The market may have been surprised by Jaguar Land Rover’s decision to offer the latest Range Rover with an I-6 gasoline engine, but it’s been on the company’s development list since the Ingenium engine series was conceived more than eight years ago. With refinement a salient Range Rover selling point, it was determined the I-6 had sufficient advantages over a V6 (including manufacture) to tip the balance in its favor.
Derived from the company’s modular (500cc per cylinder) Ingenium-series inline-4, the new 3.0-L I-6 produces 294 kW (394 hp) and 550 N·m (406 lb·ft) while meeting the EU6b emission standard when installed in the new Range Rover Sport HST (top), putting it well into the SUV muscle league. The new mill incorporates an electric supercharger powered by a 48V mild-hybrid regenerative system capable of spooling to 65,000 rpm in 0.5 seconds. It “virtually eliminates” lag from the engine’s twin-scroll turbocharger, delivering a torque rise rate during transient accelerations of up to 300 Nm/s.
With the decision to move away from outsourced (Ford and PSA) engines made several years ago, the new I-6 contributes to Land Rover’s commitment of delivering an electrified option on all new models from next year. It will appear first in the new Range Rover Sport HST, and is manufactured on a new line at JLR’s Wolverhampton facility. Automotive Engineering spoke with JLR’s engine programs chief Jon Harris for details on its development.
Automotive Engineering: Ingenium is a multi-role (gasoline and diesel) modular engine range, but was a 6-cylinder gasoline envisaged from its concept, and if so when was that?
Jon Harris, JLR chief engineer, engine programs: The 6-cylinder gasoline engine was envisaged from the conception of the Ingenium engine series more than eight years ago. Initial focus was put on the 4-cylinder gasoline and diesel 2.0L engines but the 6-cylinder 3.0L engine was always planned and the factory footprint provisioned from the outset.
AE: You are using a 48V mild hybrid system. Can you put some more detail on that?
JH: The engine is fitted with a belt-driven integrated starter/generator (BSG) which replaces the alternator. The machine acts as the electrical energy supply system for the vehicle and stores lost energy in a 48V battery during a vehicle over-run condition. The energy can then be reapplied as torque assist through the belt drive system to allow the combustion engine to run in a more efficient, optimized state delivering improved fuel economy. The BSG system also facilitates seamless engine stop/start events that are almost imperceptible.
AE: JLR decided to use an electric supercharger and twin-scroll turbocharger for the I-6; can you provide some detail about the decision to use it?
JH: We have worked with Valeo as the Tier-1 supplier to deliver the electric supercharger system which works alongside the main engine turbocharger to deliver pressurized air into the engine. Vehicle drivability is a key attribute for Jaguar Land Rover and the selection of the engine boosting system is directly linked to the delivery of this attribute. The electric supercharger system was developed to capitalize on the available energy from the 48V system and deliver class-leading levels of drivability by accelerating its compressor to 65,000 rpm in 0.5 sec.
AE: What fundamental changes were made to the Ingenium engine to successfully add two cylinders? And can you provide some thermal efficiency numbers for it?
JH: The I-6 modular engine architecture includes a new cylinder head, cylinder block and crankshaft to add the additional two cylinders, whilst maintaining high levels of commonality with many of the sub-level components. The core engine combustion system has been evolved increasing gas tumble motion by 40% and introducing improved valve profiles through the hydraulic valvetrain. A two-stage intercooling system for the charge-air system has been incorporated directly within the architecture and mounts to the top of the engine. This delivers reduced air volume and accurate control of the boosted air temperature, assisting in delivering economy, emissions and performance. The new Ingenium gasoline 6-cylinder achieves a BSFC of 229g/kWh.
AE: Was the I-6 purely in-house designed and developed, or did you work with an outside consultancy?
JH: The I-6 was purely engineered in house at the Jaguar Land Rover engineering center in Whitley, Coventry.
AE: Meeting crash safety criteria was one reason for V6 use rather than an I-6 use in the past; has that picture now changed? Also, was cost a driver – i.e. only needing one cylinder head, one manifold set, etc. for the I-6?
JH: When deciding on the engine configuration, the in-line vs. V engine layout was an important strategic decision and many factors were considered. For example, refinement, vehicle and engine assembly process commonality, design synergy with the modular Ingenium family, weight and cost were all part of the overall business decision.
AE: Are the more technically advanced systems now available the enablers for JLR’s I-6 design? Your use of an e-supercharger would be an example.
JH: High levels of technology have been integrated into the I-6 gasoline engine design to deliver a combination of world class attributes. The hydraulically continuously variable valve lift (CVVL) system launched on the 2.0L I-4 engine has been adapted for use on the I-6. Fuel injection pressures have been up-rated to 250 bar and ignition coil energy is raised to 108 mJ. The air supply into the engine is from a combination of the 48V electric supercharger and a twin scroll turbocharger.
AE: What is the weight comparison between your I-6 and a V6 solution, each with comparable power output and torque?
JH: The new Jaguar Land Rover engine I-6 engine has delivered a 12kg weight saving vs. the outgoing V6.
AE: Could the electrified I-6 concept set a new global standard in premium power, NVH, and overall smoothness – rather than the less politically correct V8?
JH: The electrified straight six engine is planned to be an important long term product for Jaguar Land Rover. The expectation is that some customers will move to an electrified I-6 powertrain who previously have driven V8 powered products.
AE: All OEMs benchmark technology – what competitors did you benchmark regarding specific output, NVH, overall mass, etc?
JH: The technical teams at Jaguar Land Rover benchmark core technologies, performance, economy, NVH and weight vs. our key premium competitors. We expect that the new engine will also create benchmarking interest in its own right from the industry and Jaguar Land Rover's competitors.
AE: Where is the apparently fading diesel engine in all this? Is JLR continuing to develop diesel; has there generally been an over-reaction to diesel emissions (CO2 remains impressively low)? Does it have a future in a hybrid world?
JH: We believe there remains a strong role for diesel and gasoline alongside BEV powertrains, and they all form part of our strategy. In recent years there has been plenty of misinformation around diesel technology. Depending on how the customer uses their vehicle should inform the correct choice of powertrain. Our investment into clean diesel is paying off; Jaguar and Land Rover models are among the cleanest diesel cars on the road today. This has been recently highlighted by independent testing by AIR. Particularly for our SUVs, customers enjoy the effortless torque and the added capability a diesel provides, especially when towing.