The VR5 engines are a family of (petroleum fuelled)

Internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal comb ...

s developed by the

Volkswagen Group Volkswagen AG (), known internationally as the Volkswagen Group, is a German public multinational conglomerate manufacturer of passenger and commercial vehicles, motorcycles, engines and turbomachinery. Headquartered in Wolfsburg, Lower Saxon ...

and produced from 1997 to 2006. They are derived from the

VR6 engine The VR6 engine is a six-cylinder engine configuration developed by Volkswagen. The name VR6 comes from the combination of German words "Verkürzt" and "Reihenmotor" meaning "shortened inline engine" referring to the VR-engine having characteristi ...

family, also developed by

Volkswagen Volkswagen (VW; )English: , . is a German automotive industry, automobile manufacturer based in Wolfsburg, Lower Saxony, Germany. Established in 1937 by German Labour Front, The German Labour Front, it was revitalized into the global brand it ...

, but with one fewer cylinders. The VR5 is highly compact, thanks to the narrower angle of 15° and a

displacement Displacement may refer to: Physical sciences Mathematics and physics *Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...

of . The VR5 was the first production block to use five cylinders in a VR design with a 15-degree angle.

Technical Information

A VR5 engine block houses two staggered rows of

cylinders A cylinder () has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infinite ...

within a single, short and wide bank – one row of two cylinders and the other having three. This narrow-angle, single bank block makes the five cylinder engine as short as an inline three cylinder, while also having ''single''

inlet An inlet is a typically long and narrow indentation of a shoreline such as a small arm, cove, bay, sound, fjord, lagoon or marsh, that leads to an enclosed larger body of water such as a lake, estuary, gulf or marginal sea. Overview In ...

and

exhaust manifold In automotive engineering, an exhaust manifold collects the exhaust gases from multiple cylinders into one pipe. The word ''manifold'' comes from the Old English word ''manigfeald'' (from the Anglo-Saxon ''manig'' anyand ''feald'' old and ref ...

s. In a

transverse Transverse may refer to: *Transverse engine, an engine in which the crankshaft is oriented side-to-side relative to the wheels of the vehicle *Transverse flute, a flute that is held horizontally * Transverse force (or ''Euler force''), the tangen ...

layout the three-cylinder row is located towards the front, and in a longitudinal layout towards the right. Due to the narrow bank-angle of the two cylinder rows, the arrangement works as a zig-zag staggered, W-patterned inline five-cylinder. The engines have a firing order of 1-2-4-5-3. The VR5 was initially made with 2 valves per cylinder as the AGZ engine from 1997 until 2000, resulting in a 10 valve engine producing at 6000 RPM and of torque at 3200 RPM. The engine was updated in 2000 as the AQN/AZX engine adding an additional 2 valves per cylinder and variable valve timing, resulting in an 20 valve engine now with 4 valves per cylinder, producing at 6200 RPM and at 3300 RPM. Both versions of the engine had cast aluminium alloy

cylinder head In a piston engine, the cylinder head sits above the cylinders, forming the roof of the combustion chamber. In sidevalve engines the head is a simple plate of metal containing the spark plugs and possibly heat dissipation fins. In more modern ...

s and cast iron cylinder blocks.

Valvetrain and cylinder head

The AGZ had 10 valves in total with 2 unequal sized valves per cylinder and chain driven

camshaft A camshaft is a shaft that contains a row of pointed cams in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition syst ...

s. When this was updated the AQN/AZX engine had 20 valves in total, with 4 unequal sized valves per cylinder. Due to the use of a single

, a key design principle of the VR engines, exhaust and intake ports were of unequal length between the two cylinder banks. To mitigate this, Volkswagen used unequally sized valves to ensure even flow and power output from the cylinders.

Engine block and pistons

The AGZ engine used a cast iron cylinder block with five staggered cylinders. Each cylinder was bore x stroke, resulting in per cylinder with a 0.90:1 stroke ratio creating an

undersquare Stroke ratio, today universally defined as bore/stroke ratio, is a term to describe the ratio between cylinder bore diameter and piston stroke length in a reciprocating piston engine. This can be used for either an internal combustion engine ...

/long stroke engine. The top of each

piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder (engine), cylinder a ...

was angled to accommodate for the use of the 15° narrow V angle.

Aspiration, fuel system, and engine management

The AGZ engine was managed by a Bosch Motronic M3.8.3

engine management system An engine control unit (ECU), also called an engine control module (ECM), is a device that controls various subsystems of an internal combustion engine. Systems commonly controlled by an ECU include the fuel injection and ignition systems. The ...

and the AQN/AZX engine by a Bosch Motronic ME7.1 engine management system. The engine used multi-point common rail sequential

fuel injection Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of a fuel injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines. All c ...

, with fuel injected indirectly into the lower

inlet manifold An inlet manifold or intake manifold (in American English) is the part of an internal combustion engine that supplies the fuel/ air mixture to the cylinders. The word ''manifold'' comes from the Old English word ''manigfeald'' (from the Anglo- ...

section just before the cylinder head intake ports. Fuel and air delivery was controlled by a cable operated

throttle body A throttle is a mechanism by which fluid flow is managed by construction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases (by the use of a throttle), but usually decreased. The term ''throttle'' ha ...

, with a potentiometer monitoring throttle position and allowing the Motronic ECU to deliver the correct amount of fuel. The engine also had a vacuum actuated variable intake manifold, controlled by the ECU via a valve part of the engines vacuum system. The valve is opened and closed depending on engine load, engine speed and throttle position. This allows the engine to take advantage of pressure waves created by the intake valves opening and closing. The VR5 was used in the Volkswagen Golf Mk4, Bora, New Beetle and Passat B5. The engine was also included in the Seat Toledo Mk2, a saloon car made by Volkswagen Group's subsidiary

SEAT A seat is a place to sit. The term may encompass additional features, such as back, armrest, head restraint but may also refer to concentrations of power in a wider sense (i.e " seat (legal entity)"). See disambiguation. Types of seat The ...

References

{{reflist Volkswagen Group engines Piston engine configurations V5 engines V engines