If Downpipes are illegal, how do people get away with using them?

[MikeLowrrrey]

Some websites list Downpipes as not for use on pollution controlled vehicles. Is there anyway to bypass this in a city that requires emissions testing? I imagine cities that don't require emissions it doesn't matter and guys freely install downpipes

[elterrible987]

are you talking straight pipe? because they have larger diameter downpipes to replace the stock that still use either the stock or a new catalytic converter. but there are a lot of places that dont do any emissions testing these days so it wouldnt matter there.

[FFailed]

Don't buy cat less downpipes?

[kovalchuk71]

In NC, you can throw one code during inspection and pass.

You can also “modify” the ECU so it isn’t detected.

[nosirrahx]

If Downpipes are illegal, how do people get away with using them?

[BJoe]

The people that are using them either are using them on race cars that aren’t on the street and registered as such (which is still “legal”, for now), running them on the street in areas where there are no emissions checks and law enforcement either hasn’t looked or could care less, even though it is a violation of the law, then there are those who are running them in areas that do check and have yet to be caught without by the police and then swap the non legal parts for legal when they have to take them in for testing.

That said, in the pre-OBD2 and E85 days, I knew guys that would use gutted cats then ran denatured alcohol when going in for their tests to keep up the appearance of being legal. The alcohol would allow what gas it was blended with to burn cleanly enough to get past the stations sniffer equipment and the gutted car would keep the appearance of a functional cat when going through the test station and if a local cop got nosy for any reason. There were now down stream O2 sensors or standardized diagnostic protocols to plug in for at the time.

[Firefightn24]

No emissions checks in lots of the country. Where I'm at you can go a county over and not worry about it. Motorcycles aren't checked either where I'm at.


Or stick em on for the inspection and take back off once done... but that's a hassle.

[blazenbb]

You go to one of the thousand emission shops and give Jose an extra Benjamin and tell him it needs to pass

[Jax05]

Some websites list Downpipes as not for use on pollution controlled vehicles. Is there anyway to bypass this in a city that requires emissions testing? I imagine cities that don't require emissions it doesn't matter and guys freely install downpipes

They have to list them as such, due to federal regulations.

There are few ways you can bypass it:
1. buy down pipe that has high flow cat (and put O2 spacer if needed so car is not throwing CEL) so you can pass visual and OBD. If they do sniffer test you'll probably fail
2. live where they don't do inspections (btw removing cat on a street car is still illegal even if your city/county doesn't do inspections).
3. find a shop that takes 'tips'
4. put stock back in for inspection

The people that are using them either are using them on race cars that aren’t on the street and registered as such (which is still “legal”, for now), running them on the street in areas where there are no emissions checks and law enforcement either hasn’t looked or could care less, e

Absolutely not true lol

You can also “modify” the ECU so it isn’t detected.

You can modify ECU so that the rear O2 has an infinite value and therefore it wont trigger CEL, but you'll fail readiness test and therefore fail emissions regardless