New Performance Diesel For Alfa 147
Published: 19th July 2003
Fiat Group, which was first to the passenger car market with direct injection diesel technology back in 1986, was last year awarded the prestigious Economist Innovation Award (Energy and Environment category) for its ground-breaking work in developing the 'common rail' diesel technology that is now used by every major European car maker.
Alfa Romeo was itself first to the market with a JTD common rail direct injection diesel engine, when the Alfa 156 was launched in 1997. This crucial lead in diesel technology has not been squandered and, in a new, 16-valve Multijet guise, the exceptionally reliable, 1.9 litre 4-cylinder common rail turbodiesel has been further perfected to provide optimal performance, maximum fuel efficiency and minimal CO2 emissions.
The new 1.9 litre 140 bhp Multijet engine, with four-valves-per-cylinder driven directly by twin overhead camshafts, features a large number of technical advances to increase performance and engine torque at low speeds, whilst reducing noise and vibration.
Key components of the engine are brand new, such as the twin overhead camshaft cylinder head with hydraulic tappets, steel connecting rods and crankshaft, pistons with an internal channel to carry cooling oil to the little end bearings, and connecting rod bearings made out of a different material to those of the 115 bhp JTD unit. The intake and exhaust manifolds are also new; the latter being of a special high-strength material, the former manufactured from pressure cast aluminium.
There are new, electronic EGR and exhaust gas cooling systems.
The lubrication circuit features a new oil pump and external air/oil
radiator, and the cooling circuit comes with a new pump. This long
series of improvements has culminated in a smooth, reliable, quiet
and powerful engine, with remarkably low fuel consumption.
The adoption of the Multijet system has made this new 1.9 JTD 16V
engine the first of its type in full production. It is based on
the same Unijet common rail principles as the 8-valve unit, i.e.
high injection pressure and electronic injector control.
Within a Unijet engine, a pilot injection raises temperature and pressure inside the cylinder to improve combustion at the time of the main power stroke. However, by dividing the main injection into a number of smaller injections, a Multijet engine affords a fuller, more gradual combustion whilst the amount of diesel burnt at each stroke remains the same; thus abetting smoother, quieter combustion, reduced emissions and increased performance.
The Multijet engine differs from its Unijet counterpart in two essential areas; the injectors and the electronic control unit.
