customblackbird

iTrader: (15)

5.3 with a custom cam, porter heads and a billet 78/75 single turbo. 3” down pipe to a 3” eBay electric cutout under the pass seat, 3” catback all the way out the back with a single inlet/outlet borla ProXS muffler and single 3” driver side exit. The car was very quiet and still fast through the full exhaust but it robs at least 2-2.5psi and kills any turbo spool noise bc of back pressure. Opening the cutout sounds great bit it’s too loud all the time, flick the switch and it’s instant 50+rwhp and lots of spool noise. Cruising with the cutout closed through the full exhaust was dead quiet.... too quiet. So I decided to take the plunge with a 4” catback to help bring back some boost and spool noise and provide the growl the car deserves. I tried 4-5 years ago with a home
made 4” catback with the same motor but it had a centri supercharger and No cats (dual 3” to 4” merge) and it was just way to loud on the street at cruising rpms. I attribute the loudness to the supercharger and no cats (think louder than a NA car). A turbo car is quieter all around due to the turbo acting like a muffler. So I hope this setup is quieter than my other 4” setup and will provide the flow needed to make the turbo sing. I still have the cutout incase I want to open it to help with flow even more.

well here we go! Got it yesterday and I got a 7” round x 18” case vibrant 304 straight through perf core muffler with an overall 22” length. The muffler is big but I wanted the largest case I could fit to help with noise given my experience before. Opened the hawks box and found a mufflex over axle part... wow they are just using the mufflex parts, not that I’m upset about it. The catback fit like a glove even with the stock PHB support and has better over axle clearance and ground clearance than my summit 3” catback. I can’t believe they are able to fit the 4” pipe in the stock routing... it’s crazy. Either way I’m super happy with the fitment and the muffler fit with no trimming. I made my own bracket for the tail pipe and fit it up tight to the car to help hide it. Painted it black to help hide it. I also wrapped the muffler bc I had the wrap and I hate chrome or polished anything. If this works out and I don’t hate it I will pull it and creakote the whole exhaust like my hotside.

i haven’t started the car yet but ground clearance is great but my car isn’t stock. I have 18” wheels with DRs on the back and taller tires on the front. 27.7” rear tire and 26.7” front tire. Car has 29.25” rear quarter height and 27.5” front fender height But that car is lowered with weight jacks. I plan to take a video of it running and posting it with a video I took of the 3” catback to compare.

Started it up and shocked by how quiet it still is. Here are some videos. These idle shots are outside in the same spot so the sound should be close (nothing to echo off of)

here is the before video with the borla proXS muffler idling.

here is the after video with the 4” catback


Driving the car down the highway with 4” catback

honestly I took the car out for a drive and the car is much quieter than I thought. It’s louder than the borla 3” but not as loud as I was expecting. I was able to get alittle more turbo spool through the full exhaust but still nothing compared to what the cutout provides. Overall the car is still pretty quiet and I can cruise down the road with the windows down and not hear the exhaust much. Depending on how I feel I can always do a muffler delete or put something smaller in

CKone

iTrader: (2)

Looks beastly 😎

customblackbird

iTrader: (15)

More pics comparing the 3” to the 4”.

customblackbird

iTrader: (15)

yea I forgot how big 4” really is lol.

customblackbird

iTrader: (15)

How I mated my 3” vband flexpipe after my cutout to the 4” intermediate pipe.

honeslty it was a very easy install for me. 1 vband flange, 8” of 3” exhaust pipe and 2 lap joint band clamps (4” and 3”) and it was in. Dented the floor plan a smidge and cut a small piece of the seat belt anchor bracket and it was installed. The pipe end by the axle could have tucked up higher but do to how I had my DP and cutout tucked up so well the 4” pipe was a lot more work to fit just do the DIA and proximity to the floor board (how I had it). Either way I’m happy with the ground clearance and not worse than my 3” catback.

I added some reflective adhesive heat barrier to the gas tank and behind the rear seat.

customblackbird

iTrader: (15)

Videos posted to the 1st post of borla catback
and 4” idling as well as driving.

customblackbird

iTrader: (15)

If anyone is wondering my smaller oval case vibrant randomly shipped 3 weeks early from Jegs and arrive today. It?s a 5x9x15 case with 20? tota
length however it?s really 5.5?x9?x15? and a 19?
overall length. The way I fabbed the exhaust it fits the 22? long 7? DIA round muffler better after test fitting tonight. The smaller vibrant is a direct swap for the Hawks muffler delete pipe (same 19? length) and it?s a good bit cheaper than the maggy. The 7? round only hangs .75? lower than the oval so im fine with that and its not lower than my rear. I did not like how much gap is above the oval muffler than the heat shield... almost wished I could tuck the over axle pipe up higher and if I could then I would run the oval smaller muffler. I def picked up power over the 3? catback and got alittle more turbo whine but still
nothing compared to the cutout being open. got nothing bad to say with this hawks/mufflex catback, lots of ground clearance and great fitment.

anesthes

iTrader: (12)

So I started thinking about exhaust after our conversation the other day, and I ordered a bunch of 3.5", enough to build the downpipe and do an over axle 3.5".

Now, I've got two problems one I don't really like loud and two I like the symmetry of dual exits.

So I've got a 3.5- 2x2.5 merge pipe. I'm thinking of going 3.5" over the axle and then transitioning to a pair of 2.5" mufflers, kind of like the hooker setup:


I realize that the spare tire area might need some trimming but, I was thinking I could probably fit either up to a 7" round muffler.

Magnaflow makes an 18x6 with a 24" total length MPE-12646

https://www.summitracing.com/parts/mpe-12646

So I was thinking a pair of these would both flow well and likely quiet down the car vs a single 3.5.

There is some questions as to tailpipe length, which would effectively be non existent. I've always been told having more tailpipe quiets down the high noises and keeps the lower notes, although honestly the LT1 mufflers on my C4 sounds pretty amazing and they have no tail pipes:



I have a set of these, they are oval 15x9x7 case so likely wouldn't fit without removing some of the trunk which is probably not worth it, but they manage to sound good but not overly loud. I wonder how much the design of the tail pipe / tip impacts the sound?

-- Joe

customblackbird

iTrader: (15)

No one makes a fbody specific 3.5" inlet and dual 2.5 or 3" outlet muffler? I've done dual muffler configs in this car with 4" by running a afterburner in the stock location (single 4' in/out) and then a 90 into a dynomax ultra 18" and then a turn down (not a dual exit tho). That really quieted down a blown 5.3. If you could run a round perf core muffler in the stock cat area/tunnel and then into a factory style dual exit that would prob be your best option. Do one of these and add a muffler up front - https://mufflex-performance.com/1982...lowmaster.html

I also think the dual 2.5" is probably going to hurt flow at the 650hp level... your in dual 3" territory and single 4". I bet that mufflex kit linked above and an added muffler would be fantastic. You could also add in some resonators where the tailpipes are and they are small enough to fit in the stock frame locations and would help cut down added noise. You can make the tailpipes pretty easily with 90* and a resonator and a tip of your choice. That would allow max clearance under the car and up front. I wouldn't bother with a 3.5" catback since the 4" fits so d@mn good with the factory frame/suspension parts.

Any time I've tried to do dual mufflers (dual 3" with mufflers under the rear seats) under the car (mid system) vs the stock location I didn't notice any big changes in sound on this car same motor combo. Another option for you could be a Speed engineering dual 3" system and then you can put your muffler choice in there location if you wanted more sound reduction.

anesthes

iTrader: (12)

My buddy has the 4" mufflex setup on his car and it's absolutely obnoxious. I was thinking of oval muffler in the "cat area" but the problem is my BMR suframe connectors won't allow me to run the downpipe in the traditional thirdgen routing. So I need to run it down beside the transmission.

I'd be open to using a 4" catback or mufflex back pipe if one was available local and cost effective, but when I looked them up online the price was outrageous. I was able to buy a bunch of stainless 304 bends and straight pipe for like $110 shipped, and I figured the 3.5" is way better than the 3" hooker aero chamber catback I was going to use.

I figured the dual 2.5 mufflers would be fine because they are the same flow as a single 3.5".

There is a lot of theory in splitting the exhaust into two mufflers vs one for noise reduction, although I also think a big old oval muffler in the cat area could be helpful too. I just don't want to modify the subframe connectors.

anesthes

iTrader: (12)

So I thought this over a bit more, and I think I'm going to cut the BMR subframe connectors out after all. I didn't realize southside machine is back in business, looks like someone re-opened with the same designs. I ordered a pair of their subframe connectors. This will let me route the downpipe in the stock location, and then I can put a race muffler where the cat's would normally be.

I have a pair of SLP powerflo mufflers. I'll probably run the 3.5" all the way to the back and then just split into the two 2.5" exits. The mufflers are fat case through design.


Basically, I'm doing the SLP "loud mouth" style exhaust, with their SS mufflers, in 3.5".

customblackbird

iTrader: (15)

Sounds good. I turbo car will sound much quieter than a NA car.