Quite a few years ago (can’t remember exactly) the EPA upped the mileage requirement on all emissions equipment. A few existing items were upgraded and required to last 70,000 miles instead of the original 50,000 requirement and new items were added to the list. While EGR and the pump were part of the original EPA requirements the actual exhaust pipe system was not, due to the tremendous cost and OEM resistance. I can’t remember the steel company but a new formula was created to be low cost (relatively) and malleable. That is when EPA include the exhaust system under the 70,000 requirement. 409 stainless was created solely as a cheap material to meet EPA mandates. It is still more costly than aluminized tubing so you will find 409 used sparingly unless it is an expensive car (i.e., more profit for the OEM). On cheaper cars, 409 is used only where aluminized tube will not survive the 70,000 mile mandate. This is typically, but not always, in the headers, and CAT. I haven’t cared to keep up with the EPA so my numbers above are probably wrong or outdated. I agree that 409 is mislabeled. However, even from the beginning 409 was called stainless because of its nickel content which is far less than either 304 or 316. It was marketing swill and it perpetuates to this day. Corrosion resistant steel (CRES) and stainless are words used almost synonymously on most drawings and specifications. Those in the industry who see either word will ask for further specification of either 304 or 316 because of the tremendous cost difference. You can never rely on the word “stainless” due to the tremendous range of alloys, properties, and cost. Much marketing of 409 in the aftermarket is relying on the consumers lack of knowledge. YMMV
Topic: Getting ready for Bonneville(rebuild) (Read 1910866 times)