Quote:
Originally Posted by Blue Angel
I'm very curious how these modern diesels control for adding power... if the air is available is it just a matter of adding more fuel? I know how to tune gas engines, but diesel is a completely unknown concept for me.
This car must have a very effective EGR system then, because I have put about 15,000km on it since buying it a year ago and have yet to top up the DEF tank. That, or the DEF tank is just huge?
So far I have been completely unaware of any regen cycles taking place. From what I've read it should be obvious when a regen cycle is happening as your mileage will suffer terribly. I've noticed nothing out of the ordinary so far, and I don't think I use the car on the highway more than most people would. My commute is actually very slow, travelling about 50MPH with the cruise on for about 15 min. which doesn't seem like much time/load to facilitate the burning of soot in the DPF? When I do have it on the highway I tend to drive it harder just for that reason, but it's not a regular thing.
...and is the reason I was so interested in this car. For a big heavy AWD sedan it's phenomenally frugal. I average about 8-8.5 L/100km (27.5-29 MPG), and do much better on long trips. I got 5.7 L/100km (41 MPG) calculated at the pump on a 3.5 hour highway trip in January with four brand new snow tires, averaging around 60 MPH.
One thing I'm curious about is cold weather operation. A gas car runs rich to warm up the catalyst, which can take quite a while with light-footed driving, or while idling, and can result in fuel contaminating the oil. I don't believe diesels have this issue and would be much more efficient in the winter because of that, no? I didn't notice much change in fuel economy in the cold last winter and I'm wondering if that's why?
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1. Modern diesels work about the same as oldschool ones in that regard, but they do add some EGR especialy under low load to keep NOx down
2.That's what the EGR is supposed to do, the filling intervalls can depend on driving conditions though.
3.You might not even notice the car initiating a regen cycle when driving on the highway as it just injects a little more fuel after combustion to get the exaust gas temps up enough.
Plus highway driving means you might not even need regen cycles at all as there your EGT goes up sufficiently on its own.
4. Yep, diesels can be very efficient, yours is actualy not that efficient by diesel standards.
Take a look at the Passat 1.9 TDi or a Lupo 3L
5. Diesels hate the cold.
As they are so efficient under low load and move that much air, they take a long time to warm up.
In idle they might not even heat up at all, so if it gets very cold where you live, consider a block heater.