Sean03S55

There are no check engine lights and the car sounds really cool but it's kinda loud at full throttle especially in the higher revs.

I do still wanna check for any stored codes as the car seems to as though it may have actually lost just a touch of power.

There was a problem though, After they already cut the exhaust we found it was 2.75" and not 3" and they can't even get that size piping. So, from the primary cat's it's the stock 2.75" to the point where the secondary cat's used to begin and then changes to 3" mandrel bent down to where the resonator used to end and changes to stock 2.75" piping again out to the mufflers.

I figured because it finishes in 2.75 it shouldn't really kill too much back pressure and removing the secondary cat's would maybe even give it a slight increase in feeling.
The car doesn't even seem to have so much of a problem with wheel spin in
1st lately and it usually did. It may seem a little stronger in the higher revs and I'm not even sure about that.

I'm gonna check for any codes tomorrow at the dealer when I get my oil change

stevebez

Loss of back pressure has dropped your cylinder pressures resulting in loss of power ... easy to remidy as you can now run higher boost more effiiciently ... unless ecu is deciding to play power police...

Sean03S55

I forgot to mention the car is an E63.

stevebez

Hmmm interesting ... back pressure affecting that car too - I reckon its ecu.

Sean03S55

If only I had dynoed before and after then I would know for sure if it lost power and how much.

I found 2.75" piping and mandrel bends on ebay. I wonder if it would be worth changing to so it's the same diameter all the way through. I doubt that 3" section is really hurting performance though. I have to get it back on a lift and make sure there are no leaks at the welds, I don't know if I like this exhaust shop too much.

It's only the first day driving since the change, if it doesn't get any better maybe I'll put the cat's back in and just leave the resonator out but this time order some 2.75" piping.

oldgixxer

Here's a thought:On a N/A engine if you free up your exhaust flow but are not increasing any intake flow,what kind of HP gains were you expecting?It's not going to boost power any since your not increasing the air coming into the engine.If you alter the exhaust flow without increasing intake flow you will lose power 9/10 times.
Just my opinion........

Sean03S55

I wasn't really expecting much of a gain but I also wasn't expecting any loss.

What do you guys think, I should just return the cats and get 2.75" for the resonator section? Or if the loss isn't even because of removing the cats but from using the 3" section.

oldgixxer

Highly doubtful the 3" section had any negative effects.
If it were my car,I would put everything back on&wait for good quality set of equal length headers&a full exhaust designed specifically for the 63.
But even with that,unless the car is able to breathe better I dont think the exhaust would be worth more then 15-20hp and cost thousands of dollars

jpohl402

Would carbon fiber engine boxes be considered increasing intake flow ?

jangy

Maybe 10hp or so depending on brand. Initial styles actually lost small power.

Roupin

From experience with N/A engines (and verified on a dyno), there is no loss in power when opening up the exhaust. The reduced backpressure just pushes up the powerband slightly higher in the rpm range. You feel less kick off the line and at low revs, but it's not "lost"...just closer to redline.

Of course, that's within limits as well. A poorly made low restriction exhaust will reduce power, but just pulling off a few things off a stock setup isn't that dramatic.

Roupin

One more thought...reset your ecu.

biltrite88

I've owned my CLS for 3 years and just got around to doing the res delete this morning. Mine looks exactly like VirtualRain's picture in the first post. Took 1 hour and total cost was around $220.
I can't believe I didn't do this earlier, it's awesome!
Highly recommend for anyone who wants more low end growl and bark in the exhaust. Sure, it's not as refined as the AMG exhaust but it's way better than stock.
Removing the resonator opens up more flow so you get a more/louder sound, then you can fine tune the note from there.
Stop thinking about it and just do it. If you don't love it you can add an x-pipe or new mufflers and adjust to your taste.

pgolfco

I removed just the resonator on my 2013 CLS550 and although the sound was much improved, I like the sound of the vehicles in the videos that had the resonator AND the secondary cats removed as well.

Any check engine lights or codes pop up for those of you who had the secondary cats removed as well?

Please let me know.

Thanks!