~Alfa Romeo 164 Q4~
M   E   C   H   A   N   I   C   A   L   S

This article is taken from Leo Kan´s page I´ve added the scanned manual 4WD part at the bottom.

Autoweek, January 10, 1994
TOP-DRAWER ALFA 164      Luca Cifferi

Subtitle: Advanced 4wd puts all the power on the pavement - even in performance driving
Photo caption: Alfa Romeo's new Q4 - a 4wd Quadrifoglio - gives wonderful V6 engine sounds and amazingly neutral road-hugging handling in comfy, sporty sedan package

With its seemingly progressive farewell to the U.S. market, Alfa Romeo will not import the Q4, the four-wheel-drive Quadrifoglio. It's a pity because this $40,000 Alfa is the best 164 ever built.

As a four-seater 4wd sport sedan it has no rival in the world, though you can find something below and above it in Audi's line - either the five-cylinder 2.2-liter turbo or the 4.2-liter V8 Quattro S4.

And while both BMW and Mercedes offer all-wheel-drive, their versions are designed more for skiing enthusiasts than sports car enthusiasts. Forget Acura, Lexus or Infiniti: There's no 4wd in these Japanese luxury channels.

So what is this Alfa 164 Q4? It's simply the latest evolution of the 3.0-liter, 24-valve 230 hp V6 Quadrifoglio, fitted with the most sophisticated (and complicated) 4wd system to ever appear on a production road car.

Called Viscomatic, this system was developed by Alfa in conjunction with 4wd specialist Steyr-Puch of Austria. It represents a further development of the experimental ideas introduced on the Proteo coupe. This was a concept car that Alfa developed in total secrecy from its Fiat bosses at corporate headquarters in Turin and unveiled with great fanfare at the 1991 Geneva Motor Show.

A huge amount of work (and money: $34 million) went into the Q4's development, because of its radically innovative design and high level of sophistication compared with similar permanent 4wd systems.

It's interesting how the Viscomatic system splits the torque between the front and rear axles. It uses a variable viscous joint continuously driven by an electronic control unit mated to an epicyclic differential. The control unit tells the viscous coupling to cut in every time the speed difference between the two axles exceeds a "memorized" value. If slip between the two axles is excessive, the differential and viscous coupling reduce the transmitted torque. It does this by decelerating the external casing of the coupling itself.

The amount of drive torque transmitted to the rear axle can be adjusted from zero (making it essentially front-drive) to 100 percent (making it pure rear-drive). Both these extremes occur only when the front or rear wheels lose their grip entirely.

The Viscomatic's electronic control unit communicates instantly with the microprocessors in both the Bosch Motronic engine management system and the ABS. The control unit continually processes information on running conditions, such as the angle and speed of each wheel, the steering angle, brake-pedal pressure and whether or not reverse gear is engaged.

The Q4 4wd system also includes a conventional (free) front differential, and a Torsen differential at the rear. The Torsen splits the torque transmitted to the rear wheels in real time, on the basis of the instantaneous grip of each one.

When traveling at a constant speed on a dry road, the system splits torque in proportion to the load on each axle. In other words, torque is split constantly between the two axles according to total drive torque required, steering angle, instantaneous slip between the two axles and vehicle speed. In the case of light braking, a larger amount of torque is transmitted to the front wheels. While the load is proportionally increased on this axle, the drive to the rear axle remains engaged. This way all four wheels transmit engine braking momentum to the ground, lessening the demand on the braking system.

An interesting feature of the Viscomatic system is the absence of stress on the steering wheel when comering. In fact the system recognizes a cornering maneuver from the steering angle, and adopts a specific drive torque split.

When grip is reduced by slippery roads, the system uses specific computer maps that guarantee constant traction no matter the conditions.

What is the result for the driver of this boatload of technology? For starters, the good power and the massive torque, 206 lb ft at 5000 rpm, of Alfa's melodious V6 are always maximized and transmitted to the road in the most effective way. With no wheelspin, no torque oversteer, the system always delivers an extremely responsive and neutral car. The Q4 truly handles like the proverbial train on rails. And this happens with superb acceleration: from 0 to 100 km/h (62 mph) in just 7.5 seconds. Top speed is electronically limited to 150 mph.

As impressive as those numbers appear, the real excitement comes from the car's ability to go much quicker than you'd expect from a four-door sedan, thanks in no small part to the short-ratio Getrag sixspeed gearbox. The engine's staccato is as stirring as the ride, especially knowing that the technology is enabling you to get virtually everything out of the car. Though it's easy to get lost in the excitement, a glance at the fuel gauge will bring you crashing back to reality. Wringing all you can get out of the Q4 comes at cost of getting just 11.4 mpg. It's a small price to pay the piper for a great dance.

The Viscomatic part of the 1994 Q4 manual :