Ignite Energy Resources and TRUenergy Plan Direct Coal-to-Liquids and Coal Drying Demo Project for Supercritical Water Technology
Study Finds Ozone, Nitrogen Change the Way Rising CO2 Affects Earth’s Water

Audi’s A4 2.0 TDIe: 4.6L/100km (51 mpg US) and 120 g CO2/km; Stop/Start and Energy Recuperation

The A4 2.0 TDIe. Click to enlarge.

Audi has introduced its fuel-consumption optimized version of the A4 mid-size sedan, the A4 2.0L TDIe, in Europe. Noted by Rupert Stadler, Chairman of the Board of Management in his talk at the 120th Annual General Meeting of Audi AG in May, the A4 TDIe consumes an average 4.6 liters of diesel per 100 kilometers (51.13 miles per gallon US gallon) and consequently emits 120 g CO2/km.

The A4 Saloon TDIe adopts the 100 kW (134 hp) 2.0-liter TDI engine first seen in A6 TDIe. (Earlier post.) The turbocharged diesel features high pressure common rail injection and incorporates stop/start and energy recuperation systems. Further fuel savings come from grille and under-body modifications to enhance aerodynamics.

The A4 2.0 TDIe delivers peak power at 4,200rpm and 320 N·m (236 lb-ft) of torque from 1,750 rpm. Equipped with a six-speed manual transmission, the car reaches 62 mph from rest in 9.5 seconds and continues to a top speed of 143 mph (230 km/h).

The start-stop system cuts engine power at idle when the clutch pedal is released and the gear lever is in its neutral position, and then restarts in two-tenths of a second—more rapidly than comparable systems—when the clutch is depressed. With the system’s help, economy is boosted and CO2 is reduced by approximately 5g/km, but if required it can be deactivated at the touch of a button.

Recuperation technology provides further fuel and CO2 savings by recycling a proportion of the wasted kinetic energy which is generated under normal braking and normally dissipated as heat, and storing this temporarily in the vehicle battery to reduce the engine load when the car subsequently accelerates again.

The achievement of ‘e’ status in the A4 has also been helped by a 5% increase in the six-speed manual transmission’s final drive ratio, by the installation of a power steering pump which operates only on demand and by the use of low rolling resistance tires.

An additional streamlining underbody trim panel, extra enclosure for the radiator grille and sports suspension settings which help to reduce drag through a 20mm ride height reduction.

The TDIe also features a special instrument cluster with an efficiency-focused version of the Driver’s Information System (DIS) which recommends gear shift points and gives situation-specific driver advice on how to optimize fuel efficiency based on sensor analysis of driving conditions and driving style. The recommendations provided by the system, incorporated into the dashboard, have been shown to improve fuel economy by as much as 30%.



A nice motor, with a decent blend of performance and economy without looking like an eco-trolley - I'd definitely have one of these on my short list for a new car (if I had the money).


I was amused to see the same 134 hp as the 2010 Prius; auto-stop at lights; regenerative/recouperative braking; and more efficient power steering. These are all technologies found in the 2010 Prius. But I'm sure the mileage is highway only, which may not be such a problem in Europe where public transportation is more common. However, urban commuting is a major part of USA driving.

Still, any journey begins with a single step and they have stopped digging the hole deeper.

Bob Wilson, Huntsville AL


Demonstrates once more what can be achieved by good engineering design using existing technology. Buying one of these vehicles would save sleepless nights worrying about the life of the battery in a hybrid.


I just love the:
"Recuperation technology provides further fuel and CO2 savings by recycling a proportion of the wasted kinetic energy which is generated under normal braking and normally dissipated as heat, and storing this temporarily in the vehicle battery to reduce the engine load when the car subsequently accelerates again."

What they do is just switch off the alternator for the lift-off moment, which is very good thinking, but they call it a kinetic energy recovery system when it is just an alternator functioning while braking (which any alternator does) and that is only good marketing.

Well, if it helps selling them....
The rest is good, I have to admit, and all that without another battery or electric motor.

Plus you have an Audi, and that is not only fashionable, it's also good quality.


The mileage isn't highway. It's a combined cycle assessment which makes an assumption about the porportion of urban and highway miles driven.

My wifes's old 1997 Audi A6 which has a five cylinder 2.5TDi (140bhp) unit can get 60 mpg (50mpgUS)on the Highway and by that I mean 70mph on motorways in sixth gear. Combined cycle its 46mpg, let down by a poor urban cycle - but then these cars are meant for the highway, not for city streets. Still very good for a car the size of a small barge and something that the more modern V6 could not replicate but I digress.

Highway miles, you'll be looking at something like 55 - 60 mpg(US) for the Audi A4 because of the use of a taller sixth gear ratio, better aerodynamics and so on. The regenerative breaking and start-stop will be aimed at reducing urban consumption.

Now if we can replace petroleum with Biodiesel, we'll be rockin'!


"Further fuel savings come from grille and under-body modifications to enhance aerodynamics."

That's the problem of car design; aerodynamics is done, if done at all, as an afterthought. Most cars only go into the windtunnel after the 'stylists' have drawn up the design.

If you really want a fuel efficient car you HAVE to start with the aerodynamics. Case in point: This DIYer- http://aerocivic.com/ -doubled his fuel efficiency by spending $400 at a local hardware store.


A very good example of what can be done with a large enough vehicle for just about everybody. The station-wagon version is more than adequate for families and so is the similr VW Jetta - Diesel (wagon or 5-door version.

A Prius III with an up-to-date 1.4/1.8 diesel could do about 65 mph on highways and about the same in most city driving. The on-board Prius NiMH battery pack is NOT a problem for 10+ years. Toyota Lithium battery pack should do even better starting in 2012.

When the majority drives similar 60+ mph vehicles @ under 100 gr/CO2/Km, oil import and air pollution will be greatly reduced. Reduced fuel consumption + non-fossil fuel production could help keep crude oil price low for a long time.

Of course, other transportation vehicles, (buses, trucks, rails, ships, aircraft etc) could also reduce fuel consumption by up to 50% and reduce air pollution even more. They have to get on board too.

The next step (2012+) would be affordable mass produced 100+ mph mid-size PHEVs. The new-GM Volt will not be alone. Many others will be there.

The final solution, i.e. affordable mass produced mid-size BEVs with 500+ Km range may not be around for another 5 to 10 years. Battery technology has to improve from 100 Wh/Kg to 400+ Wh/Kg and price has to come down from about $1000/Kwh to under $250/Kwh before such vehicle become common place.


I think people look at Prius and Civic hybrid interior room numbers and still can not believe that they are roomy. But when it comes to Audi A4, Camry hybrid or Fusion hybrid, they believe that they are more roomy.

It is a perception that does not go away with measurement numbers. If they can get an A4 or other sedan with better mileage, they are interested. Now they just have to make them more affordable and they might have a winner.

Paul W

2002 TDI Jetta. 52 mpg combined last tank.
I would like to own one of these but I plan on driving my TDI for some time to come.
Biodiesel, algae and clean diesel is a what the US needs in a big hurry.


Come on guys, you can't compare an Audi A4 with a Prius or a Jetta. They don't come even close regarding comfort, quality or performance. Audi makes sport sedans which aim at a completely different market. You can't really expect them coming out with a 100mpg or an EV model.


You could have two groups, the rich that really don't care, so all this in a luxury sport sedan is not important. Then a second group that would like to buy a hybrid, but can not afford to.

The comments to this entry are closed.