Need help picking M&K exhaust

[dirtyduck]

Hey all,

I've got an Euro model 1984 911 Carrera 3.2. I live in California so a cat has been added in order to pass SOG. Otherwise, the car is totally stock.

I'd like to swap out my exhaust for a 2-in, 2-out system and think I've decided to go M&K. However, I've found two different models with a significant price difference but I don't understand what the real difference in the exhaust is.

First is the "MKM29" for $795. Tailpipes spacing is 12″ on center with 2.5″x8″ tailpipes
https://mkexhaust.com/dual-inlet-911-s/

Second is "MKM29ST" for $1,196. Tailpipes spacing is 11″ on center with 2.5″x8″
https://mkexhaust.com/911s-street-muffler/

The $400 difference can't possibly be for the 1" difference in tailpipe spacing. What am I missing? What's the difference here? Which is "better"?

I'm mostly looking for an improvement in exhaust tone. I'd like a lower tone, louder 'growl' but I also need to pass smog. Any advice would be greatly appreciated!

[jac1976]

The street version has baffled pipes. Whether that accounts for the total cost delta, I cannot answer. It may have to do with tuning and/or other R&D to comply with emissions testing. Call or email Brian, he is extremely easy to reach and will help you decide which muffler best suits your needs. Whichever you choose, rest assured you are getting the highest quality product. I have no affiliation nor am I a “money is no object” guy. However, I will spend my money on quality products and customer service and will support and promote those enthusiasts/vendors that provide such support to the community.

[darrin]

per M&K website, "our street version [is]designed to pass CA and track 95dB sound requirement when used on stock engines. A less aggressive idle than our sport version but retaining that raw sound that just rips when you get on the cam! Average cabin sound level at cruise is similar to stock."

Are you changing out headers as well? If not, believe you'd want a 1 in muffler, like this one. https://mkexhaust.com/single-inlet-911s/.

[jac1976]

Originally Posted by darrin

Are you changing out headers as well? If not, believe you'd want a 1 in muffler, like this one. https://mkexhaust.com/single-inlet-911s/.

Yes. This would be the first thing to address. I totally overlooked that.

[dwelle]

if you change the headers you won't pass CA smog...

[Joe Bob]

Dual exhaust tend to drone at 3K rpms....right in the sweet spot.

[dirtyduck]

Awesome help guys, many thanks.

Right, if I don't change headers that means 1-in, for the 2-out, I totally missed this. And, since I need to work within the CA SMOG tolerance, I suppose swapping out headers is out of the question.

Also, I've read a little about the drone issue with dual exhaust. I saw two Carrera's with dual outlet yesterday on the ACH canyon run and both sounded awesome. But, does anyone know if the baffles fix the drone? And, is the drone really that big of an annoyance or is it really just more about personal preference?

[OldSpool87]

Drone will wear you down. I have a dual out M&K with SSI style headers. One pipe is capped internally and the other has a Quiet Riot baffle. I run at Limerock which has a very low sound restriction (80db?) and have not had issues. No drone with one capped. You can’t tell by looking at it.

[RarlyL8]

First thing you gotta do is decide if you are staying with the OE heat exchangers or going with headers. If you want to remain 100% smog compliant and wish to maximize power we have a CARB CA compliant active exhaust system for the Carrera.



If you have a cat and want a different look and sound we have the single inlet GT3 and S tailpipe configurations along with the standard single out mufflers.

These same CARB cats can be plugged in and used with our tuned headers however that would not be visually correct as you would have 2 cats instead of 1 (go figure).
There are many differences between our Street (ST) and Sport (S) mufflers. Both are dual inlet and both can have S or GT3 tailpipe spacing. Sports are designed for guys who like it loud, but there are drawbacks to this. The more loud a muffler is the less it hides. If you have a slight miss it will now be audible, if the engine is out of tune you get less than good tones, and yes it the harmonics of the induction cams and exhaust system don't cancel you get drone. Quiet the muffler and all this is muted or goes away. That is the reason for the Street Series Mufflers. They are more quiet and utilize baffling that disrupts the pulse harmonics that cause drone. They are also physically a bit larger to reduce back pressure that is added by baffling.

[SalazarS2K]

I have a dual in dual out with my 993 headers. I also got dual silencers from car chemistry to keep the sound reasonable.

[salayc]

Originally Posted by SalazarS2K

I have a dual in dual out with my 993 headers. I also got dual silencers from car chemistry to keep the sound reasonable.

Love to hear some details about the inserts. I have an MK exhaust and it's a quality product, but LOUD, even with baffled tailpipes.

[SalazarS2K]

Originally Posted by salayc

Love to hear some details about the inserts. I have an MK exhaust and it's a quality product, but LOUD, even with baffled tailpipes.

So my MK muffler was an earlier prototype to fit my 3.6 with 993 headers, and before baffles was a “thing.” I did some research and found these guys: https://www.carchemistry.com/silencer-insert/

The sound is quieter than my old Triad muffler but semi wife approved. Haven’t dynoed the car with this setup, but horsepower wasn’t the main goal here.

[famoroso]

You're in SoCal. Let's connect so you can hear my M&K Active Exhaust pre-muffler and 1 in/out...





We can discuss some of the different exhaust configurations I've tried.

[jac1976]

Frank,
Are you going to bring that exhaust cap to market?

[rosenbergendo]

MKM28 Sport. Absolutely love it. Great quality!

[Solamar]

Here's another CA friendly option that also keeps heat -

Stock heat exchangers, M&K cat by-pass for off highway track days and M&K one in one out muffler. When required I easily swap the by-pass for my original cat. Very similar to Frank's above, with the exception of my heat is back dated (simplified) and Frank has the fancier muffler with a vac assisted muffler by-pass.

Sounds great, zero drone, and substantially lighter than stock.

[David Inc.]

Originally Posted by SalazarS2K

I have a dual in dual out with my 993 headers. I also got dual silencers from car chemistry to keep the sound reasonable.

I've been thinking about getting inserts myself for my 2-in-2-out, but I've had them ceramic coated and hate the idea of drilling through them now for set screws. Does anyone know if there are alternatives for exhaust pipe inserts that don't require set-screws that can be removed without too much difficulty?

I have some thoughts about how to make one but usually when I think of something "new" someone has already made it!

[salayc]

Originally Posted by David Inc.

I've been thinking about getting inserts myself for my 2-in-2-out, but I've had them ceramic coated and hate the idea of drilling through them now for set screws. Does anyone know if there are alternatives for exhaust pipe inserts that don't require set-screws that can be removed without too much difficulty?

I have some thoughts about how to make one but usually when I think of something "new" someone has already made it!

Maybe JB Weld for exhausts to hold the inserts in?
Alternitively, I'm going to try packing the tips with stainless steel wool made for this purpose.

[famoroso]

Originally Posted by jac1976

Frank,
Are you going to bring that exhaust cap to market?

No way. That's a custom piece!

What I did not want to do was bring a scratched tip to market.

[jac1976]

Originally Posted by David Inc.

I've been thinking about getting inserts myself for my 2-in-2-out, but I've had them ceramic coated and hate the idea of drilling through them now for set screws. Does anyone know if there are alternatives for exhaust pipe inserts that don't require set-screws that can be removed without too much difficulty?

I have some thoughts about how to make one but usually when I think of something "new" someone has already made it!

Maybe something like this...

https://www.amazon.com/gp/product/B0085PCREY/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1