so in my e83 x3 m54b30 3.0i awd automatic, there are 2 precats, 1 in each manifold. I'm just wondering where the post cat(s) are, I looked at the exhaust and, according to a (now known to me) mistranslated chart, it was "converter and pipe," but in fact was the first resonator. Are there really 2 resonators and a muffler, alongside only precats, or is there a post cat in the system there I'm just not seeing? To me it seems like an odd system, but it is german space magic we're talking about.
According to the parts lookup, the catalysts are part of the 2 exhaust manifolds. That's it. Everything else is not catalyst.
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yeah, that's it. the 2 cats in the exhaust manifold. which is a good design compared to the honda's, you can't really steal these without taking the whole car.
"Precats" sounds like you're referring to the upstream oxygen sensors. The post-cat sensors are located in the downpipes just downstream of the catalytic converters. A "cat" is neither pre- nor post-... it is simply THE catalytic converter, and each one is part of its respective exhaust manifold.
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