Volvo 3.0 SI6 T6 Engine: B6304T2/T4

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Introduction

Production of Volvo’s turbocharged ‘Short Inline 6’ (SI6) engine (code: B6304T2) commenced in 2007 at Ford’s engine plant in Bridgend, Wales.The turbocharged SI6 engine was based on the3.2-litre naturally aspirated SI6 engine, but had narrower cylinder bores and a shorter stroke. As such, the SI6 T6 engine had 82.0 mm bores – spaced at 91.0 mm intervals – and a 93.2 mm stroke for a capacity of 2953 cc. Key features of the SI6 T6 engine included its:

• Cylinder block and bedplate which were produced from high-pressure die-cast AlSi9Cu3 aluminium alloy;
• Cast-in iron cylinder liners which were thermally sprayed for a porous AlSi12 coating;
• Gravity-cast AlSi9Cu3 cylinder head which featured cross-flow cooling;
• Double overhead camshafts (chain-driven by gears at the rear end of the crankshaft);
• High-pressure die-cast aluminium camshaft cover which incorporated integrated upper cam bearing halves and oil distribution grooves for Variable Cam Timing (VCT);
• Twin-scroll turbocharger which provided peak boost pressure of 0.7 bar (10.1 psi);
• Four valves per cylinder with variable intake and exhaust valve timing (rather than intake only as for the naturally aspired SI6 engine);
• Conventional port fuel injection (PFI);
• Compression ratio of 9.3:1 (compared to 10.8:1 for thenaturally aspirated SI6);
• Denso engine management system for the fuel and ignition systems; and,
• Mass of 190 kg (212.5 kg when installed).

Unlike the 3.2-litre naturally aspirated SI6 engine, however, the turbocharged SI6 engine omitted the:

• Variable Intake System (VIS); and,
• Cam Profile Switching (CPS) system for variable intake valve lift.

The turbocharged SI6 engine also had different machining and manifolds. While the SI6 T6 engine was 8 per cent smaller than the naturally aspirated SI6 engine, peak power and torque were 20 per cent and 25 per cent greater, respectively.

Compact design

Like the naturally aspirated SI6 engine, the turbocharged SI6 engine was mounted transversely. To minimise their exterior dimensions, both engines had a Rear End Ancillary Drive (READ). With READ, ancillaries such as the power steering pump and air conditioning compressor were positioned behind the engine (i.e. above the gearbox) and belt-driven via gears at the rear end of the crankshaft. Furthermore,

• The alternator was directly driven and installed on the engine block; and,
• A fluid-type internal viscous damper (IVD) – which compensated for vibration in the six-cylinder engine’s relatively long crankshaft – was integrated into the engine block.

Compact dimensions also improved occupant protection since there was additional space for deformation in the engine compartment and reduced the risk of head injuries for pedestrians and cyclists by creating additional space for the bonnet to crumple.

Twin-scroll turbocharger

For its twin-scroll turbocharger, the SI6 T6 engine’s exhaust gases were divided into two outflows -half from three cylinders and half from the other three cylinders – to reduce interference between the exhaust gases and turbo lag. These 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. Boost pressure was controlled by a conventional wastegate on the compressor side. On the intake side, an electronically controlled dump valve helped reduce the ‘whoosh’ noise when the throttle was released and enabled more precise boost control. Peak boost pressure for the B6304T2 engine was 0.7 bar (10.1 psi).

From the turbocharger, the compressed air was fed through an air-to-air intercooler to reduce its temperature and increase its density.

B6304T4 engine (2010 update)

In May 2010, Volvo announced that it had upgraded its T6 engine to reduce internal friction and increase its torque output to 440 N. From a subsequent announcement, AustralianCar.Reviews understands that a Diamond-like Carbon (DLC) coating – which had self-lubricating properties – was introduced for the valve tappets to reduce camshaft friction. Other changes included:

• Denso ‘Super Ignition’ spark plugs for better cold starting performance and longer service life;
• Revised frame bearings within the crankshaft;
• A low-friction accessory drive belt tensioner;
• Engine management software that was optimised for fuel economy;
• Revised mapping software for the ‘Geartronic’ transmission that allowed a new ‘Sport’ mode; and,
• An aluminium water pump housing.

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Volvo B6304T2 T6 and excessive oil consumption

In April 2012, Volvo issued Technical Journal 24643 for Volvo vehicles that had B6304T2 and B6304T4 engines and were manufactured prior to 4 May 2011. According to the Technical Journal, these vehicles may exhibit the following symptoms:

• Low oil level;
• Excessive oil consumption;
• Poor idle quality;
• White smoke from the exhaust;
• An oil smell; and/or
• Illumination of the yellow warning symbol and ‘Low oil level’ or ‘Oil level low’ messages in the Driver information Module (SIM).

To determine if the vehicle had an oil consumption condition, 

• The engine should be inspected for external leakage on and around the engine, especially around the cylinder head/cam cover/timing cover area. If an external leakage was present, then the following steps were not applicable;
• An oil consumption test could be performed if there was no prior record of low oil levels and oil being added between service intervals;
• The spark plugs were to be examined for evidence of previous oil over-filling since this could be the cause of DTCs related to oil consumption (specifically DTC P030000 and/or P030600). As the Technical Journal acknowledged, these engines were susceptible to over-filling since it was difficult to easily check the oil level with the dipstick;
• A cylinder leakage test was to be performed to determine if oil consumption was coming from an area other than the cam cover;
  • If the cylinder leakage tests were OK and if the spark plug from cylinder #6 had more soot than the others, this suggested that the cam cover was not properly sealed from the factory. If so, the cam cover was to be removed so that the sealing surface could be inspected. If the sealing surface was discoloured by oil, it was most likely that there was a leak between the cam cover and the cylinder head in the area facing the positive crankcase ventilation (PCV) channel which connected the breather box and the PCV gallery. To fix, the cam cover was to be re-sealed. The cam cover seal was improved at engine production date 15 April 2010 (15041000001); and,
  • If the cylinder leakage tests were OK and there was a spark plug from a cylinder other than #6 which had more soot than the others, then the valve guides were to be inspected. Valve guide leakage was most commonly found when there was excessive white smoke from the exhaust and had been observed on engines with build dates before 4 May 2011 (040511B01272). Each valve guide was to be tested by removing the cam cover, removing the valve tappets, plugging all but one intake port and plugging all intake ports, injector ports and the PCV inlet. Air pressure could then be applied to one intake port at a time and, by using automatic transmission fluid (ATF) for colour differentiation, ripples or bubbles in the ATF would indicate a leak that required the cylinder head to be replaced.