Custom Exhaust Build Questions

[JoeK]

Upcoming on my build is a new exhaust. I’m planning on a simple 2 1/2” dual set up. I’ve got JCI headers, that a have a 2 1/2” collector, that I’ve welded a v-band to, so that’s my starting point. So far I’ve purchased a Summit aluminized universal kit, which looks like it has way more tubing than I’ll ever need. I also have a x-pipe, and a Flowmaster double 2 1/2” inlet, single 3” outlet muffler. The tubing that comes in the kit has flared ends, so where possible I intend to use the slip joint and weld around rather than use clamps. I’ve never built an exhaust, let alone done pie cuts or the like but suspect I’ll need to do some in order keep it tucked up tight. Tools I’ve got, and welding skills are marginal but I’ve got lots of material.

 

Some have said that adding universal cats can cut down on the raspy sound that you hear often on LS motors. These are pretty inexpensive, but I wonder if it truly makes a difference. And are cheap ones maybe even fire hazards.

 

Another thing I don’t see too often is flex pipes. I know CX Racing includes them on their kit, but I think of all the custom exhausts I’ve seen on S30’s maybe only 1 has had flex pipes. Is this no longer considered needed?

 

And also hangers. What are people using? I never see them in pictures. I’m figuring very few are needed. Maybe just some near the diff, and something to carry the weight of the muffler. I bought some hangers on Summit, only end up with hangers with a 1/2” dia. rod that looks strong enoug the hang the whole car from. If any body has any pictures of where they hung their exhaust, and/or what they hung it with, that would be appreciated.

 

Looking for any and all comments and advice people may have. Thanks for your time...

[ben a]

i did single instead of dual Joe i have two friends that have muffler shops and they have taken classes on LS exhaust building. 2.5" single is supposed to be good up to about 450 hp. and i am at 450hp right on the nose. they said the different pipe configurations like x and strait across mainly change sound. the classes they took showed very tiny differences in HP and torque and when the curve peaks. they said they have heard hundreds of opinions but based on the dyno which does not have opinions you can get the same results with most any config as long as you go with the 2.5 diameter pipe. i used the Dirty dingo engine mounts and a strong home made trans mount so there is almost no engine movement so no need for any type of flex pipe.  i did not use cats i put my O2s about 12" downstream from collectors. i made my own hangers. sounds very much like a stock everyday car until you jump on it which makes it even more of a sleeper. 

[socorob]

I put 2 magnaflow high flow cats on mine, and it did cut down on the raspiness/drone and quieted the car slightly. Also lowered how much I smell like fumes after driving around in the car all  day.  Don't get a flowmaster muffler, these drone a lot.

[socorob]

I also added flex pipes at the same time as the cats. 1 after each header, and i where it Ys back into single exhaust by the diff. I wish I would have cut my 3 bolt flange off and welded on V bands to my headers before I installed them. Without the flex pipes, the flange bolts would always loosen up on me. I would have to tighten them up several times a year. The flex pipes seem to have lessened that. I put V bands before the front flex pipes and after the rear one, so I can drop out the whole center section of the exhaust.

[Ironhead]

I have been planning this stage a lot even though I am not there yet...

 

I am using the 525 HP LS3 and as of now am planning to have a "Y" pipe right behind the tranny where the system merges into a single 3" setup.  The way I read exhaust research, there is absolutely no difference to the engine between a single pipe setup vs a dual pipe, as long as the total volume is equivalent, and you use a well designed X,Y, or H section.  I think the vast majority of performance oriented cars have way more exhaust (combined pipe diameter) than the engine requires, just because it looks cool.  If you have been under your Z (which I'm sure you have) you will see that this fashion is not really a good option as there is not a lot of room for exhaust, at least not if you want decent ground clearance.

 

I built a very complex dual mandrel bent exhaust for my prior track car, and the one tool which I found invaluable was a disc sander with a very coarse disc.  You can cut the tubing pretty well with just a hand grinder and a cutoff wheel, but the disc sander is invaluable for facing the tubing joints so that they fit together well and can be welded decently.  This is absolutely imperative if you will be tig welding.

 

I bought this Harbor Freight unit:

 

https://www.harborfreight.com/12-inch-direct-drive-bench-top-disc-sander-43468.html

 

It is very inexpensive and it has been completely up to the task.  Then buy 36 grit sanding discs from McMaster Carr (the ones meant for stainless steel) and you are good to go.  This setup will really dress the ends of the tube quickly.

[Redwine automotive]

,I am using a stock 2008 LS3 and at the exhaust stage now. I will be  running 2.5 into a Jone's Exhaust chambered Y, 3" single with an auger in the pipe and Magnaflow 3 chamber muffler. Should have it done next weekend and will report back.

[JoeK]

Thanks for all the great advice so far. My old school tendencies had me thinking dual all the way back was the way to go, but it looks like I'll be returning some parts to Summit. 

[LLave]

I purchased all my materials but haven't begun fab yet. My plan is dual 2.5 using:

 

JTR/Sanderson headers, long tubes would make more power, but I just don't have much room. 

 

X-pipe (If it fits, if not, h-pipe). 

 

MARMAN FLANGE - from ebay, they are a more forgiving V-band. Sort of like a ball flange meets a V-band.

 

Dual Hooker Max Flow mufflers. Modified, I cut them apart and made them a bit a smaller. I have no idea how they will sound, I imagine a bit louder, but they are fairly quite (see muffler test data below)

 

Speedway motors hangers (https://www.speedwaymotors.com/SS-Exh-Hangers-Weld-On,184894.html)

 

 

I intend on trying to leave space to add cats or a resonator if the car has too much LS rasp. Again, I haven't built anything yet, so I don't REALLY know what I am talking about. I hope to get to it later next month. 

 

 

 

Muffler Test

 

All tests via an independent lab
All tests @ 15” wc

2 “ Straight Pipe 283 CFM
2 ¼ “ Straight Pipe 365 CFM
2 ½ “ Straight Pipe 521 CFM

2 ¼” Typical Bent tailpipe 268 CFM
2 ½” Typical Bent Tailpipe 417 CFM

2 ¼” Inlet/Outlet_ Glass Pack Tips- No Louvers- Smooth 274 CFM
2 ¼” Inlet/Outlet- Glass Pack Tips-Louvered 133 CFM
Same as above set for reverse flow 141 CFM
2 ¼” Cherry Bomb 239 CFM
2 ½” Cherry Bomb 294 CFM

2 ½” Inlet/Outlet Dynomax Super Turbo 278 CFM
2 ½” Inlet/Outlet Ultraflow Bullet 512 CFM
2 ½” Inlet/Outlet Gibson Superflow 267 CFM
2 ½” Inlet/Outlet Flowmaster ( 2 Chamber) 249 CFM
2 ½” Inlet Outlet Flowmaster ( 3 Chamber) 229 CFM
2 ¼” Inlet/Outlet Thrush CVX 260 CFM
2 ½” Inlet/Outlet Maremount Cherry Bomb 298 CFM
2 ½” Inlet/Outlet Hooker Aero Chamber 324 CFM
2 ½” Inlet/Outlet Hooker Max Flow 521 CFM
2 ½” Inlet/Outlet Borla Turbo 373 CFM
2 1/2" Inlet/Outlet Magnaflow 284 CFM


Standard OEM 2 ¼” Inlet/Outlet 138-152 CFM
Standard OEM 2 ½” Inlet/Outlet 161-197 CFM

The madrel bending of the pipes done by aftermarket exhaust companies is good for 2-4 h.p. depending on the severity of the stock bends. Most local exhaust places dont have a mandrel bender so changing the pipes out doesnt do anything if pipe size it not increased.

My opinion, if its more noise and a little more power just add the best flowing stainless muffler to the current system and never do it again. If you increase pipe sizes, then a local shop and only stainless. Dont care about money but want ease and better gains than most local shops can offer with no pipe size increase, and aftermarket exhaust.

NOISE does not mean power, some think it does is why Flowmasters are sold in the numbers they are!!!

 

 

 

Thought I would add this review too.

The results in HP order:
1.Flowtech Warlock (open) 374.2 hp/ 333.1 tq
2.Bassani Real Street 373.7 hp/ 333.8 tq
3.Hooker Maxflow 373.5 hp/ 333 tq
4.Borla XS 373.3 hp/ 332.6 tq
5.Magnaflow 372.8 / 332.5 tq
6.MAC 372.3 hp / 331.5 tq
7.Flowtech Afterburner 372.3 hp/ 330.1 tq
8.Hooker Aerochamber 372.1 hp/ 330.4 tq
9.Bassani 372 hp/ 333.5 tq
10.Spintech 371.6 hp/ 332.2 tq
11.Edelbrock Performer RPM 370.9 hp / 331.3 tq
12.Borla XR1 370 hp/ 334 tq
13.Flowtech Terminator 369.5 hp / 331.3 tq
14.Dynomax Ultra Flo 369.4 / 333.2 tq
15.Flowmaster 369.4 hp / 331.8 tq
16.Flowtech Warlock 366.3 hp / 325.3 tq
17.No muffs 365.2 hp / 330.1 tq

Sound Off in Quietest to Loudest (Decibels):

1.Borla XS, 80db at idle, 90db at 2,000 rpm, 110db at WOT.
2.Hooker Maxflow, 80db at idle, 90db at 2,000 rpm, 120db at WOT.
3.Magnaflow, 82db at idle, 91 at 2,000 rpm, 114db at WOT.
4.Flowmaster, 82db at idle, 93 at 2,000 rpm, 115db at WOT.
5.Flowtech Warlock, 83db at idle, 92 at 2,000 rpm, 112db at WOT.
6.Dynomax UltraFlo, 83db at idle, 94 at 2,000 rpm, 113db at WOT.
7.Borla XR1, 83db at idle, 96db at 2,000 rpm, 118db at WOT.
8.Bassani Street, 83db at idle, 96db at 2,000 rpm, 120db at WOT.
9.Edelbrock RPM, 84db at idle, 93db at 2,000 rpm, 118db at WOT.
10.Bassani Real Street, 84db at idle, 96db at 2,000 rpm, MAX. (120+db).
11.Flowtech Afterburner, 86db at idle, 94db at 2,000 rpm, 115db at WOT.
12.Flowtech Terminator, 86db at idle, 94db at 2,000 rpm, 119db at WOT.
13.Hooker Aerochamber, 87db at idle, 94db at 2,000 rpm, 114db at WOT.
14.SpinTech, 87db at idle, 97db at 2,000 rpm, 116db at WOT.
15.MAC, 87db at idle, 98db at 2,000 rpm, 119db at WOT.
16.No Muffler, 91db at idle, 103db at 2,000 rpm, MAX. (120+db).

http://forums.stangnet.com/archive/index.php/t-392314

[alainburon]

On ‎8‎/‎14‎/‎2018 at 9:03 PM, JoeK said:

Thanks for all the great advice so far. My old school tendencies had me thinking dual all the way back was the way to go, but it looks like I'll be returning some parts to Summit. 

I'm with you man, dual all the way back is the way to go. Don't send your parts back just yet. I had my exhaust built since I don't possess fab skills. The hangers were made to fit as well. X pipe was flow tested to ensure it works properly. I don't have pictures of the hangers but I will try and get you some in the next couple of days.

Edited August 21, 2018 by alainburon

[alainburon]

OK, Sorry for taking so long to get back to you with the hanger pictures but here they are. There are 4 hangers on this exhaust. One behind each muffler and one on each side of the X pipe. The exhaust is solid and doe snot move around but has enough flexibility to move some due to the urethane bushings. 

[260DET]

Can't see the point in a dual exhaust unless it delivers more power which seems questionable,  my LS3 engined circuit race Z31 will roll with a 3" single, less weight and complication.

[alainburon]

I guess it's like most things when building a car. It boils down to personal preference. Personally I think a dual exhaust sounds much better and looks much better than a single exhaust. I know people that love the sound of a single exhaust though. So it's all about what you want. 

 

I don't race my car therefore the extra weight does not bother me at all. For racing it may be a different story though, depending on the type of racing being done. 

[jpndave]

Very nice work on the exhaust.

 

While a single can certainly give the output if sized correctly - especially torque. Duals are what I'll be using, easier to route the smaller pipes and the look as well as sound out the back are more what I want. Trying to get a 3-1/2" (that's the equivalent size to 2-1/2 duals) single pipe down the middle of the car with a T56 Magnum and all the rear components sounds pretty daunting to me. looking at the photos of alainburon's car, I don't see a 3-1/2 pipe going down there without a pretty good clearance compromise.

 

My LS3 (now a cammed 6.8L) runs nicely on dual 2-1/2 into single 3-1/2 and sounds good - in the Jeep as more a truck type application. I'll take the duals in my Z.

[JoeK]

Its feeling like what I'll be doing is a single 3". Since my collectors are 2 1/2", I'll run 2 1/2" pipe to the Y, which will be just shy of the differential. 3" out of the Y, then into a 3" in 3" out muffler. Thinking it'll be the biggest Spintech I can fit in the space where the old muffler sat.  I'm doing away with the front differential cross-member, so can tuck a little higher. The lowest part of the exhaust should be closer to centered on the wheels, which will give me some peace of mind going over speed bumps.

 

Seems like going with a single will be less fab and less parts, while still getting the performance I want. I'm still on the fence regarding the universal cats, but leaning away from them. Its always something I could add in if i felt like it. Spintech also makes hangers that are pretty simple with rubber isolators. I'm hoping I might be able use some of the existing exhaust mount points.