Originally Posted by m3an
you statement forgets that A/F can be altered via having no cats on the car. Will it? prob not, but BMW can say it will and good luck proving them wrong. And it's not the same gain as when it's cold outside, little different. Yes, federal emissions equipment has it's onw warranty but it is also ILLEGAL to remove and grounds for a warranty denial immediately.
the problem is if you remove the cats w/ are emissions equipment, then yesm the dealer can void the warranty. Most new cars are sold w/ this as a disclaimer. Yes, MAYBE you will win in court, but who has time for all that bullshit. Especially when removing the cats, BMW can easily say that the A/F ratio is now manipulated and yada yada yada your warranty is void. IMO not worth it for them to void a warranty on a new car. And yes I know all about the act, but you keep preaching about it, and it's not that simple as you make it sound
Not only does removing the cats not change the commanded AFR of the engine (that is commanded in the tune), but with a target based ECM like the M has it will have no effect because the ECM will do anything within the physical limits of the car to hit that target AFR. Even on cars that I have tuned in the past that were not target based, going to an offroad exhaust changed nothing on the AFR.
They are illegal to remove, I'll give you that one. That is why most all catless pipes say off road use only, but we all know no one takes an M off road.
I agree it is a ton of time and money to fight, and most people never will. But when you need a $20k drivetrain all because of a set of mufflers, it is the cost effective, and correct, path.