Yet another muffler mod...

calling911 · 03:28 PM

After researching to death I decided to modify my muffler.. thought Id post some pics of the carnage while the paint is drying..

I found that my muffler had been partly destroyed internally anyway.. if you look close you can see the crack where the metal was bent obviously from a severe backfire..

At this point I have elected to create the two holes as outlined in the sport muffler document that is floating around.. I'll post a sound file as soon as I can as I know many people have wanted to know what this mod sounds like without the dual pipes added.. I think adding those pipes to a chamber directly connected to the headers is going to be way too loud for my taste.

I think my next step if I take one will be to cut slits in the perforated pipe you see in the pictures..

This first picture shows part way thru the modification.. 1 window opened and another started.

Next picture shows completed modification.

Here I sit.. waiting for this paint to dry

I of course fired up the car with open pipes.. I wasnt impressed.. raspy.. sounds like a broken exhaust.. I hear people all excited about listening to straight pipes... no thanks.. doesn't even sound porsche like to me..

Note: I found no insulation material in my muffler and it was never opened.. probably stock on my 76. I also believe based on the following document that my muffler is no different than an early muffler.. this is why I went this route...

I should state my goal...

1. No drone
2. More Porsche-like, deeper sound
3. On the edge of woman friendly
4. Completely not ricer and I dont want to attract ricers at stop lights as they annoy the living hell out of me.
5. absolutely no ricer rasp.
6. Little to no cost.. so far welding supplies and a bag of play sand (for sand blasting) is my cost.. about $20. worth.

Lastly.. if you have a mig welder and think you can do this with no sheet metal experience.. forget it.

A thought about the future: If this isn't what the doctor ordered Im thinking about a single pipe in the middle as opposed to two pipe.. just a thought at this point though... Everything I read here says two pipes are two damn loud.

calling911 · 04-03-2010, 02:15 PM

May be because my muffler was blown somewhat already but I heard no real difference..

onto the next mod..

willf · 04-03-2010, 02:34 PM

hey JP: appears that you still have exhaust exiting the original tail pipe. in that case, the perforated (slotted) pipe is still functionally the only path used to flow the exhaust out of the muffler even though you cut out holes in the baffling. If you close off the original tail pipe and introduce a tail pipe (or 2) below the muffler seam or lower collector chamber... you will get louder! Cheers.

calling911 · 04-03-2010, 02:43 PM

Quote:

Originally Posted by willf

hey JP: appears that you still have exhaust exiting the original tail pipe. in that case, the perforated (slotted) pipe is still functionally the only path used to flow the exhaust out of the muffler even though you cut out holes in the baffling. If you close off the original tail pipe and introduce a tail pipe (or 2) below the muffler seam or lower collector chamber... you will get louder! Cheers.

Fully aware of that.. was hoping for something in-between.. maybe slits in the perforated pipe??

Wonder if anyone has tried a single from the main chamber instead of two.. I think thats what Im gonna try....

Fleming · 04-03-2010, 08:58 PM

JP,
try to shorten the flow route to the single tail pipe. I've mod'ed Jeff Gambles drawing/design to indicate the pipe removal that could by-pass the end chamber.

You would think it could have a pronounced change to the sound.

Bob

calling911 · 04-04-2010, 02:20 AM

Hi Bob.. after driving for a few hours last night Im gonna take back what I said.. its louder and deeper.. I dont know why it didnt seem that way at first.. but it definately made a difference..

Im not sure Im up for opening this thing back up again.. the thin sheet metal was very time consuming to weld up. Im guessing your idea is a good one but it could have consequences as well.. possibly undesirable attributes.. Im also afraid that with all these paths Im losing some "pulse" qualities.. im afraid the sound is kind of being muffled and "mushed" rather than defined...

Another thought is I might just drill some holes since I know where the pipes are and then plug weld those holes.. 4-6 1/4" holes could make a radical change..

Or... a single or a dual pipe out... if I go dual out one could be capped.

I'll try and post some sound samples as soon as possible.. I wish I had taken some recordings before I did the mod but alas I did not..

jm993rs · 04-04-2010, 10:57 AM

anybody have the same pics of alfter 74 exhaust and what work have the exhaust I have two exhaust and I would make this upgerade for one.

calling911 · 04-04-2010, 11:20 AM

Quote:

Originally Posted by jm993rs

anybody have the same pics of alfter 74 exhaust and what work have the exhaust I have two exhaust and I would make this upgerade for one.

This is a after 74 exhaust..

80-911SC · 80-911SC's Garage

Quote:

Originally Posted by jm993rs

anybody have the same pics of alfter 74 exhaust and what work have the exhaust I have two exhaust and I would make this upgerade for one.

hit the spell check button, and are you trying to make a two a one ? or do you have two and would like to make one of them a two outlet ?

jm993rs · 04-04-2010, 03:45 PM

sorry for my english but , I dont speak very well and my english is very llittle.

the muffler of the pics is pre-74 and have 75 the same of 3.0 and 3.2 .

I have two mufflers one is on the car in perfects conditions and i would make the modification on the other for when I would to go in to a track make more sound with the muffler modification.

is possible ??? are the muffler pre 74 inside the same of 75,76,77 and more ???????

thanks for the answers .

80-911SC · 80-911SC's Garage

the 74 + are very similar, the photos above I believe are 74+

If your only reason for modification is for more sound for the track you may want to check the allowable db's on your track. Also any other modifications and a description of your car would help people to assist you. As far as i have heard a 3.0L with only the double out done to the muffler will not make much difference but may drop your low end a bit and offset the top end just a hair.

calling911 · 04-19-2010, 02:19 PM

Here is a sound clip..
http://monkeyfoundation.giving.officelive.com/Documents/76mufflertest.mp3

I'll try to get one on the road.. sounds better on the road. Wish I had the original to compare it to.

dion914-6 · 04-19-2010, 02:36 PM

JP,

I'm thinking of doing the same thing with a pre-74 muffler that has trashed internals. I bolted it up to a 3.2, and it sound like a VW bug running on 2 cylinders! Then the dead mouse spit itself out of the tail pipe.....

I don't know what I'll find when I open it, but it may give me the ability to create whatever I want. I couldn't get your sound file to play.

Dion

calling911 · 03:21 PM

Quote:

Originally Posted by dion914-6

JP,

I'm thinking of doing the same thing with a pre-74 muffler that has trashed internals. I bolted it up to a 3.2, and it sound like a VW bug running on 2 cylinders! Then the dead mouse spit itself out of the tail pipe.....

I don't know what I'll find when I open it, but it may give me the ability to create whatever I want. I couldn't get your sound file to play.

Dion

Should ask you to download it.. doesnt work with google chrome so may not work with macs.. works on IE7 for me.. maybe right click on the link and see if that helps..

Im not thrilled with the sound.. has some rasp to it.. every time I hear a dynamax sound file it sounds the best to me..

One thing to remember.. some people dont know how to set microphone gain.. sound files sound cool when the gain is set too high.. but its not accurate.

dion914-6 · 04-19-2010, 03:20 PM

Thanks. Chrome is my problem. I'll use IE.

I have a Bursch Sport on it now, and it's too loud at highway speeds.

Thanks,

Dion

calling911 · 03:27 PM

Quote:

Originally Posted by dion914-6

Thanks. Chrome is my problem. I'll use IE.

I have a Bursch Sport on it now, and it's too loud at highway speeds.

Thanks,

Dion

Bursch is supposed to be close to dynamax.. is there a sport and non-sport?

This is the sound I seem to like.
http://www.youtube.com/watch?v=HNt2Ucn_30c

Remindes me of the start of the movie Lemans

and this one sounds horrible until he hits like 4k I think
http://www.youtube.com/watch?v=BWcUFOOUcjA

dion914-6 · 04-19-2010, 03:28 PM

That sounds similar to mine. Imagine that in a modified 3.2 914-6 with stock 901 gearing on the highway.

3100 rpm's at 72 MPH. I can also setoff car alarms in most parking garages. Looking for something a little more like yours!

Dion

calling911 · 04-19-2010, 03:34 PM

Quote:

Originally Posted by dion914-6

That sounds similar to mine. Imagine that in a modified 3.2 914-6 with stock 901 gearing on the highway.

3100 rpm's at 72 MPH. I can also setoff car alarms in most parking garages. Looking for something a little more like yours!

Dion

I thought about trap doors with springs... its been discussed here many times.. but nobody has pulled it off it seems..

dion914-6 · 04-19-2010, 05:02 PM

I just started a new thread so I didn't hijack yours too much, but thought you might want to see what I found tonight.

Sport muffler mod-surprises found and opinions wanted

Dion

dion914-6 · 04-19-2010, 05:57 PM

JP,

Here is a short video that I took about 3 years ago while still in Ohio, and the car had a 2.0 Six in it with the Bursch exhaust. It sounds similar with the 3.2, but a little deeper. The sound quality sucks because of the reverb in the garage, but I think you'll get the idea.

YouTube - 914 day

Dion