rbohgan

good to know thanks! ill be taking it into the shop next weekend prob and will update with progress- since no one else has documented.

if anyone comes across a vid of how it sounds do share

AMG 17GT

This^^^^^ and is why I will probably do it.

Just not sure C is the same.

Andyroo

Be aware that your downpipes have to be cut to take the secondary cat out, but it can be reversed with a bit of welding.

rbohgan

really? didnt know they had to be cut. will check it out and post updates when i get to it next week. so all will know for future lol

Vic55

I saw the schematics of the C63 exhaust and you are right; its called a catalyst not a resonator.

rbohgan

^cool looks like we have clarification. thanks

AlexZTuned

For reference (#1 and #2):

AMG 17GT

Alex thx.

Would you happen to have schematic for GT. ? I'd like to compare the 2. Thx.

AMG 17GT

Done today.

Perfect mod. Doesn't affect everyday driving, and surge in exhaust decibels under load is exquisite ....

rbohgan

awesome. i havent had time to take mine to shop yet. any videos? i came across this video online:

Sanch

Hey mate, can you give us more details of what is involved?

I know the secondary cats have to be cut out but is there a pipe to replace it? I imagine once its cut out there will be a gap?

My shop advised it can't be done and recommend changing the down-pipes instead.

How is the sound on idle? - more raw?

rbohgan

should be the cats are cut out and a new pipe welded in its place.

AMG 17GT

A simple pipe exchange yes.

I was particularly interested in the idle and normal daily noise. It's slightly elevated.

But on throttle it's a blast 20% more. Do it.

Sanch

Def doing it, just notified the shop haha

Andyroo

Sounds like your shop would rather you spend $4000 getting downpipes and having them fitted than $200 having the cats cut out and pipe welded in place!

maxbeard4

Hi,

Regarding this Mod to the secondary cats, do you have to drop the transmission or anything to remove the cats? how do you actually get to the down pipe to cut the secondary cat out.

Also you might find this useful....

I have modded the Back box on my C63s, If you open the back box you will see 2 pipes, one for quiet mode and one for loud(Race), You will see there are little slits around the smaller pipe which is the pipe used when you have the exhaust flaps open (Loud). If you cover these up you gather much much louder bangs on down shifts and all round louder volume. you can cover them up by welding them up with a metal plate.

NARCOGP

Just a note from me, i removed my 2 secondary cats from my RS3 a few years ago, we used a cutting torch and a chisel and removed it in about 20 mins.
Leaving the exhaust pipe looking stock but the cat removed and not having to weld any piping

rbohgan

so I was planning on getting cats removed today...when I looked under car and realised its already been done. LOL the last owner had it done. I bought my car with like 8k kms on it. so I saved a couple hundred bucks there! I had no idea it was done cos I havent heard the sound of another c63 yet. so with this done it does have some nice pops and a good sound. but I'd want louder so im looking at doing more. headers or anymore thoughts?

Here are some crappy videos from my iphone so you can hear sound. bit choppy at start. it vibrated my phone so mic cut in and out so i laid phone down at end to hear better.

https://www.dropbox.com/s/tw6131iwiv...1080p.mov?dl=0

Andyroo

In your photo, that's not where the secondary cats go, that's where the factory valved h-pipe goes:
The secondary cats are right at the front, at the bottom of the downpipes.

rbohgan

ah its on the bottom of downpipes! ok i see it on the diagrams now. dam ill need to call him see if hes even willing to cut those off for me...

AMG 17GT

Haha yes they are in front of that straight bar. That must come off to remove.

Andyroo

No reason why he shouldn't be! Easy job

Sanch

Finallllly!!!

I have found a shop that has done a few of these and will be taking my car to them end of this month.

Unfortunately, flat out this month and can't do it any sooner.

Looking forward to that extra 20% on kick down yewwwwwww.

I was also looking into these new FI downpipes with cats - They are not catless, I can't stand the catless fuel smell even though its better sounding and performance.

This is plan B if I want it louder but it will also involve a tune

Pic below - left with cats and right catless

See63esS

Get a before and after video together for all of us on the fence.

Sanch

Will try my best, I tried to get one from the shop.

Seems the sound cannot be captured properly on videos.

I will do a review though for anyone wanting to tip over that fence