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Comment by smileysteve | Hacker News Reader

This hyperbole doesn't really withstand the thought process; There is little reason that the exhaust shouldn't be cleaner than the air it is taking in.

1. There is an air filter that immediately takes out large particles (dust, dirt, mites, etc)

2. Emissions systems use hot wires to detect airflow precisely

3. O2 sensors readily adjusting fuel on the fly to ensure a complete burn.

4. A catalytic process using space metals that further ensures a clean burn

Effectively, whether it's dusty, a cow has farted around you, or a chicken farm is producing ammonia; the modern ICE has the ability to detect this scenario and adjust faster that 8k times a second.

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I know you have some solid points here, but all I can think about now is that we live in a world where a sensor exists that can detect cow farts at a rate of 8k per second.

This frustration arises from the situation that there are places where there is already more poison in the air than what comes out of the tailpipe of a modern, warmed up petrol vehicle. Los Angeles and Beijing are two examples where I have personally seen this situation on bad days. We are at the point now where mixture control and exhaust treatment leave nothing but carbon dioxide and water being emitted from a properly running automobile.

With regard to parent's assertions: 1. The intake air cleaner is to keep particles out that will damage the engine (and eventually lead to lower performance and emissions control malfunction); 2. Whatever airflow meter, or not, on an engine is for combustion control, but its performance affects emissions output; 3. Exhaust o2 sensors, for 10-25 years depending on make and model, have already been telling the control system the results of combustion on each cylinder, for every combustion; 4. The catalysts are not magic. They are meant to react with specific products of combustion; There is nothing in an automobile, nor should there be, to detect and react with things like methane and ammonia. The only time you see a dust/smog detection is in luxury models that adjust the cabin ventilation in the presence of this for comfort of the occupants. There are no adjustments happening at a rate of 8 kHz: combustion in a cylinder is not even happening at this rate.

I pointed out methane because the modern sensor pack can and will detect fuels or inert gases in the air and reduce/add the amount of fuel added added to approach stoich.

Then the combustion and catalytic process will break apart that ammonia and encourage its nitrogen to linger on its own as the hydrogens burn up or find some oxygens.

"here is little reason that the exhaust shouldn't be cleaner than the air it is taking in."

And it isn't anyway. Just stand next to a running engine in a badly ventilated area for a while and you'll know that engine doesn't make things better.

Actually, if you run a modern engine in a closed garage now, your eyes won't burn, you won't choke and it won't kill you. While this is a stupid thing to do, the bad stuff is only coming out before it's warmed up (meaning closed loop and catalyst warm enough to function) and if you back your car into the garage you can tell the difference the first time you do a cold start.

Better and Cleaner are 2 different things; No matter what, an ICE is going to output CO2 and H20; and depending on the fuel a few extra Cs.

CO2 or H2O concentrations are enough to make things worse for an engine or a human, but are not necessarily dirty.

NOX and CHs however are not as "naturally" in the air and producing them definitely makes the air "dirtier"

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