a buddy of mine will be going catless on his CLS63 and I was thinking of potentially doing the same if the garage can give us a good deal for both. And then I started thinking maybe doing a res delete as well? im not completely satisfied with the aftermarket exhausts, so this might be a quick and cheap option just to get more sound

Should I do one or the other? both? what should i expect after the fact? few hp gain? better sound? drone? decreased efficiency? bad smell? will I pass NJ emissions?

thanks!

 

Deleting the cats might free up a few Pony's. Deleting the resonators will definitely make it louder but doubtful it will relieve much power as they probably dont restrict flow much, if any. I am only basing this on cars I have had in the past and not this one, since I actually think it sounds pretty good.

 

It is your lucky day lol,,

I have done all of the above you mentioned. First I had a resonator delete (both of the mid resonators) and kept the rear mufflers and catalytic converters. Didn't make difference except under medium throttle. Then deleted the Cats and that made it significantly louder. Later I added Spires stage 2 exhaust so basically my current setup is clear all the way from the extractors (Exhaust manifold) all the way to the spires rear mufflers. Sounds Amazing!!!

As far as power goes you will pick up a minimum of 10 wheel horse power if you delete the cats and resonators. I tested my vehicle on dyno before/after. Mind you mine is an XF 5.0 NA yours is supercharged so chances are you WILL get more whp than I did.

Pros of decatted exhaust are better gas mileage, less heat especially if your cats are old or starting to fail, great mid and top end power.

Cons: Gas smell (Especially on cold startups) and it takes about a minute longer to warm up your car. If you were someone say who used to warm up their car for a minute I would say it would now require two minutes or a minute and half to get the same temperature. I highly highly suggest you get a tune so you don't run into any trouble and to not have to look at the annoying CEL

 

You will probably lose power on a supercharged car, or at best gain nothing, unless you get the tune adjusted to compensate for these changes to the exhaust. Naturally aspirated engines respond differently to such changes.

 

I wrecked one of the cats on my 07 XKR and my mechanic recommended just removing them both. I followed his advice but that made the car undriveable due to how loud the exhausts became. We therefore removed the centre resonator and put some custom ones in place. It is still quite a bit louder than stock and I love the sound below about 2500 revs but above that it is a little jarring. We are just coming out of winter here and the exhaust note with the windows up is not pleasant either because you lose the deeper notes but with the windows down it sounds awesome.

My biggest gripe though is the exhaust fume smell. My wife has commented a few times on the fact that my clothes smell of exhaust fumes after parking the car in the garage. It seems to permeate everything so I am looking at putting cats back on the car.

I have in the meantime had a tune put on the car and there was quite a jump in my terminating speed on the standing quarter and it is far easier to spin the rear wheels than before so you can get a decent performance boost from it. As Cambo mentioned, I seemed to lose power with the cats removed but the tune restored that and more. I am back on the factory tune now though so have lost the performance boost.

 

Just wondering...I am getting the 200 CEL cats from Velocity AP soon. Will there be gas smell with those or do I get the better flow without the smell? ... maybe that a question for them...