larger turbo may = better fuel economy

Our turbos are so puny, engineered to kick in at a hair past cruising position on the accellerator. When we cruise at 60mph, if we want to slowly pass someone, our turbo spools up right away, increasing air flow throught the MAF, and increasing fuel supply to match. If we installed turbos with slightly bigger turbine sections we would firstly, reduce the amount of backpressure the engine recieves (equals to better off boost fuel economy) secondly, the turbo wouldn't kick in right away, but instead the diesel's torquey nature would be adequate, and at 50% throttle travel, the turbo would start making boost. More eficcient turbo equals to better off boost fuel economy.
I have owned many turbo cars, and most cars have a certain threshold of throttle input before there is enough exhaust energy to spool the turbo, but my tdi is not like that. I have to admit though, that is what makes this engine loads of fun to drive!!

nah she was too short, and I would only buy a car that got better MPG vs the VVT-i Corolla she just got last year. So the has a V40 with a high CR 10.3 motor, lowPresTurbo. in the USA it has only a 5 speed auto and variable exhaust timing for light off of the cat.The car CAN run on 87 to 93 octain. No I'm not kidding, in fact using 89 cuts down on boost and her MPG goes up! The Corolla could only take 89 in the winter and 93 in the summer without lots of pinging.

helps on a gasser, really no help on a VNT TDI, for one your MPG is dependent on you foot. The TDI is a lean burn engine in all conditions. Second the VNT has very minimal backpressure so you don't save anthing during normal driving by having a bigger turbin. But as stated above on a gasser, a much large turbo like a t4/t3 on my 1.8 liter really does little to hurt overall MPG during sane driving. In fact my turbo Integra got about the same overall MPG as the stocker. Gassers are not lean burn engines and slowing down boost slows down the amount of fuel needed, improves MPG. Just like my wife's twin scroll Volvo, I can get 37 MPG city no problem, but my wife gest 26 MPG. Why? she drives on boost, all the time. Sure a big turbo would help a little, but I'm sure she would find ways to use that boost too.

Lou:

Does your wife drive an S80 with a 2.7/8L transverse mounted 6 cylinder and two small Garrett turbos? What is it, about 247 HP and the NA version around 197?

I believe this is the only front wheel drive car with a 6 cylinder turned sideways between the wheels.