The Ferrari F355 adopts a stress-bearing frame of welded, varaible section steel tubes plus a tubular sub-frame that holds the engine and suspension assemblies. Tha layout adopts the racing model format with a central stress-bearing shell to which the engine assembly and suspension are attached. The monocoque construction technology also involves the use of sophisticated laser welding techniques for the double-thickness sheet steel. This means that torsional and bending rigidity are enhanced while reducing weight. The independent suspension system adopts unequal-length, non parallel wishbones with springs and aluminum gas dampers plus anti-roll bars.
The F355 incorporates a damping management system with two different (sports and comfort) programs. Within each program, damping force varies on the basis of the vehicle's speed. An electronic control unit adjusts the system automatically in order to adapt the vehicle's response to each new situation. This involves two sensors that transmit the values of longitudinal, vertical and lateral acceleration to the control unit where they are instantly processed and converted into a damping variation. Rack and pinion power steering is standard, with mechanical steering available on request.
The braking system adopts four self-ventilated discs with 4-cylinder aluminum calipers. The ATE Abs can be cut out as necessary. The wheels are 18" with magnesium rims. These combine with the aluminum dampers, brake calipers and hub carriers to lighten the unsprung masses in a way that further enhances roadholding and performance. The tires were developed in collaboration with the manufacturers for even greater stability and grip without detriment to comfort, handling and safety. Particular care was taken to enhance the tire's capacity to absorb bumps in the road-surface, and over the careful design of the noise-reducing tread. The new directional design of the front tires makes for optimum safety in aquaplaning conditions. The rear tires feature a new asymmetric tread design to ensure that traction and braking are on a par with the vehicle's performance. The 21.7 U.S. gal. fuel tank is in light alloy.
The cylinder head layout on the F355 derives from Ferrari's long experience in Formula 1. The Ferrari engineers have created an extremely compact high-swirl combustion chamber with an 11:1 compression ratio. The 15°30' to 22°30' included angle is also significant. The use of five valves per cylinder makes it possible to combine high revs with high intake permeability in a way that maximizes overall engine efficiency. The pistons are made of a forged aluminum alloy with a distinctly lower than average apparent density (K=0.44) and are coupled with Nicasil-coated "wet" steel liners in the aluminum engine block. For optimum engine efficiency at high speeds the F355 adopts Ti6a14V titanium alloy, finite element designed conrods previously seen only on Formula 1 engines.
The F355 also features Bosch Motronic M2.7 electronic injection-static ingition management. The dry sump engine oil circuit incorporates twin scavenge and one pressure pump plus a thermostatic control valve.
The intake system draws in air through the c-pillars, each of which feeds its own intake duct. This ensures a dynamic supply of air at ambient temperature for optimum engine performance even in very hot weather. In addition, head losses are minimized by the use of two large filter panels. The Bosch M2.7 twin injection system adopts hot wire air-flow meters. The intake ducts feature an extra-large internal volume and progressively tapered ports. The intake manifolds adopt single throttles with evolving profile to ensure prompt engine response combined with smoothly progressive performance at partial throttle. The exhaust system is in insulated stainless steel with 4-2-1 manifolds for each cylinder bank. The system features a twin-branch delivery to the catalysts: one main branch to a ceramic matrix catalyst and one by-pass branch to steel matrix catalysts. The by-pass branch only comes into play at high speeds in response to the opening of a throttle valve controlled by the Motronic system. This optimizes engine performance by reducing exhaust back-pressure.
The on-board diagnostics conform to the toughest of the current regulations (California OBDI). The new transverse gearbox offers 6 speeds plus reverse, all synchronized and with a shorter engagement travel. Ratios are designed to make the most of the torque curve, thereby enhancing the driveability and sporty performance of the car. The gear shifter adopts a lever which actuates a rigid rod and is fitted with axial ball bearings. The differential is multi-plate limited slip type with different locking values in drive and lift-off. The single 9 3/4" dry plate clutch is hydraulically actuated. The clutch housing is made of magnesium alloy. A water/oil heat exchanger ensures that the gearbox oil is rapidly brought to the correct operating temperature.
NOTES
Aerodynamics
The development goal for aerodynamic characteristics was twofold:
Thanks to the experience gained with Formula 1 cars in the wind tunnel with boundary layer belt, the underbody was integrated into the overall aerodynamic effect, achieving a result consistent with the continuous improvement of Ferrari cars in this field.
Chassis
The generous 375 hp of the power unit and road grip available from the 18" tires required complicated finite element calculations as well as the simulation of behavior in different load situations, achieving excellent values of torsional and bending rigidity, weight and therefore safety in all conditions of use.
Suspension
The suspension mechanism has benefited from a very specific tuning:
Engine
The outstanding performance of the new engine can be synthesized by the 107 hp/litre achieved with a displacement of 213.3 cu.in. The parameters by which engine quality is assessed attain the very highest standards. The brake mean effective pressure (BMEP) which represents thermal stress, is equal to 1.5 kgt/cm2. The mean piston speed (Cm), which indicates mechanical stress, is equal to 21.8 m/sec. Weight, reliability and easy maintenance are the outstanding characteristics of this engine, which develops 375 hp at 8500 rpm.
Timing
The secret of the high engine efficiency lies in the cylinder head with five valves per cylinder. Radial intake valves make it necessary to use conical cam profiles produced on a specially built machine tool. The high rotational speed made it necessary to adopt special cam lift to guarantee both reliability and long-term performance. In particular the lobe of the central intake valve is slightly offset compared to the lateral valves, to reduce pulse stress and the emission of unburned hydrocarbons.
Ferrari 355 Design Features
Ferrari 355 Interior
Ferrari 355 Statistics
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