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Hersbird · 06-08-2018, 07:39 PM

I would guess the first cat is kept smaller for faster lightoff and the 2nd cat to finish the job. The first cat is actually called a "pre-cat" in that case.

06-08-2018, 07:39 PM	#6 (permalink)
Hersbird Master EcoModder Join Date: Feb 2014 Location: Missoula, MT Posts: 2,668 Dark Egg - '12 VW Touraeg Thanks: 305 Thanked 1,187 Times in 813 Posts	I would guess the first cat is kept smaller for faster lightoff and the 2nd cat to finish the job. The first cat is actually called a "pre-cat" in that case.