Standard Injection

There are four versions of the standard fuel injection systems used on the Rover V8 engine:

  • Lucas 4CU
  • Lucas 14CUX
  • GEMS
  • THOR

This system is often referred to as 'Flapper'. This nickname is derived from the air flow sensor that is used to manage the fuelling system. The 'air flow meter' resides in the inlet tract, usually just behind the filter, and by the use of a spring loaded 'flap', tells the management system how hard the engine is 'sucking' in the air. This then allows the engine to adjust the time that the injectors open per pulse and therefore controls the amount of fuel being delivered. In conjunction with the airflow meter a 'Throttle Potentiometer' is used to determine the amount of throttle being applied. There are a two other sensors that have a bearing on the fuel delivery, firstly the engine temperature is measured by a sensor on the inlet manifold and secondly the rpm of the engine is picked up from the negative side of the coil. All of this information is fed back to the Electronic Control Unit (ECU) which then adjusts the injectors 'pulse width'.

Although this is a fairly basic system with an almost 'linear' approach to the mapping of the fuel delivery, it can be effective in high performance applications where the engine is almost entirely run at very high throttle positions and idle / fuel economy are of less interest. The system is very old now and some parts have become completely obsolete, the throttle potentiometers are almost impossible to find although modifications can be made to run a newer version.

Flapper systems are found, in the main, on early SD1 cars (both single and Twin Plenum), early fuel injected Range Rover Classic, TVR 350i, early TVR 390i and some Morgan V8's. There were also a number of modified versions with adjustable ECU's made by Mark Adams (Tornado). As mentioned earlier this is a fairly basic system with a number of inherent drawbacks but is still functional and can be modified and tuned for greater performance if wished.

Often referred to as 'Hotwire', this younger version of the Lucas system utilises an 'Air Mass Meter' which reads air mass by means of a heated wire inside the airflow meter. The system itself is very similar to the Flapper version but with a few 'upgrades'. The injectors are slightly better and the measurement of air mass rather than air flow means that the system works better over a range of atmospheric conditions. Basically speaking the air intake 'mass' is more accurate because it changes as air density, temperature and humidity change. This means that the Hotwire system can cope better with changes in atmospheric pressure and temperature and therefore the engine tends to run equally in all conditions. Unfortunately the fuel mapping system is not greatly enhanced and is still a little two dimensional for high performance use but the system is definitely an improvement over the Flapper.

Hotwire systems are very widely used and can be found in TVR Griffith & Chimaera, TVR SEAC, TVR 390i, Westfield, Range Rover Classic and many other uses of the Rover V8 engine. For the most part it is well supported and spares can be found quite easily for most of the components used. The system is quite sensitive to adjustment and it does pay to have someone who knows the system well to set it up, even small adjustments can make a substantial difference to the way it runs.

There are a wide range of enhancements available for the Hotwire system. Mark Adams produces the 'Tornado' chips which do a far better job of controlling the fuelling than the standard versions. Fitting larger plenums, inlet manifold and trumpet bases can enhance power output enormously. The system can also be modified to use a larger air flow meter and even higher flow injectors should they be necessary. The Hotwire system can be set to use narrow band Lambda sensors for fuel adjustment below 3000 rpm which can help with fuel economy and idle control, this can equally be disabled with a simple resistor change.

There are of course also a number of concerns! The Hotwire system is renowned for losing idle control... this is usually caused by a failure in the 'stepper motor' that controls an air bypass to the plenum but is also somewhat attributed to ECU faults and sensor faults elsewhere in the system. Whilst this is not usually damaging to the engine it can be very frustrating and difficult to cure. We would strongly recommend that a only seasoned professional attempts the set up of the system! Trying to make adjustments with little knowledge of the system can result in engine damage and large bills!

This system is found in the main on Range Rover P38 vehicles, either 4.0 or 4.6. The GEMS system is not dissimilar to the Hotwire system in many respects but does have some notable differences. Firstly GEMS systems use Distributor-less Ignition (DIS or Coil Pack) rather than a standard distributor. This is a far better system for the delivery of a spark to the plugs and limits failure points by the removal of a distributor, rotor arm and spark delivery cap. Secondly this system is under constant Lambda sensor control. Twin Lambda sensors in the exhaust manifolds control the fuelling across the rev range by reading the air / fuel mixture in the exhaust gasses and adjusting the input fuelling to achieve an ideal burnt emission. This is excellent for maintaining emission control and means that very little adjustment is required in the system when setting up. Unfortunately this does not enhance power output. Generally speaking, a performance engine will run slightly 'richer' than normal at high load and high rpm and GEMS does not allow for this. The result is, when everything is working correctly, a very smooth engine and smooth power delivery but not much 'go' above 3000 rpm, not ideal for a sports car or race vehicle but better for a road going car where performance is not a big issue.

There are some enhancements to be made. There are chips available which alter the target fuelling and therefore performance but they are never going to be capable of turning a stock road engine into a high performance, fast road car whilst being controlled by their emissions. All in all the GEMS system is very good but does have it's limitations.

I really have no idea why this system has been given the name 'Thor'!! This is the BMW-inspired injection system fitted to very late Range Rovers. It is identifiable by the inlet manifold which replaces the Plenum chamber found on earlier versions and resembles a bunch of bananas! Although the engine management system bears the efficiency and accuracy of the BMW lineage, power output above 3000 rpm is seriously hampered by the inlet manifold arrangement. The engines produce good torque figures and do run well, but power is definitely sacrificed.