M&K Active Exhaust for SC/Carrera

[famoroso]

Received my Active Exhaust pre-muffler last week. Working on install. Very much looking forward to getting it dialed.

Two mods that I am VERY fond of for 3.2s are the KW V3s and Sal Carceller MAF / injectors / DME ECU. They represent quantum leaps in technology and decades of development past what was available in '84 - '89. M&K's development of a valved exhaust may well be the third candidate for that list.

Added bonus is that the M&K Active Exhaust pre-muffler is lighter than Dansk pre-muffler, stock cat and gutted stock cat...
http://forums.pelicanparts.com/porsche-911-technical-forum/1070460-m-k-active-exhaust-install-87-3-4-stock-cat-s-dansk-bisi-etc-weights.html



Kudos to Brian for continuing to innovate in this space.

[rw229]

This is the premuffler, not sport cat? What muffler are you going to use? I have interest in this and looking forward to another review.

[famoroso]

Yes, the pre-muffler version.

I am going to start with a Dansk SS Sport muffler, w/ 84mm tip. I like the muffler a lot, but would ultimately prefer something lighter and slightly more aggressive, sound wise.

As such, I'm leaning towards an M&K 1 in / out. I'm undecided as to whether I will go with the 2.5" or 3" version. I'm trying to get an in-person listen to both prior to deciding. I've located a local car with pre-muffler + 2.5 that I'll take a ride in this weekend. We'll see.

[NeedAJoker]

Anyone ever install one of these? Feedback?

[Funracer]

I believe TIRWIN has one. PM him maybe?

[darrin]

I went with the active cat version, feeding my original/stock 1 in 1 out (which is still going strong at 18x k miles). Finally gives my '86 Carrera a real (but not overwhelming - still have the baffle in place) exhaust note when I go hard on the throttle (nice burble which turns into a pretty good growl as the revs rise). Cruising/easy on the throttle with active valve closed and car sounds like it used to (mostly fan noise). Did this in conjunction with an engine rebuild to 3.4l, so can't really speak to whether it boosts power. Happy camper!

[NeedAJoker]

Originally Posted by darrin

I went with the active cat version, feeding my original/stock 1 in 1 out (which is still going strong at 18x k miles). Finally gives my '86 Carrera a real (but not overwhelming - still have the baffle in place) exhaust note when I go hard on the throttle (nice burble which turns into a pretty good growl as the revs rise). Cruising/easy on the throttle with active valve closed and car sounds like it used to (mostly fan noise). Did this in conjunction with an engine rebuild to 3.4l, so can't really speak to whether it boosts power. Happy camper!

Great feedback, thanks! It really seems like this could be a good option so was surprised to see the thread died in 2020 and not much of a peep about them I can find in 'search' since.

[darrin]

Agree, surprised this doesn't get much feedback -- and do feel that the reduced back pressure when the muffler bypass valve kicks in has gotta be good for something beyond the great sounds I hear on throttle in tunnels, off of jersey walls, etc.

[NeedAJoker]

I can see maybe SSI's in my distant future, but considering I have a large list of things that need attention first, as well as a really decent looking OEM muffler, and am in a State w/o emissions requirements, is there anything I am missing? My CAT is the only part of my exhaust that looks terrible so ditching it would give me joy.

If nobody changes my mind I will order one Monday and report back after this Winter's refresh if not this Fall.

[scarceller]

Do not put SSIs on a 3.2L engine, you will get better results with stock setup and cat bypass. The very best setup for the 3.2L exhaust are the Long Tube headers from MK Exhaust, they are the perfect length that is matched to the 5800RPM tune point of the 3.2L intake plenum. Then mate up a decent muffler to those headers and magic happens.

Originally Posted by NeedAJoker

I can see maybe SSI's in my distant future, but considering I have a large list of things that need attention first, as well as a really decent looking OEM muffler, and am in a State w/o emissions requirements, is there anything I am missing? My CAT is the only part of my exhaust that looks terrible so ditching it would give me joy.

If nobody changes my mind I will order one Monday and report back after this Winter's refresh if not this Fall.

[NeedAJoker]

Thanks Sal. Looks like I have some more reading to do. Will probably just push this part of my build to next year. Appreciate the insight.

[darrin]

NeedAJoker -- believe Sal's point here is that SSIs do not provide any real upgrade over the stock 3.2 exhaust setup with a cat delete. Brian/M&K's active premuffler takes things a step beyond a cat delete as it (at least partially) bypasses the back pressure created downstream of the cat/premuffler by the muffler itself. And, the beautiful noise it creates at full throttle sure doesn't hurt on the "butt dyno" front. Here's a direct link to the M&k active premuffler https://mkexhaust.com/active-exhaust-with-pre-muffler/

[scarceller]

Correct, but the long tube headers with a decent 2in1out muffler will beat the results of any cat delete even that active exhaust cat delete will not beat a properly built long tube header. I have dyno results that show huge gains in long tube headers. See this thread:
http://forums.pelicanparts.com/porsche-911-technical-forum/1077817-84-89-3-2l-upgraded-3-5l-267-wheel-hp.html
and this one also:
http://forums.pelicanparts.com/porsche-911-technical-forum/962997-1984-911-3-4-sleeper-hotrod-end.html

It's expensive for the long tube headers and a decent muffler but worth every penny!

Originally Posted by darrin

NeedAJoker -- believe Sal's point here is that SSIs do not provide any real upgrade over the stock 3.2 exhaust setup with a cat delete. Brian/M&K's active premuffler takes things a step beyond a cat delete as it (at least partially) bypasses the back pressure created downstream of the cat/premuffler by the muffler itself. And, the beautiful noise it creates at full throttle sure doesn't hurt on the "butt dyno" front. Here's a direct link to the M&k active premuffler https://mkexhaust.com/active-exhaust-with-pre-muffler/

[darrin]

Sal - Absolutely, couple the M&K long tube exhaust with your MAF / injectors / DME ECU setup (fixing any vacuum, etc. issues in) and you'd have an amazing 3.2 motronic system/upgrade. Was recommending the active premuffler to needajoker as an interim step if he was looking to replace his cat now and do a more comprehensive exhaust upgrade later.

[coughpls]

Sorry a little late to this thread .. but put me down as a fan of the active exhaust .. i love the ability to modulate the sound .. impressive

[NeedAJoker]

Thanks guys. Thank you Sal for clearing up the SSI thought, and thanks darrin, you are right in this being a nice in-between for what I want to do now vs future possibilities. That build you linked Sal is impressive but quite a bit over my head at the moment.

You aren't late cough, haven't made the purchase yet so appreciate the feedback.

[famoroso]

Originally Posted by darrin

Sal - Absolutely, couple the M&K long tube exhaust with your MAF / injectors / DME ECU setup (fixing any vacuum, etc. issues in) and you'd have an amazing 3.2 motronic system/upgrade. Was recommending the active premuffler to needajoker as an interim step if he was looking to replace his cat now and do a more comprehensive exhaust upgrade later.

This is precisely what I did.

Went from Dansk SS pre-muffler, to...



M&K Active Exhaust pre-muffler, to...





M&K long tube headers with 2 in / 1 out M&K muffler...

[coughpls]

For those who failed physics .. and maybe its just a case of diminishing returns .. but what are the benefits of moving away from the Active Exhaust to the Long Tube headers? Is there a significant difference?

[917_Langheck]

Originally Posted by coughpls

what are the benefits of moving away from the Active Exhaust to the Long Tube headers?

The significant move would not be from Active Exhaust (AE) to Long Tube Headers (LTH), as the AE was attached to original equipment exhaust (OEE). The significant part is moving from OEE to LTH.

By going to fully equal length (proper length is important here as the exhaust pulse wave length needs to be matched by the tube length) headers that route to a merge collector then to the muffler the exhaust pulse phasing is maximized to properly scavenge and back-pressurize the cylinders.

The OE exhaust is a constrained compromise (referring esp. to SCs and Carreras in this case) between banks, with a long collector tube issuing from cyl 4-6 and merging in whatever phase with the collector from cyl 1-3, which itself is shorter than the collector from 4-6, then dumped into a single tube into the AE/OEE muffler. The AE in this scenario acts like a open, single pipe header, bypassing the final exhaust system (muffler). Just like taking the header caps of the Lake Pipes of old.

Most importantly, the exhaust system needs to be sympathetic with the induction system, in concert with the combustion process; these separate pieces work together like a woodwind instrument, and if any one part of the system is not compatible with the other parts the music sound like scheisse.

Bill Verburg and Sal Carceller have separately issued several posts on exhaust phasing of various systems.