Audi "Ultra" tdi engines

[Condi]

The Audi tdi engines are available in "Ultra" and standard editions, with the Ultra generating the same power with more economy, partly as a result of running a leaner mixture according to the bumf. If there is no difference in power output (190HP engine available in Ultra and "non ultra" forms) then a) how does it generate the same power from less fuel, and b) why would anyone buy the "non ultra" engines if there are no down sides?

[CraigyMc]

Condi said:

The Audi tdi engines are available in "Ultra" and standard editions, with the Ultra generating the same power with more economy, partly as a result of running a leaner mixture according to the bumf. If there is no difference in power output (190HP engine available in Ultra and "non ultra" forms) then a) how does it generate the same power from less fuel, and b) why would anyone buy the "non ultra" engines if there are no down sides?

It's not just the engine, it's the car too.

The lower fuel use ones come with lower drag wheels and the like.

[Screenwash]

Didn’t they have smaller fuel tanks too, to save weight and hence improve efficiency?

[phumy]

Better combustion

Lighter cars

Less rolling resistance

[CraigyMc]

Screenwash said:

Didn’t they have smaller fuel tanks too, to save weight and hence improve efficiency?

In the case of the Audi tdi ultras, no.

This set of cars has direct equivalents from BMW (320d efficientdynamics)and Mercedes (c220d bluetec).

All are available with around 109g CO2/km emissions, and around 70mpg/1000 mile range from around 160bhp, 8s to 60 and 140mph.

Of the three the BMW is generally best regarded for real world economy, and they have done it longest.

[Dimebars]

Screenwash said:

Didn’t they have smaller fuel tanks too, to save weight and hence improve efficiency?

A larger fuel tank and AdBlu tank was a no-cost option on A4 models

Mine at the time wasn't specified with it and the fuel tank only held ~40 litres from memory

[Condi]

Is there any disadvantage to the Ultra engine over the standard/non ultra engine? Acceleration 0-60 is the same (apparently), and mpg is better, so what's the catch?

[CraigyMc]

Condi said:

Is there any disadvantage to the Ultra engine over the standard/non ultra engine? Acceleration 0-60 is the same (apparently), and mpg is better, so what's the catch?

You won't get to select large wheels (so it'll look less "good" if that's your thing), and runflats generally won't be available because to cut the drag this class of car usually runs some type of eco tyre.

There isn't an engineering catch to making a car less draggy. There may be styling or handling/grip downsides as I mention.

On the 320d, BMW opted to give the motor less power (even though the hardware is identical, they tuned it for less peak power) simply to stop the "eco" model being faster than the one with sporty (draggy) bodywork.

Only downside I've found with my E90 320d is that the gearing is tall enough to make traffic jams a drag. Obviously that doesn't apply to all 3 manufacturers, or any auto.