Saab at work on diesel hybrid? — Autoblog Green This is interesting, but I wonder if it is viable. In my experience diesels do not run efficiently when they are not fully warmed up. How do you get around this in a hybrid use-case, where the engine will be turning on and off a lot, at least in city use?
Is that true of modern diesels? At least, are they anymore suspectable to to cooling and warming inefficiencies than a petrol engine? The Prius has always gone through a warm up phase when first turned on. Even if the system is already warm. There are other sources of heat in a hybrid. Inverters generate a fair amount. No reason why that heat couldn't be used to heat up the engine. Plus, diesel engines need to be more robust to deal with the greater forces than a petrol, thus more mass. While this means initially warming it up will take longer, it also means it will take longer to lose the heat.
My two cents... Diesel engines run a bit colder if under low throttle operation, because of big air flow through the engine. The turbo does not deal very well with on-off operation if the oil is hot. IMO, diesel engines do not fit so well in a full-hybrid solution...neither in a AER like a Volt, because of weight...
Diesel engine in a hybrid doesn't need a turbo, since torque is provided by the motor. I hope they make it, it will be a popular fleet choice in europe...
Turbo is not there for torque only, it is for efficiency purposes also, since it increases volumetric efficiency. Turbo and diesel are fond of each other...
