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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.

arthuruscg
arthuruscg New Reader
12/6/21 12:59 p.m.

Even if the car passes the sound limit, if it's still FU loud to the course workers, don't be surprised if they are more stringent with the cone penalties.

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) SuperDork
12/6/21 4:18 p.m.

One of the old school tips I know of will not be popular but it should work.  
 

Exhaust systems are usually based on volume and flow needs of the hot gasses exiting the combustion chamber.  As those gases travel they cool fast, so volume drops considerably.  To get quiet you run a smaller diameter pipe after the muffler as your tail pipe.  Changes in pipe diameter have different resonant frequency too.  It should work (never tested it personally), but no one like small tips or tailpipes.  
 

I had a friend that did this on his high hp Hit Rod Power Tour project.  It was relatively quiet for the power made.  He also used large well baffled Walker mufflers.  You want big 1970s luxo barge mufflers and reduced pipe from the primary to the tail pipe.  

wspohn
wspohn SuperDork
12/7/21 11:58 a.m.

I built a straight 6 and started out with custom headers we made, 2" pipes and decently long well made glasspacks.  The thing would set off car alarms all around it when you fired it up, not even revving it.  The solutions was simply to fit tip resonators to the existing system - took all of the rasp/rap out of it and tamed it without adding appreciable back pressure.

67LS1
67LS1 Reader
12/7/21 10:39 p.m.

I can see from the previous posts that quiet is a subjective thing. I've been going for dead silent and not having much luck. 

I've got a tiny 3.6L/217ci engine in my 66 Chevelle and since I don't like the cadence of a V6 I'm trying to make it quiet. I'm on my third set of mufflers.

I tried to find a 60's Cadillac muffler but no one makes them. They all crossover to the Walker Quietflow lll which isn't quiet at all. I went from those to Dynomax Super Turbos and it's better but still not "quiet".

I also tried capping one tail pipe at the tip, essentially having one side past the X pipe as the worlds biggest helmholtz resonator and while it helped a little it wasn't enough

I'm going to add resonators just after the cats and try that. Last resort is to step the tail pipes down from 2.5" to 2".

Mr. Peabody
Mr. Peabody UltimaDork
12/8/21 8:35 a.m.

You have too much exhaust on that car.

It should be a 2 into 1 with a flex pipe just after, then a resonator/glass pack and a good sized muffler.  That should fix the loud and the drone. Or if you have room you could split it back up after the diff and add two mufflers there.

RustBeltSherpa said:

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

 

Look again at the picture. There is a jack stand by his waist. 

67LS1
67LS1 Reader
12/16/21 11:27 a.m.
Mr. Peabody said:

You have too much exhaust on that car.

It should be a 2 into 1 with a flex pipe just after, then a resonator/glass pack and a good sized muffler.  That should fix the loud and the drone. Or if you have room you could split it back up after the diff and add two mufflers there.

The car the engine came out of (2013 Camaro) had 2.5" all the way to the rear bumper. It did have mufflers with internal helmholtz tubes and they were mounted all the way at the rear bumper. It also had 4 cats, not 2 like I'm running. It had an X pipe too which I'm thinking of changing to an H pipe.

I've also wondered about flex pipes. The donor car didn't have them and someone told me there more for front drive applications. What would flex pipes do in my situation?

Mr. Peabody
Mr. Peabody UltimaDork
12/16/21 12:44 p.m.

I know what a Camaro has, but you don't want to do that, thus my suggestion.

Look at all the applications for the 3.6 and you'll see that there's more than one way to skin a cat. That resonance you're feeling, like it's just below your feet? The flex pipe should significantly reduce that.

infernosg
infernosg Reader
12/16/21 2:10 p.m.
infernosg said:

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.

I didn't realize I'd already posted in this thread but figured I'd give an update from a N/A rotary perspective. Since July I've had a second Burn's race muffler installed on the car. So I have: 2" primaries merged and expanded to a single 3" pipe, which has 12" L x 4.5" dia. and 17" long x 6.25" dia. Burn's race mufflers in series. I also modified the exhaust tip to be angled 45 deg downward. As expected the overall noise reduction was minor. If anything the frequency has been attenuated so it's not quite as ear-splitting but it's still very, very loud.

67LS1
67LS1 Reader
12/19/21 5:25 p.m.
Mr. Peabody said:

I know what a Camaro has, but you don't want to do that, thus my suggestion.

Look at all the applications for the 3.6 and you'll see that there's more than one way to skin a cat. That resonance you're feeling, like it's just below your feet? The flex pipe should significantly reduce that.

I already have the full 2.5" mandrel bent exhaust, catalytic converters through an X pipe, Dynomax Super Turbos to tips under the bumper. I did this because the Camaro had the same. I'm not arguing that it's to big or not, but it's what I have.

But I do wonder about the flex sections you mention. Compared to Vibrant Ultra Quiet resonators, either installed right after the cats. 

Picture is with Flowmaster 50 Series Delta Flows which in retrospect we're not much louder than the Dynomax Turbos mufflers and a WAY deeper tone. 

Uncle David (Forum Supporter)
Uncle David (Forum Supporter) Reader
12/19/21 6:30 p.m.

As noted up-thread, 2" tailpipes will help, and since it's a Camaro, you should be able to find them in stock.

dean1484
dean1484 MegaDork
12/20/21 8:03 a.m.

Years ago GRM did an article where they tested a bunch of mufflers on the same car and put them on a dyno. Should did that up it would probibly be relevant to this.  

67LS1
67LS1 Reader
12/20/21 3:40 p.m.
Uncle David (Forum Supporter) said:

As noted up-thread, 2" tailpipes will help, and since it's a Camaro, you should be able to find them in stock.

Actually it's a 66 Chevelle. The engine came from a Camaro.

But I get your point, you'd think that 2" mandrel bent tailpipes would be a pretty easy thing to find for a Chevelle. Nope. Everything is 2.5 or 3 or bigger.

i may have to give up on the mandrel bending and have a local shop make them.

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) SuperDork
12/21/21 1:40 p.m.

Two different sized mufflers will help too.  

67LS1
67LS1 Reader
12/22/21 3:39 a.m.
AnthonyGS (Forum Supporter) said:

Two different sized mufflers will help too.  

Do you mean in series, so 4 total? Or different left and right?

DaleCarter
DaleCarter New Reader
4/10/22 12:47 p.m.

     I autocross an old Spitfire with a bridge-ported 13B rotary and it was STUPIDLY loud, despite the muffler. I added a large diameter SuperTrapp to the tailpipe and solved the noise problem. I have not had the car on a dyno yet, but my times and subjective "feel" say any power lost doesn't matter.

     I track a Panoz GTS with an LSX that had "NASCAR" mufflers when I bought it. The mufflers were, basically, a bulge in the open exhaust. The car was SO loud, that I could not hear my radio comms, despite molded ear monitors. Vibrant resonators solved the problem.

      Regarding sound... the weighting used on the SPL meter is critical. Also, a 3db increase means the sound is TWICE as loud.

      Basically, I hate loud exhaust systems and think that they are not worth the cost to event organizers for the miniscule power improvement.

stigskov
stigskov New Reader
4/10/22 1:49 p.m.
Alfaromeoguy
Alfaromeoguy HalfDork
4/11/22 12:40 a.m.

In reply to Andy Hollis :

under the car...no body stands? just a jack?

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