When containing six cylinders, a VR engine's cylinder block consists of two cylinder banks (left: 1-3-5; right: 2-4-6) while there is only a single cylinder head covering both rows of cylinders.
Description:
The name VR6 comes from a combination of V engine (German: V-Motor), and the German word "Reihenmotor" (meaning "inline engine" or "straight engine") - and so is described as a "Vee-Inline engine" (VR-Motor). It shares a common cylinder head for the two offset banks of cylinders. It has a specific sound that is unique and different than either inline or "V" engines. The engine is currently in use in a variety of VW models, one such example is the Volkswagen Passat NMS.
This engine configuration was also adopted for the Horex VR6 Motorbike.
The Volkswagen VR6 was specifically designed for transverse engine installations in front wheel drive vehicles. The narrow angle of 15° between the two 'rows' in the VR6 engine is a more compact size than a wider angle V6 design. This made it possible for Volkswagen to install 6 cylinder engines in existing 4 cylinder cars. The wider configuration of a wider angle V6 engine would have required an extensive redesign of the vehicles to enlarge the engine compartment. The VR6 is also able to use the firing order of an inline 6 engine.
The narrow angle between cylinders allows the use of just one cylinder head - whereas wider angle Vee engines require two separate cylinder heads. This arrangement also allows for two overhead camshafts to drive all the valves. This simplifies engine construction and reduces costs. In early 12 valve VR6 engines, there were two overhead camshafts with six cam lobes on each. The forward camshaft has three intake valve lobes and three exhaust valve lobes to control the frontmost three cylinders. The rear camshaft is designed the same way, but controls the rearmost three cylinders. The operating principle of this design is most similar to a single overhead camshaft (SOHC) design. Later 24 valve VR6 engines still had two overhead camshafts, but with 12 cam lobes each. However, the operation of the camshafts in the 24 valve engine is different from that of the earlier 12 valve engine, in that the front camshaft only operates the intake valves, and the rear camshaft only operates the exhaust valves. The operating principle of this design is most similar to a double overhead camshaft (DOHC) design...
There are several different variants of the VR6 engine. The original VR6 engine displaced 2.8 L and featured a 12 valve design (two valves per cylinder). These engines produced a DIN-rated power output of 174 HP, and 240 NM (177 lb-ft) of torque.
History and evolution
The Volkswagen Group VR6 engine was introduced in Europe by Volkswagen in 1991, in the Passat and Corrado; and in North America the following year. The Passat, Passat Variant (estate/wagon), and U.S.-specification Corrado used the original 2.8 L design; the European-specification Corrado and the 4WD Passat Syncro received a 2.9 L version with 140 190 HP. This version also had a free flowing 6 cm (2.4 in) catalytic converter, sharper camshafts, 4 bar (58 psi) fuel pressure regulator, enlarged inlet manifold, and larger throttle body.It was also sold to Mercedes Benz for use in their vans, and designated as M104.900.
The 2.9 L engine, as destined for the Corrado, was originally designed to benefit from a dual-tract variable-length inlet manifold - called the VSR (German: "Variables SaugRohr"), and made by Pierburg for Volkswagen Motorsport. This gave extra low-down torque, but was deleted before production on cost grounds, and was instead offered as an aftermarket option. This design was later sold to Schrick, who redesigned it and offered it as the Schrick VGI ("Variable Geometry Intake").
In 1992, with the introduction of the Volkswagen Golf Mk3, a six-cylinder engine was available for the first time in a lower-midsize segment hatchback in Europe. North America waited until 1994 to receive this engine; at the same time, the European model started to use the 2.9 L in the VR6 Syncro model. The corresponding Vento/Jetta VR6 versions appeared in the same years.
Volkswagen Group removed a cylinder from the VR6 in 1997 to create the VR5 (aka 'V5'), the second block to use an uneven number of cylinders in a Vee design after the Honda V3 triples of MotoGP fame. This version, which had a 2.3 L capacity, was capable of 150 HP, and had a maximum torque of 210 NM (155 lb-ft). It was introduced in the Passat in 1997, and the Golf and Bora in 1999.
Further modifications were added to the design in 1999, with the introduction of the 24 valve 2.8 L VR6. This engine produced 204 HP and 265 NM (195 lb-ft) of torque. The new version was not available in the Passat (as it was incompatible with the then current generation's longitudinal engine layout), but was introduced as the range-topper in the Golf and Bora for European markets under engine codes AQP and AUE from 1999. The VR6 name was dropped as a commercial designation, and the 4WD system (now renamed 4motion) became standard on the V6 (VR6) in Europe. The corresponding multi-valve V5 was only released in 2001, with a 20 HP power increase, to 170 HP. The multi valve V6 (VR6) was introduced in North America in 2001 aboard the T4 Eurovan, producing 204 HP, and in the GTI in 2002 (where it retained the VR6 name).
In 1999, an updated 12 valve VR6 model was released for the North American market A4-platform Golf Mk4/GTI/Jetta product line. This new VR6 improved performance via updated camshafts, variable geometry intake manifold, an increased compression ratio of 10.5:1, and updated emissions equipment. Power increased to 177 HP @ 5800 rpm, while torque increased to 245 NM (181 lb-ft) at 3200 rpm. This engine option was available from 1999.5—2002, when it was replaced by the revised 24 valve engine, engine code BDE, at the same time as the European market also introduced this revised engine.
In 2001, the VR6 was enlarged to 3.2 L, to create a limited production, high performance, 228 HP version of the New Beetle called Beetle RSi. The Beetle RSi was the first production vehicle to use the 3.2 L 24 valve VR6 engine. This engine was later used in the Mk4 Golf R32, and was also introduced in the original Audi TT. According to Volkswagen Group, these variants produced 250 HP in TT trim (engine ID code: BHE), and 241 HP in R32 trim (engine ID code: BFH/BML).
The then range-topping 3.2 L VR6 was later used in the current Audi A3 and the Mk5 Golf R32.
In 2005, the European market version of Volkswagen's sixth generation Passat, now with a transverse engine layout, went on sale with a revised version of the 3.2 L VR6 as its top spec engine. For North America, the Passat received a new 3.6 L VR6 with a narrower 10.6 degree cylinder angle, producing 280 HP. These revised 3.2 and 3.6 feature Fuel Stratified Injection (FSI). This new 3.2 FSI VR6 develops 250 HP @ 6250 rpm, and 330 NM (243 lb-ft) @ 3000 rpm. The introduction of the Passat VR6 also marked the first time a VR6 powered vehicle was made available in North America before Europe.
The Passat R36, available from early 2008, received an uprated version of the 3.6 FSI VR6 engine, with 300 HP @ 6600 rpm and 350 NM (258 lb-ft) @ 2400 rpm, standard 4motion four wheel drive, and standard Direct-Shift Gearbox (DSG).
The first generation Porsche Cayenne base model is powered by a 3.2 L VR6 engine producing 250 HP; modifications in the exhaust manifold allow power to peak at 6700 rpm. This is the same 3.2 L motor found on a Volkswagen Touareg and Volkswagen R32.
Detailed specification:
Volkswagen Group identifies the original VR6 by the chassis "AAA" engine ID code. It operates on the four stroke cycle, has an engine displacement of 2.8 L. The 2.8 L VR6 cylinder bore diameter is 81.0 mm (3.19 in), and the piston stroke is 90.0 mm (3.54 in), although some European engines had a displacement of 2.9 L (this variant identified by the "ABV" engine ID code). The 2.9 VR6 cylinder bore diameter is 82.0 mm (3.23 in), and the piston stroke is 90.0 mm (3.54 in). The "Vee" angle is 15°, and the compression ratio (CR) is 10:1.
The drop forged steel, six throw crankshaft runs in seven main bearings; unlike the majority of wide angle V6 engines which have only four main bearings. The connecting rod bearing journals are offset 22° to one another. Two overhead camshafts (OHCs) operate the automatic hydraulic valve lifters which, in turn, open and close the 39.0 mm (1.54 in) intake valves and 34.3 mm (1.35 in) exhaust valves. Since the two 'rows' of pistons and cylinders share a single cylinder head and head gasket, the piston crown (or top surface) is tilted. Intake and exhaust valves need different camshafts to vary valve overlap (they may be coaxial like in some 90° V8).
Because of the cylinder arrangement in the VR6 - with two rows of combustion chambers within the same cylinder head, the intake and exhaust ports between the two rows of cylinders are of varying lengths. Without compensation, these varying port lengths would result in the two rows of cylinders producing different amounts of power at a particular engine RPM. Depending on the specific generation of VR6, the difference in port lengths are compensated for by specific tuning of the intake manifold, the camshaft overlap and lift profile, or a combination thereof.
The fuel injectors, operated by the Bosch Motronic engine control unit (ECU) system, are mounted behind the bend of the intake manifolds. VR6 engines also use an additional auxiliary electric pump to circulate the engine coolant whilst the engine is running, and also during the cooling fan 'after-run' cycle, in addition to the belt-driven main water pump.
The centerline of the cylinders are also offset from the centerline of the crankshaft by 12.5 millimetres (0.49 in). To accommodate the offset cylinder placement and narrow "Vee" design, the connecting rod bearing journals are offset 22° to each other. This also allows the use of a 120° firing interval between cylinders. The firing order is: 1, 5, 3, 6, 2, 4.
The VR6 engine is currently used by Volkswagen in:
-Volkswagen Passat CC
-Volkswagen Phaeton
-Volkswagen Touareg
-Volkswagen Passat NMS
The VR6 engine was used by Volkswagen in:
-Volkswagen Golf Mk3
-Volkswagen Golf Mk4
-Volkswagen Golf Mk5
-Volkswagen Vento/Volkswagen Jetta Mk3
-Volkswagen Bora/Volkswagen Jetta Mk4
-Volkswagen New Beetle
-Volkswagen Corrado
-Volkswagen Passat (B3, B4, and B6 chassis)
-Volkswagen Sharan
-Volkswagen Transporter/Caravelle/Multivan T4 and T5
-Volkswagen Eos
The VR6 is also used in other Volkswagen Group products, namely:
-Audi A3 Mk2
-Audi TT Mk1 and Mk2
-Audi Q7
-Porsche Cayenne
-SEAT Alhambra
-SEAT León
-Škoda Superb (B6, 3T)
The VR6 is also used by other manufacturers, namely:
-Artega GT
-Ford Galaxy (first and second generation)
-Mercedes-Benz Vito/ V class
The VR5 was used by in the following Volkswagen Group products:
-Volkswagen Golf Mk4
-Volkswagen Bora
-Volkswagen Passat (B5)
-Volkswagen New Beetle
-SEAT Toledo Mk2
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| VR5 |
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