Driving satisfaction, Alfa Romeo style
 

The new Alfa Romeo MiTo is self-avowedly an Alfa to the core, for example in its uncompromising sense of control and driving satisfaction. Driving comfort and dynamic behaviour have always been specific features of Alfa Romeo cars: on this car, they amount to a real strength.

The innovative Alfa D.N.A. system

The new model is the first Alfa Romeo car to benefit from the Alfa D.N.A. system, an innovative device that modulates the main driving parameters (engine response, stability control and power steering). Until now the exclusive preserve of racing cars or supercars, the Alfa D.N.A. system acts on the engine, brakes, steering, suspension and gearbox, allowing three different vehicle behaviour modes based on the driving style best suited to the situation or the customer’s wishes: supersporting (Dynamic), town driving (Normal), maximum safety even in low grip conditions (All weather).

The selector is located in an ergonomic position – in front of the gear lever on the tunnel - and allows one of the three modes to be selected by simply moving the lever (the choice is displayed by the lighting of a specific led and also by a message on the control panel). In detail, for those who desire a relaxed drive in total safety, in Normal mode the individual components involved in the Alfa D.N.A. system are as follows: engine tuned for performance, very slight Vehicle Dynamic Control and DST (Dynamic Steering Torque) alert to prevent oversteer.

If you prefer to use your Alfa Romeo MiTo for more sporty applications, all you have to do is then move the lever to Dynamic position: when in this mode, the Alfa D.N.A. offers a unique driving experience because the system makes the VDC and ASR less intrusive (this means the vehicle dynamics are a little more free of the electronic control) and simultaneously activates the Q2 Electronic system. Still in Dynamic mode, the Alfa D.N.A. also acts on the steering and engine to offer a truly comprehensive and entertaining sporting experience. The steering is less power-assisted and offers a more sporty sensation to ensure perfect control. Last but not least, the engine becomes even more responsive with an even prompter response and – with 155 bhp and 120 bhp JTDM Turbopetrol engines, it can even count on an over-boost facility. Altogether, the Alfa Romeo MiTo with Dynamic selection is the ideal choice for entertainment in full safety.

Lastly, the third mode accentuates the effect of traction control and increases sensitivity to mu-split (this DST active electronic steering function cuts in when driving over surfaces with different levels of grip (in winter, for example, it is often the case that two wheels are on ice while the other two are on asphalt). When ‘All Weather’ is selected on the selector, the Alfa D.N.A. system makes the car easier to control over road surfaces with low grip (e.g. on wet surfaces or snow), taking action to control vehicle dynamics because the VDC cut-in threshold is lowered.

The new Alfa Romeo MiTo suspension systems

One of the briefs given to the designers allocated to the ‘Alfa Romeo MiTo’ project was to create a suspension capable of higher-category performance levels. The devices therefore had to ensure great driving ease and precision, outstanding road-holding and the best possible acoustic and vibrational comfort. Hence the choice of two tried and tested layouts - a MacPherson layout at the front and a semi-independent layout with torsion beam at the rear. This choice was made to guarantee ease of driving and maximum weight containment, guaranteeing the handling goals that Alfa Romeo cars have always strived to attain.

In particular the following operations have been carried out to add an exclusive touch to the Alfa Romeo MiTo suspension system. Firstly, the ground tracks are amongst the widest within the relevant segment (front equal to 1483 mm and rear equal to 1475 mm) to emphasise the promptness of response, stability and control even under extreme conditions. The rim channels are also wide in relation to the size of the tyres in order to optimise the handing performance of the tyres, while the stiff, low front or rear springs give the vehicle a sporting ride and feeling in terms of appearance and function.

The rear torsion beam with ‘C’ cross section also features high torsional stiffness to enable it also to act as an anti roll bar, thus ensuring optimum roll performance and helping maximise the promptness of response. Lastly, and certainly the most distinctive feature of the Alfa Romeo MiTo suspension, the front and rear shock absorbers feature a coilover fitted inside the shock absorber that acts in parallel with the main spring during the extension travel with the main purpose of reducing roll.
 

Front suspension

The Alfa Romeo MiTo adopts a MacPherson configuration that certainly represents the best front suspension solution for front-wheel drive transverse-engined minis. This solution optimally safeguards the space inside the engine compartment while simultaneously guaranteeing an excellent compromise in terms of handling and comfort due to the kinematic configuration that is similar in certain respects to that of the more sophisticated double wishbone layout - and also due to the reciprocal distance to the attachment points on the body.

In particular, the main components of this structural configuration are as follows: Two-part wishbones in pressed steel (with a patented ‘butterfly’ construction configuration), offering a considerable weight saving; A front suspension beam offering great structural stiffness with the transverse link near the front arm attachments; Split dome pads (dual-path configuration) to filter out road vibrations more effectively while ensuring high structural stiffness to benefit driving precision; Anti-roll stabiliser bar with rods equipped with ball links for anchorage to the shock absorbers that allow greater stabilising efficiency and a more prompt dynamic response when cornering; Coil springs produced using the side-load method for optimisation of the thrust axis with the aim of reducing tangential forces on the shock absorber pushrod and thus internal friction (system hysteresis) with consequent better absorption of minor road surface roughness; All versions are fitted with double-acting telescopic hydraulic shock absorbers with a 22 mm rod diameter for great lateral stiffness to promote good road holding on corners, with a rebound spring fitted inside that operates when the shock absorber is under compression to help reduce roll.

Rear suspension

The semi-independent, torsion beam architecture represents an outstanding rear suspension solution for front wheel drive minis because it takes up less room, guarantees lower weights and also offers a good compromise in terms of handling and comfort. These benefits are guaranteed by the torsion beam that changes shape to allow the wheels to follow road surface roughness while also reacting to the torsion to perform the function of an anti-roll bar.

In detail, the components characteristic of the Alfa Romeo MiTo rear suspension include a torsion beam with C-shaped cross-section for great torsional stiffness and pressed wishbones made out of two halves; differential stiffness slotted bushes for securing the rear axle to the body to ensure good filtering of longitudinal roughness and great stiffness in the event of lateral loads to optimise stability - and lastly, very stiff coil springs to ensure a sporting ride.

Suspension with coilover springs

The front and rear shock absorbers with coilover fitted as standard over the whole range feature a spring between pipe and pushrod, that is secured to one end of the tube in the upper part of the shock absorber and acts during the extension stroke. The point at which the spring starts to act changes according to the length of the spring, which therefore acts in parallel to the main suspension spring.

In detail, fixing the length of the internal shock absorber spring and thus the point at which it acts effectively stabilises the driving condition when the internal shock absorbers spring begins to act and thus contributes to overall vehicle rigidity. As a consequence, fixing the point at which the springs begin to take effect on shock absorbers with coilover springs and producing a car that behaves like a conventional car under normal driving conditions. Under sporty driving conditions, however, the shock absorbers come into play by increasing rollover stiffness, thus benefiting dynamic performance. In the event of high lateral acceleration levels, the Alfa Romeo MiTo equipped with contracting shock absorbers therefore behaves in much the same way as a conventional car with stiffer suspension tuning. In situations where the lateral acceleration values are lower, the shock absorber coilover springs do not cut in and the Alfa Romeo MiTo, unlike cars with stiffer suspension tuning, does not penalise comfort under non-sporting driving conditions.

Another aspect that deserves highlighting is the fact that when the shock absorber coilover springs intervene during a cornering manoeuvre, only the inner wheel shock absorber springs work (by stretching) while the outer wheel shock absorbers do not work (remaining compressed). Under such conditions, the stiffness configuration is therefore asymmetrical and this alters the car’s dynamics during rollover motion, with two consequences: the outer wheels sit more firmly on the road to promote tyre grip (and the hence the transmissible lateral forces) and the roll centres are lower for greater stability.