SilverDameon55

I'm looking to play with the stock exhaust and wanted to know a few things.
1) if I cut out the 2nd cats, will I throw a code?
2) if I only cut the resonator out and replace it with 2 individual pipes, will that throw a code or be beneficial for sound & power?
3) if I cut out both (depending on codes etc) 2nd cats & resonator and replace them with 2 individual pipes + an "X" pipe, will that be good?

thanks.

jumph4x

Just had this done. No code, slight but nice upgrade to the sound, no power difference.

If you look at the stock resonator from the inside, all it represents is a mesh pipe that matches the diameter of the exhaust system within a larger container pipe. There are no direct obstructions to the air flow.

Essentially what a resonator does is, despite being somewhat of a misnomer, is diffuse resonance points in the exhaust system but breaking down the wave 'period'. Instead of the sound being concentrated at certain fundamental frequencies, those peaks are removed and re-distributed as smaller secondaries throughout the frequency range.

Strigoi

The secondary cats are downstream from the O2 sensors. You can remove them and it won't cause any codes. Same goes for the resonator.

I had the resonator removed on my E63. All it did was make the car quite a bit louder. No codes, no performance difference.

SilverDameon55

Ok so cutting out just the resonator will at least give me some sound bite but no performance. Now what if I were to cut the secondary cats & resonator out and do the whole "x" pipe thing vs 2 individual pipes? I for sure want the sound part but it would be nice to have a bit of performance with it.

Strigoi

I don't know if you actually gain any performance by removing the secondary cats. I haven't done it since the car wouldn't pass smog then.

SilverDameon55

Luckily here in FL we don't have emissions. I just want to make sure I don't mess anything up by changing the flow of things. I can't imagine removing the secondary cats and resonator would do any harm per say to the power....especially since I'll replace the missing section with the "X" pipe to even out the flow. I'll make sure I make some sound clips for all.

Strigoi

The only worry would be emissions. Since that doesn't apply to you then go for it.

PieRat

So from a previous thread I believe the way it works is removing either the primary or secondary cats net's 12hp, adding an x-pipe adds another 8 hp. So removing the secondaries + adding an x-pipe should be good for 20 hp. If memory serves this is wheel hp.

I believe placing the x-pipe where the secondaries is best. That is where the factory crossover is and putting the x pipe as far forward as possible helps reduce drone.

MACEDON

I have both cats and res removed, in that case it will throw an error. Got a tune through eurocharged and told them to code out the check engine light and to tune for no cats, then delete CEL with any reader.

You gotta get it tuned for the extra airflow apparently.... worth the $400.

AMG Lover, KRK

If you have no issues with emissions whatsoever, I recommend removal of all cats as well as the resonator, doing so will definitely increase your power, it will be best if you throw a headers

I don't like the X pipe, I always go with the straight pipes for best performance in a forced induction engine.

SilverDameon55

Is it really better to go straight pipe VS an "X" with a forced induction car? I thought an "X" was always better to help with back pressure and such? Also anyone have a sound clip of just straight pipes with the factory mufflers?

Vader55

Muffler is the problem on E55's period - so freaking quiet, run different straight through muffler's or no muffler's with X-pipe and K&N's and you can leave your Cats if you have emissions bs like I do here in Cal.

duke749

cut both out if you want sound second cats kill more sound then the resonator
I've put some photos of my c55 pipes on my profile