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Exhaust for a 3.6

Hello
I want to share with you what I did for a 3.8 conversion on my '71. I had already B&B 1 3/4 headers with heater boxes and I wanted to keep the banana muffler but the 3.2 Dansk units are incredibly restrictive so I opened up a 2 into 1, redesigned the interior as a fast-flow, x-pipe and added a second out, making it a 2 into 2, the expansion chambers where then filled with metal fiber and the whole thing closed. I was at first hopeful but weary of this experiment, but it turned out great. It now has a stock sound with a deeper lower tone and no drone at all, and the engine has released all it's might, it pulls fantastically all over the power range. I have yet to Dyno it but it seems immensely better with my new muffler and a great choice for those who want to keep the exhaust looking and sounding stock but with a faster-flowing 3.6-3.8 appropriate diameter muffler.
MD











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Old 07-18-2015, 10:21 PM
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enzoducoing,

That's impressive work! Great job.
Old 07-19-2015, 03:17 AM
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I used a 997 center muffler with B & B Muffler





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Old 07-19-2015, 04:36 AM
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If you have some $$$ already set aside for the exhaust,just purchase a bolt on header and muffler system from Fabspeed ...

I have that in my 89 with a 95 3.6 conversion and i'm very satisfied with the fit and the sound ,the total price is quite reasonable as well !

Cheers
Phil
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Old 07-19-2015, 09:23 AM
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Quote:
Originally Posted by enzoducoing View Post
Hello
I want to share with you what I did for a 3.8 conversion on my '71. I had already B&B 1 3/4 headers with heater boxes and I wanted to keep the banana muffler but the 3.2 Dansk units are incredibly restrictive so I opened up a 2 into 1, redesigned the interior as a fast-flow, x-pipe and added a second out,

Where did you get the perforated pipe?
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Old 07-19-2015, 09:37 AM
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I am a little later here. Look up Unobtainium Welding. They build some AMAZING stuff for 996 Turbos (I have one and was looking at their stuff for it) and others. They are ZERO drone. They use a very interesting design to cancel out the drone, and their stuff is art work. I heard one that had no mufflers.......just pipes.....and although loud there was no drone. Interesting stuff.

Unobtainium Welding Website
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Old 07-19-2015, 03:51 PM
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what if we took the basic foundation of the 993 exhaust

and instead of putting the mufflers (x2) behind the rear wheels we tuck them behind the rear bumper- a little less exhaust piping but should be quiet and not drone like the stock exhaust? any thoughts on this?>
Old 11-25-2015, 11:52 AM
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I've made up a couple of exhausts for my 3.6, first one was with headers and a Magnaflow silencer which is a fairly tried and tested setup for a 3.6 conversion and pretty cost effective. If you want heat you can always go with 993 heat exchangers and a Timmins 'happy crab' type of arrangement.

Regarding X pipes, well, you will just have to make your own mind up on that!! Have a quick read of my thread below!

My Ti exhaust project

I will say that exhaust sound, noise levels, drone etc etc is very subjective and you can't beat listening to someone else's car and going for a drive in it to help decide what is best for you. Youtube clips only tell half the story.

Good luck.
Old 11-29-2015, 02:17 AM
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Here is my new Setup with s-car-go race headers, gt3 rs muffler and a customer connection that uses electric cutouts- I will update with a video of it open vs closed- later on
https://www.youtube.com/watch?v=5uRlhb68__U
Old 02-21-2017, 02:44 PM
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[QUOTE=saxen;8707742]Hello everyone.

I am getting ready to drop a 1995 3.6 v-ram modified engine into my 1981 sc.
My car is on the lighter side of things and has very little sound proofing for the interior. For the last two years I have been running race headers and a 2IN2OUT m&k exhaust. I cap one side for the street and run both open on track days. That exhaust was loud, very loud. The bigger issue was the drone the car gave off. I could not drive the car without ear plugs. The car sees around 8k street miles per year and 10 track weekends per year. I may put some interior back in the car to help with the sound. The car is fun, just too loud.

So..
After I do the swap I would like to have a local shop build my exhaust. I have $2000-$4000 set aside for this exhaust build. I care more about a drone free setup and a quiet"ish setup than max hp- 300+ in a 2200 lb car will be more than enough. I don't want the car to be too quiet but very much on the lower end of things. I would like to use the stock headers if possible.

I would like ideas on how to do this exhaust. I know there is a company that modifies the 993 mufflers, is there anyway to build an exhaust with the modified parts to keep quiet? Or use gt3 stock mufflers with modified piping?

I think two sepperated exhausts / an exhaust that doesn't murge 3+3 would prevent drone. I. Also down for electric cut offs for street and track.

The room will be limiting. Here are a few ideas below but reall is I think they will be loud.
Some of the pictures have mufflers tucked behind the rear wheels. My oil tank will be in the way, but maybe room somewhere else, or maybe I need to move that tank.


I swapped out my 15 year old B&B exhaust out with the a new B&B and I am very happy with the new muffler. No resonance and nice throaty sound. I gave $875 for the muffler and used the my existing B&B headers
Old 02-21-2017, 05:50 PM
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02 sensor is on the right side.



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Old 02-21-2017, 06:31 PM
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3.6 exhaust 86 carrera

Simple /effective and surprisingly quiet.
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Old 02-21-2017, 07:13 PM
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993 into 1980 SC

In my conversion, we ran the stock 993 manifolds (with heat) into the catalytic converter and welded pipes onto the converter...Car is CA and needs to be smogged.

The sound is fabulous. Sounds like a race car but is very street-able. It burbles when you wind it up and shift.

In 5th gear at RPM it is quiet enough. That said, it's a week end/track car and not a daily driver.

Re running without sound deadening:Years ago we stripped all sound deadening out of the car and glued in aluminum sheeting that has air pockets. No weight and it was quiet.

Maybe not what you need but it works well.

No drone.

Last edited by thotdoc; 02-21-2017 at 08:56 PM.. Reason: added no drone
Old 02-21-2017, 08:54 PM
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simply run a Magnaflow from your stock 993 headers and you're done. @$150.00..
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Old 02-21-2017, 09:40 PM
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I am waiting for this currently:

Bigger "SSI" system

They are working on a presentation/press release which should be available next days hopefully.


Falk
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Old 02-22-2017, 02:40 AM
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Quote:
Originally Posted by rattlsnak View Post
simply run a Magnaflow from your stock 993 headers and you're done. @$150.00..
This is probably the simplest most cost effective way to go.

A variation is what I did, B&B headers/964 heat pipes/Flowmaster muffler. It's loud, a Maganflow would quit it down a lot.


The Eisenmann Exhaust System is probably a very good if expensive solution for street 3.6s, especially if stock mufflers can be used.

Some general comments about design
our flat 6s have a nearly perfect even firing order and firing interval(per knowledgeable exhaust designers). The interval between pulses on each side is 240 this allows relatively plenty of time for evacuation of the pipe. Remember that at 6500rpm each cylinder is firing 54 times per second, this puts 162.5 pulses of spent gas into each collector every second. This situation is much more easily handled than that on an odd fire engine like most American V8s that at the same rpm put 217 pulses into each collector every second and on top of that the odd fire design always has at least 2 cylinders firing consecutively into a single collector, the pulses are much closer together and much more jumbled as a result.



Here is a view of what a single pulse does, the aim of a header is to get the low pressure reflected wave to arrive at the exhaust port during the overlap period when both Intake and exhaust valves are both off their seats, this is the so called 5th cycle or aka exhaust scavenging. W/ our engines in stock form there is very little overlap, 964 cams have ~9 of overlap, SC/Carrera have none((it's actually -1.5) this means that there is little to no opportunity for exhaust scavenging to occur. By contrast an early 911S cam has 57 of overlap and can profit mightily from this effect.



When designing an exhaust the goal is to speed the gas flow, fewer straighter bends are better, fewer less abrupt transitions are better(the reflected waves are generated by abrupt transitions), smoothly guided merges are better at angles < 5 or 6. A muffles system will negate most of the reflected wave anyway.

In a muffler perforated pipes are more efficient lowers than reflection barriers, volume matters- the bigger the muffler the more efficient it can flow and the more efficient it can silence. Multiple silencers that choke different frequencies of sound will sound better, the main reason to connect left and right banks of an even fire system is for sound reduction


Dinan uses a beautifully designed system on their BMW mufflers, I'd love to see something like this offered for our cars
  • large volume
  • separated flow
  • perforated pipe
  • multiple sound chokes- both the main expansion chaber and multiple resonators


While the Magnaflow is one of the quieter aftermarket, reasonably priced mufflers for our cars, it suffers from one glaring issue, the merge is more of a head on collision which does nothing good for flow a secondary issue is the small can size


Here is a nicely designed stock type muffler
  • large volume
  • perforated pipe
  • multiple varied frequency chokes


Porsche did a decent job on the 993 side mufflers too, though smallish they do a surprisingly good job of flow and silencing the exhaust one of the best features is the separated flow

Standard 993


a common mod


an even better common mod


stock 993tt even better
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Old 02-22-2017, 04:52 AM
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The 2-in 2-out Magnaflow on mine droned like a mofo. Inserting a baffle into one of the outlets helped greatly, but it still wasn't fun on long highway trips. I then switched to a 2-in 1-out Magnaflow. No drone, but the piping is kind of funky due to the limited space.

Old 02-22-2017, 06:48 AM
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Foggert , where in NJ are you I'd love t hear this as I am about to do the 3.6 swap.
Shot me a PM
Old 02-22-2017, 08:17 AM
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Fascinating post, Bill. I've been looking to quiet my 3.6 down, but nothing fits back there. I've thought about cobbling together half a 993 system with half a 3.2 system, but the only bit of this I understand is the plumbing, not the pulses, or how the various chambers interact with each other.

Something tells me there is room for improvement over the 3.2 banana exhaust that was slapped on there.
Old 02-22-2017, 11:27 AM
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Quote:
Originally Posted by Tremelune View Post
Fascinating post, Bill. I've been looking to quiet my 3.6 down, but nothing fits back there. I've thought about cobbling together half a 993 system with half a 3.2 system, but the only bit of this I understand is the plumbing, not the pulses, or how the various chambers interact with each other.

Something tells me there is room for improvement over the 3.2 banana exhaust that was slapped on there.
For a single inlet the old Andial/Tezet setup was one of the best
large volume very long internal perforated pipe, great flow



Chevrolet C5 mufflers look almost identical to the stock 993 mufflers seen above

As to the modified 2 in/2 out banana, it can certainly be improved
one way is to use 2 parallel `2.5" perforated pipes, left in goes to right out and right in goes to left out ~65mm+/-outlets ~65mmm pipe

or do a double Tezet w/ a serpentine for each side,


rather than a solid out let use resonator tips or add a Helmolz resonator before the muffler on each side


Don't forget that all the above mufflers need to also have f/g or ss scrubble wrapped around the perforated pipe, the more the better. Again using resonator tip helps alot

Burns makes some great rebuildable mufflers that incorporate these ideas, you'd need at least 2 x22" w/ probably 2.25" or 2.5" cores, hang them parallel to each other in the stock transverse muffler position, run the left in to the right corner out and the right inlet to the the left corner out.

here's what the Burns looks like
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Old 02-22-2017, 02:36 PM
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