How to Build an Inexpensive, Quiet Exhaust That Doesn’t Cost Horsepower

Andy
By Andy Hollis
Oct 2, 2021 | Exhaust | Posted in Shop Work , Product Reviews , Exhaust | From the Dec. 2010 issue | Never miss an article

Quiet. Powerful. Inexpensive.

Pick two of the three above qualities, and that pretty much sums up the choices most of us face when designing an exhaust system. Traditionally, it’s been impossible to tick all the boxes.

That pleasant-sounding, budget-priced street muffler is most l…

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MrFancypants
MrFancypants Reader
8/12/20 10:15 a.m.

I'm guessing that noise would go down if the SCCA required all cars running internal combustion engines be equipped with catalytic converters.

spacecadet (Forum Supporter)
spacecadet (Forum Supporter) GRM+ Memberand SuperDork
8/12/20 10:44 a.m.

In reply to MrFancypants :

in fact it wouldn't... this car was built for a class that required catalytic converters back then, and still requires catalytic converters to this day.

 

MrFancypants
MrFancypants Reader
8/12/20 10:50 a.m.
spacecadet (Forum Supporter) said:

In reply to MrFancypants :

in fact it wouldn't... this car was built for a class that required catalytic converters back then, and still requires catalytic converters to this day.

 

I said "all" cars, not "this" car. Noise at events would go down if all the straight piped cars had catalytic converters. Maybe it still wouldn't be enough, but it would be an improvement.

John geyer
John geyer New Reader
8/12/20 5:46 p.m.

No science just 40 years experience on Brits and VDubs(water cooled). Header, no cat, 2 inch piper, a 24 in glass pack and a 12 in Thrush muffler. All the flow and street level burble.

bobzilla
bobzilla MegaDork
8/12/20 5:54 p.m.
MrFancypants said:
spacecadet (Forum Supporter) said:

In reply to MrFancypants :

in fact it wouldn't... this car was built for a class that required catalytic converters back then, and still requires catalytic converters to this day.

 

I said "all" cars, not "this" car. Noise at events would go down if all the straight piped cars had catalytic converters. Maybe it still wouldn't be enough, but it would be an improvement.

Not really. Some of the loudest vehicles I've heard were with multiple catalysts. I don't know where you're trying to take this but it's not working out. 

frenchyd
frenchyd PowerDork
8/12/20 6:38 p.m.

In reply to MrFancypants :

I met the 93 DB at 50 feet with no mufflers at all.  The trick is larger diameter tailpipe. (Stock 2 inch switched to 2&1/2 inch )  then aim the turn downs (4 ) to 1/2 way between exhausts at the ground. The concept was that the multiple tailpipes canceled the noise along with turbulence underneath dispersed  noise reflecting off the ground and the chassis before it tumbled out.  And wandered over to the DB meter. 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
8/12/20 6:57 p.m.
MrFancypants said:

I'm guessing that noise would go down if the SCCA required all cars running internal combustion engines be equipped with catalytic converters.

Modern converters are worthless as mufflers.  Very free flowing, no baffle or absorption effect to damp out sound pulses.

 

Now, the bad old pellet-bed converters that gave converters a bad name... Those ones will quiet an engine right down.

NorseDave
NorseDave Reader
8/12/20 9:06 p.m.

It's a bit of an annoying article to try and navigate on this website, but I found this article to be pretty informative:

http://www.superchevy.com/how-to/exhaust/0505phr-exh/

I spent a while a few years ago turning it into a readable PDF so if anyone wants a copy shoot me a msg. 

jwagner (Forum Supporter)
jwagner (Forum Supporter) Reader
8/12/20 9:52 p.m.

Good article, and relevant to one of my next upgrades on my Mazda3, but I'm not sure that the two stage Burns, which starts at $574, is inexpensive exactly. 

Vracer111
Vracer111 HalfDork
8/13/20 4:29 a.m.

I really like the 2-stage Burn's quiet muffler over the Burn's race muffler in a custom center exit exhaust I made for my FR-S. Noticeable difference in loudness and much deeper, throatier, and smoother sound compared to the more buzzy and raspy race muffler. It's about double the price though... really would like to put one on the MR2 project. I still used hearing protection (Etymotic earplugs designed to still keep sound fidelity) when driving it though... still louder than most off the shelf catbacks.

 

If you want to somewhat hear the difference:

Here's it with the 17" length, 2.5" in/out, and 3.5" body, Burn's race muffler  https://youtu.be/IUDk_0bZrFs

And here's it with the 17" length 2.5" in/out, and 4.5" body 2-stage muffler (go to 50 seconds in) https://youtu.be/61BeAJ4dI4k

MrFancypants
MrFancypants Reader
8/13/20 8:48 a.m.
bobzilla said:
MrFancypants said:
spacecadet (Forum Supporter) said:

In reply to MrFancypants :

in fact it wouldn't... this car was built for a class that required catalytic converters back then, and still requires catalytic converters to this day.

 

I said "all" cars, not "this" car. Noise at events would go down if all the straight piped cars had catalytic converters. Maybe it still wouldn't be enough, but it would be an improvement.

Not really. Some of the loudest vehicles I've heard were with multiple catalysts. I don't know where you're trying to take this but it's not working out. 

I have not heard a single car, modern or old, that didn't become louder after removing the cats. Even modern turbocharged cars that tend to make less exhaust noise because of the turbo increase in volume with the removal of cats.

I can't believe this is a point someone would actually disagree with.

volvoclearinghouse (Forum Supporter)
volvoclearinghouse (Forum Supporter) PowerDork
8/13/20 9:07 a.m.

Just gotta say...I love the juxtaposition of articles on the right side of the screen:

volvoclearinghouse (Forum Supporter)
volvoclearinghouse (Forum Supporter) PowerDork
8/13/20 9:13 a.m.
MrFancypants said:
spacecadet (Forum Supporter) said:

In reply to MrFancypants :

in fact it wouldn't... this car was built for a class that required catalytic converters back then, and still requires catalytic converters to this day.

 

I said "all" cars, not "this" car. Noise at events would go down if all the straight piped cars had catalytic converters. Maybe it still wouldn't be enough, but it would be an improvement.

Aftermarket cobbled-on cats on cars that never had one would cost more than a regular muffler, and not be as effective at reducing the noise.  And cats on a car not designed for them aren't all that effective at cleaning up the exhaust, either.  And will likely clog quickly and then be more of a problem. 

Here's an exhaust I just did on a '67 Volvo.  Stock 4-1 log manifold, 2" pipe, free magnaflow muffler someone gave me off their project.  The roar of the carb intake is louder than the sound out the side of the car.

 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
8/13/20 9:56 a.m.
MrFancypants said:
bobzilla said:
MrFancypants said:
spacecadet (Forum Supporter) said:

In reply to MrFancypants :

in fact it wouldn't... this car was built for a class that required catalytic converters back then, and still requires catalytic converters to this day.

 

I said "all" cars, not "this" car. Noise at events would go down if all the straight piped cars had catalytic converters. Maybe it still wouldn't be enough, but it would be an improvement.

Not really. Some of the loudest vehicles I've heard were with multiple catalysts. I don't know where you're trying to take this but it's not working out. 

I have not heard a single car, modern or old, that didn't become louder after removing the cats. Even modern turbocharged cars that tend to make less exhaust noise because of the turbo increase in volume with the removal of cats.

I can't believe this is a point someone would actually disagree with.

All cars will become lighter if the driver removes their wallet.

Therefore, all drivers should leave their wallet with the starter before every run.

 

I have installed cats on desmogged cars and not noted any significant reduction of noise.

Tcampos
Tcampos New Reader
2/2/21 3:12 p.m.
NorseDave said:

It's a bit of an annoying article to try and navigate on this website, but I found this article to be pretty informative:

http://www.superchevy.com/how-to/exhaust/0505phr-exh/

I spent a while a few years ago turning it into a readable PDF so if anyone wants a copy shoot me a msg. 

hey I know its a couple months later, hopeful not too late. Id love a pdf version of that article. Id really appreciate it.

email my if that works t_campos@ymail.com or let me know where I can download it. Thanks!

jkstill
jkstill New Reader
5/25/21 10:57 a.m.

I built a new exhaust for my single turbo 1993 RX-7 a couple years ago.

There is one 17 inch Burns Stainless 2 stage muffler, with 3.5 inch exhaust tubing.

Without the turndown, the sound level at the one event where it was measures was 95db.

Anyone familiar with the sound level of rotaries will realize that is fairly impressive.

93gsxturbo
93gsxturbo SuperDork
5/25/21 1:21 p.m.

You guys should watch Engine Masters.  They have done 3 or 4 different muffler and exhaust shootouts, and unless its a 1000HP drag engine, there isnt a huge difference in horsepower between mufflers and exhaust diameter.  Headers do tend to make a big difference though.

The good ol Dynomax Super Turbos cost maybe 3-5HP on a 500-600HP engine.  Well within the margin of error on the dyno.  So add a few mufflers, enjoy a quiet car.  On a 120HP Civic, you would be hard pressed to notice the 1HP or less you are losing.  

rustomatic
rustomatic Reader
5/25/21 2:02 p.m.

Did somebody say turbo?  When you're considering spending hundreds on a muffler (not exactly "inexpensive"), you might as well make it worth while . . .

1988RedT2
1988RedT2 MegaDork
5/25/21 2:36 p.m.
rustomatic said:

Did somebody say turbo?  When you're considering spending hundreds on a muffler (not exactly "inexpensive"), you might as well make it worth while . . .

Exactly.  Even on a rotary, a turbo is really all the sound mitigating equipment you need, and instead of costing horsepower, it can actually give you a pretty nice bump.  laugh

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
5/25/21 9:32 p.m.
1988RedT2 said:
rustomatic said:

Did somebody say turbo?  When you're considering spending hundreds on a muffler (not exactly "inexpensive"), you might as well make it worth while . . .

Exactly.  Even on a rotary, a turbo is really all the sound mitigating equipment you need, and instead of costing horsepower, it can actually give you a pretty nice bump.  laugh

The problem with rotaries is that they don't tolerate any exhaust backpressure.  This was one of the benefits of the RX-8's side exhaust ports, the much earlier exhaust closing makes the engine a lot less sensitive to backpressure, so an OEM-quiet engine could make power like a 6 port FC with an antisocially loud exhaust system.

On the other side, with a high overlap engine, the difference between a chambered muffler and a straight through muffler can be 6 inches of vacuum at idle. Like, with a chambered muffler it idles at 2" at 1500, but with a straight through muffler it idles at 8" at 1500.  Or you can turn the idle down to 1100 and annoy the neighbors less...

fidelity101 (Forum Supporter)
fidelity101 (Forum Supporter) UltraDork
5/26/21 1:57 p.m.

In reply to jkstill :

good feedback, stock port? 

 

I was just eyeing replacing my existing muffler as I think its broken internally...

thashane
thashane GRM+ Memberand New Reader
5/27/21 10:02 a.m.

This is relevant to me. I like having a quiet car, but I'd also like to know where the engine is with a helmet on, and the windows down.

I think I'll start with a quote from local muffler shop, see what they can do regarding a single exit exhaust, instead of the dual exit.

We also have a straight piped or almost straight piped Toyobaru at local events. Painful as a course worker,  must be <25 to like it

RustBeltSherpa
RustBeltSherpa New Reader
5/28/21 2:37 p.m.

I hope there was something else holding up the Civic besides the floor jack. Not the best angle/optic for less-experienced  wrenchers

 

infernosg
infernosg Reader
5/28/21 3:16 p.m.

Another rotary guy chiming in. I have just one one Burn's single stage race muffler (17" long x 6.25" body) and as one would expect it's stupid, stupid loud. I'm going to experiment with adding another, smaller single stage muffler (12" long x 4.5" body) a little upstream and adding a tip turn down but I'm not expecting miracles. The Burn's 2 stage muffler intrigues me but I've stayed away due to the concerns Pete mentioned. Even with my current setup I start to see a little vacuum being pulled at WOT over 5000 RPM or so.

jkstill
jkstill New Reader
6/7/21 12:21 a.m.

In reply to fidelity101 (Forum Supporter) :

modest street port.  at the the time it was a turbonetics t40s.

The car now has a BW IWG 7670, but haven't yet run an event with it.

jkstill
jkstill New Reader
9/30/21 10:34 a.m.

In reply to fidelity101 (Forum Supporter) :

update: at ProSolo, the sound was measured at 100.2.  Possibly the weather caused the the higher reading, as compared to previous.

I had fashioned a shorty 3 inch muffler into a clamp on with turndown, which then passed the 95 db sound. 

Since then I have added a Borla muffler midway in he exhaust.  It has quieted down, though I don't know the numbers.  Seat of the pants says the power hasn't suffered.

A previous attempt at one time with a Magnaflow muffler in the same position caused a noticeable power decrease.

 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
9/30/21 3:09 p.m.

In reply to jkstill :

I am curious about your experiences with Magnaflows killing power.  I tested them on a 750hp V8 with a single 3" exhaust and noted no backpressure difference compared to before splicing in the mufflers, plural, in series.

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