The Audi A8 gets a TDI engine option for 2014 (on sale spring 2013). The current body style was introduced in 2010. While you might associate a diesel engine with the noise and smell of a big truck instead of a flagship car, the Audi A8 TDI delivers a luxury car experience. There's no diesel odor from the exhaust and the engine is very quiet from inside and outside the cabin. Aside from better fuel economy, the biggest advantage of the diesel engine is that engine torque is right in the driving engine rpm so that the engine is more responsive vs. an equivalent gas engine.
Major highlights of the TDI: fuel economy is rated at 24/36 mpg city/highway. Diesels have greater fuel economy once they're fully broken in so I would expect around 30-33 mpg mixed driving after a year. The EPA rating is 33%/29% better city/highway fuel economy than the gas version. The aluminum chassis and body panels mean a lighter car vs. the competition. Standard quattro AWD and air suspension. The diesel engine option costs $4000 more than the gas engine. Maximum acceleration is slower (6.4 seconds 0-60mph if you can call that slow) but engine torque is up by 25%.
Standard A8L TDI: The base A8L TDI has quattro, 19" alloy wheels, power closing doors and trunk, parking sensors w/rear view camera, power adjustable steering column, front seat memory, 4 zone auto climate control, rain sensing wipers and auto headlights/dimming mirrors, and keyless entry and start. MMI Plus (navigation w/voice control and touchpad input), bluetooth and homelink are also included.
The L versions (all TDI in North America) increase the wheelbase and length by 5" over the standard wheelbase cars. It's all in the rear seat area so rear passenger headroom increases by 1" and legroom by 5". The increased wheelbase also smooths out the ride, increases the turning circle, and adds about 33 lbs.. Below are some videos showing the front and rear interior. (Optional Bang and Olufsen stereo system and rear seat center console shown)
Premium trim level: The premium trim level adds the front comfort package, full LED headlights, side assist, and pre sense rear.
Front and/or rear comfort package: The front option adds 22 way adjustment, heating, ventilation, and massage functions to the front seats. The rear option adds power adjustable rear seats.
Full LED headlights: This removes the cornering Xenon HID headlights and adds LED low and high beam headlights. The color (5500K) is slightly more day like than Xenon HID and uses slightly less energy. The module is not serviceable and is made up of a few LED for the cornering lights, 22 LED each for the DRL and turn signals,10 LED for the low beams, and 8 LED for the high beams. An internal fan cools the LED modules. Below is an animation of the DRL, turn signals, and low/high beams, and a thumbnail picture of the headlight module, click to enlarge.
Cold weather package: Adds heated steering wheel, heated rear seats, and ski pass through/bag on the rear seats.
Bang and Olufsen Advanced Sound System: 1400 watts, 2 amps, 19 channel, 19 speakers including the subwoofer, Dolby Digital 5.1. This adds the pop up tweeters by the a-pillar. All speaker covers are silver metal grilles.
Night vision assist: This adds a night vision display on the instrument cluster display. It uses infrared heat signatures to flash and sound a warning if it detects pedestrians up to 300 ft away in the road. There is no active infrared lighting which means it can only see a differential in heat as in people or animals vs. their surroundings. The maximum temperature pedestrian warning can work at is 82.4F (28C). The field of view is 24 degrees. The camera lens is behind the first ring on the Audi badge on the front grille.
Car and Driver magazine (June 2012) said that it was the best setup out of the BMW, Mercedes Benz, and Audi systems but that night vision is a distracting gimmick. Below is a test of the systems, the video beings in the segment where they test the pedistrian highlight function which these systems are intended for (and not driving without headlights).
Solar sunroof: this uses solar panels on the sunroof to vent the interior cabin when the car is off.
Side assist: Side assist uses radar sensors to look behind the car and in the blind spot to detect other cars or motorcycles. It only works between 18.6 mph (30 km/h) and near the top speed of the car up to 70 meters behind the car. When a vehicle is in the blind spot the lights turn on. If you activate the turn signal in that direction while a car is in the warning area, the lights will get bright and flash. The light intensity can be adjusted and the system can be turned off entirely. NOTE: These systems can cause a pop or K band radar
detector false alarm. The V1 Valentine seems to
have this problem the worst but you can disable its pop radar function.
Driver assistance package: This combines lane assist, headlight range control, pre-sense, and adaptive cruise control. They're all in the same package because they share sensor components.
Lane assist: If the driver has not used the turn signal, it activates a buzzer in the steering wheel to warn that the car is drift out of the lane. This uses a camera on the rear mirror mount behind the windshield (25 fps, up to 197 ft ahead and 40 degree field of view) to monitor the area in front of the car. It's active above 40 mph (65 km/h) and only if the driver has not used the turn signal. The intensity of the buzzer and how far you drift out of the lane before the warning is activated is adjustable. It does not work on snow covered or dirty roads. The buzzer is in the lower left steering wheel spoke.
Headlight range control (high beam assistant): The same camera looks for cars ahead and dips the high beams in response to oncoming traffic or cars ahead. It's networked with the GPS system (MMI plus) to raise the headlights on highway on ramps and turns on cornering lamps when approaching intersections.
Pre-sense plus: This minimizes rear end collisions when you hit a vehicle to the front. If the car sees itself rapidly approaching a vehicle to the front, it sounds a warning sound, increases the brake pedal response, and stiffens the suspension (to reduce CG shift) to give the drive better braking if they press the brake pedal in the first warning stage. If the brake pedal is not pressed, it reaches the stage 2 warning and gently snugs the seat belts. The seat belt tension is calibrated when the engine is started. If the brake pedal is still not pressed it reaches the stage 3 warning - the car will lightly apply the brakes at 9.8 ft/sec (3 m/s), close the windows/sunroof, and turn on the hazard lights. The car can still avoid an accident in optimal conditions. If the brake pedal is still not pressed during stage 3, it's too late to avoid a crash and the car enters stage 4. The car fully tightens the seatbelts, applies the brakes at 16.4 ft/sec (5 m/s), less than what a driver could apply, to reduce the intensity of the crash. This system can reduce the speed of the crash by up to 25 mph at average highway speeds vs. without the system.
*NOTE: The A8L TDI comes standard with pre-sense basic and rear. Plus is optional and is part of the driver assistance package. Pre-sense basic closes the windows and snugs the seatbelts if the car is sliding or maximum braking is applied. Pre-sense rear sees vehicles about to rear-end you and closes the windows/sunroof, tightens the seatbelts, and moves the seatback and headrest forward to help minimize whiplash.
Adaptive cruise control: This uses the camera plus 2 radar sensors in the front corners to control the cruise control distance. It can be used from 0-155 mph and can gently brake the car up to 13 ft/sec (4m/s) all the way to a stop. Like pre-sense plus, it cannot make sudden or full power stops. It can sense traffic up to 820 ft in front of the car and cruising range is adjustable. It's also networked with the GPS and can detect if the car in front has their turn signal on to make more intelligent decisions about stopping.
Camera assistance package: This adds a virtual 360 degree cameras to the backup camera and adds junction camera. It uses cameras at the corners of the car which can be viewed individually or combined to create a virtual bird's eye view from above. LED headlights required.
You're probably comparing the A8L TDI to the gas A8L and the only other large diesel luxury sedan, the Mercedes Benz S350 Bluetec diesel so here's a chart showing the differences. The major highlights on the A8L are the aluminum body which weighs about 4400 lbs (2000 kg), about 400 lbs lighter than the MB S350 Bluetec. This results in better fuel economy and performance with less power. The price difference for the TDI is $4000 more than the gas A8L and $10,000 less than the MB S350 Bluetec. All cars have all wheel drive and air suspension standard. The quattro drivetrain power split is 40 front/60 rear. The diesel A8L gets 33% better city and 29% better highway fuel economy than the gas A8L.
|Audi A8L gas||Audi A8L TDI||MB S350 Bluetec|
|approx. price range US$||$79,400||$83,300||$93,000|
|engine (all V6 diesel)||333hp/325 lb-ft||225hp/406 lb-ft||240hp/455 lb-ft|
|EPA mpg (US cycle)||18/28||24/36||21/31|
|CO2 emissions (euro cycle)||224 g/km (360 g/mile)||176 g/km (283 g/mile)||?|
|curb weight lbs (kg)||4409 (2000)||?||4784|
|frontal surface area sq.ft (sq.m)||25.94 (2.41)||?|
|length in. (mm)||207.4 (5267)||206.5|
|width in. (mm)||83.1||83.5|
|wheelbase in (mm)||122.9 (3122)||124.6|
|trunk capacity||18 cu.ft (510 liters)||?|
|F/R brake rotor size||14.0 (356)||?|
|F/R brake caliper||12.9 (330)||?|
|front int room(head/leg/shoulder)||37.2/41.4/59.1||37.8/41.9/58.8|
|rear int room (head/leg/shoulder)||39.1/42.9/57.8||38.5/42.3/56.9|
|truck capacity (cu ft)||13.2||16.4|
|emissions||no Adblue for gas engine||Adblue||Adblue|
|transmission||8 speed transmission||7 speed transmission|
|towing: gradient/unbraked trailer||?||4850/1653 lbs||?|
|sunroof||standard, opt pano, opt solar panel (vents interior)||standard, optional pano sunroof|
|headlights||cornering HID, optional LED headlights||cornering HID headlights with range control|
|other lighting||LED taillights, LED DRL||LED taillights, LED DRL|
|stereo||Bose, optional Bang and Olufsen||Harmon Kardon, optional Bang and Olufsen|
|misc. features||4 zone climate standard, nightvision camera, power closing doors and trunk, optional acoustic glass||nightvision camera, massaging heat/vented seats|
3.0L TDI engine: This engine is also used in the Audi Q7 TDI, Audi A6 TDI, VW Touareg TDI, and Porsche Cayenne diesel. The engine was all new for 2010 in Europe and was introduced to North America for 2013. Some highlights are separate coolant loops for the cylinder head and block which means faster warm up (the block water is not circulated during initial warm up) and faster cabin heat (the head coolant is shared with the cabin heater). 2 timing chains instead of 4 + a toothed belt, lighter weight, and different tuning mean slightly higher fuel economy than the older TDI engine. Below is a dyno chart of the V6 TDI engine and a diagram showing overall dimensions of the car (click to enlarge).
Rear passengers get their own control knobs and lower, center, and upper air ventilation. 4 zone auto climate control is standard.
8 speed transmission and quattro: The A8 still uses a traditional torque converter automatic transmission vs. a DSG/S-tronic dual clutch gearbox. There's probably 2 reasons: the lower production numbers, existing A8 quattro drivetrain, and parts sharing with the Touareg/Q7/Cayenne. The traditional transmission is smoother and should be slightly more reliable than dual clutch but has greater powertrain losses. The transmission gear selector is shift-by-wire, meaning there's no mechanical connection to the transmission. The flat gear shift handle is inspired by a yacht throttle (their words, not mine). The parking brake is automatically applied when the car is shut off. The gear ratios for the A8 transmission are listed below. The top 2 gears are double overdrives.
The power split for quattro is 40% front/60 rear. The maximum power split is up to 60 front, up to 80 rear.
Stereo system options:
The standard system is the Bose 600w system with 12 channel digital amp, 14 speakers including the subwoofer, and 5 channel surround sound. The speaker grilles have silver rings around them. The head unit includes a DVD drive that can play DVD movies, MPEG4 videos, HD radio, has two SD card readers for loading audio files, and a dual radio tuner. Sirius XM is built in with a 90 day trial subscription included. A 4 year Sirius XM traffic subscription is included.
The optional Bang and Olufsen system is 1400 watts, 2 amps, 19 channel, 19 speakers including the subwoofer, Dolby Digital 5.1. This adds the pop up tweeters by the a-pillar. All speaker covers are silver metal discs. An illustration of the B&O system is below, (click to enlarge).
Air suspension: All long wheelbase cars get an adaptive air bag suspension instead of spring suspension. The advantage of airbags is that it can raise or lower the car's ride height for better mpg and handling or ground clearance. It also self levels for loading or towing. A small air compressor powers the system and a small 5.8L reservoir ensures quick response.
In auto mode, at speeds of 75 mph for more than 30 seconds, the car is lowered 20mm (7.9"). In dynamic mode the car is always lowered 10mm (.39") and another once the 75mph/30sec requirement is met. In comfort mode it never lowers automatically In lift mode, the car is raised 25mm (.98"). Lift mode can only be used below 50 mph.
The suspension control arms are forged aluminum. The front brake rotors are 2 piece aluminum hat/iron disc rotors which saves weight vs. 1 piece cast iron rotors. The aluminum control arms and rotor hats reduce unsprung weight considerably which benefits handling and comfort.
The display is 8" color high resolution. The touchpad can be used for radio and navigation function. Bluetooth is standard. The climate control knobs are a separate panel from the MMI radio/nav/settings panel.
Audi MMI Bluetooth tutorial
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