Do you think we're seeing the beginning of the end of diesels, at least for passenger cars? Diesel cars' emissions far higher on road than in lab, tests show | Business | The Guardian
There appears to be an attitude that diesel testing was separate from diesel operation. This same attitude may have corrupted their gasser testing. The technology of high, power stroke expansion ratio and 3-way catalytic converters gives spark ignition engines a distinct advantage. Then there are the other, not yet deployed valve technologies. Bob Wilson
I don't think the fact that laboratory tests are different than real world conditions is surprising at all. And the numbers revealed may well be within acceptable/expected limits.
This actually old news, and the difference between the test and real world for some brands could be traced to the NEDC test cycle. It makes the EPA ones look like running a marathon. So when the test regulations don't reflect the conditions the cars are actually driven at, don't be surprised if the cars emit more out on the road. I hope diesels don't go away. A renewable fuel for them looks like a better bet than for gasoline, and we'll need them until non-hydrogen plug in FCEVs come along.
There's a lot of issues with the current European testing regimes. First off, it seems that while it's illegal to detect the exact test profile and change emissions behavior in response to that (as Volkswagen did), it's perfectly legal to detect conditions that are outside of those in the test profile, and change emissions behavior. More throttle than the test would ever use? Shut off emissions controls. Colder than the test ever tests? Shut off emissions controls. This crap doesn't fly in the US, where any deviation in emissions strategy is an auxiliary emissions control device that must be approved by the EPA, even if it's one that reduces emissions (specifically so that ones that increase emissions can be denied). Second, the test is designed to be easy enough that absurdly slow 1970s city cars can actually complete the test without failing for accelerating too slowly. This means that a modern car barely needs the throttle breathed upon. Third, there's straight-up cheating that's actually legal in the European tests. Taping over seams and removing roof rails and mirrors that are standard on a model to reduce aerodynamic drag, disconnecting alternators or pre-charging 12 volt batteries, overinflating tires (but not above tire sidewall pressure, Volkswagen got caught doing that), special lubricants just for the test (but not when the "special lubricants" are just normal engine oil cut with diesel fuel, Volkswagen got caught doing that, too), using the lightest possible configuration of a model (or sometimes even lighter than the base model by removing even more weight), programming the dyno for "inertia classes" even though modern emissions testing dynos can be programmed for an actual weight, using tires different from those shipped on the car, adjusting toe-in for optimum efficiency even if it's outside of the normal alignment specifications, adjusting brakes, and then... European roll-down coefficients must be done on test tracks with maximum 1.5% slope, with the test done in opposite directions to compensate for wind. Note the plural. Test tracks. The opposite directions don't have to be on the same track. Therefore, they can go downhill both ways if the track is specially constructed for this. (And this report on that cheating dates back to long before Dieselgate in its current form broke: http://www.transportenvironment.org/sites/te/files/publications/Real%20World%20Fuel%20Consumption%20v15_final.pdf) This is why NEDC testing is a complete mockery. It'll be interesting to see what happens with the gas engines, too. While properly tested diesels require absurdly complex emissions control systems to be in actual compliance... direct injection gasoline engines at high load are more likely to emit NOx (although the three-way catalyst helps a lot more, if they're not lean-burn engines) and particulate matter (direct injection makes mixing harder, which means there's both hot spots on the edge of a fuel droplet (creating more NOx) and cold spots in the center of the droplet (creating more PM), and turbocharged engines typically have to run richer to avoid detonation (destroying fuel economy, and spewing particulate matter). Don't be surprised if gasoline particulate filters become a thing, as well as potentially AdBlue for gasoline engines (especially if they have to go lean burn to meet fuel economy standards). Also don't be surprised if the industry's push towards turbocharging gets reversed, and if the manual transmission dies due to lack of control over emissions (that's part of why it's dying in the US, sadly). It'll also be interesting to see what happens to Europe's CO2 targets after this - they were set based on a belief that NEDC was realistic, and not under the belief that the automakers would cheat so brazenly on the test. I'm predicting that the response, however, will be to accelerate the transition to BEVs (which is already happening anyway), rather than raise the targets to compensate for a more realistic testing cycle - they're the class of vehicle that can most easily be made to emit no CO2, they're probably the ones that will be hurt the least in a move to WLTP anyway, and they have no tailpipe emissions (which solves the smog problem caused by cheating diesels in Europe, as that's entirely a tailpipe emissions problem). I also believe that, of ICE manufacturers, Mazda (although their gasoline engines are DI) and Toyota are the best positioned to come out of this with the least pain. Both of them have been far more reluctant to go for turbocharging everything gasoline, and both of them have shown a preference for Atkinson cycle to reduce pumping losses (with Mazda using wide-authority cam phasing to switch between Otto and Atkinson cycles on demand). Mazda's likely going to lose the least fuel economy in the move to WLTP of any ICE manufacturer, whereas Toyota's positioned to do quite well on emissions tests, with their hybrids (most are port-injected gas engines, and all have eCVTs that shut off the engine during light load regimes, making them best able to respond to emissions test demands).
The early studies showing diesels emitting more NOx on the road did the same happening with gasoline cars. Just nowhere near the amount the diesels did.
In light of prevelance of european cheats, I wonder if Lance Armstrong is going to ask for his tour de france trophy money back ....
