The Audi TDI – Tech Workshop 2014
The new 1.4 TDI
The new 1.4 TDI follows the two-liter four-cylinder engine as the second engine in the Volkswagen Group’s modular diesel engine platform (MDB). The three-cylinder unit is designed as a transverse engine and will enter volume production shortly. It has a displacement of 1,422 cc. The stroke of 95.5 millimeters (3.8 in) is taken from the 2.0 TDI; the bore has been reduced from 81.0 to 79.5 millimeters (3.2 to 3.1 in). Cylinder spacing is 88.0 millimeters (3.5 in).
Unlike the predecessor engine used through 2005 in the Audi A2, the new 1.4 TDI has a lightweight crankcase made of an aluminum-silicon alloy – a rare exception in its competitive environment. The crankcase is produced via gravity chill casting, which enables particularly high strength, density and homogeneity. Targeted ribbing and detailed measures affecting the engine periphery minimize noise emissions.
The crankcase weighs just 17 kilograms (37.5 lb) – 12 kilograms (26.5 lb) less than the cast iron block used previously. The engine has a total weight of 132 kilograms (291.0 lb). The thin-walled piston sleeves made of cast iron are thermally joined; the weight of the pistons and connecting rod has been reduced. Piston clearance, ring contour and ring pretensioning have been optimized for low friction losses.
A balance shaft rotates in the opposite direction of the crankshaft. Its drive unit has been integrated into the “duopump”: the oil pump and vacuum pump share a common case. The oil pump switches between three pressure levels as necessary. Another efficiency measure is the separation of the coolant loops for the cylinder block and the cylinder head. The block loop can be deactivated during the warm-up phase. Only the head loop, which also supplies the heat exchanger for the cabin heater, is active here. This thermal management concept quickly brings the 1.4 TDI up to operating temperature following a cold start.
Elaborate needle bearings are used in the drive system for the camshafts. The shafts are mounted in a separate frame and joined to it during engine production. The new valve drive module combines high stiffness with low weight.
The common rail injection system produces 2,000 bar of system pressure. Solenoid valves open and close the nozzle needles in the seven-hole injectors. The high pressure enables an even finer atomization of the fuel in the combustion chambers, and thus more efficient, lower-emissions combustion.
The turbocharger in the 1.4 TDI features pneumatic adjustment of the turbine wheel vanes. The intercooler, which is water-cooled via a separate loop, is mounted on the cylinder head. The low-pressure exhaust gas recirculation system (AGR) is also water-cooled and discharges directly upstream of the turbocharger. It reduces NOx emissions when the engine is hot and at intermediate and high loads, while the uncooled high-pressure AGR is primarily responsible for the phase following a cold start. The new engine complies with the limits of the Euro 6 standard. The entire emissions control system is compact and designed for minimal flow losses.
The new 1.4 TDI produces 66 kW (90 hp) and delivers 230 Nm (169.6 lb-ft) of torque between 1,500 and 2,500 rpm.