There are only 2 fixes possible, 1 lower the engines performance, basically the fuel burns at a lower temp and less efficiently... so less performance and less NOx created..
The other is adding a DEF system where chemicals are injected into the exhaust which break the NOx chemicals down.
That’s your only options.. barring some radical new solution no one has thought of... IF VW lowers the performance of the cars, they lose the gas mileage which was really the thing folks bought these cars for, not so much the reduced NOx.... and the other would be close to impossible to retrofit a DEF system into a passenger car these days...
Personally I think this is much ado about nothing, not that VW didn’t break the rules about air quality, they should pay the price for that... but I think most owners bought the car for the mileage benefits, and any air quality claims were secondary... I am sure some it may have been a factor in their original decision to purchase, but the main thing is the gas mileage for most.
I think most drivers feel the same way you do, I get 40+ or 50+ MPG highway, that’s why I bought this thing.. NOx wasn’t even a consideration.
Of course if NOx is a major consideration for a VW owner, they could always have someone reprogram their cars computer to step back the compression and heat, to lower the NOx, but the downside is going to be lower MPG and overall performance.
If I had one of these cars (and I did seriously consider a TDI for a while, because of the mileage, and I had had a good experience with a VW I owned in the past) I would probably just want to be made square on the resale value hit at most... but I tend to drive cars until they fall apart anyway, so even that’s not a huge deal for me.
My biggest concern would be the State inspection for emissions would start to declare my car was not legal to drive on the road at its annual inspection, because if that happens I would be literally screwed out of the car.
Otherwise, I wouldn’t be losing sleep over the NOx issue.. VW’s represent such a small percentage of cars on the road, and when you futher limit it to TDI models, in America anyway, the output over the lifetime of these vehicles is not something that is going to destroy the planet.
Yes VW should pay a heavy price to governments for their deceit on this issue, but other than that as a customer, where the main concern was mileage as the reason I chose the car, as long as I can keep driving the car as is, I personally am not going to get worked up over it.
Thing is, some of the VWs that cheated on emissions (and mileage! Remember, emissions wasn’t the only thing that was lied about) actually had a DEF system and still did not comply.
In order to bring the cars into compliance, VW will have to reduce their performance and mileage. It’s that simple, there’s no such thing as a free lunch.
It should also be mentioned that Navistar tried the same EGR-based solution that VW was using, couldn’t get it to work within even the much looser compliance required of medium and heavy trucks, ate a huge fine and almost killed the company. In the name of fairness, VW should be required to pay at least the same fines per engine and have to perform the same restitution.