Touareg: 2006 V8
Join Date: Sep 2006
Location: Wytheville VA USA
Second Vehicle: 2004 V6
Thanked 315 Times in 275 Posts
I followed the tdi debacle and these are my impressions/opinions from that time. My belief is the cold man of winter grains was informed and approved of the program.
Despite orders, some of the VW "rogue engineers" were insiders that kept pressing to improve the emission system. Working around the accountants and upper management hurdles, these engineers managed to sneak hardware improvements and fixes slowly (one by one) onto the tdi vehicles. At the rate they were going, somewhere around the 2020 model, VW would have finally been emission legal.
The later models had some of the hardware fixes already implemented. I know the last models were getting close to being legal. The early models were not even close.
The early systems had converters that were undersized. If you ran the correct amount of adblue thru them, the converters would literally fall apart while under warranty. To prolong the life of the converter, the adblue was deliberately under utilized in earlier model years.
In fact, one of the bombshells of the hearings was about the adblue system failures. VW was unhappy with the amount of adblue warranty failures. VW released a software update that was applied to the vehicles. In fact, the update was to allow the cheat system to more easily detect when the vehicle was being tested, using the angle of the steering wheel. All this update did was to turn down the emission system, so that the adblue was used less, aka pollute more. But, it did delay most of the adblue failures until after warranty was up. It did not stop the failures, but in my opinion it shifted the cost onto the owners.
The later models had larger converters and the adblue was turned up to properly treat the emissions.
VW spent a ton of time optimizing the emissions in the end. You can reduce emissions before the tailpipe by better air-fuel mixes which would mean that you could then use less adblue.
It is possible that the slight reduction in the 2016 is due to better optimization.
Remember, it can be the exact same engine but it could have different emission cats and adblue systems between those years.