Missing From the Volkswagen Diesel "Fix" Messaging -- How Much Performance Will Your Car Lose?

Nowhere in this video does it mention how much of a performance hit one's car will take in the modifications.  My guess is a lot, or else they would not have risked so blatant of a legal evasion in the first place.   If I had a VW diesel there would be no way I would take the car in for this modification, certainly not before others have had a chance to share their experience.   My guess is that VW will require dealers to make these changes whenever a car comes in for any sort of service, so I wonder if there will be a boomlet for non-dealer VW shops who are willing to fix your air conditioning without implementing these changes?


  1. xtmar:

    I don't know the legality of it, but I assume they (EPA+CARB) could coerce people to get the fix by requiring it to be done before the registration is renewed as many states require a clear emissions test prior to renewing the registration. Alternatively, it may be totally optional and people will pay a premium to buy what amounts to a pre-chipped car.

  2. Mr. Generic:

    It'll depend on the state. I suspect states that have yearly emissions tests will check to see if your car has had the fix. (The emissions testers will plug into the car's computer and I believe they can read the car's software/firmware version). From what I've read, the VW cars are emitting 40 times the allowed NOx emissions, so that'll have to be stopped.

  3. John_Schilling:

    From what I've read, the VW cars are emitting 40 times the allowed NOx emissions...

    Actually, that's one of the other pertinent pieces of information that never quite makes it into the press releases, though this time from the critics' side.

    What you've read, if you look at the fine print, is that VW cars were emitting up to 40 times the allowed level of emissions. Never the mean or the median emissions level, or the frequency with which the 40x level was seen.

  4. herdgadfly:

    So the EPA is recalling 482,000 VW diesels while the world has a total of 11 million of the company's small diesels operating. In the humongous volume of atmosphere that encircles the earth, what possible effect could less than a half million tiny diesels have on pollution of any kind? Folks, there are 1,015 BILLION vehicles operating in the world every day (and that doesn't include off-road vehicles or heavy construction rigs).

    The EPA has got to go away!

  5. bigmaq1980:


    Expect to see more owners looking at options like this, if forced to adjust the factory settings.

  6. Eric H:

    It's my understanding that the performance hit takes place at the upper end of the engine speed (RPM). How often do you run your car to redline? Also, as others have noted, in places where testing is a requirement, they're going to force you to do it. I have a pre-cheat TDI that came under the emissions testing requirements starting this year.

  7. Sam P:

    After skimming the original report (here), the emissions values are almost certainly a mean value, due to the measuring equipment used. It basically measures cumulative NO_x emissions, so then they divide that by the route distance for emissions as grams per km.

    The money graph on the report is on page 62. Presumably vehicle A is the Volkswagen equipped with a turbocharged diesel with the Lean NO_x Trap (LNT) for NO_x emissions reduction. The other two vehicles use a urea-based Selective Catalytic Reduction (SCR) system and I don't know what make/models they were.

    Vehicle B has NO_x emissions also well above the EPA standard, though only about half as much as vehicle A. Vehicle C is much lower most of the time but on one of the two particularly challenging routes is well above the EPA standard, about half the emissions as vehicle B. The other particularly challenging route they have no data for vehicle C.

    According to this article (in IEEE Spectrum), the problem appears to be that the catalytic converter needs to be hot to work and to keep it at the required temperature the engine may need to run richer (more fuel) than otherwise necessary for the desired power output. So fixing the code in the engine computer will result in poorer fuel efficiency. However, the proposed fix appears is some sort of grating/filter on the air intake which I suspect will restrict air intake (that's one way to make the fuel mix richer) and I suspect that will reduce performance.

  8. randian:

    You might wonder the same about EPA's push for strict motorcycle emissions. Also, newer EPA regs are essentially pointless, they reduce the emissions of modern gasoline engines from less than measurable (when warm, practically all emissions are made when cold) to a fraction of measurable. Surely worth the billions of dollars it will take to accomplish it. Of course, it's not really about emissions at all anymore, since EPA has an institutional hatred of automobiles. Just keep squeezing for no reason other than to hamper them.

  9. Bram:

    Detuning the engine will probably involve a serious hit to gas mileage - the reason people bought those cars in the first place. The gas mileage hit is going to lead to a whole new batch of lawsuits.

  10. Mike Powers:

    heh. I love the idea of a market for "pre-ban Audis", just like there are pre-ban AR-15s...

  11. Mike Powers:

    I love the article. "The fix is really simple! We just put this little plastic cap over one of the tubes! No big deal! alsowereprogramyourcarsotheenginesucksNO BIG DEAL, SIMPLE FIX!"

  12. marque2:

    I thought Diesels rev much lower than gas cars. I can see "high revs" for a diesel.

  13. NUT BAG:

    If you don't live in an area where they test, I'd leave it alone. If you do take your car in for service the dealer may arbitrarily do the re-tune, I believe they have to. If the car is out of warranty take it to an independent shop, they are less expensive and will probably do a better job.

  14. Mike:

    I bet that big hit on performance would probably lower the target emissions by something minuscule such as 0.02% This happened with the Navajo Generating Station. The NGS operators had the choice of three emissions control technologies to add to their coal power plant.

    One reduced emissions a certain amount, and cost a certain amount to install. The second technology reduced emission more than the first, and more even more. The third reduced emissions more than the second, but only marginally. But the cost was astronomically higher. NGS decided the second technology would be the best.

    But the EPA fought them for years to get them to install the third and most expensive technology. Not only was it the most expansive, but it required the ongoing purchase of materials (chemicals?) to feed into the technology to make it work. (Reminds me of DEF!)