Hi guys, I am new to the mini world. I recently got an 06 MCS. Whenever I accelerate moderately hard for 20-30 seconds. I get this smell, like rotten eggs or similar (inside the cab). I know that I need to change SC oil to service it but it is not easy task. Especially in my country so I will have to tackle that myself. But I wanted to know if a bad cat would send out that smell or if you had experienced something thing like this. Thank you.

 

Check your crank pulley. It has a rubber core that deteriorates over time. When that happens the outer pulley doesn't spin as fast as the core. The two parts rubbing against each other creates a burning smell. Easiest access is thru the passenger-side wheel well once the fender liner is removed.

 

+1 = undoubtedly the OEM crank pulley.
I've been through at least 4 (OEM/factory) in my Mini since 2004.
I'd suggest replacing it with a PRW (fluid filled) or an ATI super damper.
They may cost more (unless gawd forbid - you go to the dealer for another OEM/factory) but piece of mind for miles upon miles, years upon years down the road.
I would avoid replacing the crank pulley with another same OEM/factory unless you don't mind having to replace it more than every so often...Or worse - (perhaps) causing catastrophic damage to your motor when they finally do will fail.

 

Inspect your harmonic damper before changing it out but you are correct that rotten egg smell is an indication of a fouled catalytic converter.

 

Good to know.
I've never experienced it myself and never even considered that it maybe a fouled cc.