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There's either some bias or flat out ignorance with this author. I'll start with: > In other words, a driver who steps on the accelerator of a diesel car may b

There's either some bias or flat out ignorance with this author. I'll start with: > In other words, a driver who steps on the accelerator of a diesel car may be filling the lungs of nearby pedestrians, cyclists, infants in strollers and other drivers with potentially deadly particulate matter. Driving a diesel car is nothing like driving a gasoline car. In a gasoline car, when you "step on the accelerator" you follow the horsepower curve, revving the engine to 5000-5500 (perhaps higher) RPMs before shifting. This is because the torque curve in a typical gasoline vehicle follows the horsepower curve until you get close to the red line, typically 6500-7000 in modern cars. In a diesel passenger car (using a VW TDI as a reference) the torque develops early, peaking at about 2000-3000 RPM, then falls as you go past 3000. So if you want to get going fast in a TDI, you keep the shifting going on at around 3000. With the way the DSG and ECU work in a TDI, that means running at about 1/3-1/2 throttle. Definitely not "stepping on it". Also note the red line on a TDI is 5000 RPM. As a side note, the TDI ECU's algorithm for detecting faulty inputs imposes about a 1.5 second delay on actually opening the throttle if you floor it from a dead stop. It's very counterintuitive if you need quick acceleration, you have to give about 1/4 throttle, then slowly increase as the car starts moving. Again, if you want to go fast, the car actually incentivizes NOT stepping on it. Second, and this is the one that everyone seems to fail to notice. The TDI passes emissions when the bypass mode is disabled, putting the ECU into normal mode. What normal mode means is the car more frequently cycles the Diesel Particulate Filter (DPF), which reduces NOx emissions by accumulating soot in the DPF then burning it by passing unburned fuel through the engine 1 out of every 4 cycles while the system is in a DPF cycle. The unspent fuel lands on the soot, then the heat from the following combustion cycle ignites it and dumps mostly ash/greatly reduced NOx down the tailpipe. There are of course performance and fuel efficiency issues with normal mode. With proper tuning of the software it should be able to both meet emissions standards without sacrificing too much in the drivability department. A decrease in mileage is inevitable though. VWs mistake in all this was failing to accept a 28/38 MPG (or 27/37) rating, and insisting on 30/40 MPG (which likely came at the behest of VW Marketing). Had they been willing to accept slightly lower MPG numbers, they would have been in compliance with the law. To me, all the kerfuffle seems a little overblown. I don't give VW a free pass for breaking the law, they need to be held accountable. But this whole idea that diesel is doomed seems very off kilter to me. Diesel produces fewer greenhouse gases, converts hydrocarbons to kinetic energy most efficiently of all internal combustion engines, has fewer emissions from ancillary chemicals than gasoline like acetone and toluene (both unregulated at present). It truly is the way forward until we can retool the worldwide vehicle fleet to be driven by electricity (30 years minimum if we start right now). When I look at this anti-diesel campaign, I look at it through the lens of the Saudi's fear not of peak oil, but of peak demand. Diesel threatens to lower the plateau of peak demand. http://www.bloomberg.com/news/articles/2015-04-12/saudi-arabia-s-plan-to-extend-the-age-of-oil http://www.bloomberg.com/news/articles/2015-04-12/saudi-arab...

sxcurry 11y ago
Thanks for the reality check on this poorly written article. I think the NYTimes should have asked you to edit it!
- ars 11y ago
  Hardly a reality check, his post was quite misleading.
caf 11y ago
converts hydrocarbons to kinetic energy most efficiently of all internal combustion engines Doesn't an LPG ICE convert the chemical energy in the hydrocarbon fuel more efficiently (although there is less embodied energy per unit mass of LPG as compared to diesel fuel)?
ars 11y ago
> the torque curve in a typical gasoline vehicle follows the horsepower curve It does that because the laws of physics require it. Diesel is not exempt from the laws of physics: horsepower = torque * rpm. This is not an approximation, it's an exact relationship, diesel works identically. You can put different gearing on diesel or gasoline to make them work however you like - the only thing that matters at the end of the day is horsepower, once you know the horsepower torque and rpm can be traded off against each other. > Had they been willing to accept slightly lower MPG numbers, they would have been in compliance with the law. If it were so simple to just change the programming VW would have released a fix already for their illegal cars. But they have not because what they are trying to do (clean diesel) actually appears impossible. It's not the simple MPG change you are trying to make it out to be. > But this whole idea that diesel is doomed seems very off kilter to me. Diesel produces fewer greenhouse gases, converts hydrocarbons to kinetic energy most efficiently of all internal combustion engines, has fewer emissions from ancillary chemicals than gasoline like acetone and toluene (both unregulated at present). Now it's you that is trying to mislead people. They are only efficient if allowed to pollute! If you restrict them from polluting they are NOT more efficient than gasoline. (Which you touched on just one paragraph before, and then seemed to immediately forget.) You simply can't have it both ways, and making clean gasoline is much easier than clean diesel. > has fewer emissions from ancillary chemicals than gasoline like acetone and toluene Maybe less of those, but far more of much much more harmful stuff. Both of those have very short lives in the atmosphere and cause very few problems. Acetone is actually pretty much non-toxic, it's made naturally in the body. And Toluene is only mildly toxic - I'll take both over what diesel produces.

sxcurry 11y ago

Thanks for the reality check on this poorly written article. I think the NYTimes should have asked you to edit it!

ars 11y ago
Hardly a reality check, his post was quite misleading.

caf 11y ago

converts hydrocarbons to kinetic energy most efficiently of all internal combustion engines Doesn't an LPG ICE convert the chemical energy in the hydrocarbon fuel more efficiently (although there is less embodied energy per unit mass of LPG as compared to diesel fuel)?

ars 11y ago

> the torque curve in a typical gasoline vehicle follows the horsepower curve It does that because the laws of physics require it. Diesel is not exempt from the laws of physics: horsepower = torque * rpm. This is not an approximation, it's an exact relationship, diesel works identically. You can put different gearing on diesel or gasoline to make them work however you like - the only thing that matters at the end of the day is horsepower, once you know the horsepower torque and rpm can be traded off against each other. > Had they been willing to accept slightly lower MPG numbers, they would have been in compliance with the law. If it were so simple to just change the programming VW would have released a fix already for their illegal cars. But they have not because what they are trying to do (clean diesel) actually appears impossible. It's not the simple MPG change you are trying to make it out to be. > But this whole idea that diesel is doomed seems very off kilter to me. Diesel produces fewer greenhouse gases, converts hydrocarbons to kinetic energy most efficiently of all internal combustion engines, has fewer emissions from ancillary chemicals than gasoline like acetone and toluene (both unregulated at present). Now it's you that is trying to mislead people. They are only efficient if allowed to pollute! If you restrict them from polluting they are NOT more efficient than gasoline. (Which you touched on just one paragraph before, and then seemed to immediately forget.) You simply can't have it both ways, and making clean gasoline is much easier than clean diesel. > has fewer emissions from ancillary chemicals than gasoline like acetone and toluene Maybe less of those, but far more of much much more harmful stuff. Both of those have very short lives in the atmosphere and cause very few problems. Acetone is actually pretty much non-toxic, it's made naturally in the body. And Toluene is only mildly toxic - I'll take both over what diesel produces.