Redefines refinement for a sports utility vehicle.
F or those familiar with the S320, the ML320 sports the very same engine but with an ECU which has been mapped differently for use in a SUV. The all-aluminium alloy engine is a torquey V6 featuring three valves per cylinder and twin spark plugs (for details refer to technical chronicles at the end of the article) per cylinder with maximum power output of 218bhp at 5600rpm and max torque of 310Nm generated at 3000rpm. This is mated to the excellent, tried and tested Mercedes-Benz 5-speed automatic transmission which features electronic control, torque converter lockup clutch and touchshift. The M-class has continuous 4-wheel drive. A dual-range transfer box, directly flange-mounted on the automatic gearbox, apportions the input drive between front and rear axles whilst a central differential balances speed differences between the two axles. The whole continuous four-wheel drive system is run by Mercedes-Benz's latest version of its four-wheel electronic traction system, 4-ETS.

The touchshift mechanism which does duty in all the other automatics in India now gets even better with the option of holding down the gear lever in the minus position and the 'box automatically choosing the most optimum gear for that situation, whether for accelerating or for slowing down. If the gear lever is held in the minus position, the electronic system will keep shifting down till the most appropriate gear is found.

	The 3.2-litre V6 feature innovations like three valves per cylinder and two spark plugs per cylinder, increasing efficiency and reducing cold start emissions by 40 per cent.

A switch on the dashboard provides the option to shift to the 'low range' whereby the dual range transfer box switches from the 1:1 ratio normally employed to a 2.64:1 reduction. The 4-ETS and traction control programmes also bring into play certain extra features which aid in the sort of driving that would be required when the low range mode is employed. Together with the electronic stability program (ESP), the 4-ETS system uses microcomputers to transfer the drive torque onto both the front and rear axles, systematically applying brakes to spinning wheels and ensuring that those wheels which have good road adhesion are given the most traction. In this way the 4-ETS system does away with the need for the conventional locking of differentials and in fact works even better as while the conventional differential lock ensures that both the right and left wheels get equal torque whether or not either of the wheels is spinning, the 4-ETS system works even more effectively. In the case of three of the four wheels spinning, the one wheel that has traction will be given optimum drive power, which will not be wasted on the spinning wheels (for details of the 4-wheel drive system please refer to the technical chronicles). The 4-wheel drive system on the M-class features a few more innovations like the quicker application of brake pressure on spinning wheels by use of an intelligent brake force booster. The brake pressure is released in response to the driving speed, wheel acceleration and accelerator driving position. The 4-ETS system also comes into operation when the driver has to use both brake and accelerator (in low range) simultaneously when moving off on steep gradients. This system provides even more safety on slippery downhill gradients because the electronics automatically identify such situations and intervene the moment a wheel loses grip and the engine braking cannot be fully exploited. The 4ETS system will then apply brakes to those wheels that have a good grip on the road, thereby assuming the role of engine braking. The brake force released by the traction system corresponds exactly to the braking torque normally made available by engine braking and thus ensures that the vehicle maintains a constant speed without the driver having to do anything. This feature comes into play at speeds of less than 20kmph and in low range.

The description of the powertrain of this SUV makes more than just interesting reading but what that translates into while driving, is sheer joy. What strikes one most about the M-class is not only the refinement of the powerful and torquey engine but also the smoothness by which this driving power is transferred to the wheels. If the engine, which has already attracted rave reviews in the S-class, is good, then the transmission, combined with all its electronic gadgetry is even better.