Originally Posted by 6Speeder

Seeing as the car already has an x pipe, has anyone just cut off the second cats and replaced with a small section of exhaust pipe? Seems like it'd do the same thing at a LOT less money.

Originally Posted by neilvosko

why not just remove the stock cats ?

Originally Posted by Kracka

After reading a thread on here about adding an aftermarket X-pipe to an otherwise stock exhasut system (https://www.corvetteforum.com/forums...stock-npp.html) I decided to start looking into it further. There aren't many options on the market yet, but I picked up what is currently the most popular (Corsa Double Helixx) plus another that I think will also prove effective and popular (Borla part #60547) to compare them side-by-side with the stock X-pipe and ultimately decide which, if any, to install on my car (2014 Z51 w/NPP). Until now, my exhaust system was 100% stock. Due to a past history of going overboard on modding my street vehicles, when I ordered this car last winter I promised myself I'd take it slow and only add modifications that don't have any drawbacks to drivability and livability, plus remain somewhat emissions and hopefully warranty friendly. It's not my DD car, but I do take it on quite a few roadtrips, dinner on the weekends, etc. in addition to performance driving orientated events

Stock exhaust specs
-catted downpipes: 3.0" outlets
-X-pipe: 3.0" inlets w/3" cats*, reduces to 2.75" immediately post-cats, single 2.75" X-crossover, expands to 2.875" at the outlets to slip over the axle-back pipes
-NPP axle-back: 2.75" inlets

The stock X-pipe weighs in at 22.6 lbs, which includes the clamps (welded on) so for comparison sake I'll subtract 1 lb. and call the stock X-pipe to be an equivalent of 21.6 lbs.

*The factory X-pipe cats are not monitored so they can be removed without throwing any check engine lights or error codes.

Borla X-pipe specs
-3.0" inlets, smooth taper to 2.75" after the inlet flange
-2.75" piping with the exception of the in/outlets
-single 2.75" X-crossover
-explands to 2.875" at the outlet to slip over the factory axle-back.
-15.8 lbs for a savings of 5.8 lbs vs. stock

Corsa Double Helixx X-pipe specs
-3.0" inlet
-3.0" piping
-two 3.0" X-crossovers
-3.0" outlet (I noticed that this has to basically be crushed to securely clamp over the stock axle-back pipes, not ideal in my opinion as it seems prone to leaks and internal turbulence)
-19.6 lbs for a savings of 2.0 lbs vs. stock (Corsa claims a 2 lbs weight savings so my measurements confirm this)

Corsa (top) vs. Borla (bottom):


Borla (top) vs. Corsa (bottom):


Stock/Borla/Corsa:


Corsa/Borla/stock:



Stock impressions
For factory exhaust piping, it is very nice in design with decent welds, bends, and transitions. If it wasn't for the cats, I'd probably say it wouldn't be worth the bother to replace unless you wanted to be very particular about some of the bends having a slight crush to them.

Borla impressions
This is a very nice pipe, I feel this is what the stock pipe could have been like if manufacturing costs weren't a concern as it has smoother bends than the factory pipe with no crush to them at all. It is similar in design to stock and follows the stock pipe routing almost exactly. One benefit to that is how it looks nearly factory once installed and partially hidden by the stock tunnel brace. Unless a trained eye knows exactly what they're looking for, I can see this pipe flying under the radar when it comes to warranty claims.

Corsa impressions
This pipe is a beast, it's large and heavy, but seemingly designed for excellent flow (Corsa claims +20% compared to stock). This pipe has the fewest and smoothest bends of the three so that is a plus in my book. The double X does change the tone of the exhaust; some say it makes the car sound more exotic or European vs. the throaty rumble of an American V8. I do wonder if it adds unneeded internal turbulence though? This pipe seems to be the most popular on the market right now, but my guess is that's because it was the first one to become widely available and the fact it's straight 3.0" in design.

My conclusion
I decided to keep the Borla X-pipe on my car. I like the design of it, the weight savings, and it's somewhat stock appearance. Considering the NPP axle-back is also 2.75" in diameter I do not feel I'm giving anything up in regards to the Borla 2.75" vs. Corsa 3.0", but that is just my somewhat experienced guess. The exhaust tone sounds similar to stock, just a bit louder and sharper with the removal of two catalytic converters. They all install very easily with simple hand tools, 1 jack, and 1 jackstand. I'd suggest a 3/8" drive ratchet with an extension or two, sockets in the 13-18mm range, a 15mm wrench (ratcheting if you have it to speed things up), a flat head screwdriver for prying off the gaskets and rubber hangar, and a hammer to pound the gaskets on to the new pipe. You can just jack up one side of the car; I jacked up from the passenger side rear point (just in front of the rear wheel) and put the stand under the passenger side front point (just behind the front wheel).

Originally Posted by Kracka

That would work fine if you have access to the tubing (would need a slight bend or angle cuts), saw, and a welder. For the rest of us DIY in the garage guys, a simple bolt-on part makes more sense.

Here is my review of the stock vs. Borla vs. Corsa X-pipes, which includes side-by-side pictures and data:
https://www.corvetteforum.com/forums...-vs-corsa.html

Originally Posted by nolove10s

Do aftermarket x-pipes void the warentee? Sorry for the dumb question, I have never owned a car under warentee before.

Originally Posted by Kayir

that clip was literally the FIRST startup after installation. I have an AFE intake and a stock exhaust otherwise so that's it. The sound has "broken in" since installation and while that first one was probably the loudest, it still sounds as amazing as that day. . .deep, gurgly, mean. . .the guys I drive with who have some insane cars (911s, 458, v10 R8) have desbribed the sound as "perfect" and I couldn't argue too much.