Volvo Revised N Compact (RNC) Modular Engine

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Introduction

Volvo’s ‘Revised N Compact’ (RNC) engines were a family of modular five-cylinder engines that were first introduced in the second-generation Volvo S40 and Volvo V50 in 2004. As such, the RNC engine’s external components were designed and packaged to minimise its dimensions. The RNC engines were subsequently introduced in the second-generation Volvo C70 (2006), second-generation Volvo S80 (2007) and the Volvo C30 (2007).

The RNC engines were manufactured at Volvo’s plant in Skövde, Sweden.

Commonalities with RN engines

The RNC engines had the same technologies as the RN engines such as:

• A cylinder block and lower crankcase manufactured from high-pressure die-cast aluminium, featuring a reinforcing ribbed structure and cast in oil channels and coolant ducts. The same casting was used for the RN and RNC engine blocks;
• A chill-cast aluminium alloy cylinder head;
• Grey iron cylinder liners that were cast-in during the die-cast process for the cylinder block;
• A forged crankshaft and forged connecting rods;
• Aluminium pistons;
• Double overhead camshafts driven by a toothed belt with automatic belt tensioner;
• Four valves per cylinder;
• Pent-roof combustion chambers; and,
• Coil-on-plug ignition.

Changes for the RNC engines

For compactness, the following changes were introduced for Volvo’s RNC engines:

• The inlet manifold was compact-cast in fibreglass-reinforced plastic and routed over the engine. For naturally aspirated engines, the plastic intake manifold was also used as a cover for the engine (turbocharged RNC engines had a separate cover);
• The air cleaner housing and control module box were integrated;
• The alternator, water pump and air conditioning compressor were of compact design, with the latter re-positioned for collision protection;
• The exhaust manifold outlets were angled down towards the engine block. For turbocharged RNC engines, the exhaust manifold and turbine housing were also integrated into one part;
• For turbocharged engines, the manifold was cast together with the turbocharger housing; and,
• RNC engines had two drive belts: one for the alternator and one for the air conditioning compressor. The drive belts were made from reinforced rubber (Poly-V) and tensioned by their own mechanical tensioners.

Asa result, RNC engines were 200 mm slimmer (including manifolds) and 25 mm shorter. These changes also made the engine lighter and contributed to improved occupant protection since there was additional space for deformation in the engine compartment. In a collision, the engine could be shunted 150 mm to the rear before the block came into contact with the cross-member near the bulkhead. Furthermore, there was 70 mm of free space above the engine between the cylinder head and bonnet so that the bonnet could crumple in the event of a pedestrian/cyclist collision and reduce the risk of head injuries. For safety reasons, the fuel injectors were also installed in an aluminium section.

Although the RN and RNC blocks were the same, machining for cooling and oil lubrication was different. As such,

• The RNC engine had larger coolant ducts and a ‘more directed’ flow between the exhaust ports and around the spark plug wells;
• The RNC engine had ducts for crankcase gases beside each cylinder’s intake port;
• For the RNC engine, the thermostat mounting was moved to the block on the intake side of the engine (just above the starter motor) whereas it had previously been mounted on the cylinder head;
• In place of where the thermostat was for the RN engine, the RNC engine had an engine mount. The RNC engines had pendulum suspension-type engine mounts such that they were suspended within the engine bay (i.e. hanging down) rather than resting on a sub-frame; and,
• For the RNC engine, the oil filter was positioned in front of the block (previously part of the oil sump). Furthermore, the oil separator (or oil trap) was integrated into the oil filter and part of the intake manifold. The oil separator consisted of one chamber, three cyclonic separators, one spring-loaded membrane and a plastic cover. While the chamber roughly separated oil and exhaust gases, finer separation occurred when the gases were ducted to the cyclones. The separated oil would then run to the bottom of the cyclones and into oil pan.

Other changes for the RNC engine included:

• The introduction of a graphite coating for the cast aluminium pistons that was approximately 0.01 mm thick. While the graphite coating would wear over time, it would never completely disappear since it penetrated the outer layer of the piston;
• The Continuously Variable Valve Timing (CVVT) system was revised – the CVVT solenoid was re-located, the oil filler pipe was moved to the side nearest the solenoid because of the new intake manifold and there was a greater range of adjustment. While not all engines had exhaust camshaft adjustment, AustralianCar.Reviews understands that inlet camshaft adjustment for all RNC engines was 50 crankshaft degrees.

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B5254T3: Volvo S40/V50/C30/C70 T5 & Ford Focus ST/RS

Introduction

The rest of this article will consider the B5254T3 engine due to its popularity in Volvo’s P1 T5 variants (i.e. the S40 T5, V50 T5, C30 T5 and C70 T5), the 2005-11 Ford Focus ST/XR5 Turbo and the2009-10 Ford Focus RS.

The B5254T3 was based on the B5254T2 RN engine that was introduced in 2003 and which powered the following vehicles:

• The Volvo S60 2.5T (2003-09);
• The Volvo V70 2.5T (2003-08);
• The Volvo XC70 2.5T (2003-07);
• The Volvo S80 2.5T (2003-06); and,
• The Volvo XC90 2.5T (2003-12).

Block

Like other RNC engines, the B5254T3 had a high-pressure die-cast aluminium block with a cast-in iron cylinder liners and a reinforcing ribbed structure. The B5254T3 engine, however, had 83.0 mm bores and a 93.2 mm stroke for a capacity of 2522 cc.

Crankshaft, connecting rods and pistons

The B5254T3 engine had a forged crankshaft which weighed 21.606 kg; this was 47 grams heavier than the B5254T2 crankshaft due to the different balancing required for the pendulum suspension motor mounts. Attached to the crankshaft, the B5254T3 engine had 143 mm long connecting rods that weighed 644 grams and fracture-split big ends (caps). The upper and lower bearings were made of copper-lead alloy.
The silicon-aluminium alloy pistons that had play of approximately 0.04 mm between the piston and cylinder before a graphite coating was applied. The graphite coating was approximately 0.01 mm on either side of the piston. As noted above, the graphite coating would wear over time but would not completely disappear since it penetrated the outer layer of the piston. The pistons weighed 412 grams with piston rings, snap rings and wrist pins. In isolation, however, the pistons weighed 290 grams each. The wrist pins had a 21 mm diameter and were 60 mm long.

Cylinder head and camshafts

The B5254T3 had a gravity die-cast aluminium alloy cylinder head that was mounted on a Multi-Layer Steel (MLS) gasket. The double overhead camshafts had direct-acting mechanical shimless tappets that actuated four valves per cylinder. Furthermore, the B5254T3 engine featured sintered valve guides and seals. The intake and exhaust camshafts featured variable valve timing with an adjustment range of 50 and 30 crankshaft degrees, respectively.

Turbocharger and intercooler

For Volvo’s turbocharged RNC engines, the exhaust manifold was integrated with the turbine housing. The exhaust manifold had a MLS (Multi-Layer Steel) gasket and two slits were machined into the manifold to cope with heat expansion. From the exhaust manifold, exhaust gases would cause a turbine on the end of the turbo shaft to spin and an impeller at the opposite end to force compressed air into the induction system. The B5254T3 engine had a KKK K04-2080 D turbocharger which provided peak boost pressure of 0.65 bar. The Turbo Control Valve (TCV) was mounted in a bracket to the right of the turbocharger.

After the compressed air exited the turbocharger it was routed to a rectangular charge air cooler (or intercooler) that was mounted in front of the radiator assembly (behind the air intake in the spoiler) to reduce the temperature of the intake air and increase its density.

Oil filter and separation

The oil filter and cover for the B5254T3 engine were the same as those used on Volvo’s D5244T/T2 diesel engine. Oil separation, however, was similar to other RNC engines in that the oil separator was integrated into the oil filter and part of the intake manifold. The oil separator consisted of one chamber, three cyclonic separators, one spring-loaded membrane and a plastic cover. While the chamber roughly separated oil and exhaust gases, finer separation occurred when the gases were ducted to the cyclones. For the B5254T3 engine, however, gases also went from a diaphragm to a T-coupling and, from there, to either reed valves in the intake gasket or to the turbocharger (depending on engine load and speed).

Injection and ignition

The B5254T3 had sequential electronic fuel injection via injectors that were located on the lower manifold to mix the fuel with the turbulent air. Furthermore, the B5254T3 engine had a compression ratio of 9.0:1 and Bosch ME 9.0 engine management system.

Transmissions

The B5254T3 was mated to M66W manual and AW55-51 automatic transmissions.