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But a gas car with no cats, tuned for maximum power is not really comparable to a diesel truck rolling coal. One might leave soot on its own rear bumper, the ot
by hnov 4y ago
But a gas car with no cats, tuned for maximum power is not really comparable to a diesel truck rolling coal. One might leave soot on its own rear bumper, the other covers everything behind it in disgusting soot.
- TylerE 4y agoThere are tons of exhaust pollutants that are not visible.
- sudosysgen 4y agoThose are all exarcebated by the incomplete pollution of trucks rolling coal far more.
- bumby 4y agoTo say they are "all exacerbated" isn't quite accurate. Air/fuel mixture affects the various emissions differently. For example, going from lean to stochiometric will increase NOx but decrease CO.
- sudosysgen 4y agoLean/Stoichiometric is one thing, you still can (in theory) have perfect combustion on that part of the axis. Running very rich will increase both NOx and CO, for example.
- bumby 4y agoIt's a bit more complicated than just air-fuel ratio. The primary mechanism in NOx formation is combustion chamber temperature, while the primary mechanism in CO formation is incomplete combustion of HC. If you look at most emission maps, the NOx is decreasing rapidly while CO is relatively flat or increasing. My main point is that combustion is complicated and not as simple as "just do this thing to reduce all emissions". It's often a balancing act, which is why European regulations may be more favorable to diesels than American regulations and the opposite is true for gasoline.
- sudosysgen 4y agoI definitely agree that within reasonable combustion regimens it's a balancing act. However, when you run your fueling extremely rich like someone that is rolling coal, NOx is going to be higher than in any reasonable tradeoff, because if the irreversible damage to the catalytic converter. It will be far worse than any conceivable lean air mixture.
- bumby 4y agoAh, ok, I'm tracking your perspective now, thanks for continuing the conversation. Yes, I wasn't really speaking to the damage to the catalytic converter. But I think you may have it reversed? Under lean conditions, the Rh2O3 layer in the cat reacts with the Al2O3 to create an inactive oxide. This degrades the ability for NOx reduction.
- sudosysgen 4y agoUnder very rich conditions, unburnt fuel will combust in the catalytic converter, drastically increasing the temperature and greatly speeding up oxidation, which degrades its effectiveness with regard to all pollutants, including NOx, and oftentimes pretty dramatically.
- bumby 4y agoHigh temps in the catalytic converter can sinter the precious metals, reducing the surface area of catalytically active surfaces, but I believe the effect is much more pronounced in CO and HC activation. The conversion of NOx is much more constant.
- sudosysgen 4y agoAh, I was under the impression this wasn't the case, so you're probably right. Do you have a source I could refer to?
- 4y ago
- chucksta 4y agoAlso generally speaking the volume of the motors, diesels are usually larger displacement engines
- bumby 4y agoDiesel and gas have different emission profiles and the regulations don't get evenly applied. For example, harsher regulations on oxides of nitrogen will impact diesels more than gas. As someone else eluded to, "soot" may not be the best proxy for "emissions".
- hnov 4y agoTrue, there are plenty of invisible emissions causing chronic air quality issues, but um an over-rich diesel exhaust in your vicinity is rather acute.