Originally posted by NS_Sailor I've just skimmed through the posts and I feel something is missing from the conversation
VW is not the only diesel engine maker having issues with emissions Every engine maker including those who make engines for trucks, buses and heavy equipment has the same problem, that is how a Diesel engine works.
The Diesel Engine depends on compression to generate the heat required for combustion and without enough heat in the cylinders it is impossible to get complete or perfect combustion especially when the engine is idling or operating low horsepower output.
The only way the diesel engine can generate enough heat in the cylinders for complete combustion is to maintain maximum the load on the engine, operate the engine with the coolant as hot as possible and keep the engine's fuel system in optimum condition. Running the engine at maximum power fuel economy suffers so car makers have gone from 3 or 4 speed transmissions to 5, 6 and even 7 speed transmissions to reduce the engine load and improve fuel economy. Engine makers have also gone to turbocharging to increase power output but the turbocharger only improves combustion at high loads such as driving the Autobahn at 200 Kmph is totally ineffective city driving.
So the only way to improve the performance on a diesel is to run around town in 1st or 2nd gear with low HP Engine
Question: How about sticking a small diesel generator into a hybrid? Like one where the diesel engine is only used to generate electricity, and never driving the wheels? That way any excess power produced by the engine can be used to charge the batteries. It would make for some odd noises, but it could keep emissions even lower and save fuel. Propulsion would come only from the electric motors, the generator will create power when it is needed, i.e. driving fast or the battery is about to die. The BMW i3 for example is an electric car that, as an option, has a small petrol engine that generates power if necessary. Such a car wouldn't have range anxiety. Granted diesel engines are a bit heavy and big, but it may make sense for bigger cars, or maybe teeny tiny diesel engines for smaller cars...
The turbocharger does help in city driving, it gives you some nice off the line performance, and since the turbo kicks in at pretty low revs, say 1500 or so, you do get to use it plenty. IIRC though at least with turbocharged petrol engines you need to keep the engine below those revs for good fuel consumption, once the turbo "kicks in" FC goes through the roof.