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EPA emissions limits are based on grams of pollutant per horsepower-hour. In order to reach compliance, your emissions control equipment needs to reduce polluti

by hapless 11y ago

EPA emissions limits are based on grams of pollutant per horsepower-hour. In order to reach compliance, your emissions control equipment needs to reduce pollution much faster than it reduces efficiency. It's not uncommon for illegally chipped/straight-piped trucks to see 50% improvements in fuel efficiency, but they're belching out tens or hundreds of times the volume of common pollutants (depending on the pollutant)

abakker 11y ago
Thanks for that info. Out of curiosity, is there any accounting for the other emissions involved in making the fuel, though? Full transport and refining is energy intensive. on-vehicle emissions controls are also costly, and also use energy to make. Finally, petroleum is a finite resource. I am all for emissions controls on vehicles if they genuinely reduce net emissions. If the reduced fuel economy doesn't equal out though, then at best, we're simply moving the emissions out of cars and into refineries/shipping/factories instead.
- hapless 11y ago
  I have a hard time believing that we're moving the emissions. 1. The efficiency/emissions tradeoff is almost entirely a diesel problem. For intrinsic reasons, gasoline engines suffer much less from emissions controls. The relevant systems are both much less complicated and much less intrusive. There is very little efficiency gain available by e.g. removing your catalytic converter. (The vapor reclamation requirements can be very complicated, but those parts do not intrude on the function of the engine, so they are not making the system less efficient) 2. The math doesn't work out on the back of a napkin. Emissions controls can reduce total tailpipe pollutants by as much as 99%. Even if it caused 2x the fuel consumption, how on earth would that result in a 100-fold increase in emissions in the distribution chain?

by hapless 11y ago

abakker 11y ago

Thanks for that info. Out of curiosity, is there any accounting for the other emissions involved in making the fuel, though? Full transport and refining is energy intensive. on-vehicle emissions controls are also costly, and also use energy to make. Finally, petroleum is a finite resource. I am all for emissions controls on vehicles if they genuinely reduce net emissions. If the reduced fuel economy doesn't equal out though, then at best, we're simply moving the emissions out of cars and into refineries/shipping/factories instead.

hapless 11y ago
I have a hard time believing that we're moving the emissions. 1. The efficiency/emissions tradeoff is almost entirely a diesel problem. For intrinsic reasons, gasoline engines suffer much less from emissions controls. The relevant systems are both much less complicated and much less intrusive. There is very little efficiency gain available by e.g. removing your catalytic converter. (The vapor reclamation requirements can be very complicated, but those parts do not intrude on the function of the engine, so they are not making the system less efficient) 2. The math doesn't work out on the back of a napkin. Emissions controls can reduce total tailpipe pollutants by as much as 99%. Even if it caused 2x the fuel consumption, how on earth would that result in a 100-fold increase in emissions in the distribution chain?