M&K Active Exhaust for SC/Carrera

[RarlyL8]

Happy 4th of July!
M&K has completed development of an active exhaust for the Porsche 911 SC and Carrera. We started with our MKM32 performance premuffler which gives the best performance increase using the OEM exchangers. A valve was added to bypass the main muffler and the system then went to the dyno to tune the design for optimum performance and power. Final pull on the completed prototype showed 201.5hp to the wheels on our bone stock '87 Carrera with OEM muffler. Along with the extra 18.5hp comes an aggressive sound that is neighborhood friendly and can be tuned to your liking using our optional tailpipe silencer. Idle and cruise are stock quiet, the valve opens only under engine load, which you control with your right foot. We are working on a chip now tuned exclusively for our system which should nearly double the power increase.
Pelican has the info on our new system and should be posting it up any time.
Here are a few pictures of the system and a video showing the contrast in sound.
Have a safe 4th and get out and DRIVE!

[QueWhy]

Really cool. I wonder if it will pass the muster with the California emissions nazis, might be a nice option for them. Luckily I don't have to worry about that nonsense, I'm hoping to get my 2in1out and SSIs installed this weekend.

[Marwil]

The active exhaust solution is a great one. I've run small spun cats off my SSIs into a 2.5 inch Magnaflow 2 in 2 out. Way too loud and the drone was wicked. I installed a vacuum operated valve on the right side and in cut the deep droning immeasurably but step on the go pedal and it sings. The ideal solution would run the cats into a 2 in and 1 out muffler.

Brian, I wonder if you are considering running small cats off your headers so they could feed into your series of mufflers. Completely self-interested on my part as I will be upgrading to a 3.2 shortstroke and the SSI's may be too small.

Cool looking stuff!

Mark

[RarlyL8]

Yes a cat could replace the premuffler on the active exhaust, if interest is strong enough we will build that version.

Yes we are working on a dual cat solution with headers that uses any of our dual in mufflers. In the testing phase now which takes some time. Have to test different cats and fitment with both the 915 and G50 trannies.

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[tshebib]

Brian,
I have a 3.6 VRAM in my 80SC. It has the "Happy crab" muffler with stock 993 heat exchangers. I think the tailpipes are 2.5".
The drone and db's are starting to wear thin. Do you sell the vacuum activated valve on it's own? I'm thinking having the valve on one pipe and maybe a baffle on the other pipe would help keep the dbs down when cruising. Or maybe you have a full muffler setup to address this. I track the car occasionally with our local PCA club so would like to have increased flow when pushing it.
What are your thoughts?

[RarlyL8]

Yes we have a muffler with 993 Bischoff flange inlets. Standard is single out but we have done custom GT3, S and R tailpipe configurations. Shoot me an email for pictures and info.

[danco_]

This looks good Brian. Did you have a chance to take in car or drive by videos at WOT? I’d be curious how this sounds from those perspectives. Thanks!

[tirwin]

Brian,

This is very interesting.

I have a OEM heat exchangers + test pipe + 1-in/2-out muffler on my ‘83. I measured 86dB at idle about a meter from the tailpipe. Any idea what your idle dB is for comparison? I used an iPhone app called “db Meter Pro”. Do you think this would tame the idle sound even with a 2-out?

What’s the rough opening rpm? Just wondering what the sound would be like at interstate cruising in 5th gear.

How would this compare to HP/torque gain from SSIs?

[tshebib]

Originally Posted by RarlyL8

Yes we have a muffler with 993 Bischoff flange inlets. Standard is single out but we have done custom GT3, S and R tailpipe configurations. Shoot me an email for pictures and info.

email sent

[RarlyL8]

Brian,
This is very interesting.
I have a OEM heat exchangers + test pipe + 1-in/2-out muffler on my ‘83. I measured 86dB at idle about a meter from the tailpipe. Any idea what your idle dB is for comparison? I used an iPhone app called “db Meter Pro”. Do you think this would tame the idle sound even with a 2-out?
What’s the rough opening rpm? Just wondering what the sound would be like at interstate cruising in 5th gear.
How would this compare to HP/torque gain from SSIs?

The only thing that may change the static dB level in your current system is the premuffler part of the active exhaust. The premuffler is a bit more quiet than a test pipe. With this system the main muffler sets the baseline for how loud your exhaust is at idle and cruise.

The valve opens at about 6" of vacuum so there is no RPM setting involved. Your right foot controls when it opens. Drive like there is an egg under your accelerator peddle and the valve will not open, stab the throttle and it opens. This is demonstrated in the video posted above. The engine is revved quickly from idle to 6000rpm and the valve stayed shut so the exhaust was stock quiet. The throttle was then stabbed to 6000rpm and the valve was open creating the sport sound. While cruising the valve is closes so the sound would remain the same as it is now.

It well documented that our premuffler shows the same gain in HP when installed on a Carrera as SSI exchangers and a dual inlet muffler. This is not a fair comparison however as SSI primary pipes are not optimal for the 3.2L engine. Our premuffler has oversized inlets, F1 style merge collector with 2.5" straight through to the outlet. The active exhaust valve is sized to give the best HP gains regardless of the main muffler used. We also have a tuned tailpipe that knocks the sound level in half for those who prefer a less aggressive acceleration note. You have the ability to tune the sound level to your liking. A lot of R&D went into this system, much more than just a pipe with a valve on it dumping exhaust. Several styles and brands of valves were tested as well for longevity, heat tolerance, and durability to fully close and open every time for years of enjoyment!

.

[rokemester]

It would appear that this exhaust set up would provide easier access to the lower valve cover and valves for adjustment vs. the stock catalytic converter and heat shield on a 3.2 G50. True?

[tirwin]

Originally Posted by RarlyL8

The only thing that may change the static dB level in your current system is the premuffler part of the active exhaust. The premuffler is a bit more quiet than a test pipe. With this system the main muffler sets the baseline for how loud your exhaust is at idle and cruise.

The valve opens at about 6" of vacuum so there is no RPM setting involved. Your right foot controls when it opens. Drive like there is an egg under your accelerator peddle and the valve will not open, stab the throttle and it opens. This is demonstrated in the video posted above. The engine is revved quickly from idle to 6000rpm and the valve stayed shut so the exhaust was stock quiet. The throttle was then stabbed to 6000rpm and the valve was open creating the sport sound. While cruising the valve is closes so the sound would remain the same as it is now.

It well documented that our premuffler shows the same gain in HP when installed on a Carrera as SSI exchangers and a dual inlet muffler. This is not a fair comparison however as SSI primary pipes are not optimal for the 3.2L engine. Our premuffler has oversized inlets, F1 style merge collector with 2.5" straight through to the outlet. The active exhaust valve is sized to give the best HP gains regardless of the main muffler used. We also have a tuned tailpipe that knocks the sound level in half for those who prefer a less aggressive acceleration note. You have the ability to tune the sound level to your liking. A lot of R&D went into this system, much more than just a pipe with a valve on it dumping exhaust. Several styles and brands of valves were tested as well for longevity, heat tolerance, and durability to fully close and open every time for years of enjoyment!

.

Thanks, Brian. 2 more questions.

What’s the ground clearance? I have an awful driveway and wondering about scraping.

Are you open on Saturdays? If so I might just drive over.

[RarlyL8]

Yes access to the valve covers should be the same as with our premuffler. The valve and tailpipe are on the opposite side of the pipe.

The picture posted shows the system with the optional tailpipe silencer installed. The silencer exits right below the fender at about the same level as the OEM muffler tailpipe. Tailpipe delete is recessed several inches so no problem at all. I'll post a better picture of that area.

Yes shoot me an email if you would like to see and hear the system in person, anyone is welcome to do that.

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[tirwin]

Thanks again, Brian. Nice work. You've given me something else to think about.

I need a good excuse to drive over to Huntsville anyway -- friends and family over there. I'm out of town the next 2 weeks. I'll reach out before I come over. I have some long term ideas for the car I'm thinking about. Would like to ensure whatever I do fits into future plans.

[2jmotorsports]

My favorite part is how the bypass looks like a turbo screamer pipe. I guess it still is a N/A screamer pipe.

[RarlyL8]

Yes the little tailpipe does look and sound like a waste gate dump pipe, ha!

Here is a picture of an earlier prototype that had the valve angled higher. I changed that angle in order to add the tailpipe silencer. I still have this one if ground clearance is an issue. Remember the main muffler dictates sound but also may have a different tailpipe than stock. If yours turns back straight instead of pointing a but down like OEM then you have more ground clearance.

[dw1]

Excellent concept & execution. My only concern is that the "open pipe" (premuffler only) will be too loud. I've been in a 3.2 running only a premuffler is it was a problem at higher RPMs & highway speeds - that is, it attracted unwanted attention from the rozzers (you know, those folks who "protect & serve").

Do you have dB values for open/closed?

That being said, I still love the active exhaust concept for our older cars. In fact, I was trying to block the second pipe in my 1-in-2-out using an active valve and my efforts were wonky at best. I didn't think of doing it back at the premuffler.

[Canada Kev]

I wonder if there is there some way one could MacGuyver this to turn on manually or at least disable it so that an inadvertent full throttle application wouldn't open the valve at an inopportune time?

[robcf]

From what I can see the valve is held closed by manifold pressure at low throttle angles and opens when manifold pressure increases at greater throttle angles.

For this reason you could add a small vac reservoir and pneumatic valve to hold the exhaust valve shut when operation is not desired.

Furthermore, you could add an RPM switch so that the exhaust valve will not open until a threshold is achieved irrespective of throttle angle.

[RarlyL8]

Excellent concept & execution. My only concern is that the "open pipe" (premuffler only) will be too loud. I've been in a 3.2 running only a premuffler is it was a problem at higher RPMs & highway speeds - that is, it attracted unwanted attention from the rozzers (you know, those folks who "protect & serve").

YOU decide how loud the open valve is by adding the optional tailpipe silencer. I designed this silencer using the dyno to tell me how far I could restrict it until the system started losing power. The baffled tailpipe silencer is about 1/2 as loud as the open tailpipe.
>> Please note that the open tailpipe is not overly loud. Half of the exhaust still goes through the main muffler. The video in post #1 is with an open tailpipe, no silencer.
To me the tailpipe silencer is perfect. It gives the engine a performance sound like you would have in any modern sports car. Not loud but with authority. The open tailpipe gives a sport exhaust sound like our 911S or 911GT3 muffler with headers.

I wonder if there is there some way one could MacGuyver this to turn on manually or at least disable it so that an inadvertent full throttle application wouldn't open the valve at an inopportune time?

Remember you control when the valve opens by how much load you put on the engine. You can see in the video above that I revved the engine pretty quick to 6000rpm and the valve did not open. The engine can be accelerated without opening the valve. You will learn really quick how to modulate the throttle to control the sound. Also remember that you control the sound level with the optional tailpipe silencer. There really is no concern whatsoever that this system is too loud. A concern might be that you find yourself tipping into the valve all the time because it sounds so good! We also offer an optional cap if you wish to silence it completely for whatever reason.



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