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Our Long-Term MPG Results May Shed Light on Future Emissions Recall Expectations - 2013 Volkswagen P

Edmunds.comEdmunds.com Posts: 10,112
edited September 2015 in Volkswagen

imageOur Long-Term MPG Results May Shed Light on Future Emissions Recall Expectations - 2013 Volkswagen Passat TDI Long-Term Road Test

Our long-term MPG tests of a 2013 Volkswagen Passat TDI diesel and its gasoline counterpart may shed light on how any future recall fix may affect performance.

Read the full story here


Comments

  • ebeaudoinebeaudoin NE IllinoisPosts: 509
    Excellent post, thanks Dan. Like you said, only time will tell the outcome of this scandal. It's really a shame that it happened at all.
  • schen72schen72 Posts: 433
    If I owned a TDI engine, I'd be more worried about longevity. VWs are already not known for longevity, and would any recalibration of the programming make that even worse?
  • schen72 said:

    If I owned a TDI engine, I'd be more worried about longevity. VWs are already not known for longevity, and would any recalibration of the programming make that even worse?

    Agreed. there has to be some reason that VW did not want the diesel cars to run that way all the time. The fact that mpg drops to the point that it "merely" matches the EPA estimates doesn't seem like enough of a reason to do this since the EPA numbers are high enough to make most consumers happy. So it's got to be something else. Either the cars lose a lot of power, or reliability becomes enough of a concern for VW to be worried about significant warranty costs (or both).
  • You guys will definitely have to pick up a "fixed" future model of VW (presuming they are still around next year LOL) to compare or ideally keep the one you have until the "fix" is applied and do some more longer term comparison.
  • You people at "edmunds.com" have always been too eager to swallow the claims of manufacturers. Perhaps, if I needed their cooperation to keep my website profitable .. as you do .. I'd be a journalistic coward, too. Let's face it, "edmunds.com", you let us all down by not using your previously vaunted "engineering expertise" to maintain a skeptical distance from VW claims. You had your heads up your tailpipes. And consequently, we will never be able to read another post from you with the same degree of trust.
  • This is a great analysis that gives a sense of what the fuel economy of "fixed" VWs may look like. What this doesn't capture is how the "fixed" cars will drive. I imagine these cars will be both less efficient and less powerful once they are "fixed."
  • vvkvvk Posts: 196
    VW owners should avoid visiting dealer service to keep the "good" software. Otherwise, their cars will become weaker and thirstier.
  • nate001nate001 Posts: 102
    I keep seeing the 40 times number, but have yet to find any hard numbers, what legal limit is and what the cars tested at. If there broke the law (and they did) then they need to correct the issue. The part that is being ignored is that with a software re-calibration then these cars get significantly better mileage, the change is so significant that VW cheated to get the mileage. To me not having hard numbers it makes a big difference if they are 40 times over 1PPM or 40 times over 5000PPM, The higher mileage and higher NOx may be better for the environment then having to drill and refine more oil or mine for toxic lithium to use in Hybrid and electric cars.
  • nate001nate001 Posts: 102
    vvk said:

    VW owners should avoid visiting dealer service to keep the "good" software. Otherwise, their cars will become weaker and thirstier.

    There is already talk about some states requiring proof of the repair before registration can be renewed.
  • You people at "edmunds.com" have always been too eager to swallow the claims of manufacturers. Perhaps, if I needed their cooperation to keep my website profitable .. as you do .. I'd be a journalistic coward, too. Let's face it, "edmunds.com", you let us all down by not using your previously vaunted "engineering expertise" to maintain a skeptical distance from VW claims. You had your heads up your tailpipes. And consequently, we will never be able to read another post from you with the same degree of trust.

    We tested these Passats in the real world, with real drivers, for a year. There's no skepticism required when we test the vehicles for 20,000 miles and keep copious records of fuel economy. As a matter of fact, that's a big portion of the test - confirming or busting their claims. And the TDI beat the EPA's claims, handily.
  • carboy21carboy21 Posts: 760
    edited September 2015
    Getting much higher mileage is good for the environment then putting more gas in the gas guzzling cars. VW did a favour to all the motorists but is punished by the gasser lobby. Do not neuter your existing TDIs !
  • If I'm not mistaken, isn't part of the issue or perhaps some of the reasoning behind the manipulation to avoid adding a DEF system as used in more expensive models from BMW/MB with larger engines? Doesn't DEF legitimately make the emissions cleaner thus the apparent greatness of the 2.0TDIs without it? If so, then how does the Passat fit in all of this since you said it DID have DEF unlike the other models in question? Would the Passat with the illegal software still have been compliant with regulations due to its DEF even if the software was turned off?
  • Great post Dan. I have seen speculation elsewhere that TDI's often outperform EPA ratings because the NOx compliant mode involves a mixture that is effectively richer (not the correct term for a diesel, but close enough). I didn't know that the EPA fuel ratings were reverse engineered from emission testing (I can't believe I have never read that before). I have argued on other forums that TDI owners won't likely be able to sue over reduced MPG's because the recalibrated ECU would just reduce the experienced MPG to the rated figure. It is nice to have some science to back that up.
  • schen72 said:

    If I owned a TDI engine, I'd be more worried about longevity. VWs are already not known for longevity, and would any recalibration of the programming make that even worse?

    Any longevity issues that VW has, and I think you are wrong in general, I see 6 figure VW's all the time, they certainly don't apply to TDI versions which are renowned for going 200 and 300k miles as well as their excellent fuel economy.

  • carboy21 said:

    Getting much higher mileage is good for the environment then putting more gas in the gas guzzling cars. VW did a favour to all the motorists but is punished by the gasser lobby. Do not neuter your existing TDIs !

    Releasing 40 times the nitrogen oxide limit is "good for the environment"? VW may have made the car drive better but at the cost of everyone else that needs to breathe the air. Other companies were able to create a great driving car AND meet all emission standards.
  • Correction needed. Passat 1.8T is not available with the DSG. It totes a conventional 6-speed automatic - the console shifter has the "DSG" logo embossed on only Passat TDI and not Passat TSI. Only Passat TDI (all auto TDIs) are equipped with the DSG.
  • Very lucid explanation of how EPA fuel economy estimates are calculated and how VW's emissions exploit can impact real-world fuel economy. Thanks.
  • schen72 said:

    If I owned a TDI engine, I'd be more worried about longevity. VWs are already not known for longevity, and would any recalibration of the programming make that even worse?

    I haven't seen long-term reliability problems with VW drivetrains. The diesels, especially, run for multiple 100k miles. What I'd be worried about right now as a diesel owner is what the forthcoming fix for the emissions problem will do to performance, fuel economy, and-- as a result-- resale value.
  • socal_ericsocal_eric SoCalPosts: 189
    If Edmunds is at a loss to explain the better than rated mileage with the VW TDI-powered car, instead of speculating that it might be related to the calibration programming, why not add another diesel passenger car sample to your long-term fleet? The Cruze Turbo Diesel which has SCR and full after-treatment is closer a Jetta but would be a nice comparison of an affordable diesel passenger car from another manufacturer to see if it's just the nature of the diesel engine operation and your driving or if it might have been something VW that produce abnormal results. I'd suspect you'd also exceed EPA numbers, just like it's easy to exceed them with the much larger Ram 1500 EcoDiesel.
  • For years, diesel VW owners have been claiming that they get better mileage than the EPA ratings. This 'tell' that something was amiss has been around for a long time.
  • socal_ericsocal_eric SoCalPosts: 189
    sharpend said:

    For years, diesel VW owners have been claiming that they get better mileage than the EPA ratings. This 'tell' that something was amiss has been around for a long time.

    Most diesel owners, whether trucks, passenger cars or SUVs usually note getting better than EPA mileage. I'd find it much more likely the real-world driving difference compared to EPA test procedures just happens to favor diesel applications more than gas.
  • I have argued on other forums that TDI owners won't likely be able to sue over reduced MPG's because the recalibrated ECU would just reduce the experienced MPG to the rated figure. It is nice to have some science to back that up.

    This assumes that the "fixed" vehicles actually hit the EPA number in the real world. It also assumes that no dealers ever promised customers that they will beat the EPA numbers with their diesels.
  • A "fix" will still need drivability on par with the current real-world-non-environmentally-friendly ECU program, or at least better than the current cheater 'test' program would probably return.

    Most manufacturers today tend to make compromises between fuel economy and drivability in order to get good EPA numbers while still keeping customers from revolting over the way their car feels and responds in normal driving (and there are usually still complaints). If what has been said about the 'test' ECU program is true, using it basically would result in greatly reduced drivability, so not a choice, Volkswagen may have to do some compromising in the reprogrammed 'fix' code to still meet emissions requirements while still compromising fuel economy a bit to meet owners expectations, reducing real-world fuel economy.

    I would expect that if the current EPA numbers are based on the cheat ECU program, then retesting with a 'fix' will lower the EPA ratings. The car might still get better than EPA ratings, in line with most diesels today, but only in comparison to the new ratings, and probably not the old.

    Maybe a comparison with the Chevy Cruze Turbo Diesel isn't so far off the mark after all..
  • Legacy, very true, which is why I qualified my thought with "likely". In the end we will have to wait for a 'corrected' version that can be tested. It is worth noting, as Eric did above, the Edmunds LT Ram diesel has also exceeded its EPA rating on numerous ocassions. So it may be that the EPA test understates diesel milage in the way it seems to overstate some turbo gas engine *cough* Ecoboost *cough*
  • agentorangeagentorange Posts: 893
    edited September 2015
    Would somebody explain to me about the real world programming. Did the software ADD fuel to create more NOx but somehow get BETTER than EPA mileage derived from lab measurements when the engine was fed LESS fuel. Saying things don't add up is correct, but it might be other way around to what most on here are saying. Now, if it turns out that the fix for NOx emissions makes the engine less efficient then I guess there will be some grumpy TDi owners whose cars won't go so well and use more fuel doing it.
  • One thing I will say is that it is likely that all diesel cars will go DEF from here on. That frosts my chops because the DEF tank usually replaces the spare, and no spare means no sale to me in this state.
  • My understanding was that the 2012 and 2013 Passat TDI's were NOT in the list of ones that cheated. Can you confirm?
  • socal_ericsocal_eric SoCalPosts: 189

    Would somebody explain to me about the real world programming. Did the software ADD fuel to create more NOx but somehow get BETTER than EPA mileage derived from lab measurements when the engine was fed LESS fuel. Saying things don't add up is correct, but it might be other way around to what most on here are saying. Now, if it turns out that the fix for NOx emissions makes the engine less efficient then I guess there will be some grumpy TDi owners whose cars won't go so well and use more fuel doing it.

    If you lean the fuel mixture (i.e. ratio of fuel-to-air) in a diesel the cylinder pressures and combustion temperatures increase significantly which increases the amount of oxides of nitrogen (NOx) that forms. To be able to operate in a lean burn mode, which does lower some of the other exhaust gas components such as carbon monoxide and hydrocarbons, nearly all recent diesels engines use a NOx "trap" catalyst that adsorbs excess NOx during lean burn operations for better economy, then when the engine briefly runs very rich the catalyst begins to regenerate and break down the NOx back into harmless nitrogen and oxygen.

    To lower NOx on a diesel they could have done a few different things. They could have run the engine lean and relied on the NOx trap to capture the oxides of nitrogen but not allow the engine to go back to a brief period running very rich and catalyze it correct, but I'm not sure if the trap/catalyst VW used has enough capacity to last for the ~9 minutes of the test without ever going back to rich operation.

    They could also artificially richen the mixture which means there is more fuel compared to the amount of air in the cylinder, which means less nitrogen from the air that can combine with oxygen into NOx particles during combustion. The richer mixture also helps cool the combustion chamber which also lowers NOx. The down side is that the CO, CO2 and hydrocarbon would normally spike higher when the engine is run richer. These and other diesel engine do use a diesel oxidation catalyst (similar to the catalyst in a gasoline powered engine) that can process some of these molecules.

    NOx and particulates are usually the most difficult parts to clean/neutralize in diesel exhaust emission, but the particulate traps work really well to capture and later burn fine particulate matter. The NOx is still a problem because to get better economy and efficiency the diesel engine needs to run lean which increases NOx produced. The NOx trap/catalyst by itself was able to meet older diesel exhaust emission standards but the most recent tier/bin standards are much tougher. That's why the selective catalyst reduction (SCR) systems in newer diesel vehicles usually have to include urea injection (i.e. diesel exhaust fluid (DEF)) to increase the efficiency of the NOx catalyst.

    It's possible VW richened the mixture to reduce NOx and relied on the diesel oxidation catalyst to handle the CO, hydrocarbon, and oxides of sulfur just for the test, but if they ran the engines like that in the real-world it would excessively load the oxidation catalyst and might damage it over time. Another problem with running rich is that when more fuel is burned it increases carbon dioxide (CO2). The oxidation catalyst also breaks down carbon monoxide (CO) into water and CO2 making this slightly less likely they significantly richened the mixture.

    There's a few other ways they could have possibly tailored the emission results when the test vehicle is on a chassis dyno and not under the normal operating loads normally experienced out on the street (e.g. no wind resistance, etc.). If significantly less engine power was required to spin the giant roller drum on the dyno than is required to move the car, they could have altered the fuel injection timing to produce a cleaner combustion process at the expense of power. The engines in question don't have variable valve timing, but that's another way a manufacturer could tweak the combustion process.

    Thinking about it from a technical standpoint, a more likely scenario is the calibration (software tuning) engineers partially activated the throttle plate and opened the exhaust gas recirculation (EGR) valve while testing. Normally diesel engines don't have a throttle body/plate and are inherently lean burning, instead rely on the amount of fuel injected to produce power. Having no throttle to restricting air flow along with the higher energy density of diesel fuel is what allows them to be more efficient compared to a gas engine.

    Many new diesel engines do have a throttle body (plate) in the intake tract that can be closed under certain engine loads to allow the engine to more easily draw in recirculated exhaust gas form EGR system (upstream in the intake manifold from the throttle plate) instead of outside air. Creating a slight vacuum with the throttle plate allows the cooled exhaust gasses to be pulled into the intake tract and since they've already been burned once they don't contain as much oxygen. That means less power will be created but there's also less oxygen molecules to form NOx.

    If VW activated and closed the throttle plate during the test it would reduce NOx while also keeping the other emission elements in check. They probably couldn't run like that all the time because it would have a significant impact on the amount of power the engine could produce and might also impact economy from the greater intake restriction.

    That's just my speculation of some of the ways they could have gotten the car to pass testing on a chassis emission dyno and then run differently out on the open road. Until the code is examined or reverse engineered from data logging and testing, we probably won't have an answer as to exactly how and when they got the 2.0L TDI engines to pass. And until we know what they did it's going to be difficult to figure out what might need to be changed going forward to get the vehicles to comply and the modifications required.

    I'm sure VW has already been formulating a plan, possibly including costly hardware changes, but until a technical paper comes out we may have to play the waiting game.
  • Well done Dan.

    How this mess plays out in the coming months will be interesting to observe. The categories are technical solutions, financial reimbursement for owners, dealerships and various governments. The last category is how to manage outliers.

    There will be a technical solution to get the emissions back in line, which will involve software and perhaps hardware changes. The impact on fuel consumption and engine longevity may be factors.

    Owners will expect to be reimbursed. The questions are what to be reimbursed for and by how much? Reimbursement for historical usage is not likely. Reimbursement for potential loss of future engine longevity or diminished future value is most likely. Expect a lot of discussion on this legal aspect.

    Dealerships will want to be compensated. Again, the challenge will be by how much.

    Governments will want to be compensated for two reasons. One as a form punishment. The second may due to impact on health care costs due to increased pollution. This latter point is hard to measure, unlike GM's faulty ignition casualty numbers.

    How will outliers be managed? There will always be people who do not want to have their car repaired, as they do not want to have their fuel consumption and potentially engine longevity compromised. Should these people be forced to comply? Can outliers be caught?
  • socal_ericsocal_eric SoCalPosts: 189
    One other suggestion to Edmunds, in addition to possibly adding a Cruze Turbo Diesel to your fleet to compare and see how it's mileage stacks up against EPA ratings, it would be great if you bought an affected late model, used TDI Jetta to compare both cars and also document before and after mileage, drivability, etc. when VW finally starts rolling out their fix, whatever that ends up being.
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