Volkswagen Group introducing Modular Transverse Matrix this year; new engine families, lighter weight construction, powertrain flexibility
|Drive systems in the MQB. Click to enlarge.
This year, Volkswagen Group will introduce the Modular Transverse Matrix (MQB, modularen Querbaukasten) for the Volkswagen, Audi, ŠKODA and SEAT brands. (At the Tokyo Motor Show, Volkswagen unveiled the first model publicly shown based on the MQB: the Cross Coupé all-wheel-drive (AWD) plug-in hybrid vehicle (PHEV). (Earlier post.)
Volkswagen says that its MQB strategy represents a turning point in the design and production of its future automobiles with transverse-mounted engines. The Modular Transverse Matrix standardizes many vehicle component parameters across brands and vehicle classes. At the same time, it offers access to new technologies. The MQB extends from the A0 to the B segment.
At the Volkswagen brand, for example, it covers the following models: Polo, Beetle, Golf, Scirocco, Jetta, Tiguan, Touran, Sharan, Passat and Volkswagen CC. In the future, all of these models could theoretically be produced on the same assembly line, despite their different wheelbases and track widths. It will be possible to produce MQB models of different brands together. The first new vehicles to be produced based on the MQB will be the successor to the Audi A3 and the next-generation Golf.
One of the prominent characteristics of the Modular Transverse Matrix is the uniform mounting position of all engines. Two systems integrated in the MQB strategy which play a key role here are the modular gasoline engine system (MOB) with the new EA211 engine series (40 kW / 54 hp to 110 kW / 148 hp). This range includes the first four-cylinder engine with cylinder deactivation (ACT)—and the modular diesel engine system (MDB) with the also new EA288 engine series (66 kW / 89 hp to 140 kW / 188 hp).
The new engine series will reduce the Group’s engine and gearbox variants in the MQB system by approximately 90%. In addition to standardizing conventional internal combustion engines, the MQB also enables an identical mounting position for all current alternative drive concepts without limitations, from natural gas and hybrid versions to the pure electric drive. Volkswagen has already announced the launch of the latter within the MQB in 2013 in the new Golf Blue-e-Motion.
EA211 series gasoline engines
|Modular layout of the EA211. Click to enlarge.
The EA211 family engines comprises both three-cylinder and four-cylinder engines. The engines of the EA211 series made their premiere at Volkswagen with the production launch of the up! (no MQB) as a three-cylinder MPI engine. Now the TSI sixteen-valve, four-cylinder engines of the EA211 series (TSI: direct injection with charging) at the power levels 63 kW / 84 hp and 77 kW / 103 hp (each 1.2 liter) as well as 90 kW / 121 hp and 103 kW / 138 (each 1.4 liter) – are also setting new standards in the Modular Transverse Matrix for energy efficiency, lightweight construction and high torque performance.
The engines, with a 10.5:1 compression ratio, deliver maximum torque of 165 or 175 N·m (122 or 129 lb-ft) from the 1.2-liter versions and 200 or 250 N·m (148 or 184 lb-ft) from the two 1.4-liter versions at a low 1,400 rpm. The torque values also stay at their maximum level up to the 4,000 rpm mark.
Fuel consumption values of the EA211 engines were reduced by 8 to 10%, in part due to reduced internal friction, lower weight and optimized thermal management; in conjunction with the new ACT cylinder deactivation system, the savings potential can be as much as 20%.
|Cylinder deactivation. Click to enlarge.
Active cylinder management (ACT) debuts in 1.4 TSI with 103 kW. At low and medium load, two of the cylinders are shut off, which reduces fuel consumption in the EU driving cycle by 0.4 l/100 km. The shut-off is always active when engine speed is between 1,250 and 4,000 rpm and torque is between 25 and about 100 N·m (18 to 74 lb-ft).
If the driver presses the accelerator pedal hard, cylinders 2 and 3 begin to work again, without a noticeable transition. The high efficiency of the system does not have any negative effects on smooth running: even with two cylinders the excellently balanced 1.4 TSI runs just as quietly and with low-vibration as with four active combustion chambers. All mechanical switchover processes take place within one-half camshaft rotation; depending on engine speed this takes just 13 to 36 milliseconds. Accompanying interventions in ignition and throttle valve processes smooth the transitions. With an accelerator pedal sensor and intelligent monitoring software, the system can also detect irregular driving profiles—such as during a drive through a roundabout or in sporty shifting on a highway. In such cases, cylinder shut-off is deactivated.
Altogether, the components of active cylinder management weigh just 3 kg. Their actuators, the camshafts and their bearing frames are integrated in the cylinder head; two low-friction bearings reduce friction of the shafts.
The engines of the EA211 series are also characterized by a new mounting position. In the familiar gasoline engines of the previous EA111 series, the (‘hot’) exhaust side was at the front, and the engines were mounted with a forward tilt. By rotating the cylinder head, the new generation of EA211 engines that is launching with the introduction of MQB is tilted towards the firewall (bulkhead between engine compartment and passenger compartment), just like the diesel engines. From now on, the gasoline engines also share this with the diesel engines of the EA288 series: they are now also inclined towards the rear at an identical inclination angle of 12 degrees. The advantage is that the exhaust line, driveshafts and gearbox mounting position can be standardized.
A BlueMotion Technology pack (Stop/Start system and battery regeneration) is tailored to the EA211 gasoline engines.
The EA211 is a complete redesign; only the cylinder spacing of 82 mm was adopted from Volkswagen’s successful EA111 engine series. To ensure a uniform mounting position of all engines in the MQB, engineers rotated the cylinder head of the petrol engine. At the same time, it is now tilted towards the rear. That it is also built in an especially compact way is reflected in its mounting length that has been shortened by 50 mm. This is an advantage that passengers will experience directly in the form of an even more spacious interior.
With an ultra-rigid crankcase made of die-cast aluminium, the new gasoline engines are lightweight at 112 and 114 kg (247 and 251 lb); on the 1.4 TSI, the weight advantage compared to the grey cast iron counterpart from the EA111 series is a considerable 22 kg. Engine developers reduced the main bearing diameter of the crankshaft on the 1.4 TSI from 54 to 48 mm; the crankshaft itself was lightened by 20%, while the weight of the connecting rods was reduced by 25%. The rod bearing pins are bored hollow, and the aluminium pistons (now with flat piston crowns) have now also been weight optimized.
To utilize exhaust energy optimally in hot operation and, on the other hand, to cool more effectively at high loads, the exhaust manifold of the new EA211 engines was fully integrated in the cylinder head and provided with its own cooling jacket. Volkswagen engineers also devised a dual-loop cooling system. The base engine is cooled by a high-temperature loop with a mechanically driven coolant pump, while a low-temperature loop, powered by an electric pump, circulates coolant to the intercooler and turbocharger housing as needed. Passenger compartment heating comes from the cylinder head circulation loop, so that it warms up quickly, like the engine.
By means of innovative construction of the exhaust manifold, Volkswagen was able to use just a very narrow single-scroll compressor in turbocharger selection. This reduced the weight of the cylinder head turbocharger component group. On the EA211, the intercooler is integrated in the induction pipe which is made of injection-moulded plastic. The advantage is significantly accelerated pressure build-up, which leads to very responsive downsized engines.
Volkswagen has also significantly reduced internal friction in its new generation of engines. The overhead camshafts are driven by a single-stage, low-friction toothed belt design with a 20 mm wide belt and load-reducing profiled belt wheels. Actuation of the valve drive via roller cam followers and an anti-friction bearing for the highly loaded first camshaft bearing also lead to reduced friction resistances. To ensure that the engine takes up as little mounting space as possible, ancillary components such as the water pump, air conditioning compressor and alternator are screwed directly to the engine and the oil sump without additional brackets, and they are driven by a single-track toothed belt with a permanent tension roller.
To reduce emissions and fuel consumption further, and to improve torque in the lower rev range, the intake camshaft on all EA211 engines is adjustable over a range of 50 degrees crankshaft angle—on the 103 kW / 140 PS 1.4 TSI, an exhaust camshaft adjuster is added. It sets the desired spread of control times and thereby allows even more spontaneous response from low revs; at the same time, torque is improved at high revs.
Five-hole injection nozzles spray at up to 200 bar. The maximum injection pressure of the new TSI version (direct injection engine) was increased to 200 bar; state-of-the-art five-hole injection nozzles deliver up to three individual injections to each of the cylinders via a stainless steel distributor bar – extremely precisely. In designing the combustion chamber, Volkswagen also paid particular attention to achieving minimal wetting of the combustion chamber walls with fuel and to optimized flame propagation.
In keeping with the same-parts principle of the MQB strategy, not only are the cylinder head, the engine block, crankshaft, connector rods and bonnet modules produced uniformly and highly flexibly, but the components for fuel induction (such as the charge air pathway, the air filter, induction pipe, intercooler, throttle valve and control drive) are also identical across all variants. This uniform basic architecture has let Volkswagen AG achieve global network capability in production and assembly as well as global procurement synergies.
Natural gas and ethanol versions. The 1.4-litre version with 90 kW also serves as the basis for a natural gas version—traditionally known as EcoFuel at Volkswagen. In this case, the engine produces 81 kW / 109 hp. Fuel storage, e.g. on the Golf, is provided in two underfloor natural gas tanks and a 50 liter gasoline fuel tank. They extend the range by 420 km to 1,300 km (261 to 808 miles) without imposing any limitations on interior space.
Valves and value seat rings are reinforced in the EcoFuel version, to handle the higher loads that occur in natural gas combustion. For the same reason, low-wear spark plugs and a PVD (Physical Vapor Deposition) coating of the first piston ring are used. The modifications made for CNG operation essentially make the EA211 engine suitable for use with bio-ethanol (E85) and pure ethanol (E100) as well. This means that a future-assured EA211 version will now be available for markets in Sweden and Brazil.
EA288 series diesel engines
The new EA288 generation TDI engines will be available in 1.6 and 2.0 liter displacement versions. Maximum torque is between 250 and 380 N·m (184 and 280 lb-ft).
Compared to the previous EA189 series, the diesel emits up to 7 g/km less CO2; total emissions were reduced by up to 45% in the Euro-6 version. Individual engines show performance gains of up to 12%; in certain drivetrain configurations the improvement is as much as 26%.
Coverage of all legal emissions levels worldwide, the implementation of two engine displacement classes and differentiation of the power range show the variability of the EA288, which is being used as the standardized diesel base engine series in the modular diesel system (MDB). The design of modular components gives engine factories the ability to react flexibly and quickly to changing market conditions and customer wishes. Many key components of the EA288 series TDI engine—such as the valve actuation module, fuel induction and exhaust gas recirculation—enable this on the emissions side due to their modular construction. Later this year, Volkswagen AG will offer a version of the EA288 engine, which already fulfills the Euro-6 standard and will apply to all new vehicles, but will not go into effect until September 2014.
Except for the cylinder spacing and stroke/bore ratio, everything else is new. Just like the new petrol engines (EA211), with the introduction of the modular transverse matrix, the only dimension of the new four-cylinder diesel that is the same as that of the previous model is the cylinder spacing.
Emissions-relevant components are either implemented in modular construction to conform to the specific emissions standard, or they are prepared in the mechanical design of subassemblies, such as fuel injection, cylinder pressure sensor, turbocharging and intercooling within the fuel induction module. These actions make the TDI, as noted, fit for the upcoming Euro-6 emissions standard today; in addition, they enable compact construction. Compliance with the Euro-6 standard is already built in: the standard requires a further reduction in nitrogen oxides (NOx) in the exhaust stream from 180 to 80 mg/km in diesel engines. Three different types of exhaust gas recirculation (EGR) are used, depending on emissions requirements:
- Cooled high-pressure EGR without low-pressure EGR.
- Cooled low-pressure EGR without high-pressure EGR.
- Cooled low-pressure EGR and uncooled high-pressure EGR.
Like the internal engine modifications, the emissions control components are modularly constructed. In the MDB, the arrangement of these components close to the engine is new. To fulfill various emissions standards around the world, the following emissions control components are used either individually or in combination:
- Oxidation catalytic converter
- Diesel particulate filter
- NOx storage catalytic converter or selective catalytic reduction system (SCR)
For vehicles up to the Golf class, a NOx storage catalytic converter handles the main reduction in NOx emissions. Meanwhile, in larger and therefore heavier models, Volkswagen utilizes SCR (Selective Catalytic Reduction) technology with AdBlue injection, such as is used today in the new Volkswagen CC BlueTDI. Various other design modifications optimize fuel economy and comfort as well:
Low-friction bearings and two-stage oil pump reduce friction. Along with reducing hazardous emissions, Volkswagen has tuned all sub-assemblies of the new TDI for minimal internal friction. These actions include piston rings with less pre-tension, improved rib cooling between the cylinders and the use of low-friction bearings for the camshaft (drive-side) and the balancer shafts. In the oil circulation loop, energy balance was optimized by a two-stage oil pump with volumetric flow control, depending on power demand.
Quickly up to temperature. An innovative thermal management system implements separate cooling circulation loops for the cylinder head and the cylinder crankcase during the hot operating phase. This allows the engine to heat up to its operating temperature faster. Another independently controlled cooling loop enables optimal regulation of charge air temperature with additional emissions control benefits.
Balancer shafts for the 2.0 TDI. Two low-friction bearings are used in the balancer shafts. They eliminate free inertial forces that occur in any piston engine system. Having a positive effect on acoustic comfort are the toothed belt drive of the oil and vacuum pumps operating in the oil sump and the encapsulated injection nozzles.
Lightweight construction in the MQB
All vehicles that are based on the MQB will be at least 40 kg lighter than their immediate predecessors;the MQB succeeds in sustainably overcoming the upward weight spiral and indeed reverses it. This, in turn, improves the fuel economy of all MQB-based models.
The Modular Transverse Matrix has developed basic components for many new models that offer further gains in functionality and performance, and yet which are significantly lighter in weight than those of the platform on which today’s compact class vehicles from Volkswagen AG are based.
Together with the producing factories and the supplier industry, Volkswagen has scrutinized the weight of all components, and they were optimized for their specific functionality. This systematic approach has succeeded in reducing weight in nearly all subassemblies of the modular transverse matrix.
The modularly constructed underbody structure of the MQB has around 85% high-strength steel content. Extensive use of extremely strong, hot-formed steels, whose strength is more than four times greater than that of conventional body steels, has reduced vehicle weight by approx. 18 kg, and this was achieved while improving crash properties. To further exploit weight-saving potentials in the future, preparations were made in the MQB to replace steel panels by aluminium. The component system also includes the underbody structures for electrically powered vehicles and hybrid models.
Components were weight-optimized in the interior as well. Examples of this are the front and rear seating systems, the load-bearing structure of the dashboard and the air conditioning system. The total weight of interior components on future models will be more than 10 kg lighter than in previous models. Also made lighter in weight are the electrical system components of the MQB; around 3 kg was saved here as a result of detailed optimizations.
In the powertrain, the weight of all engine/gearbox versions was further optimized, and the 1.4 liter gasoline engine with 90 kW illustrates this well. In production, it will be more than 21 kg lighter; the majority of savings was realized by the use of aluminium in the cylinder crankcase.
Due to further optimized designs and material selection, the weight of the running gear can be by more than 6 kg. Driving and comfort properties are improved at the same time, because of reductions in moving masses.
The MQB will allows the Group to produce both high-volume and niche models at the highest quality and extremely competitive costs over the long term and worldwide—vehicles that are individually tailored to the requirements of very diverse markets such as Europe, China and America, as well as emerging markets such as India. In parallel, Volkswagen Group will significantly reduce vehicle weights with the launch of the first MQB model series and will introduce 20 innovations in the areas of safety and infotainment, which until now were reserved for higher vehicle segments.
These include the new multi-collision brake; after an initial collision, it helps to reduce the intensity of secondary collisions by automatically initiated braking. Very recently, ADAC awarded this system the ‘Yellow Angel’ award for innovations. The multi-collision brake will be standard equipment in the next generations of the Audi A3 and the Golf.
Within the Group, the MQB developed under the auspices of the Volkswagen brand is supplemented by the Modular Longitudinal System (MLB) from Audi, the Modular Standard System (MSB) with Porsche as the competence centre and finally the ‘New Small Family’—the most compact vehicle model series with the Volkswagen up!, SEAT Mii and ŠKODA Citigo.
Volkswagen has been selected as one of five finalists for the ‘Innovation Award of the German Economy – The World’s First Innovation Award’ for the Modular Transverse Matrix; the winners will be announced 11 February.