MARK ADAMS - Range Rover P38A GEMS 4.6 Litre

What do I get?

You are bidding for updated software to install into a Lucas-Sagem GEMS Engine Mangement computer.  The software is supplied in two EPROM chips (there are two computers inside the unit) with the two necessary decoder boards, all packed in an anti-static shipping box. These parts are shown in the picture at the top of this listing. Fitting instructions are supplied, with full colour photographs.

This software is intended for the 4.6 Litre engine, where the car is still using the standard Land Rover ERR722 fuel injectors. For best results the fuel pressure should be set to the standard 2.5 Bar, since the fuel injectors are operating well within their maximum flow capacity.

What are the benefits?

The Lucas-Sagem GEMS system is one of the most sophisticated Rover V8 engine management systems available. It responds exceptionally well to a software upgrade. The software upgrade itself is carried in a pair of EPROM chips to replace the existing ones within the ECU.

As you would expect, the upgrades are fully compatible with the standard vehicle diagnostic and security systems. Service and fault diagnosis procedures are unaltered, and the upgrade is undetectable to Land Rover TestBook. For both 4.0 and 4.6 engines you gain approximately 10-15BHP, and the engine will rev much more smoothly and eagerly. Improvements in fuel economy of 10-15% should also be seen.

Normally these engines are not very interested in revving much further than 4500RPM, and they also feature a flat spot on full load between 1750 and 3250RPM. Most of the available response is seen on the first and last 25% of the throttle pedal travel, whilst the 50% in the middle doesn't make much difference. 

Such characteristics are not unique to the Lucas-Sagem system. This behaviour is displayed by most modern cars, which have to comply with very tough exhaust emission legislation as the first priority. Emission standards for manufacturers are so demanding that they need to use every trick in the book to ensure compliance.

Many other operating characteristics are addressed. These include idle speed, idle stability, shift patterns, cold starting, crank fuelling, rev limit, etc. Even the rate of engine acceleration is controlled by the ECU, and this too has received attention to make the response more sporty.

Therefore this is a thorough treatment of the entire set of operating characteristics that goes far beyond ignition or fuelling adjustments. GEMS systems have two computers in the ECU, hence this is a two-chip solution.

How does it work?

Modern cars are also developed to be suitable for sale in very large world territories without modification (e.g. Europe, North America, etc.,). Therefore they need to cope with very poor quality fuel in some territories, and extreme operating conditions. This must all be achieved without suffering engine damage, so they are engineered for worst-case scenarios.

Since we already know the vehicle territory and conditions, some of the compromises that are necessary to the manufacturers may be removed during the upgrade process.

The toughest emission test to pass is the warm-up phase, where most of the unwanted emissions are produced. This test gets more difficult to pass as engine capacity increases. 

To assist with this part of the cycle, the engine is run with part-load ignition advance that leads to quick catalyst warm-up. A natural consequence of this is that the engine loses efficiency, which is bad for economy. Fortunately for us this situation can be easily corrected with only a marginal increase in catalyst warm-up time, and no effect on warm operation. The pay-off is a big improvement in fuel consumption!

Typically there is an improvement in fuel economy of approximately 10-15%. This is partly because the car has much more mid-range torque, so it does not need to be driven so hard. You should see a minimum of 10% improvement (on a healthy vehicle) no matter how you drive it.

Under high engine load and speed conditions, there is the danger of detonation and pre-ignition. This can have a disastrous effect on the pistons if it is allowed to persist. The Lucas-Sagem GEMS system features a very sophisticated knock detection system to detect and correct this situation. Each cylinder is monitored and mapped individually in real time.

However in an aluminium engine such as the Rover V8, there is so much mechanical noise transmitted through the block at high load and speed that it becomes difficult to detect the onset of this condition. The manufacturers are therefore obliged to ensure that the situation never occurs in the first place. This is achieved by retarding the ignition and drowning the engine in fuel.

By correcting the fuelling to provide a more uniform progression to a richer mixture under full load, and providing the appropriate amount of ignition advance, the full potential can be safely revealed. This gives a much more linear throttle response, where power output is proportional to throttle position. This is always done in the context of the likely quality of the fuel that will be used by the vehicle.

The standard system is mapped up to 5500RPM. Whilst this may be adequate in a standard Range Rover, it is not adequate for the more highly tuned variants. This is especially true for manual transmission applications in lightweight sports cars. In these cases the map is typically extended up to 6500RM, and beyond if appropriate.

Special versions of this software are available to accommodate non-standard engine sizes and installations.

Overseas Postage

If you are overseas please make contact and we'll advise of the postal charges applicable.

 

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On 31-Aug-06 at 12:44:42 BST, seller added the following information:

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On 31-Aug-06 at 13:25:46 BST, seller added the following information:

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