The Audi TDI – Tech Workshop 2014
The new longitudinally-mounted 2.0 TDI
The 2.0 TDI is a true all-rounder in the Audi model lineup. From the Audi A1 to the Audi A6, the two-liter, four-cylinder engine powers a wide variety of models. In the Audi Q5 mid-size SUV, the 2.0 TDI is designed to be installed longitudinally and offers impressive emissions controls that satisfy the EU 6 standard.
Two versions with 110 kW (150 hp) and 140 kW (190 hp) are available. Maximum torque is 320 and 400 Nm (236 and 295.0 lb-ft), respectively. With the 110 kW engine, the Audi Q5 accelerates from 0 to 100 km/h (62.1 mph) in 10.9 seconds. Top speed is 192 km/h (119.3 mph), and average fuel consumption is 4.9 liters of fuel per 100 kilometers (48.0 US mpg), a CO2-equivalent of 129 grams per kilometer (207.6 g/mi). These same figures for the top-of-the-line four-cylinder diesel are 8.4 seconds, 210 km/h (130.5 mph), 5.7 liters of fuel per 100 kilometers (41.3 US mpg) and 149 grams CO2 per kilometer (239.8 g/mi).
The 2.0 TDI with its 1,968 cc of displacement (bore x stroke 81.0 x 95.5 mm (3.2 x 3.8 in)) was systematically designed for low efficiency losses. The toothed belts for the camshafts and ancillary components run smoothly and quietly. The two balance shafts, relocated upward from the oil pan to the crankcase, are mounted on roller bearings with oil mist lubrication. Needle bearings are used for the drive wheels of the camshafts as well.
The shafts are pressed into a separate bearing frame, and the new valve drive module exhibits high stiffness and low weight. The valve star in the cylinder head is rotated 90 degrees. Both camshafts actuate one intake and one exhaust valve per cylinder. The intake camshaft can be adjusted hydraulically by as up to 50 degrees. The variable timing improves filling of the combustion chambers, swirling, effective compression and expansion duration.
The common rail injection system produces up to 2,000 bar of system pressure. Solenoid injectors atomize the fuel via eight-hole nozzles. A mini-rail in the injector provides for an additional fuel volume. This minimizes the shock waves at the nozzle needle and ensures defined injection volumes. A sensor in one of the glow plugs analyzes pressure conditions during combustion. The measurements influence engine management.
At the pistons, reduced stress on the rings results in smooth running; in manufacturing the engine, a honing process in fine machining of the cylinder liners guarantees high precision. The two-stage oil pump saves drive energy. The thermal management system is flexible. The coolant loop in the cylinder block can be deactivated during the warm-up phase via a switchable pump in order to quickly heat up the motor oil. The cylinder head microloop is driven by an electric pump and supplies both the cabin heating system and the low-pressure exhaust gas recirculation system.
With its emissions control system, in which an oxidation catalytic converter and a diesel particulate filter with an SCR coating (SCR: selective catalytic reduction) are mounted close to the engine, the new 2.0 TDI in the Audi Q5 complies with the limits of the Euro 6 standard. The uncooled high-pressure exhaust gas recirculation (AGR) system, which is active following a cold start and at very low loads, runs horizontally through the cylinder head. The very compact low-pressure AGR is mounted directly on the engine and is cooled. It covers the majority of the operating range and is designed for low flow losses.
The turbocharger’s variable turbine geometry (VTG) is actuated pneumatically. The water-cooled intercooler is integrated into the induction pipe. This type of construction leads to short gas paths, high control quality and very good efficiency.