Muffler for '78SC that sounds like my Cayman S

[lespaul]

I have listened to nearly all the sound clips and read nearly all the muffler threads and still do not know which way to go.

I have a '78SC 3.0 with OEM heat exchangers, no CAT (by pass pipe instead), with a one in one out OEM muffler.

I want a deep throaty sound, with burble on deceleration -- like my Cayman S in Sport Mode. I don't mind louder than most and, where I live in VT I will not experience much drone since I rarely drive on highway at a constant RPM/speed.

All I want to replace is the muffler on my set up. So it is one in -- and I like the look of 2 out.

What are my top 2 or 3 options for muffler replacement?

[Gretz]

I’d love to hear the answer on this. The closest I’ve gotten is a Dynomax 17676 with custom tubing. I tried the M&K GT3, which is a work of art, but doesn’t sound quite like what I’ve been looking for. I have heard from others that an actual 991 GT3 muffler sounds fantastic.

[Fly911]

You will never get an air cooled Porsche to sound like a water cooled one...4 valves per cylinder, variable cam timing, intake resonance chamber, and typically better designed headers, the water cooled Porsches sound great! Especially with a good exhaust system (not only muffler).

Exhaust sound is MUCH more than just the muffler. In fact, the exhaust sound is also more than just what exhaust system you have. I have done some experimenting with my various Porsches.

My first observation was with my 996. I changed to a K&N cone filter, and the exhaust sound changed! So the intake also makes a difference. I then got two muffler bypass pipes, and the sound was loud and awful. So I changed back. Sold that one, and the new owner put a Fabspeed X-pipe on it, and it sounded fantastic!

A Porsche engine puts out 6 exhaust pulses for every 2 rpm, 3 pulses on each cylinder bank. If you have two separate systems (one for each cylinder bank) like the 996, your exhaust will basically sound like two 3 cylinder engines in some kind of symphony.

With the header design used from 1975 to 1994 (911 and 964), with a cross over pipe and one outlet, the exhaust pulses did not come out in a sequential fashion, but with pulses from the left bank "kolliding" with pulses from the right bank.

To get the exhaust pulses to come ut sequentially, (i.e. L-R-L-R-L-R), you need headers with equal length, and combine the L and R pulses in an X-pipe or Y-pipe. Even with equal length headers, and separate mufflers, you won't get the right sound. You will have L-L-L on one side, and R-R-R on the other side. In and X-pipe or Y-pipe the left and right pulses comes out in the order they were produced. The sound frequency will be twice of the single left and single right exhaust systems. You have probably heard the 997 and 991 GT3's with the exhaust in the middle, and the high pitch sound.

I also experimented on my 986 and 987.2 Boxsters, with Y-pipe design mufflers, and they sound very GT3-ish, especially above 5,000rpm.

I also experimented with my 993. The 993 got much better headers, but they were not equal length. The 94-95 models were equipped with Bishoff mufflers, that had and internal Y-pipe, while the 96-98 had Gillet mufflers with two separate outlets. The 94-95 sounds better.

I mentioned that the air intake makes a difference in exhaust sound. I mounted ITB's on my '87 Carrera, in combination with equal length headers, and several different muffler combinations. I have a 2 in and 2 out muffler that sounds good, and an X-pipe with 4 resonators that sounds better. Then I have a Y-pipe that really screams like a GT3 on high RPM, but it's very loud. Then I have a OEM 997 GT3 titanium muffler. That is the best sounding muffler for any Porsches, both water and air cooled.

Last but not least, cam shafts play a big role in exhaust sound. With longer duration, higher lift, and long intake-exhaust overlap, the exhaust will get a deeper throatier sound on low RPM, and scream on high RPM.

The 911 SC has the mildest cam shafts for any type of 911, and no matter what you do on the exhaust side, you will never get the Cayman sound. To get the best sound without modifying the engine itself, you should buy a good set of headers (Fabspeed, Billy Boat, S-Car-Go, SSI, Eissenmann, etc.), and a sport muffler with and internal X-pipe and two outlets.

[lespaul]

Fly 911,

Thank you for the very through evaluation and explanation! I learned a lot. I guess my objective of a "Cayman S" sound is unlikely to be met no matter how much I spend on my SC. But I still want to get as close as I can without changing my headers at this point, so I am likely to opt for a good one in two out Sport Muffler.

Given those limitations, what Sport Muffler do you suggest? M&K, Dansk, Dynomax, Flowmaster, . . . ???? Or with my OEM set up, will any of these sound any better than my stock OEM muffler?

[stownsen914]

The dual center exit mufflers do give an early 911 a higher pitched exhaust note. Not saying it will be just like a Cayman in sport mode, but you might get close. Let’s see if you get any specific recommendations here.

[Flojo]

Originally Posted by lespaul

What are my top 2 or 3 options for muffler replacement?

won't work due to the engine you have. its natural "output" can't be sound-redesigned. its in its nature of ccm, outletdiamater, reving and so on.

Same as a 3,0 with SSI will never sound like a 2.0/2.4

if you stil have the original exhaust setup (one in, one out) then a DP Motorsport may lead to more growling.

I went the SSI route adding a Dansk 92.510 (2in, one out)… but now swapping for a Dansk 92.515 (2in, 2 out).
going for SSI also saves you a ton of weight and less heat at the gearbox.

[msmall215]

Originally Posted by lespaul

I have listened to nearly all the sound clips and read nearly all the muffler threads and still do not know which way to go.

I have a '78SC 3.0 with OEM heat exchangers, no CAT (by pass pipe instead), with a one in one out OEM muffler.

I want a deep throaty sound, with burble on deceleration -- like my Cayman S in Sport Mode. I don't mind louder than most and, where I live in VT I will not experience much drone since I rarely drive on highway at a constant RPM/speed.

All I want to replace is the muffler on my set up. So it is one in -- and I like the look of 2 out.

What are my top 2 or 3 options for muffler replacement?

This is a 2-2 that a shop built for me...definitely deeper than some of the others out there. Based on a Vibrant muffler with some custom piping.

[lespaul]

Thanks Flojo. Good information. Here is something I found based on it.

This may be an option if I want to spend $1000.

https://rennlist.com/forums/911-forum/1151807-my-1978-911-sc-getting-a-dp11-exhaust-and-fabspeed-cat-bypass.html

https://www.dp-motorsport.de/en/produkt/rear-silencer-for-911-g-model/

[theiceman]

so if i understand your request ... you are trying to get your air cooled car to sound like a water cooled car which is trying really hard to sound like an air cooled car...

put SSIs on it and a 2-1 bischoff from around a 74 and you will be done ..

[Quasimoto]

Thanks for reminding me that I need to order a Sport Exhaust kit for our Cayman...

[tirwin]

Have you disconnected and capped the vacuum line on your decel valve? That will give you decel gurgles. Make sure your AFR is 12-12.5 at WOT.

Test pipe if you want more aggressive. Pre-muffler if you want tamer.

This is my setup. Test pipe with 1-in/2-out. Bought this muffler from a fellow Pelican. Think he got it at a swap meet. We haven't been able to figure out who made it. But it is awesome.



Edit: for some reason linking videos in posts is erratic lately. Gimme a sec to work on it.

Edit edit: fixed. I don't know what is going on. It just started working.

[Marwil]

Question for msmall215 regarding the vibrant muffler. Do you know what the Vibrant part number is for the muffler or what the diameter of the inlets are?

[msmall215]

Originally Posted by Marwil

Question for msmall215 regarding the vibrant muffler. Do you know what the Vibrant part number is for the muffler or what the diameter of the inlets are?

It’s 10632: https://vibrantperformance.com/catalog/product_info.php?cPath=1527_1032_1535_1110&products_id=1837&osCsid=6581cf41676e23cdb06bd5584113e327

It’s essentially reversed so you’re using the 2.5 inlets on the sides and have the 3 in outlet which I have the stinger style tip welded on.

[blackrado]

sorry to resurrect,

i was looking at this Vibrant muffler that MrSmall used...but they also offer a slightly smaller diameter one. (2.25 and 2.5 vs 2.5 and 3").

Anyone have any experience with that? I am looking to put it on a 3.0 with the Melissa cams and early style heat exchangers.

MrSmall was using the 2.5/3", but i thought the heat exchangers were 2.25... If so, i may stay the same diameter rather than step up.

OR PLEASE CORRECT ME IF I AM WRONG ABOUT THE DIAMETER OF THE HEAT EXCHANGERS

thanks

[MARISOL78sc]

Originally Posted by lespaul

Thanks Flojo. Good information. Here is something I found based on it.

This may be an option if I want to spend $1000.

https://rennlist.com/forums/911-forum/1151807-my-1978-911-sc-getting-a-dp11-exhaust-and-fabspeed-cat-bypass.html

https://www.dp-motorsport.de/en/produkt/rear-silencer-for-911-g-model/

That is my Rennlist thread and car. The DP muffler does sound amazing with a deep growl and cool pops on decel, huge improvement over stock paired with the Cat Bypass but really does not compare with the sound of my Cayman S Paid $50 for the muffler!.

[David Inc.]

Originally Posted by lespaul

Fly 911,

Thank you for the very through evaluation and explanation! I learned a lot. I guess my objective of a "Cayman S" sound is unlikely to be met no matter how much I spend on my SC. But I still want to get as close as I can without changing my headers at this point, so I am likely to opt for a good one in two out Sport Muffler.

Given those limitations, what Sport Muffler do you suggest? M&K, Dansk, Dynomax, Flowmaster, . . . ???? Or with my OEM set up, will any of these sound any better than my stock OEM muffler?

Any muffler you use will lead to more volume, more growl, but without changing the headers it will stay at a much lower frequency than on the Cayman. With my '82 I started stock, put in a fabspeed cat-bypass, then a muffler bypass, and finally swapped the headers and put on a Dansk 2-in-2-out GT3 muffler. Here is the progression, I'm sure you can tell that going to the headers produced the most drastic change in tone, and honestly I could listen to it all day long now.

Stock headers and muffler, cat-bypass:
https://youtu.be/1BD3H_ZXOSg

Stock headers, cat-bypass and muffler by-pass:
https://youtu.be/Jq59G7wuEHw?t=46

Praise be to SSI headers with Dansk GT3 style muffler:
https://youtu.be/GhWPfONFbnk

It's worth the extra money on the headers, it's so so worth it.

Edit: Whoa, youtube put ads on the headers video, I didn't realize I was a celebrity now.