Rover K-Series from the MG-F mounted in the chassis.

Rover K-series Engine, General Information

Rover makes the ideal engine for the Lotus Elise. It is light and compact.

It was originally conceived as a 1.4 liter in an all-alloy, belt-driven twin-cam 16-valve K16 version and was later enlarged by a longer stroke to 1,796cc for the MGF. The engine design was published in 1973 and then originally showed in 1984 and later appeared in the Rover 200 in 1989, and in the MGF launched in 1995.

The weight was 287 lbs (130 kg) with transmission and originally produced 118 hp, an excellent power to weight ratio. It used hydraulic, self adjusting tappets and Bosch multipoint fuel injection.

The engine was constructed in layers of alluminium alloy held together by ten 16 inch through-bolts, from head, through the cylinder assembly and into the crank webbing. This added strength by keeping the structure in constant compression. In stead of fixing the crankshaft in place with separate main bearing caps bolted to the underside of the block, the K-series borrows from racing engine practice. Thus, it uses a deep sided bottom casting, another ladder like the cam-bearing one above, and closed by the sump, which is a conventional steel pressing. When bolted in place, the combination of the main bearing ladder and the block gives the K-series engine an immensely stiff bottom end. This means the engine can safely exploit high crankshaft speeds, vibration is reduced, there is better support for the main bearings, and because the engine is deeper and stiffer in all places, it can be made lighter.

In 1997, Lotus displayed the Very High Performance Derivative (VHPD) version of the K series engine. This engine featured a modified cylinder head with solid valve lifters which allowed an 8000 rpm limit, carbon fiber air box, oil cooler, and lightweight exhaust. This version produced 190 hp.

In 1999, Lotus introduced the 111s version of the Elise. It provided 143 bhp at 7.000 rpm and 128 ft-lb (174 Nm) with the new variable valve control (VVC) version of the K engine. There were larger inlet and exhaust valves, a new aluminium inlet manifold, and a revised plenum chamber. The sequential fuel injection had adaptive control and distributorless ignition used individual coils for each cylinder.

Finally, in June of 2002, Lotus introduced the S2 Elise. The engine continued to use the variable valve control system but now has higher compression, larger intake and throttle body, and modified exhaust. The engine now used the Lotus K4 engine management system, allowing it to produce 156 bhp at 7,000 rpm. The torque now peaked 550 rpm earlier but was still the same 129 ft-lb (175Nm).

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