komp55

The factory center resonator has always been known to have a crossover passage in it, allowing exhaust pulses to balance out. What I could never tell was how large the actual crossover port was.

This weekend I was working on an exhaust project and decided, in the interest of "science", to sacrifice a spare and unneeded center resonator to take a closer look at the factory exhaust design. I cut the resonator in half at the location of the crossover port to get a nice cutaway of the port itself.

The port was actually larger than I expected, measuring 2 3/4" long by approximately 11/16" tall. The length, of course, is equal to the diameter of the factory exhaust tubing.

shardul

iTrader: (1)

Nice info.
That is why it is recommended to add a x pipe if you delete the resonator for sound purposes

GregD

I always wondered what it would sound like if I ran a Magnaflow true-X muffler in place of the resonator. I have a totally stock exhaust with muffler delete. I wonder if the magnaflow would alter the sound at all since they are a bit similar in design to the stock resonator(both having crossover). does anyone have any thoughts on this?

shardul

iTrader: (1)

sound difference will be very minimal

GregD

Yeah, thats what I kinda thought.

Exotic-metal55

What are the reducer looking tubes further back in the resonator? They look smaller than the 2 3/4 exh. tubing? May be a restriction?

Exotic-metal55

Magnaflow Tru x resonators are nice but I think to long and wide to fit in place of the stock resonator. I wanted to add one on my CL but room is tight.

komp55

Those are the perforated tubes that allow exhaust gas expansion into the sound absorbing matting. I seriously doubt much, if any, restriction is created since the resonator is a straight through design.

stevebez

So been womndering about this centre resonator and the cross over piece...

So why would they add a link pipe ahead of this in OEM config ... although it is ahead of the rear cats so perhaps that why ... balancing out pressures ahead of ar cats ?

So link pipe without rear cats and with oem resonator seems kind of pointless?

komp55

I don't know for certain, but I always thought the crossover pipe ahead of the secondary cats was for balancing the exhaust pulses and maybe also for emissions control (in the event the efficiency of one of the primary cats has decreased).

With that crossover pipe ahead of the secondary cats, the second crossover port inside the resonator remains somewhat of an enigma clothed in a mystery. Maybe it's for exhaust resonance control? Or maybe more likely, maybe a failsafe crossover system in the event one of the secondard catalysts becomes blocked? Your guess is as good as mine!

I'm still of the opinion that a well-designed X-pipe used ahead of the factory resonator is the optimal set-up, since it's pretty well documented that an X-pipe creates more HP and torque than an H-pipe (and most likely, more than an oblong shaped crossover port within the resonator itself. Seems like the resonator is too far rearward to be the optimal location for a system's only crossover when it comes to the scavenging effect of an X-pipe..

My other issue is resonance. I've tried just an X-pipe with stock mufflers (behind MBH headers with high flow cats), and for my personal liking, the cabin resonance was simply unacceptable at certain RPMs. With the factory resonator reinstalled, the exhaust note is perfect inside the cabin. Now my final step is to install a 3" X-pipe upstream of the resonator. Two different commercially purchased X-pipes I tried didn't fit right, so now it's a custom fabrication project to make it the way I want it to fit. I'm just waiting for a needed part to come in, so I can finish it up.

GregD

Does anyone have the dimensions of the factory resonator? just curious how big it is.

Toadster

4.25" H x 19" L x 9" W

GregD

Thanks toadster. It looks like the only magnaflow Tru-X option with 3inch in/out is the 12469 which has an 18 inch body length(24 inches total). It is a 5x8 inch can so it might be doable. The question is whether or not it is worth the effort for what might be a minimal sound difference.
-Greg

Toadster

i just lopped mine off and put in straight pipes - there's already an H-pipe just before the catalytics anyways... so there's some x-over already

http://e55-amg.blogspot.com/2012/03/...ting-mods.html

GregD

I am running straight pipes instead of mufflers. If I delete the resonator, it will be way too loud for me. I was debating the magnaflow Tru-x muffler in place of the resonator to get a bit of a different tone possibly.

Toadster

still have cats in place? if not - then yes pretty loud - if you still have them, you may be ok...

GregD

Yup, cats are still in place.

SavMan

I am now starting to panic after reading some of the posts, until recently my car had

PLM headers, primary 200 cell cats, x-pipe and then standard including center resonator.

I dropped it off on Monday for a new system with no cats, x-pipe and only rear boxes.

Will be picking it up tomorrow and started to get seriously worried about noise levels

stevebez

That is going to be waaay loud ....

I would say chopping cats has doubled the sound level for me ... chopping res would be 4x is my guess.

At mom my car is not a DD and its fine I can accept the sound level ... it only really get loud if I punch it....

Kickem

Hey komp, that sacrificial resonator looks very familiar....


I just recently deleted 2nd cats, res and stock mufflers and adeed the Magnalow Tru-x double in / double out in place of my resonator. When I was running this set up at first the drone was WAY too loud for me so we added a couple bullets (12" I think) where the stock cans used to be and this is the sound I have now: http://www.youtube.com/watch_popup?v...s6wk&vq=medium

It still has some drone between around 1800 rpm and 2k rpm (you can actually hear it in the video as he's working it up to 3rd gear) that I could probably live with but my girlfriend absolutely hates it so I'll probably take it back to my buddy and see what we can do about it.

And this is what it looks like installed:

GregD

I'm at work so Youtube is blocked. can't wait to hear it. Seriously, get rid of the bullets and put a jpipe where the mufflers go. It does not alter the sound but it will kill the drone by about 90-95%, plus they are cheap to do. Mine are about 28-29 inches long and curl up into the fender where the mufflers are. At least I now know that the magnaflow fits. Did you do everything at once or did you do things one step at a time. Still wondering what the sound difference might be between stock resonator versus magnaflow truX muffler in its place.

Kickem

Probably should have done it in phases but we were excited to see what it would sound like so we removed everything from the 2nd cats back and got to work with the Magnaflow. I like the tone it has now and it certainly seemed like the car could breathe better and also improved throttle response but the drone was the price to be paid. I'll suggest J-pipes in place of the bullets and see what we get. Thanks!

My laptop speakers don't really do the exhaust sound on the video clip justice but when I bluetooth it from my phone to my car audio you can really hear it roar.

GregD

I loved the sound of the muffler delete but the drone between 1800-2200 made my ears bleed. after a week, I just couldn't stand it any longer. You won't be disapointed with the j-pipes. I was extremely skeptical that they would do anything but they definitly killed the drone.

SavMan

I just picked my car up and as most have said it is way to loud, I have no cats and no resonator. They also had new rear boxes but the shop called yesterday to say the would need to put the originals back on as it was just insane.

I drove back carefully thinking the ecu may need time to adjust (my map already had rear 02 sensors switched off) but the car is seriously running rich. When you stand at the rear it's almost as if you are filling up at the gas station! Will it need to get remapped or will the ecu compensate itself. Already driven 70 miles and still the same.

SavMan

After disconnecting battery for 30 mins AFR's have returned to pre decat levels, still have the fuel smell but that's the price for no cats.
Will look at putting my 200 cell cats back in or adding the magnaflow above.