Am planning on an ECU re-map and am considering removing the secondary cats. Anyone done this ?
Any effect on the exhaust noise level ? Am looking for a bit more sound !
Is it worth doing for a performance increase ?
Thanks in advance
mick
'06 Aero Blue Coupe

 

As has been discussed here many times, there is very little performance to be gained. Sound is another story, deleting the back cats with no other mods should result in a slightly deeper tone. You could install and X pipe there which also would deepen the tone a bit. As long as the resonator and muffler are intact, it will not get significantly louder.

 

No performance gains, but most who have done this go a step further. They will do the resonator delete and change the muffler....

 

You know.. I installed my magnaflow like Monday or Tuesday.. and this evening was the first time to take her out.. (rain mud etc.).. and now I'm anxious to hook up Torque Pro to check the HP reading.. PO cored the stopped up cats and man she just seemed like there was another 5-10 HP in her. If not.. well I'm digging her new notes! LOL

 

Jim,
May well have discussed several times, but not easy to find every post across all the sub-forums !
Anyway, I looked at the SLK320 forum and lots of stuff there about removing secondary cats. Common theme is they were fitted by M-B to pass California emissions and highly recommended to remove if not needed to pass a test. Also, agree with you, no real performance gains. What's interesting, 2 ECU re-mappers in UK (inc Eurocharged) recommended their removal before the re-map ?
Luckily I have a specialist exhaust shop (LongLife) 1/2 mile away from me and they do re-mapping as well as cat removal service. Am taking the car to them to see what they can do. Basically I want the re-map for the extra power/drivability etc. and a little more noise, but no too much !
Mick

 

Well, after scouring the forum, convinced myself secondary cat removal was the way to go. Had the cats removed yesterday and the re-map done in one go. Did some research on re-maps here in the UK and happy that the LongLife offering was as good as the others (circa 20-24 HP gain). Turned out the guy who runs the LongLife franchise is a friend of my son, got a slight reduction and a very neat job! Problem is, I never gave the car a good thrashing before the mods, so I don't have a base line to compare against. Never the less, very pleased with the results and the slight increase in sound.
Fitter has quoted me for a replacement free-flow stainless back exhaust box, with OEM tips and options on how noisy I want it to be. I'll see how current set-up works and sounds and make a decision later.
Mick

 

Mick, I replaced the rear cats and "H" pipe with a stamped "X" pipe, which gives a much freer flow and really cuts down on the interior resonance/drone. Bought mine here: Fantastic prices! (I used the 2.25")

Results for X-Pipes

 

How much lower in timber did your exhaust note get? My plan is to replace the CATs with a Y pipe 2.25 into 3, then through a 3 in by 12 resonator to the muffler, bypassing the stock resonator which will make a unique paper weight.

 

Did mine a little different. "X" pipe taps directly into resonator which acts as my muffler because I deleted the heavy AMG muffler off the back. Nice girgle out the back @ idle and timber is pretty calm and civilized in the cabin. WOT's a whole different story altogether, but I like the looks she gets when they hear me leaving them behind! Reminds me of an uncorked Porsche.

 

Hi,
My exhaust man says 'X' joint not required on my car. Says 'X' joints are for cars that have completely separate systems for each bank of a V engine, enables the two banks to be connected.


My stock system is quite simple - down pipes from each primary cat, along to the secondary cats and then out into a 'Y' joint, then single pipe straight into the muffler. No resonator, is the resonator a US requirement ?


Mick
'06 Aero Blue Coupe
UberMapped

 

I believe you will find the resonator only on the SRT6's, but when I installed my OBX Racing cat back on my NA, it included a resonator.

 

Find another exhaust guy. Your's is a putts. Our "V" engine has 2 - 3cylinder banks. Hence the "2" downpipes. Only the SRTs have a resonator. Removing the rear cats and replacing with straight pipes will give you one heck of a drone inside the cabin. The "X" pipe eliminates that drone and assist in the flow and scavenging effect which provides more linear flow and thus more horsepower and fuel savings to boot. The X pipe is just an improved form of the H pipe which was conceived in the 60s by the mfg to cut down on exhaust noise inside the cabins from the larger V8s they were installing.

I'm running without a muffler and have no problem hearing my music or talking to passenger. When I get on it all noise is heard at the rear of the car. Many who have done the Ansa or Magnaflow systems and left all else intact complain of the loud drone produced around 50-60 mph. The "X" pipe eliminates that!

 

Syfi,
I'll reserve judgement on whether I think he's a 'putts' or not, my quote was my interpretation of his response when I asked about an 'X' pipe, not his exact words. Haven't driven the car on the highway at 50-60 MPH yet.


Anyway, I've done a lot of reading on the benefits of 'X' pipes on V engines (most references focus on differences between the 'H' and 'X' pipes) all have a common theme, they were referring to engines with completely separate/un-connected systems for each bank of cylinders and the 'X' (or 'H') pipe allowed the pulses on each side to mutually support each other and improve scavenging/noise etc. I haven't seen anything that specifically refers to a system like the NA Xfire where the 2 systems join together in a 'Y' before a single muffler. I totally understand the 'X' pipe principle on separate exhaust systems for each bank, just can't see how it would help a system where the 2 sides are joined/linked anyway ?


I'm no expert, just a keen and experienced DIY car/motor-bike mechanic so shoot me down if you are !


If I decide to go down the 'X' pipe route, where is the best position in the NA Xfire system ? I'm guessing, where the sec cats have been removed ?


Anyone got a good photo of an 'X' pipe installation on an NA Xfire ?


Anyone done a before and after dyno run ?


Mick

 

Remove rear cats and H-pipe, insert X-pipe (circled in red). Pic is of SRT but you get the jist.

crossfiresrt6_03.jpg

Do your mods w/o X-pipe and see how it goes. If drone becomes unbearable, X-pipe will fix it.

 

Sufi,
Thanks for the fot, makes the differences between SRT and NA clear. The secondary cats are much further back on an NA and no resonator.
Spoke to 2 Maganflow and 2 Powerflow exhaust shops here in London. All four said an 'X' pipe on my (NA) system (with sec cats and 'Y' pipe feeding single muffler) would be a waste of money.
I mentioned drone and none could comment , suggesting (like you) to see if there is any and how bad. Even though they had obvious benefits in selling/fitting an X pipe, none were keen to do it as they couldn't gurantee it would reduce/kill any drone.
One shop suggested they could install an 'X' pipe, and then feed the outputs to two separate mufflers, centrally side by side .
Still haven't had a chance to drive the car on the motorway between 50-60.
Mick

 

Sufi,
Forgot to mention, where is the H pipe in the photo ? All I can see is the left and right bank down pipes from the prim. cats, through The sec cats into single resonator box with one outlet to single muffler. Basically the difference to the SRT system is that the NA has a Y pipe in place of the resonator ?
Or am I missing something ?

Mick

 

Syfi,
Ok, I can see the H now (enlarging photo from the page didn't work) saved the fot and viewed it elsewhere.
The H and the resonator are SRT specific, so I can understand why the exhaust guys here say an X pipe followed by a Y pipe may not be a good idea ?
Mick

 

I do know a couple of members have done the X fed into separate mufflers, a true dual exhaust system with nice results. Check out this thread...

https://www.crossfireforum.org/forum...aust-help.html

 

So maybe my exhaust man isn't such a putts after all !
I think I'll get a quote for a true dual exhaust
Mick
'06 Aero Blue Coupe

 

Syfi

Do you have any pics you could post of your exhaust setup? - I thinking yours is the best solution with minimum cost....