There are a number of standard fuel injection systems used on the Rover V8 engine:
Lucas 4CU (sometimes referred to as 'Flapper') and 14CUX (usually referred to as 'Hotwire'), GEMS system as fitted to P38 Range Rovers and the very late BOSCH system sometimes referred to as 'THOR'.
Although all of these systems have distinct differences they all work upon the same basic principle of air delivery and fuel mixing.
In our efforts to increase the performance of the Rover V8 engine we strive to improve the air flow and fuel mixing qualities of the engine and therefore modifications to the induction system are commonplace. Unlike cylinder head porting and polishing we tend not to re-work the standard induction in 'stages' as there are less available steps and the best results are almost always found by going to the biggest available system to fit the cylinder heads that are already fitted. Of course there are limitations to what can be achieved from a standard system and there are a number of 'aftermarket' options available to complement the standard parts.

  • Ported inlet Manifold
  • Ported Trumpet Base
  • Ported Plenum
  • Aftermarket
Ported inlet manifold

This is the standard cast manifold (there are a number of variants but they all function similarly) which has been 'ported' out to 45mm at the trumpet base (top) and matched to stage III cylinder heads at the bottom (head side). The increased volume and smooth bore both contribute to better, faster air flow and therefore increase both performance and throttle response.

Ported trumpet base

This trumpet base has been ported through to accept the 45mm radiused aluminium trumpets as shown. The shortened trumpets allow for greater clearance inside the plenum and improved volumetric flow.

72mm ported plenum

The 72mm throttle body on the front of the modified plenum increases the surface area of the air intake by 30%. This allows for more air to be drawn through the throttle body and thereby increases the potential power output at high rpm. The fact that the surface area is increased also promotes faster throttle response.

The Carbon Plenum

A single carbon plenum is normally fitted with a larger throttle body than a standard plenum and therefore offers similar gains to the 72mm aluminium version. The wall thickness is obviously greatly reduced and the plenum therefore has a greater internal volume which promotes power output. There is of course also the aesthetically pleasing look of the black carbon.
Twin and triple throttle versions of the carbon plenum are also available. Although these do not always add a great deal to the overall available air volume they do effect the throttle response and 'driveability' of the car.

Throttle Bodies

Down draught throttle bodies are probably the ultimate in terms of air delivery and performance. Whether it be carburetors or injection bodies the fact that each cylinder has a direct 'portal' to the incoming air means that each cylinder is tunable (to a greater or lesser extent).
The individual induction tract also means that the characteristics of the engine can be substantially altered by changing the length of the inlet manifold, size of chokes and length of trumpets. Optimising all of these factors can produce some really impressive results on a properly managed system.