93' K1500 complete exhaust question?

[Schurkey]

Im still waiting to see where its against federal law to have dual exhaust.

Is a letter from the EPA, hosted on the secure EPA web site good enough for you? It's a summary of the actual laws, not the laws themselves (so it's way easier to read and understand.)

https://www.epa.gov/sites/production/files/documents/exhsysrepair.pdf

(Note: What follows is a cut-'n'-paste but with optical character recognition making a mess of some words. See the link above to download the authentic copy.)

Question 7.

Is it tampering to install a dual exhaust system on a vehicle
originally equipped with a single exhaust?

Answer z. Yes. The general rule is that a motor vehicle
emission control system (which includes the exhaust
configuration) may not be changed from an EPA certified
configuration without subjecting the repair shop to liability for
violating the federal tampering prohibition.
configuration, including the location of the converters, and
exhaust pipe diameter and length, are items specified by the
manufacturer because engines and some of the associated emissions
systems are generally affected by the exhaust system
backpressure, which subsequently affects vehicle emissions. The
installation of a dual exhaust system with two converters would,
therefore, be considered tampering. The Agency will not, however,
require a repair shop to restore a vehicle which has a non-stock
dual exhaust system to a single exhaust configuration. A shop -
may, therefore, replace sections of pipes on such a system,
except for that portion of the pipes where the original catalytic
converter would have been located. It would not be considered
tampering to install a dual exhaust system with tvo converters if
the vehicle manufacturer certified an identical engine-chassis
configuration for the vehicle model year or newer that includes
such an exhaust configuration.

This is generally referred to as "SAME NUMBER, SAME LOCATION" which means you can't put a converter on a car that didn't come with one; you can't put two on a car that came with only one, and you can't put only one on a car that came with two--except as noted above. You can't install a converter behind the transmission if the vehicle was certified with one right next to the exhaust manifold.

Being a FEDERAL law, this applies in all 50 states. Enforcement is another matter.

Another section of the same letter specifies that the "owner" can't do-it-himself legally, either.

 

[Hipster]

From the same EPA letter. I found it interesting as well that you cannot de-certify your own vehicle for off-highway use.

 

[Schurkey]

From a different letter: You (or a shop) cannot replace a faulty or missing converter with a USED converter from the exact same application UNLESS the converter has been tested to be functional.

"Remanufactured" used converters will be marked as "used", along with the EPA-assigned remanufacturer ID, the reman part number, and a date code.

 

[b454rat]

That is the first I've EVER heard that. I don't know the other states laws, so can't comment on theirs. But even in NY, I've never heard that. I've had cops question me on stuff, but never went any further. One garage did get in trouble to taking a cat off. Any vehicle I had 95 n older, cat came off. One cop tried to tell me flowmasters will illegal, and only street rods could have em lol.

 

[Supercharged111]

That's because nobody ever refers to the law, rather what they heard. That said, the law is retarded. If you can pass a sniff test it shouldn't matter what you've done to your car.

 

[Erik the Awful]

Let me play devil's advocate here:

"including... exhaust pipe diameter and length... because... emissions systems are generally affected by the exhaust system backpressure, which subsequently affects vehicle emissions."

Which would mean that changing from the stupid crinkle-bent exhaust tubing GM used to an aftermarket mandrel-bent system is illegal, even though it's 50-state emissions certified.

Also, Ian's not asking for a dissertation on legality. He's asking for a reasonable exhaust system. My opinion (like butts, everybody has one and they all stink) is to get a good free-flowing exhaust in a diameter appropriate for the engine size and performance you're targeting. Spent the extra $120 to put cats on it, because we should all be good neighbors. Muffle it enough that it doesn't rattle windows. You're not likely to find a law enforcement official who is going to get out a tape measure to check your cat's position.

 

[Schurkey]

Our various "governments"--Federal, State, County, Township, City--can't manage to deport the "11 million" Cross-Border Invaders they admit to (the real number is probably double that) so it's not surprising that State and local authorities aren't too concerned about Federal emissions regulations.

Unless Government can make a profit enforcing laws, they're generally pretty lazy about the whole business.