution: they found a thick gasket - about 1" maybe - sort of shaped like a "D." The outer diameter is probably 4" at its widest. The flat side went up against the DP. On the beveled side, he actually made the opening wider so the ball/bulb end of the Hush fit inside. It's almost like forming a ball and socket joint. Further, enough of the Hush end fits inside to give it flexibility in its angle, so it can correct for the angle at the DP. The only other mod required was some longer bolts to connect it up. Total cost = $30. Unfortunately, I can't tell you what kind of gasket it was, he just happened to find one randomly lying around.

Also, my muffler has wiggled out of center and I can't get it back. As much as the slip fit joints give you flexibility to get good clearance all around, you can only do so much and still get it lined up to the DP and get on the hangers. The muffler is still more or less pointed straight out - it's not pointed to 7 o'clock or anything - but it's not in the center of my cutout. With my gasket fix up front now, I may get back under there later and try again.

The only hiccup was these saw-tooth retainer rings that (we assume) are meant to slide over the hanger post after the hanger, like this:

[M]---U--|--

The "[M]" is the muffler, the "-"'s are the hanger post, the "U" is the stock hanger and the "|" is the ring. They were VERY hard to get on but once they were, you could tell that they would prevent any side-to-side movement along the hanger. Time will tell if mine is held steady enough to not bang anything.

My DP did not appear to have the upward tilt that others have said they have. It bolted up the turbo fine and cranked down without issue. No CEL but I've heard that may take time to surface even if the CEL fix doesn't work. Sorry I can't offer more to the people who have had problems - my downpipe was a no-brainer.

RESULTS:
I love it, I love it, I love it, I love it. At startup, there's a medium-to-low tone that's smooth with a slight rumble. Not really "louder" than stock but the tone is noticeably different. Unfortunately, I was not able to take my sound clips of the stock sound to splice into my "after" clips but I will post the after clips tomorrow. I would describe it as 2 ticks deeper and 1 tick louder than stock at idle. Also, the stealthy appearance of the twin-tip is great. Though each tip is bigger than the stock tips, the rolled edges and good fit (not low or angled) are very subdued.

Cruising on the road, any Scooby owner would have no doubt you've changed out! Again, it's more tone than volume and I would describe the difference again as 2 ticks deeper, 1 tick louder. You can hear even minor spool of the turbo and your stock bypass valve is very audible (especially if you don't crank down the screws - ZING!).

At WOT the exhaust makes its presence known. The tone seems to get even deeper and it does growl just a little louder. On the same scale, I would now say it's 3 ticks deeper, 2 ticks louder. It does not roar but the fact that it's 3" is only able to hide for so long.

My bottom line is, this is exactly what I've been looking for. I want the performance capabilities that a 3" catless TBE allows without any unnecessary attention. Brand new, this combo can be had for less than $800, so it's a great value to boot.

EDIT: added notes about catback->DP joint fitment

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[sonicblue]

Just took a little cruise today. There is definitely more low-end torque. I intentionally let myself fall to sub-2K rpms in 2nd and 3rd gear, and I actually felt pull when I hit the gas.

[Rancid]

Great review! Sounds like a great combo...Now if only I could get that refund check a little sooner...

[Lobbyist]

Requesting pics and sound clips!

[sonicblue]

coming, but I need a co-pilot to hold the cam for the ride!

[Trip McNealy]

dude, that's awesome.. i'm going for the same DP/CB setup come summer!

you said you got new gaskets & bolts from gruppe-s.. same place for the dp and cb system? or you order from somewhere else?

[MikeWRX-NJ]

did you take any messurements of the catback? I've been hearing that it bottlenecks to 2.5'' at the downpipe->midpipe... thought my info could be wrong.

[sonicblue]

Originally posted by Trip McNealy
you said you got new gaskets & bolts from gruppe-s.. same place for the dp and cb system? or you order from somewhere else?

I got my DP slightly used from another member here and the Borla from Kym at Aerosim Resarch (vendor here). The guy who sold me the DP didn't have the hardware, that's why I went to Gruppe-S ('cuz I knew they sold the DP's new).

Originally posted by MikeWRX-NJ
did you take any messurements of the catback? I've been hearing that it bottlenecks to 2.5'' at the downpipe->midpipe... thought my info could be wrong.

The catback has NO tapers at all - seems to be a common myth, don't know why. This combo yields a full 3" system.

[MikeWRX-NJ]

you have no idea how happy that makes me.

[jcwrx]

I am looking to do a Perrin DP and Borla hush with a high flow cat replacing the OEM cat.

Glad to hear you like the sound quality of the system. Do you have any issues with droning while on the highway? I know the wagon seems to have a more audible exhaust not do to the open end construction, and I have really been listening for a system that gives me a little more "tone" with out a lot more volume/decibles in the end. Your comments are appreciated.

JC

[sonicblue]

I actually did a highway drive yesterday. Ur right JC - the wagon suffers from the open cargo area, so I don't want to penalize the Borla for that.

I did notice that when cruising on the highway - i.e., you're just giving it enough gas to maintain your speed - it's still rather easy on the ears. Cruising at around 70mph on fairly smooth roads, the exhaust was just another sound you heard along with the wind and road noise. When I hit a stretch of road paved a little rougher, the road noise was above that of the exhaust.

When accelerating on the highway, the exhaust quickly comes to life. If I was going 65 in 5th gear and wanted to accelerate even mildly, wind and road noise were quickly overcome. Not "Harley-in-my-back-seat" loud by any means, nor would you have to raise your voice to have a conversation with a passenger, but it is unmistakably louder/deeper than stock at that point.

The bottom line is, from inside the car, I will never forget that my stock exhaust is gone (remember, I'm also totally catless at this point). Occasionally on my commute, I would run it to 5K RPM on little stretches just for a quick pull - I will probably look around just a little harder for po-po before I do that now, just in case, but I won't worry about waking neighbors when I do it.

[AlboWRX]

The catback has NO tapers at all - seems to be a common myth, don't know why. This combo yields a full 3" system. [/b][/quote] Its not a myth,look closely.When I installed my Hush I saw it right at the flange where it connects with cat.

[sonicblue]

The pipe has a tiny, tiny taper just because of the slip-fit connection, but I don't think it shrinks a whole 1/2"

[CirrusWRX]

off to the review forums with you!!!!

congrats and sounds like you're having fun!

[jcwrx]

I figured it not to be stock sounding, but from you post here it sound like the system is just what I am looking for. I will be running one high flow cat in the system too, so that should decrease volume just ever so slightly. Thanks again. I can't wait to put my system together.

JC

Originally posted by sonicblue
I actually did a highway drive yesterday. Ur right JC - the wagon suffers from the open cargo area, so I don't want to penalize the Borla for that.

I did notice that when cruising on the highway - i.e., you're just giving it enough gas to maintain your speed - it's still rather easy on the ears. Cruising at around 70mph on fairly smooth roads, the exhaust was just another sound you heard along with the wind and road noise. When I hit a stretch of road paved a little rougher, the road noise was above that of the exhaust.

When accelerating on the highway, the exhaust quickly comes to life. If I was going 65 in 5th gear and wanted to accelerate even mildly, wind and road noise were quickly overcome. Not "Harley-in-my-back-seat" loud by any means, nor would you have to raise your voice to have a conversation with a passenger, but it is unmistakably louder/deeper than stock at that point.

The bottom line is, from inside the car, I will never forget that my stock exhaust is gone (remember, I'm also totally catless at this point). Occasionally on my commute, I would run it to 5K RPM on little stretches just for a quick pull - I will probably look around just a little harder for po-po before I do that now, just in case, but I won't worry about waking neighbors when I do it.

[Takashi]

so where's the problem with the dp mating to the cb? it seemed like everyone was having problems with that...???

greg

oh, great review too btw!

[sonicblue]

Originally posted by Takashi
so where's the problem with the dp mating to the cb? it seemed like everyone was having problems with that...???

greg

oh, great review too btw!

:shrug: Roamin' Coyote was under my car hookin' that part up. I told him what I had heard, that some people had trouble and some didn't. All he said was, "looks like you got a good one." Not to perpetuate a possible myth about "good batches" and "bad batches," but mine definitely wasn't "bad."

[AlboWRX]

Originally posted by sonicblue
The pipe has a tiny, tiny taper just because of the slip-fit connection, but I don't think it shrinks a whole 1/2"

It doesnt look like half inch cause is too small to tell cause you got 1/4" on each side ,thats y u cant tell

[RayQuon]

So the flanges on the helix downpipe and the catback fit with no problems?...I thought there was an inherent problem since the catback is rounded to fit the stock midpipe, but the helix downpipe has a flat flange...I was under the impression that a flat flange replacement was necessary for the borla hush to properly fit with the helix dp.

here is a discussion about it from the i-club forums:

http://www.i-club.com/forums/showthr...threadid=45197

please let us know if you ran into the same complications.

[sonicblue]

OK, I'm about to get back under the car in about an hour. My muffler walked off-center and I'm getting a rattle. I will take pics of all joints/flanges/connections. Also, if I find a clearance issue down there that's causing my problem, I'll try to get pics of that, too.

We'll settle this once and for all

[aznfoos]

the ball flange slips into the resonator pipe and comes down a bit, but not by 1/2". Anyway, I dont' think it makes a big diff in your power unless you are heavily modded.

I installed mine last week, just teh cat back, and it is FAR from stock. Low grumble that sounds mean on throttle. Love it!

[sonicblue]

well, no pics taken 'cuz I was too frustrated. AFA tapers, it actually looks like the 3" tapers OUT to accept the slip-fit connection, thereby maintaining the 3" inner diameter.

But, I discovered that I do have the "misfit" at the DP/CB connection. However, I do NOT think I have a leak, so I guess the guy who has helping figured no leak, no problem - I wholeheartedly agree, I'm just concerned about the long-term results (i.e., will the connection hold up over time and continue not to leak?). I will probably investigate having a muffler shop fabricate a new piece with flat flange (and at proper angle to meet the DP correctly) to replace that small slip-fit section with ball flange.

[sonicblue]

edit for some recent developments

[jcwrx]

sonic,

Please post a sound clip of this system.

I just figured out that the Perrin DP deletes both DP & midpipe cats, so I am now in debate of going full Stromung TBE of going Stromung DP----OEM cat-----Borla Hush. Your sound clip with help me in my decision making process.

JC

[sonicblue]

as soon as my wife tracks down our Firewire cable, I'll post something. PM me and harass me if I take too long