Jaguar Ingenium petrol (AJ200 / AJ20P6)

The petrol half of Jaguar Land Rover's modular Ingenium family — 500 cc per cylinder in three, four and six — in the E-Pace, F-Pace, Velar, Defender, Evoque and Range Rover. The Ingenium diesel is its sibling.

The designation says which member, and they are not interchangeable. AJ200 is the 2.0 four, AJ20P6 and AJ300 the 3.0 straight-six, and AJ150 the 1.5 three-cylinder of the plug-in hybrids. AJ is Jaguar's prefix for every engine it has ever built and carries no family information at all — the AJ-V6, AJ-V8 and AJ16 share it and share nothing else.

The straight-six has a system nothing else in this catalogue does: an electric supercharger. It spins on the 48-volt side to fill in torque before the turbocharger is flowing, and it can fail on its own while the turbocharger is perfectly healthy — so a complaint of lost response low down on a six is a question about which of the two devices is missing, and the answer is not visible in boost pressure alone.

Being direct-injected, the petrols deposit carbon on the intake valves at mileage, which the port-injected engines they replaced did not. And the plug-in hybrids put a 1.5 three-cylinder in a heavy vehicle: a driveability complaint on an AJ150 car is a question about the hybrid system at least as often as about the engine.