> My understanding is that such parts are not by themselves illegal. The crime is actually using them on the road. My understanding was that they were legal for track purposes.
ok, it's just a single datapoint, but motocross racetracks in New England, already built in the woods away from civilization, started requiring mufflers about 50 years ago, early 1970's
In the case of gasoline cars, there are mechanisms for controlling intake air, recirculating exhaust gas, and filtering emissions directly out of the exhaust gases. All of these impact carbon emissions.
These defeat devices allow drivers to modify some or all of these attributes in favor of gaining engine performance.
Muffler delete is a known cause of misfires. It manifests as a popping sound surrounded by the other shitty sounds produced by such a modified exhaust. We have all heard it.
That's a backfire. You're right in that a muffler can diminish the volume of a backfire, and that it is caused by combustion in the exhaust.
But the incomplete ignition of fuel can occur in both stock and modified vehicles. My car is completely unmodified, but can very easily have a low quiet popping noise during downshifts. With e removal of my muffler, it would be quite loud.
A modified engine can do this to a much greater extent, depending on the modifications. Some do so intentionally with what is known as a "burble tune", which is quite annoying in my opinion. It is inspired by rally cars that would intentionally inject fuel during the exhaust stroke and fire the spark plugs to keep exhaust driven turbines spinning even when under deceleration.
A misfire is a failure to combust the air/fuel charge in the combustion chamber during the expansion stroke, and they aren't typically caused by muffler deletes.
They can lead to the popping sound you're describing, but they don't always, and they're far from the only cause, and muffler deletes aren't necessary for those either. Unburned fuel hitting oxygen in the tip of a hot exhaust and immediately burning is the direct source of the noise, and causes for that are numerous.
In my kneck of the woods we call that backfire. A misfire is when something goes wrong in the cylinder such as the spark failing. Misfire can cause backfire, but not all backfire is traced to misfire. A very rich mixture can backfire without misfire.
A backfire is when the exhaust goes back out the air intake. An explosion in the exhaust system is called an afterfire, and is far more common. Most people just say backfire for both, unaware of the other term
Ok, we have quite a few keyboard mechanics here it seems. The muffler is a source of back pressure. That back pressure is part of the highly optimized emissions systems tuning done by the manufacturer. When you remove that back pressure there is high likelyhood that the reading from the 02 sensor are going to change and cause the computer to alter the air-fuel ratio based on that change. Hence, you will likely lose power, mpg, and introduce the possibility of misfires and other unwanted behavior.
I saw this analyzed on a Chevy Silverado that would randomly misfire. Everything else checked out: fuel pressure, spark plugs, firing timing, and fuel injector pressure. The remaining item: muffler delete.
We’re not taking about mufflers. For example in California “Emissions defeat system” means you simply used an off-brand air filter that wasn’t blessed by the government.
The parts may even be more efficient and less polluting, the government bureaucracy everyone here is worshipping doesn’t give a rats behind.
Exactly. Years back, I moved to California with an 80's sports car that was admittedly quite hotrodded, but I made very sure that the hotrodding did not worsen its emissions because 1. I wanted to keep driving the car in CA and 2. I don't want to pollute. First SMOG test in CA, the car blew clean as a whistle. It met emissions standards 40 years harsher than it ever had to meet.
Except I had all sorts of aftermarket parts in there from years of repairs, none of them with the all-important California CARB seal of approval on them, so even though it blew clean, it still "failed emissions" and I had to sell it to someone out of state. I'm still bitter about it.
In Ohio in the early 2000s all us kids were removing cats and passing the sniffer test easily. There was a visual test so we would normally just hollow out the existing cats. A lot of times cars with missing cats would pass the visual as well.
This is disingenuous; you have to do a lot more than change an air filter. You would have to change the actual piping, etc. with one that the seller declined to spend the money on certifying as compliant.
Further, and most people don't know this is a thing, you CAN tune your car as much as you want and have it certified with all of those parts as a one off for about $5,000 and a six-ish month wait. This is how you can legally import overseas vehicles and get a California title and registration, but it's $5,000 per test, and it usually takes more than one if you aren't super prepared. After the certification the entire engine (including all modifications) are regarded as that being the SMOG compliant form.
One other major loophole is kit cars; SB100 allows for non-SMOG vehicles to be built as a kit. Not everyone's cup of tea, but you can build things like the Superlite GT-R [0] or SL-C [1] and never SMOG it.
Which air filter? The engine air filter? I've never had a smog check that involves looking at that one. And AFAICT there's no RFID or anything in it, so it's not something they can check remotely
ok, it's just a single datapoint, but motocross racetracks in New England, already built in the woods away from civilization, started requiring mufflers about 50 years ago, early 1970's