• How Much Power Does the VW TDI Lose in “Cheater” Mode? [Video Report]

    2011 VW Jetta TDI power loss dyno emissions test
    2011 VW Jetta TDI

    One of the unknowns in the Volkswagen diesel emissions cheating scandal “Dieselgate” is the potential power loss when an affected VW TDI car go into the “cheater” mode. Does it lose any power when being tested on the dyno? When Volkswagen releases a retrofit or fix for the emissions problem, will the corrected cars lose power in daily driving? If so, what power loss are we talking about? TFLcar wanted to find out, and this was the result.

    We talked to the local Boulder Diesel Emissions testing station to verify the testing procedures. The Denver area counties that test for diesel emissions, only test for particulates. The Nitrous Oxides (NOx) emissions are not measured at all. This is strange, because it is the main point of contention in this scandal. EPA states that affected TDI cars emit 10 to 40 times more NOx in daily driving than the “cheater” mode during dyno testing.

    The acceptable particulate level in Colorado emissions testing is 35% opacity. That means the smoke and particulates that are coming out of the exhaust pipe can block up to 35% of light and pass the test. This is a lot of smoke. Most TDIs we observed emit far less smoke. The red 2010 Jetta TDI emitted a maximum of 0.9% opacity, or 35 times better than the passing level.

    Next is the actual dynamometer testing to simulate regular on road driving on an all-wheel-drive dyno, versus front wheel only emissions testing.

    vw tdi power loss graph dyno emissions dieselgate
    Solid Red: Test #1 WHP, Solid Blue: Test #1 Torque

    The silver 2011 Jetta TDI put down 138.5 horsepower and 260.0 lb-ft of torque on the dyno with all four wheels spinning. This is the simulation of regular on road driving. We saw no warning lights or other indications from the test car with all four wheels spinning. (Two consecutive runs were performed with four wheels spinning. They were nearly identical.)

    The same car registered 136.5 horsepower and 228.4 lb-ft of torque when the rear wheel were left stationary. The same dyno was used with the same dyno technician. And the tests were performed within several minutes of each other. (Two consecutive runs were performed with front wheels spinning only. They were nearly identical.)

    The math shows a total loss of two horsepower at the peak, but if you look lower on the RPM curve the difference is significant. The car lost 15 horsepower around 2,800 RPM, and 32 lb-ft of torque near 2,700 rpm. In fact, there are power disparities between the tests going up to 3,800 rpm.

    The bottom line is, we observed a power loss of approximately 10.5% when simulating the emissions testing procedure.

    Get all the details in this video.

    Andre Smirnov
    Andre Smirnov
    Andre Smirnov is an Automotive Enthusiast, Producer, Reviewer, Videographer, Writer, Software Engineer, Husband, Father, and Friend.

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    44 thoughts on “How Much Power Does the VW TDI Lose in “Cheater” Mode? [Video Report]

    1. Very good and interesting test results; it would be good to see the emissions output under this test. Based on the emission test not on the dyne, one would think the car should pass emissions test levels under all conditions given a .9% result with a 35% limit. What the heck was VW thinking?

      1. That is just the particulate result. The primary purpose of VW using the cheating test mode was to allow elimination of the urea injection system used by most diesel cars to reduce NOx emissions, which apparently increase by as much as 40x going from the cheater test mode to real-world driving. I expect that other locations, particularly California, actually test for NOx emissions, which is important in areas affected by smog. I think most people following this issue don’t understand the potential effect of this many cars emitting that much NOx, particularly in urban areas.

        VW totally screwed this up and to me they intentionally sold cars that they knew would generate emissions at rates far above standards that directly affect air quality, particularly in areas like California. The TDI sales should remain shut out completely until all of their cars meet all standards directly from the factory and they have retrofitted each affected car to meet emission standards at the original performance specs.

        This should hurt VW, and hurt hard.

        1. I’m a Californian, I had my 2010 TDI smogged in 2013. I’m pretty sure they don’t measure NOx or anything for that matter as they did not insert a probe into the tailpipe. The inspection, aside from plugging into the OBD-II port was entirely visual.

          1. Did you keep your printout?

            My gasoline engine California smog test always gives me a printout with NOX, CO, and HC (hydrocarbons).

            1. No, he’s right. The only components if the CA small diesel car/truck smog test are passing the visual inspection for leaks, etc.; no OBD II codes; and a visual smog test: one guy revs it to about 1/3 throttle while the other guy checks for smoke. There isn’t any, as the author indicates.

          1. The punishment fine for Volkswagen is up to $38,000 per car from the US Government alone for each of the 500,000 cars that are being recalled for criminally breaking US law. Obviously, that may hurt a lot.

            And that doesn’t include the fines from the class action lawsuits for fraud that are coming up in the US.

            Germany, itself, will ban further sales of VW cars in Germany unless VW comes up with a fix for all affected cars by October 8.

            It is sad to see VW impaling itself on a sword.

            1. It gets worse.

              Automotive News just reported that the feds are looking into taking action against Volkswagen for taking $50 million in tax breaks as part of a diesel vehicle incentive program, which started around the time the company started cheating on emissions. VW might have to pay back triple the amount of cash it saved on taxes, thanks to the False Claims Act, plus $5,000 for each car sold under false pretenses.

              So that means $150 MILLION plus $5,000 x 500,000 cars for violating the False Claims Act.

              This is in addition to the fines for violating the EPA emissions program of up to $38,000 per car.

      2. Fantastic job guys on this initiative of being so fast in getting this info out there. The big issue at hand is, how is VW going to compensate all the TDI owners who now own a devalued vehicle with a negative stigma attached to it? An example: I was looking at trading in my 2014 TDI Wagon 4 weeks ago and had an offer from a dealer at $XX and I re approached the same dealer this week and the number decreased by $4,000!! with only 300 more miles on it. This made me absolutely sick to my stomach. Is VW going to stroke me a check for $4,000?

    2. I can’t believe you guys decided to do this!!! Thanks! Hopefully the news or something will found out about the test so that more people can hear. I don’t really think it was worth 15 hp and 32 lb ft torque to cheat. Maybe it’s a lot to carmakers like VW, but sure isn’t a whole lot to me. And let’s face it: nowadays people don’t buy cars for the pleasure of driving, horsepower, and torque, but for their overall reliability, value, and fuel economy. That’s why no one really wants to make manuals anymore. Most manuals sacrifice fuel economy a bit and fuel economy is very important to most people. For TDI buyers, fuel economy and environmental friendliness were probably their top concerns. So it didn’t really make sense to VW>

      1. Gonna have to say I completely do not agree with this. Sure I want the mileage because I commute kinda far for work, but the thrill of driving is absolutely why I bought a TDI. If all I cared about was mileage I would have gotten a Prius, but those aren’t fun to drive, I wanted a real car with real driving characteristics but still got good power and mileage, and TDI does exactly that. If I lose 10.1% power I will be a very unhappy person, and VW will know about it.

      2. People don’t buy manuals because they get 1-2 less MPG. They don’t buy manuals because they don’t know how to drive them, or they don’t want a clutch and shifter to get in the way of sipping their Super Big Gulp as they check their phone in traffic.

        1. Or, to be less snarky, maybe they don’t buy manuals becuase they’re going to be stuck in way too much urban-freeway stop-and-go traffic and that’s a pain in the clutch. (like in the Washington area.)

    3. You should verify your results, and run the 2 wheels turning test first, and then the 4 wheel turning test second, to eliminate errors from heat soaking the motor, and on a different day.

    4. @noble I bought my Manual TDI last year for the pleasure of driving and the power/economy mix, the ‘green’ aspect wasn’t even something that occurred to me.

    5. I am curious to see how this power loss will impact fuel economy 15 and 32 does not sound like much until you see the engine has less power going up hills, carrying cargo/people, passing, accel. Yes people dont buy cars for performance. But performance does help dictate fuel economy.

    6. I would suggest redoing this test with the closest comparable VW gasoline engine. Would go to show that it wasn’t traction control or some other non-tdi factor.

      1. Yes, but NOx measurements would be the sine qua non as this will tell you positively that the defeat device is functioning. If it had been possible in Colorado. When the experiment is reproduced in California, it should be much easier to get NOX equipment.

        California has NOx out the wazoo.

    7. While this test was done with the EA 189 motor, I’d be interested to see how a EA 288 motor performs. VW says that engine software wasn’t modified.

    8. LOL, That was the most humorous example of what happens when people attempting to demonstrate something, don’t do the research ahead of time.

      Why don’t y’all take one of those TDIs on the road and do some 0-60 accells with it, and feel what the car is doing, and watch what indicators come on.

      That car, in the 2-wheel test, was flashing all sorts of warnings that you are about to crash because the stability system can’t counteract the sliding rear wheels…I’ll bet the front brakes were hot after the test from attempting to control the torque.

      BTW, can you find the ESP disable switch in the car? Keep looking.

      1. Were you getting any mpg readings from the dashboard mpg gauge to indicate the difference in indicated mpg between two wheel dyno and four wheel dyno experiments?

    9. Just a note on terminology..

      NOx are nitroGEN oxides, which consist of nitric oxide (NO), nitrogen dioxide (NO2) and nitrous oxide (N2O).

      NO2 is the one of most interest for emissions testing. N2O is of the most interest for fire breathing hot rods. And dental hygienist parties.

    10. I bought a Ford Focus TDCi. 120kW (compared to 103kW from the VW); 6 speed dual clutch auto (same technology but smoother and better than VW); and only $27,000 drive away with a towbar fitted (about $8000 cheaper than a VW Golf). HIGHLY recommended. Handles better than a VW too. My last car was a VW Jetta and the Focus is better in almost every way.

      Just in case anyone still wants that addictive surge of torque, but is scared off VW!!

      Just for the record, although I respect people’s desire to do the right thing,, emissions and global warming and the whole greenhouse gases hoax is a myth. It’s a bit of a giggle that VW tricked their way around the super-tough regulations…just a shame they got caught.

    11. I’d be curious about seeing the hp and torque figures when doing the same exact comparative testing on the 1.88T and 2.0T VW engines. Care to try that idea?

    12. I am going to call these dyno tests bogus. How do they know the ECU is in cheat mode? It’s irrelevant that in their region they don’t have to test for NOx. They should have measured NOx. If they could control all the variables precisely on all runs, the NOx readings would confirm to them what mode the ECU was running.

      A 4w dyno may allow them to keep the traction control on, but in 4 wheel mode it causes a fwd drive to have to spin the front drums, and rear drums, and rear wheels, which the engine doesn’t have to do when they test in 2 wheel dyno mode. It would take some extremely knowledgeable and very keen nerds to normalize the results from these two dyno runs to account for this.

    13. How much do the folks at TFL actually know about cars? This video answers that question: Very little. Every single hypothesis in this video is wrong:

      1:27-1:30 – “we had a suspicion”
      3:15 – 3:27 – “the car thinks it’s on the road”
      4:20 – 4:47 – “I would think that whatever it’s done now, it’s switched off into different mode”
      7:30 – “passed with flying colors on visual particulate emissions” – particulate measurements are very different from NOx.

      Get a few senior engineers, working together with a very knowledgeably and detail-oriented emissions test shop and you will reliable answers to server your audience.

      There is enough misinformation out there on this.

    14. EPA documents show that NOX–diesel or not–varies according to a number of variables: RPMs, speed, engine temperature, ambient temperature (I think). The g/bhp.hr standard is presumably an average. Does it follow that the result of “10 to 40 times more” NOX is therefore really 25 times in EPA-speak?

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