My 3.6 will be testing mike's muffler and a larger version of it at Hoover's as well. We unbolted my Dansk Sport from my 306RWHP 3.6 and it made 20HP more almost everywhere and at 5900 it picked up 35HP and TQ with no tune changes. And the tune was pissed off. So its more than a little restricted. Very anxious to see what the Holleran's Performance engine can really do when it isn't choked down. Stay tuned, I'll throw those results in here too for comparison

I would be interested to jump in too. Just finished a 3.6 install in an 87 Carrera for a friend and we installed a 997 muffler attached to B&B headers. I expect it will see the dyno sometime in the next month after the oil cooler is sorted. Currently installing additional oil cooler capacity.

Whoops, sorry about that Mike. The Vibrant center outlet muffler is also a perfect solution for those using filpped-flange 993 Bischoff heat exchangers. Those exchangers have outlets that point toward the center, making this muffler a great solution.

Monty
 

Yes, have thought about this, but finding dyno charts as proof of little to no restriction, is surprisingly difficult!

Now if that guy would just learn how to drive a 911 properly...

Very interested now. I have the Dansk Sport and I am looking forward to see if there is a better answer.

The dyno plots are fantastic. Thank you for posting.

Any results yet? Or is the build still in process?

It’s over at Hoover’s now. We tested mikes muffler on my car and it’s still restrictive. Made 6 more RWHP but not the 30 I had with open headers. So we are working on another setup. Probably won’t have center dumps, unfortunately. But we need power first and noise control second. Exit location is a distant third

My 3.6 has B&B headers and the Dynomax Cross Flow. With both outlet open is drones too much for my taste. My solution? I put a vacuum solenoid on the second outlet and tapped it into the vacuum line that activates the flapper valve in the 964 intake. That opens at 5,500RPM. So below 5,500 the intake valve is closed for more torque, and so is the second exhaust tip (for no drone and more torque). Above 5,500 both open, and it's party time. Not dyne'd it yet, but in my mind this is the best of both worlds, and when I talked to Steve Wong (it has his chip in it too) he thought this would be a great setup. From the outside.....you can see nothing too.

I have just ordered myself a Dynomax 17552 - the one with the crossover in the middle.
Getting it fitted up next week and hope to get it dynod not too long afterwards.

There are a lot of “Mike” on this thread. I’m not sure which one you are referring to.

which one made 6 more hp? The cross-flow dual in dual out?

We had the 17231 muffler with the polished S/S headers on the dyno last week started with a set of megs with reverse cones to get a baseline for the headers then the dynomax muffler, the 17231 worked well almost no power change from the megs, If you search for Nippy his thread has pics and dyno sheets posted, also our race headers open and with our GT3 cup car muffler
Mike Bruns

Haha, that would be me. Here's a shot of the final muffler on my car:

https://farm5.staticflickr.com/4898/...21ebe9f4_z.jpgIMG_2040 by Michael Small, on Flickr

And the final dyno chart comparing M&K GT3 and new muffler:

https://farm8.staticflickr.com/7864/...571a1733_c.jpg50986793_1426246354172640_3597683208080064512_n by Michael Small, on Flickr

The one above was slapped on my car and made the extra 6. I suspect it will flow enough for a 3.2 or sock 3.6, but with the headwork, cams and ITBs on mine, it simply flows too much air

Many Mikes later...

3.0-3.2 can work well with the vibrant center out, without drone, because they are forced to mix at the exit.

Dual (2 in - 2 out) mufflers also work, but parallel flow may have less drone, and the cross flow design does have drone.

3.6-3.8 engines need even more flow capacity, and that is being developed now.

Stock or sport mufflers are good at holding the noise down, but become too restrictive as the cam and fuel delivery potential increase.

Did I get this right?

Anyone consider just running two separate mufflers, one for each bank? Kind of megaphones with more sound deadening.

I was thinking two 3.5” x 7” oval magnaflow 1in - 1 out mufflers strapped to each other. And then plumbing them as separate mufflers for the left and right engine banks.

And then use some car chemistry inserts to quiet them down for Lime Rock. (86db lint)

primary issue is that the commonly available sport muffs were really all designed in the 60's/70's and their inlets are too small to support the larger motors developed after smog hit and the factory went to single inlet. So you stuff a big motor in an early car and bolt on a cool sport muff that looks right and it chokes the engine. So bigger engines need bigger pipe. The open can designs are essentially an expansion chamber with little airflow direction and thats where you get the weird dips in the curves. Reversion is fighting flow. Using a packed muffler will mellow the tone and cut the rasp down, but internal piping can change drone. So yeah. All of that

Exactly what I've done on my mildly modded 3.6 running 1-3/4" George headers into small Flowmaster single chamber mufflers, then straight out the back. Not concerned about drone or noise on the street, but they were only registering 98db at 7000 rpm on the maiden voyage at Gingerman Raceway a few months back. Been trying to get the car on the dyno for a month but Chicago weather isn't cooperating. I've got a Dynomax 17231 to fab up too if I have any other noise problems like at Road Atlanta.

Early pics, need to slightly tweak the exhaust tip up, they're a bit lower than I'd like because of the 3.6 conversion spacers at the rear motor mounts for clearance. And if someone can tell me how to upload a sound clip I'd appreciate it.

http://forums.pelicanparts.com/uploa...1549051026.jpg
http://forums.pelicanparts.com/uploa...1549051026.jpg

Update to this thread.
I had the Dynomax 17552 fitted to the car and mated up to my georges headers.

Initial impressions, are that the volume is lower, more refined, raspy and screams when you want it to. Best part is, that there is no more drone at cruising speeds.

Now the not so good part. I have a lot of vibration between 2000 and 3000 rpm. It's mostly noticeable on deceleration. But will also do it between those rpm points, when tootling around as well.
After 3000rpm, this engine is sweet and is way outperforming the M&K by far. Have not had time to get it to the dyno but have been doing some street logging and adjusting my VE tables.

However, the stumbling/vibration/resonance betwen 2 & 3k, makes it VERY unpleasant to drive around the suburbs.
I am very new to tuning, but have been logging my VE this evening.. when I looked at the 3d graph there was a massive valley/dip at all throttle settings, right between 2000 and 3000 rpm.

Does this mean that my engine does not really like my muffler at that rpm range? And can it not be 'tuned' out by a pro?
When taking off or accelerating through that low rpm, it feels like the engine is strangled but once it gets to 3000 rpm, it's getting all the air it can breathe.

Does the Dynomax 17231, without the crossover, work better all through the rpm range?

My experience has been that twin straight-through type mufflers won't pass sound at LRP. Two different 911 powered cars making 250-300 hp. I couldn't get either to go lower than mid 90s db, similar to 175K911's experience. I didn't try Car Chemistry inserts, but you'd need to get another ~10 db out of them, which seems very unlikely.

Mike I might postulate that the crossover is creating a reversion point and that’s what you feel. Swap for a non corossover and see.