Regulators of both cars and human health want to continuously reduce certain metrics regardless of how much it might cost to do so and negative ramifications. From Eric Peters at ericpetersautos.com:
Nostalgia is more than just fondly remembering what was. It is a kind of lamenting what is. Sometimes, it can be both at once, as when what was and what is cross paths, the one arriving – the other, fading away.
Cars you can still realistically screw around with yourself, for instance. These are still around and many people still drive them daily. They are vehicles like my 2002 Nissan pick-up, which I recently relieved of one of its two factory installed catalytic converters. You may ask – why would I do such a thing? Hold that thought a moment. The point is I could do it.
I do not mean just that I could physically do it – though that is part of it. The important part is that I could do it without electronic repercussions. Shorn of the second of its two factory installed cats, the truck’s computer did not sound the alarm. Or rather, flash it. The “check engine” light (which is really a check emissions controls light) did not come on because the computer could not tell I had cut off the second cat, there being no sensor aft of where the cat had been. The one just ahead of it – which is still there – was probably installed where it was to assure that the exhaust gasses passing by had been chemically converted sufficiently by the first cat, snugged up close to the engine.
In any event, what the computer doesn’t know won’t hurt me is the point. I was able to get rid of the second cat without the truck policing me for doing it. The truck runs noticeably better now, too – which brings me to the why I did it.
The cat I cut off was as old as the truck and likely half-choked by accumulated carbon. By removing it, I restored the flow that had been lost and probably at least partially made up for the restriction of flow created by the first cat, still snugged up close to the engine, where it, too, has been accumulating carbon build-up within its honeycomb lattice of platinum and palladium for lo these past 21 years.
I also nixed the probably restrictive factory muffler for a much less restrictive (and much better sounding) “turbo” muffler.