Winter diesel

[Cogeneration]

Thanks for the invite Tenderfoot. Yes, I've been to NC a few times. Great place. Not much of a golfer but I do have some fanatical friends who are.

[Draigflag]

Does anyone see an increase in economy during winter? I was thinking as most cars are now turbocharged for power/economy reasons, does a turbocharger not benefit from cooler temperatures?

[trollbait]

Turbos and superchargers will use an intercooler to lower the intake air temperature in order to counteract the heat generated by compressing the air. Cold ambient temps seem to help them as much as naturally aspirated engines. It may allow for faster warm up of the engine, but I've dropped 5mpg in the past couple of days, and don't think going into higher boost during the first part of my drive will help that.

If there is any benefit to cold air improving engine efficiency, it is small, and up against all the negatives of winter driving on fuel economy.

[Draigflag]

Thats what I thought. I guess perhaps long distance at a constant speed there may be a small benefit only.

[Tenderfoot]

Draigflag....question for you. Your car looks to be pretty aero, and you get great mileage. Do you drive it often, or do you have another daily driver? I can't believe you have recorded only 6 fill ups. What am I missing? I know England is a small country, but come on, you must have places to go and rack up some miles. What is your secret? Here in the USA, everywhere is miles away from where we live.
Just curious.
Tenderfoot

[marrump]

I think we all experience much lower mileage in the winter. My TDI will drop from the high 30s to under 20 mpg. shorter trips, higher friction, winter tire, winter blend, idle to warm up (a hopeless cause!) are all factors. Based on my understanding of diesels I would have though colder weather would help the diesels on long trips, but it does not. I have always seen best mileage is on warm days on the highway (up to 50 mpg) on the current TDI. it seems much more sensitive to temperature than the old (1999) TDI. Gas cars have similar experience, but I dont know if the swing is as large

[trollbait]

Do diesels experience more DPF regen cycles in the cold?

[Draigflag]

Originally Posted by Tenderfoot

Draigflag....question for you. Your car looks to be pretty aero, and you get great mileage. Do you drive it often, or do you have another daily driver? I can't believe you have recorded only 6 fill ups. What am I missing? I know England is a small country, but come on, you must have places to go and rack up some miles. What is your secret? Here in the USA, everywhere is miles away from where we live.
Just curious.
Tenderfoot

Well I think the figure in my signature is UK MPG, works out about 52 US MPG, so it's not that great, but I do a lot of short trips during the week (this is my only car) which kills the MPG's. On the highway I get 74 MPG at 70 MPH, although in the government tests the car got 88 MPG. The best I had was over 95 MPG on a 30 mile low speed journey (all UK MPG's) Some hypermilers can get over 100 MPG in thier diesels over long distances, I have no idea how, but car manufactures are always coming up with neat engine map tuning to keep increasing economy. In Europe, there are strict C02 regulations, and as we know the easiest way to reduce C02 is to burn less fuel

[Draigflag]

Oh and I dont live in England, I live in an even smaller country! And everything is quite far from me too

[Tenderfoot]

I use another factor when tracking fuel mileage; days between fill ups. I think this is a significant measure of trip length without any extra logging or record keeping. As an example, if you are filling daily, or a couple of days, then you probably have fewer stop and start cycles to sap fuel compared to longer fill up dates, and more starts. This is an obvious component to explain why highway mileage is more impressive than low speed, but short distance city driving, even though slower speeds (city) will show higher mpg consumption. I wish I could duplicate the 70-80mpg figures I see on the computer while driving on the city thru streets, of course the mileage when parked for days on end is very high and does not count.