There’s an interesting corollary to this in the school bus world. Beginning in 2004, the EPA started imposing emissions standards on diesel engines and the standards have become increasingly stringent over the years. The standards govern the allowed amounts of NOx (nitrous oxides) and particulate matter to be emitted, but the units measured are per-horsepower-miles, meaning that an engine with twice the horsepower is allowed to emit twice the NOx and twice the particulate matter amounts, which has led to bus engines that have much more power than their counterparts from twenty years ago did - despite this added power being largely unnecessary for hauling kids around at relatively low speeds.
And importantly, the EPA diesel engine standards do not in any way govern CO2 output, so today’s school bus fleet is emitting far more of it than twenty years ago.
More interestingly, the emissions equipment which prevents particulate matter from entering the atmosphere does so by burning more fuel. This makes the engines emit even more co2 than they would without the emissions.
Are you sure about that? I think possibly you’re thinking of EGR (exhaust gas recirculation) which most engine manufactures used to handle the initial 2004 standards (which did not include particulate matter standards) but which is not really used any more. The main things used today are DPF (diesel particulate filter) and DEF (diesel exhaust fluid).
I’m not a diesel mechanic or anything, I just know what I know from owning a school bus (from 2003, yay!) and researching the emissions issues.
Yes I am sure about that. When the diesel particulate filters clog up with soot, the ECU triggers post injection events so that extra diesel fuel will burn in the exhaust raising the temperature of the diesel particulate filter and burning the soot out. These events cause your miles per gallon to decrease significantly.
There’s an interesting corollary to this in the school bus world. Beginning in 2004, the EPA started imposing emissions standards on diesel engines and the standards have become increasingly stringent over the years. The standards govern the allowed amounts of NOx (nitrous oxides) and particulate matter to be emitted, but the units measured are per-horsepower-miles, meaning that an engine with twice the horsepower is allowed to emit twice the NOx and twice the particulate matter amounts, which has led to bus engines that have much more power than their counterparts from twenty years ago did - despite this added power being largely unnecessary for hauling kids around at relatively low speeds.
And importantly, the EPA diesel engine standards do not in any way govern CO2 output, so today’s school bus fleet is emitting far more of it than twenty years ago.
More interestingly, the emissions equipment which prevents particulate matter from entering the atmosphere does so by burning more fuel. This makes the engines emit even more co2 than they would without the emissions.
Are you sure about that? I think possibly you’re thinking of EGR (exhaust gas recirculation) which most engine manufactures used to handle the initial 2004 standards (which did not include particulate matter standards) but which is not really used any more. The main things used today are DPF (diesel particulate filter) and DEF (diesel exhaust fluid).
I’m not a diesel mechanic or anything, I just know what I know from owning a school bus (from 2003, yay!) and researching the emissions issues.
Yes I am sure about that. When the diesel particulate filters clog up with soot, the ECU triggers post injection events so that extra diesel fuel will burn in the exhaust raising the temperature of the diesel particulate filter and burning the soot out. These events cause your miles per gallon to decrease significantly.
Hey don’t hate on factory 600+lb-ft diesels so many great engine swaps in my OSB pickups future.