SLK-Class (R170) 1998-2003: SLK 200, SLK 230K, SLK 320

SLK/R170: Post cat O2 sensor and custom down pipe back exhaust

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Old Apr 28, 2015 | 08:11 PM
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1999 SLK230
Post cat O2 sensor and custom down pipe back exhaust

Hello everyone,

For the past couple weeks, I've been working hand in hand with an exhaust fabrication shop creating a 2.5" downpipe-back exhaust for my '99 SLK230. The thing that has me a little frustrated is the fact that this car is a California Emissions compliant car so it has the weird, restrictive cat setup and a post-cat O2 sensor.

I heard of some people on here just swapping these cats for one higher flowing cat but I'm still debating on whether I should go with a cat-less design or buy a performance/california/OEM/aftermarket cat. The thing that has me stumped is the fact that half of people say that the O2 sensor controls fuel, while the other half say it does nothing but monitor.

If the O2 sensor controls fuel, then I'm going to be forced to buy a ridiculously expensive cat that I don't necessarily want. If it doesn't matter then I'll put a non-california cat on and not worry about the O2 sensor freaking out.

So, what's the word? Does this O2 sensor control the ECU in any way? Has anyone tried running a non-california cat in this car? Has anyone run an O2 simulator with any success?

Also, where I live, there's no emissions testing, so I could run open headers if I want, .

Thanks guys!
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