cal1

I just got my SL55 back from the muffler shop after having the secondary cats removed. They used a piece of 3” stainless U-bend cut to fit the two slight bends left by the removed cats. My goal was to reduce the restriction which I have heard could be worth 15HP or so and a little more exhaust note especially at WOT. I did not remove the resonators.

The “butt” dyno says I got a small gain. Throttle response seems a bit better. I also noticed the idle speed was up just a tick, maybe 50 RPM or so. After 2 days of driving, the ECU has adjusted it back to normal. This is making me think the engine is breathing a bit better, but I am no mechanic or engineer and sometimes swear the car runs better after an oil change.

As far as the sound goes, it is noticeable, but not too much so. My wife can’t tell the difference, which doesn’t surprise me. There is little difference at idle. It has more burble under deceleration and is throatier and louder at WOT. For an old guy, the sound is just right.

Below are three short sound clips. No before and after unfortunately. Notice the SC whine in the last clip.
http://www.youtube.com/watch?v=4ll-EhzcqNs

http://www.youtube.com/watch?v=Xi5oI-qNApM

http://www.youtube.com/watch?v=wd3Tfq2JlG0&feature=channel

So as far as the mod goes, I would say “do it” and if you like more sound, take the resonators while you are at it.

misterlawyer

Thanks for sharing your experience. Sounds like a nice mod. Some questions:

Do you have any idea what effect this will have on emissions? If this were done to a California SL55, would it pass smog? I thought that removing the resonators made no difference for emissions, but that removing the 2nd cats would.

cal1

You might shoot Simon at EvoSport in Huntington Beach an email: simon@evosport.com
I think they offer this mod at their shop.

jmf003

Nice clips! Love the whine on the last one!