Coffee Brake: Dieselgate, the Unshocking Scandal

The day after Dieselgate broke into the news, I was driving our TDI wagon around Mazda Raceway Laguna Seca.


Fake smoke added for effect.

by CFlo

As the owners of a 2010 Jetta Sportwagen TDI, last month my wife and I found ourselves smack in the middle of the latest auto-related media circus, Dieselgate. The Volkswagen diesel emissions “scandal.” Shocked, dismayed, betrayed? No – I wasn’t really surprised. You see, this type of thing has been going on for years in the auto industry and the public revelation of VW’s cheating on the EPA Tier 2 Bin 5 testing explained an awful lot about the seemingly magical engine we’ve been enjoying for the past five years.

What I’m saying in so many words is that this is not really a scandal. Yes, the emissions defeat mode was illegal, egregious, and a major misstep by the (former) world’s largest automaker. However, this was an extension of what most major automakers do when they calibrate for emissions. The ECU maps are calibrated for drivability, power, fuel economy, and so on in the regions where people actually drive the cars. But the maps get funky in the EPA or Euro drive cycle regions – specific sets of conditions under which the cars are tested to meet new vehicle emissions standards. Engines run differently under those conditions in order to pass emissions. Yes, Volkswagen did cross a legal barrier when they created a separate mode that was engaged only when the car determined it was being tested for the US EPA Federal Test Procedure emissions drive cycle (not the average smog test, mind you – which varies from state to state). The difference is that all of the “innocent” automakers’ cars will run just as clean if driven by grandmothers to church on Sunday as they do in the emissions cert tests. However they will start to “spew” when driven with anything resembling verve or prudence. Take a 2016 Corvette Z06 off the dealer’s lot, fit it with a 5-gas analyzer, drive it like you stole it, and prove that it passes EPA emissions limits…I dare you.

Parked in front of the late Nobel laureate particle physicist Owen Chamberlain’s house

Back to TDIs, the presence of VW’s distinct emissions defeat mode really explains quite a bit about the lack of urea injection, otherwise known as Selective Catalyst Reduction (SCR) on the early versions of these engines. When the affected EA-189 2.0L common-rail TDI engine debuted in 2009, I was surprised at its distinct lack of urea injection / SCR. You’ll find urea at every truck stop these days, otherwise labeled as Diesel Exhaust Fluid (DEF). A urea injection system squirts precisely metered amounts of the stuff into a diesel’s exhaust system, where it reacts with oxides of nitrogen (NOx) and breaks them down into diatomic nitrogen and water.

Exhaust aftertreatment devices on the 2009-2014 VW 2.0L common-rail TDI (EA-189) engine

With the Tier 2, Bin 5 standard’s super low NOx limit of 0.05 grams per mile during the FTP, every other major diesel car manufacturer turned to SCR in order to get the smog-forming pollutant down to acceptable levels – within the tested operating regions of course. However, Volkswagen announced that they had figured out a great, low cost, less complex way of reducing NOx by using super trick calibration coupled with a “lean NOx trap” or NOx storage catalytic converter (NSC – shown in the diagram above). As you can see, this trap or catalyst is just one of the myriad devices used in the cadre of exhaust aftertreatment gizmos employed on this diesel engine.

The main components of the 4-cylinder TDI’s aftertreatment system are: the oxidation catalyst, the diesel particulate filter (DPF), the aforementioned NSC, and the hydrogen sulfide (H2S) catalyst. Each one of these devices is designed to do its own special job of reducing the particular emission that it’s responsible for. Implementation of each device is handled via the engine’s ECU and the way it’s calibrated, with extensive modeling of emissions buildup over time given the car’s duty cycle, aka the history of how it has been driven. Once the ECU’s model for the buildup of a certain pollutant reaches critical mass, a regeneration mode is initiated wherein the bad stuff is burned off using extra diesel fuel to jack up temperatures. See this VW engine training guide for more details.


I won’t go into too much more detail but lean NOx traps are not unique to VW; however they do need to be regularly purged by the engine via a process called NOx adsorber regeneration. During normal operation the NOx trap stores the oxides of nitrogen and waits patiently for the regen process, which requires bursts of rich mixture operation – extra fuel injected into the cylinders – to increase exhaust temperatures to the right levels to “light off” the conversion of NOx to N2. Volkswagen claimed to have figured out the secret to keeping the NOx trap working optimally while simultaneously achieving better fuel economy than the EPA ratings. We now know that this wasn’t really possible; urea injection was ditched due to cost concerns – to save 300 Euro per vehicle. The cars end up using less fuel on the road because they are running in the defeat mode, wherein enough extra fuel isn’t burned to reduce NOx either. If we wanted better fuel economy these cars should have had SCR. If we wanted lower cost, then the adsorber regen process would need to be cycled on much more frequently, impacting fuel economy in a potentially significant way.

It remains to be seen exactly how will VW bring the ~400k US cars into compliance when the recall starts. Most likely is a software re-flash – recalibration of the ECU to cycle NOx adsorber regeneration a lot more frequently. Less likely and far more costly would be the retrofit of urea injection system to the affected earlier cars that were sold without it. Interestingly enough the 2012+ Passat TDI does use SCR / urea injection on an otherwise similar 2.0L engine…but apparently not frequently enough for it to pass either. So do the 2015+ Golf, Jetta, and Beetle models. I’ve heard doomsday speculation of VW replacing entire engines or cars as worst case fixes, but I highly doubt that would be necessary given all of the knobs the calibration engineers can turn, so to speak. I can accept that it’s going to take some time for VW to get it right the first second time.

Looking towards the front of the Jetta, we see the offending /underutilized aftertreatment doohickey: the lean NOx trap


(mid-ground, ahead of the backpressure valve and H2S catalyst).

The thing that gets me about all this “shocking news” is that it isn’t; the scandal isn’t even near unprecedented. Emissions defeat devices have been found/accused of being installed in vehicles from GM, Ford, Honda, and Volkswagen (yes, a prior case in 1973) and for heavy duty truck engines made by Caterpillar, Cummins, Detroit Diesel, Mack, Navistar, Renault, and Volvo. The collective memory for this type of thing is short…perhaps shorter than safety related scandals, such as the infamous Ford Pinto fuel tank design. More recently we have the GM ignition cylinder failures on the one hand which were all sad and avoidable — and the Audi & Toyota unintended acceleration claims on the other hand, which if you look at them, were mostly cases of confused drivers stomping on the throttle when they meant to hit the brake pedal.

That brings us to the big question: what should we do with our car? The most “DT” thing to do is just keep driving it. We’ll see how badly performance and fuel economy is affected once the recall is developed. Could I just avoid taking it in to the dealer for as long as possible? Perhaps, but I’ve heard that the CARB or the EPA could block registration if certain recalls aren’t performed (though I’ve been unable to verify this). Could I just save the current ECU calibration? Maybe. Using RossTech’s VCDS & some additional software called NefMoto, one could access the current engine calibration and download it for future use. Of course, EPA emissions standards are designed to keep our air as clean as possible, so the responsible thing to do is have the recall performed and drive it that way. The irresponsible person would then go and have the car dyno tuned afterwards. The ironic thing is that pre-1998 diesels with no aftertreatment whatsoever are smog exempt in California. I can drive my 1984 Volvo 245 Diesel with it’s factory-fitted 2.4L VW/Audi D24 engine belching PM, NOx, sulfur dioxide, CO, and CO2 into the faces of kittens and puppies riding in the minivans behind me, and it’s completely legal!

The upside for those of you who may have been considering an EA189-powered TDI recently – this could become a buyer’s market with Blue Book values down 13% on these cars, the merciless claw of depreciation starting to creep in already as a result of the scandal. The counterpoint argument is that the stop-sale of new 2016 TDIs just froze the market as-is, with the ~400,000 used models representing the entire US supply. Diesel enthusiasts can be a paranoid bunch and might start buying these cars up pre-recall to preserve the torquey, fuel efficient nature – and effectively drive up demand and prices. Weird, yes – but I can’t take credit for the theory.

So for the sake of argument let’s say it’s time to offload the car after the whole scandal blows over and the recall is performed. What are some good alternatives to a TDI 6-spd manual wagon? In the new car market, the latest Mini Clubman comes to mind – it’s now been stretched into a real wagon with four full doors for passengers and two rear barn doors for cargo (no hatch). It should be fun to drive, has a manual trans option, and is about the same size overall as the Jetta Sportwagen.

If we are talking cars that can be found 1-5 years old on the used market with the initial depreciation hit already paid for, the Jeep Grand Cherokee EcoDiesel is enticing for its monster torque, extra cargo capacity and towing capabilities. Interesting import wagons are current Volvo V60, and the BMW 328d Touring. Oh yeah, the Acura TSX wagon – that is a nice looking longroof, although maybe a bit on the bland side.

Going back a few more years, some DT-budget-friendly alternatives would be: the Mazda CX-9, BMW E90 328i Touring, Mercedes-Benz W211 wagon, the Volvo V70R, XC70, or XC90…or even a 100 series Toyota Land Cruiser. None of these could match the TDI’s 700 mile range per tank of fuel, of course, but all have other interesting virtues.

Polluting the campgrounds of Yosemite Valley

But when I consider ditching this car for one of these alternatives, I have to step back and think about something my 2.5 year old daughter recently said to me. We gave her a fortune cookie, which she has learned how to crack open, and she promptly pulled out the fortune and “read” it to my wife and I. “What does it say?” we asked her. “It says you should eat the fortune cookie,” she replied matter-of-factly. She was making this up, of course.


We chose this car for certain attributes it possessed, but now that some of those will be diminished and the fortune cookie has been cracked…that doesn’t change what we have enjoyed about it for the past 5 years. Do what you can with what you’ve got, my toddler was saying, unbeknownst to her. Eat the fortune cookie…drive the TDI.


CFlo is Daily Turismo’s co-founder and Technical Editor. When he’s not driving an “emissions spewing” TDI he’s underneath a Volvo, on top of a Land Cruiser, cursing at a broken BMW, or driving the piss out of a crapcan race car. And that’s all before 10AM.