2.5 mandrel stainless, X pipe, V band clamps in the middle, Borla Pro XS. I'm not much of a welder, or fabricator, so please don't point out the obvious thing I screwed up.

The mufflers and tips are all oriented correctly though, looks off in the pic but they are straight IRL. That was a giant pita with the one hanger on the end and two angles and rotation to get right. Someone that has more experience with such or that was less picky than I am would likely have a much easier time of it. I've done a handful of exhausts like this but none of them ever needed so much packaging and fiddling with to have them look right from the outside. I'm not in love with the visible muffler bit but unless you can offset your tips like the factory did and recess the muffler up in the quarters you're pretty well stuck with this. I see a lot of pre-built aftermarket systems are this way too. It's kinda growing on me, I matched the mounting angle of the mufflers to the rear quarter lower body line and they only sorta peek out. I used clamp on tips so they would be fully adjustable rotationally and for/aft. I hate tips that don't line up right.


It sounds.. Okay. It's louder than the Corvette Central "no drone" stock replacements byu far which had one crooked tip that drove me nuts and did in fact have a drone between 12 and 1600rpm or so. The Borla are DEEP, like bass deep, at idle and you can really hear that distinctly from the rear of the car, all the time. There isn't really any drone to speak of unless you go out of your way to lug it (manual), but that bass note is always there. It's not crazy bad, normal radio volume works, can still conversate, etc. It sounds pretty interesting when hard on the throttle, I suspect it's a lot louder outside than in. There was a noticeable uptick in performance vs a stock system with no cats. Not 20hp or anything crazy, but it feels a little more lively on roads I know how the car behaves on. For the money, not bad. I wish there was a little more cool noise on deceleration (manual) but overall it's a pretty good mild non-stock exhaust. I suspect it would perk up with a less weak motor attached to it.

 

I think it looks good, nice job.

 

nice job!

 

Nice, and nice shop. 👍👍

 

I think you did I fine job, it looks right. You are certainly a better welder than I am.

 

Looks great! I considered going with 90s to go out to the sides, probably would have made it a lot easier than the 45s I used lol.

 

Drove around a bit more yesterday evening.
I could really do with less bass out of it if I'm honest.
I'm still not sure it's drone in the traditional sense but it's a little
more than I'd prefer. Does make cool noises on the throttle over
2500rpm or so, and the idle is pretty good. I'm going to drive it
for a few weeks before I decide anything.

 

Yeah, I pondered that too. I had the stuff to do 45's originally but the advantage of 90's with a slip joint in the short section was one could more the forward part
of the muffler laterally and rotate them and tilt the for end up and down to get all the alignments right a bit easier than with 45's. If I were better at this I'd have done
45's. I still managed to screw it up once I had it all in place and ready to tack up, think I bumped something with my welding hood and didn't notice lol... ugh...

Those little pre cut shorty 90's and 45's you can buy now are life savers btw for anyone attempting this, I think I only used one full length 45 cut to size and the two 90's for the down
pipes, and in retrospect those could have been 45's or short cut 90's too but it didn't occur to me till after the fact.

Also, the flange and stubs I bought off ebay that were made by some US muffler shop were well made but while the pipe was correct to mate to the factory manifolds the flanges bolt spacing
was too tight. I don't know if these are just oddballs amongst GM's stuff or I just didn't find the right ones, even after measuring and looking I didn't see any.

All in all if I had to do it again I'd pay $1500 for a pre-built system that actually fit right, if such a thing exists. Still wouldn't pay Corsa what they want for theirs.

 

wow, nice job! wondering if it would it be worthwhile to have the car tuned for this mod? any changes to the air filtering to gain as much as you can?

 

Good job 👍

 

Don't know, car came to me with no cats and a really crappy muffler delete that was probably 30 years old.
It's stock other than the air pump delete. Motors a bit tired at 160K but runs well enough.

 

Whelp, after driving around the weekend a bit, this thing still needs something.
It's pretty good on moderate or more acceleration and idle is alright but the everything else is
pretty meh. I suspect these things need something between the muffler and motor, cats, resonators,
something. The very end of the exhaust is about the worse place to try to put a muffler to start with
in my experience, and the relatively large tube size is giving the exhaust pulses a lot of room to bounce
around and do all manner of things that aren't strictly pleasing. Is my theory anyway.

I have very limited room in the two parallel pipes to the rear (dictated by the spacing of the X pipe outlet and the available space
between the exh and the C beam and the ground) to add in resonators (which seems to be another
word for glasspack?). Gotta get it on the lift and do some measuring, I don't know that I have it in me to blow the whole
damn thing apart and do it all over again.

I could put the corvette central mufflers back on and pipe them into the rest of the new exhaust (after fixing the one stupid
tip they welded on wrong) but there's no telling if it'd be worse than it was or not. I also kinda like the larger dual tips now that
I've seen them on the car. I do appreciate the additional flow
and it's a tangible difference after driving on some more roads I know how the car behaves on.

Take this audio with a grain of salt, it is apparently not at all easy to get good recordings of exhaust.
Best heard with decent headphones.
Interior 2nd/3rd, it's louder in person but not crazy. https://recorder.google.com/9b8cba3e...6-5f47fd3df155

Hot idle, close to the tips: https://recorder.google.com/67ade09f...a-cbb56879e0ce

8' center rear mic idle rev https://recorder.google.com/a994fff9...4-7484b8f5b339

 

I fixed the vast majority of the odd noises with DEI thermal wrap. There was more oddball sound radiating out of the head pipe than I even though. All I hear now is
muffler and it's if a little bassy, pretty damned good. As a side benefit the lowering of cabin temps is really surprising. My right foot did not feel like it was about to melt after
a long drive. Will continue to evaluate but this seems to have been very worthwhile.

 

The DEI wrap does work, and all things considered it is a good investment. I have used it several times over the years, as well as one of the knock offs and the one thing I will suggest is to coat it with the DEI High Temp Silicone Spray. I will help it to last longer and perform a little better.

I am in the process of finishing up my exhaust work and discovered I will have to replace my stock cat back. I have the Borla ProXS on my short list, hearing your experience is helpful. Have you considered a couple high flow bullet cats right after the X-Pipe?

 

I considered either bullet cats or resonators and I'm pretty sure that would be a positive addition but I thought I'd try it with just the wrap first.
If I was doing it over again, I'd add cats or resonators. It's funny it's not resonance like the previous mufflers had in a low rpm/high load RPM,
but rather just they are so DEEP all the time other than on moderate to heavy throttle where they sound pretty good.
I've got to drive it some more and ponder a bit, it was pretty enjoyable this afternoon though. Way, way better than it was. I was hopeful
but am honestly shocked at the difference. When I had it running on the lift you could still hear at idle some ting'ing in the un-wrapped
parallel sections of pipe but it wasn't apparent from in the cabin like it was before. I guess one could wrap the whole length of the exhaust
but some resonators or such are probably a better solution. The only snag with putting them in that parallel pair of pipe is the spacing on the
X pipe I bought would have anything with a 4" external diameter basically touching each other. That isn't insurmountable but it's a thing, if one could
find an X pipe with a wider spacing it would be good. There are 3.5" diameter resonators and such but they aren't nearly as common, or cheap, as 4"
that I can tell.

 

I still prefer to run a cat, even though we have no emissions testing in my county, I do run the car in the shop and it does help to keep the fumes down somewhat. That isn't important to everyone but it also does help attenuate the sound a little as well. Fitting them in your situation will require more work, or you can leave it as is and see if you get used to it. I don't know about adding in resonators, from my limited understanding to be truly effective they need to be larger than the space allotted, look at the LT1 resonator, it is huge. Some say the smaller ones help with rasp but I suspect it is dependent on the rest of the system. Exhaust is fun, always has been.

I do like the sound of that Borla, which is a surprise, I remember them being more obnoxious than deep sounding. I looked on their site to see how it was constructed but they showed no graphic, so I could not see if it was overly baffled or not.

 

They are a straight through perforated pipe design like many others. Pretty small but there isn't a lot of room back there unless you angle the mufflers or can recreate the little offset from outlet to tip that the factory mufflers have. Lot of the aftermarket systems have the mufflers mounted lower and visable like I did with these. I wasn't crazy about the look but it's grown on me. They deff need to be stainless or paint them black imo. I'm still not positive what people call rasp, but I don't hear anything I'd call that at all with these. Just deep deep it idle and cruise and really throaty and pleasant under throttle. The audio I recorded does not do them justice. More work than I'm up for but it would be really interesting to hear some chambered mufflers on this same setup. I think exhausts are probably such a sum of the whole system that comparing just mufflers from one setup to another is iffy at best.

 

I figured what the hell and throw a couple cheap 12" "resonators" in there.

So the good news is it's a lot quieter, the bad news it's a lot quieter.

I'm fairly shocked how much difference these little things made really.
They completely removed the "boom" above 1500rpm, which works out okay with a stick since I can cruise at 55 or so in 5th quietly now.
Even below it's quite reduced. I'd say across the board it's 25% quieter or a bit more. Which is a bummer when I want to
stomp on it and be a hooligan and make noise. It has the same exhaust note which is pleasing and certainly
more than stock but it's not nearly as fun sounding, much reduced and refined.
I'll probably leave it be, it's more reasonable for a driver but the 18 year old that's withering away inside me really did like the noises it made before.
Idle isn't effected a ton, still very deep. I imagine with a better cam and some more compression the whole thing would sound much better.