Fiat 131 - Construction and Technology

Construction and Technology

The Fiat 131 employed construction techniques and technologies typical of its day. The body was a steel monocoque. Designed and styled on the typical three-box design, with distinct boxes for the engine compartment, passenger compartment, and boot.

The major mechanical components were also conventional and contemporary, but with some notable advances. The 131 employed a front engine, rear-wheel drive layout, whereby the engine is longitudinally mounted in the front of the car. The gearbox is directly behind the engine, and a tubular propeller shaft, under the transmission "tunnel", transmits the drive to a solid live rear axle.

The engines were all inline-four types, derived from those used in the outgoing 124 range, with a cast iron cylinder block and aluminium alloy cylinder head, either pushrod with chain drive camshaft or double overhead camshaft (DOHC), driven by a single rubber/Kevlar toothed timing belt. Fuel supply was via a single Weber ADF twin-choke carburettor, fed from a trunk mounted steel fuel tank. Traditional contact breaker ignition systems were used, usually with Marelli distributors.

The suspension system utilised fully independent front suspension, with MacPherson struts, track control arms and anti-roll bar. The rear suspension was quite advanced (when using a solid live rear axle), in that the rear axle was controlled by double unequal length trailing arms and a panhard rod, with coil springs and direct acting dampers. This design proved far superior to many of its contemporaries, especially with vehicle stability and handling.

The braking system was also typical; the front brakes were disc brakes, using a solid iron disc and a single-piston sliding caliper. The rears were drum brakes, utilising leading and trailing shoe design operated by a dual piston fixed slave cylinder. They were operated hydraulically, with a tandem master cylinder assisted by a vacuum servo using two separate circuits. A rear-mounted load sensing valve varied the bias of effort applied to the rear brakes, dependent on the load being carried (and also the pitch dynamics caused by braking effort and road levels). A centrally located floor mounted handbrake operated on the rear axle using bowden cables.