T he automotive all-wheel drive landscape is diverse and interesting . On the course of the Snow Rallye Ring, not far from the northern Finnish city of Rovaniemi, the four-wheel drive sports cars were able to demonstrate their skills on ice and snow in four test disciplines. The candidates Audi S4 and Audi TTS, Alpina B3 Biturbo Allrad Coupé, BMW 335i xDrive Coupé, Mitsubishi Lancer Evolution, Subaru Impreza WRX STi and the brand new Opel Insignia 2.0 Turbo 4x4.
Global warming, CO2 discussion, global economic crisis : Against the background of the general day-to-day events, the present all-wheel drive comparison may seem almost anachronistic. After all, four-wheel drive costs - in every respect. First of all, purely in monetary terms. With the BMW Alpina B3 Biturbo, for example, the luxury of the drive on all four wheels costs exactly 3,000 euros extra. Opel estimates the plus in traction in the case of the front-wheel drive Insignia 2.0 Turbo in the basic version at 3,180 euros, BMW in the normally rear-wheel drive 335i Coupé at 3,400 euros. All other participants in the winter excursion to the Arctic Circle are only available with all-wheel drive.
Environmentalists can consider all-wheel drive cars to be dispensable
In addition to the owner's bank account, the propulsion system, which promotes propulsion at low friction coefficients, also has a negative impact on the car's weight account. Anyone who wants to be on the road with good grip at all times in wind and weather has to cope with up to 100 kilos of love handles. And last but not least, this additional weight is of course accompanied by a certain additional consumption, which in turn increases the CO2 value. Bargain hunters and uncritical environmentalists could well consider all-wheel drive cars to be dispensable. Alone: Who - as happened more often this winter - is surprised by the harsh reality when looking out of the window in the morning and has to deliver his children to school on time despite the cuddly white splendor on the streets or under no circumstances should they miss a very important appointment , will consider itself extremely lucky to be able to rely on a modern all-wheel drive system.
Sports models tested in Finnish Lapland
The increasingly sophisticated all-wheel drive technology calms down tremendously when approaching the snowy or icy mountain at the latest. Unsteady pawing withthe front or rear drive wheels are a thing of the past. All modern four-wheel systems guarantee a plus in safety in adverse weather conditions. However, there are considerable differences in the details. In particular, sporty drivers often fear a loss of agility and driving pleasure in the case of all-wheel drive cars. Reason enough for sport auto to spare no expense and effort and to get to the bottom of the qualities of the sporty sedans and coupés that have recently come onto the market since the last all-wheel drive comparison.
The fact that Audi is competing with two vehicles is partly due to the fact that the Ingolstadt-based company represents all-wheel-drive expertise on the German market. On the other hand, different systems are used under the sign of the rings - depending on whether the engine is installed lengthways or crossways. The former is the case with the new S4. The six-cylinder compressor with gasoline direct injection, which is blessed with 333 horsepower and 440 Newton meters of maximum torque, has found space lengthways in front of and above the front axle and is then coupled to a torque-sensing center differential (Torsen differential), which distributes power variably and free of delays depending on the road conditions adapts. In the basic configuration, 40 percent of the drive force goes to the front and 60 percent to the rear axle. This has been the case since the last RS4 was launched in 2005.
The modified type of rear axle drive named by Audi Sportdifferenzial is new. In order to be able to assign more torque to the faster turning wheel on the outside of the bend within fractions of a second, the classic rear axle differential was given a superimposition step on the right and left in addition to the multi-plate clutch running in an oil bath. This always rotates ten percent faster than the drive shaft of the associated wheel. If the multi-plate clutch, which is assigned to the respective superposition stage and operated by an electrohydraulic actuator, is closed, the superposition stage, which is similar to a mechanical transmission, accelerates the respective drive wheel and then applies an additional drive torque to it.
Using three different maps stored in the new Audi Drive Select driving dynamics system, the driver can decide, depending on the situation, whether he is looking for maximum safety or driving pleasure. The former is guaranteed by the comfort mode, the latter by the dynamic mode. The auto mode marks the golden mean. In fact, the test car equipped with dynamic steering and electronic damper control delivered a flawless performance on the 1.1 kilometer long handling course in Finland, which was specially designed for sport auto .
Tire selection as a tuning measure
Even more agile than with oneExactly co-steering rear of the blessed Audi can only put the Mitsubishi Lancer Evolution in the limelight. This also fits into the picture because the all-wheel drive system of the rally base car basically works in a similar way to that of the S4. The distribution of the drive torque between the front and rear axles is done by an active center differential called ACD with an electronically controlled multi-plate clutch. In the case of the Evo, an electronically controlled planetary gear differential is responsible for the torque distribution between the right and left rear wheels. Here, too, the greater part of the drive torque is assigned to the wheel on the outside of the curve, which prevents any tendency of the Japanese to understeer just as accurately as with the Ingolstadt limousine.
Both cars circumnavigate the handling course, which consists of rhythmic alternating curves, fast, opening corners and a tightening 180-degree turn, in a very entertaining way. The fact that the Mitsubishi Evo completes the task given to it in an exemplary nimble 1,10.8 minutes is due to the extremely clever tire choice of the German press workshop. A similar nakedness as in 2007, when you sent your best horse in the stable on completely glazed winter tires (because they were previously subject to a high-speed cycle), the Hessians refused to give up and pulled the 295 hp turbo athlete in extremely soft Winter tires in Arktic specification guarantee maximum grip at low temperatures. Without this tuning measure, the Evo, which was ahead in all four disciplines, would probably have been a little less dominant.
Glorious rally history is useless
Conversely, against the background of the tire issue, the astonishingly poor performance of the Subaru, who was just as accurately positioned at the bottom of the field in all stages, is also Put Impreza WRX STi into perspective. The tread blocks of the Dunlop SP Winter Sport raised here were extremely unyielding even in the manual agility test. Correspondingly poorly, the interlocking with the rather cold underground, despite the not really arctic temperatures of minus eight degrees Celsius at the time of the test, worked. Armed in this way, the Top Impreza, equipped with a 2.5 liter turbo engine from Alte Schlag, could not achieve a top position in any special stage. In the sprint test to 100 km /h, the compact sedan suffered from the all-or-nothing attitude of its four-cylinder boxer engine with its very large supercharger, and in the slalom from its sensitivity to load changes. Gimmicks on the accelerator pedal in combination with short successive changes of direction takes the Japanese, who is exemplary in a steady driving style, really crooked. Then the 1.5-ton truck hangs out the stern emphatically.
But while the Subaru in the 18-meter slalom with the Audi S4, which is also limited in this discipline by its super-agile rear, still has a hardly faster fellow sufferer by its side, it carries the handling course that ends the driving dynamics tests alone red lantern. With 1.16.9 seconds, the WRX STi is by far the slowest car on the 1.1 kilometer circuit. The main reason for this is the overall package made up of comparatively hard rubbers with a low level of grip, an inharmoniously appealing turbo engine and only moderately gripping brake system, which was not very consistent for this test. In view of the Subaru's four-wheel drive, which has a torque-sensing limited-slip differential on the front and rear axles and a central multi-plate clutch, one would have hoped for more.
The current Impreza WRX STi does not do justice to the brand's glorious rally history on ice and snow. The five-door requires a lot of work on the wheel, without rewarding it with a decent result. Ergo, the fun factor is low.
You can read the results on page 2 and in the photo show.
Even the Audi TTS, which is also equipped with Dunlop winter tires, can rarely conjure up a happy grin on its driver on the handling course . In contrast to its lively big brother, to whom the humorous rear swings were practically put in the cradle, the 272 hp sports coupé is rather toothless and indecisive. A little drifting - okay. But the ESP, which cannot be completely deactivated here, puts an end to an all too wild hustle and bustle.
Overall, this marks the end of this with a transversely installed four-cylinder turbo engine and the all-wheel drive system that belongs to Audi with sitting at the end of the cardan shaft in front of the rear axle differential Haldex multi-disc clutch equipped 2 + 2-seater, so the more sensible variant of the Ingolstadt four-wheel group - designed to be stable and slightly understeering and, in the event of an ESP, put back on the securing electronic leash. This was not necessarily to be expected after the excellent test result of the Audi TTS in Hockenheim. The fact that strength can sometimes also lie in peace is demonstrated by the slalom TT model, which is rather good-natured and relaxed on ice and snow.
Here the little Audi has the round nose with the big nostrils, namely a long way ahead of the S4, which is quite nervous in the Wechselgasse. With an average speed of 40.5 km /h, the TTS marks exactly the golden mean in this discipline. Only when it comes to half-hearted use of the accelerator does the little Ingolstadt-born man appear to be a little undecided, without, however, immediately escaping the flag or, better yet, fleeing from the pylons. Such behaviors are also alien to the two BMW models that the TTS lovingly embrace in this test.
Big differences when braking
Both the BMW 335i xDrive Coupé and the Alpina B3 Biturbo All-Wheel Drive Coupé are foolproof and stable in the slalom. The fact that the Alpina BMW ranks just behind its largely identical brother in slalom as well as on the handling course (electronically controlled multi-disc lock in the transfer case, torque allocation between the wheels of an axle by means of selective braking interventions of the DSC) despite basically the same all-wheel technology (electronically controlled multi-disc lock in the transfer case) is partly explained by the modified vote.
Since comfort is traditionally more important in Buchloe than in Munich, the chassis design is a bit more moderate here. As a result, the Alpina B3 Biturbo all-wheel drive, like its rear-wheel-driven sister model, tends to understeer a tad more in the Supertest than the factory's Biturbo Coupé. With low coefficients of friction, the rear of the Allgäu is so stable that the two-door model almost inevitably pushes over the front axle from a certain speed and is thus prevented from making brisk progress. This is what happened in slalom. On the handling course, the Alpina Coupé also indicates understeer at the beginning, only to push the rear quite noticeably when the load changes. Behaviors that are also an issue in the 306 hp series 335i with xDrive, but are less important here due to the more restrained choice of tires - Pirelli Sottozero RSC in 225/45 R 17 format all around. With the clutch pedal, which is available thanks to the manual transmission, the BMW Coupé is also a little easier to control than the all-wheel drive from Alpina, which is equipped with Switchtronic as standard and is equipped with a Michelin Pilot Alpin of size 235/40 R 18.
The Allgäuer deserves undivided praise for his excellent decelerating braking system and the excellent sprinter qualities. In the sprint from zero to 100 km /h, the B3, blessed with a bearish torque of 500 Newton meters and a power of 360 hp, only has to give way to the Mitsubishi Lancer Evolution (8.9 seconds) in 9.5 seconds. Everyone else, including the BMW 335i xDrive (10.0 seconds), can queue up at the back. During the subsequent brake test, the Buchloer was finally master of the frozen Finnish lake: on a layered surface of rough ice, thawed and frozen snow and thin, loose layers of fresh snow, the Alpina secured itself with a braking distance of 118.1 meters from 100 km /h and an average deceleration of 3.27 m /s² undisputed first place.
Only the Mitsubishi, equipped with Arktic tires with optimized grip, and the Opel Insignia did not go too far beyond the target set by the B3 with 122.5 and 122.8 meters respectively. The delay services provided by the Subaru and BMW, on the other hand, are below average. The Japanese come from 100 km /h to 130.8, the Munich evenonly after 135.7 meters to stand. While the poor deceleration performance in the case of the Impreza can perhaps still be explained by the tires that offer little grip, such an argument cannot be used in the case of the 335i xDrive. On the one hand, because the Pirelli Sottozero RSC of the BMW worked just as flawlessly in all other disciplines as on the Audi S4 and Opel Insignia, which also have Pirelli Sottozero tires. On the other hand, because the BMW 330 xi Coupé, which competed in Rovaniemi in 2007, allowed itself a similar faux pas: Back then, the otherwise all-round convincing four-seater from Bavaria was the last one in the brake test - on identically dimensioned Goodyear Eagle Ultra Grip.
The assumption that the cause of the long braking distances is to be found in the ABS application of the BMW thus seems permissible and is supported by the comparison of the deceleration curves of the Alpina B3 and 335i xDrive. While the ABS of the Allgäu Coupé only allows itself a brief second at the beginning of the emergency braking, the anti-lock braking system of the Munich four-seater cannot decide between closing and opening for a long time. As a result, the properly dimensioned braking system of the BMW grabs up to 60.70 km /h, most indecisively. Then both three-pointers decelerate at the same level - as it should actually be in view of the identical brake systems. Against this background, the initial hesitation of the BMW at full pressure on the brake pedal is twice as astonishing.
Surprising result of the Opel Insignia
No less astonishing - albeit in a completely positive way - is the excellent performance of the new four-wheel drive from Opel. The variable drive system called 4x4 in Rüsselsheim, like that of the Audi TTS, relies on a Haldex clutch mounted in front of the rear axle, which is responsible for the situation-appropriate power distribution between the front and rear axles. Normally 90 percent of the driving force of the Insignia is brought to the ground with the help of the front wheels. Only when the system, which is listening to the signals from ESP, steering angle sensor and accelerator pedal position, registers too much slip, is a larger part of the drive torque diverted to the rear. Anyone who orders the Insignia with sports equipment - this is what sets the Opel apart from the Audi Coupé - also benefits from an electronic limited-slip differential on the rear axle included in this equipment package. Although this does not have a superimposition stage, it is able to divert up to 50 percent of the applied torque to the wheel on the outside of the curve. For this purpose, a hydraulic multi-disc clutch networked with the wheel speed sensors was installed.
The operation of the Opel all-wheel drive is roughly similar to that of the system used in the Audi S4. A fact that can be clearly felt in the driving dynamics tests.Subjectively, the Insignia 2.0 Turbo 4x4 fitted with a transversely installed four-cylinder engine comes in the agility rating right behind the Mitsubishi Lancer Evolution and the Audi S4. The fact that the extremely nimble and always foolproof acting Vectra successor still has to line up behind the BMW 335i xDrive, which requires far more work on the wheel, is due to its comparatively weak turbo engine with 220 hp. This also explains the rather mediocre performance of the Hessen in the acceleration test. Here the limousine simply lacks lumbar strength. The top-of-the-line Insignia model with 2.8-liter V6 and 260 hp, which was not yet available at the time of the test, promises to be a remedy and will be put to the test in the coming year.
The fun factor on board the turbo Opel should not be underestimated. After all, the fact that you can play and romp with impunity without fear of unpleasant consequences is extremely comforting. The result of the 18-meter slalom proves how foolproof the Insignia is even when changing direction in rapid succession on slippery surfaces. No other car rushed through the 180-meter-long Pylonengasse faster and more confidently than the Hessen-Express. With 41.3 km /h, the Opel can even buy the cutting edge from Mitsubishi's driving dynamics miracle. That one suffers in this discipline from its extremely pronounced agility, as the rear tends to rock not least due to the excellent leading front axle.
The very sturdy sports coupés from BMW, Audi and Alpina hardly ever pass the slalom course slower than the Evo and thus make up the broad midfield. The Audi S4, which came second on the handling course as a result of its very complex all-wheel drive system, however, had to line up at the rear when changing direction, because the very light rear repeatedly tried to break out. With the Subaru Impreza, which came last in this discipline, the judgment is more differentiated: As long as the STi is moved around the pylons with constant accelerator pedal position, it is serenity in person. However, if the speed is to be increased or decreased in between because the entry speed is not ideal on the way, the driver has his hands full. Then the escape from the pylon jungle often turns out to be the better choice in the Subaru. The fact that the Dunlop tires, which are extremely poorly interlocking with the ground, may have played an equally unfortunate role here as in the acceleration test from zero to 100 km /h, in which the top Impreza also makes no cuts, which describes the traction capacity of a car explicitly mentioned again at this point.
It goes more safely on all fours
What we do after the objective criteria in the three main topicsTraction, brakes and driving dynamics are ticked off, the conclusion of the all-wheel drive comparison 2009 would have arrived. One of the main findings of the trip to Finland is that here, as in all other sport auto tests, the tires are given an above-average value. Anyone who has done their homework in this regard can - assuming an otherwise coherent overall package - assume that they will be among the frontrunners everywhere. The only exceptions: the BMW 335i xDrive, which - although it is well ahead in all other disciplines - allows itself to slip on the brakes and the Opel Insignia 2.0 Turbo 4x4, which has to pay tribute to its lower engine power in the acceleration test.
Driving stability systems that cannot be fully deactivated are also punished with deductions in the A and B grades on slippery surfaces - as happened in the case of the Audi TTS. The Ingolstadt-based ESP not only slows down when it comes to chasing lap times: The fun factor on board the small Audi is also lower than in the freely playing S4. The cars that have a more complex all-wheel drive system with dynamic torque distribution to the drive wheels on the outside of the bend - such as the Mitsubishi Evo, the Audi S4 and the Opel Insignia, for example - are easy to handle and therefore extremely humorous. But even if the free play of forces is halted by selective braking interventions, as in the case of the two BMW Coupés, modern all-wheel drives appear neither anachronistic nor fun-killing. And it goes faster and safer on all fours.