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The Modular Engine Management System, or MEMS, is an electronic control system used on engines in passenger cars built by
Rover Group The Rover Group plc was the British vehicle manufacturing conglomerate known as "BL plc" until 1986 (formerly British Leyland), which had been a state-owned company since 1975. It initially included the Austin Rover Group car business (compris ...
in the 1990s. As its name implies, it was adaptable for a variety of engine management demands, including electronically controlled
carburetion A carburetor (also spelled carburettor) is a device used by an internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the venturi tube in the main meterin ...
as well as single- and multi-point
fuel injection Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of an injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines. All com ...
(both with and without electronic
ignition Ignition may refer to: Science and technology * Firelighting, the human act of creating a fire for warmth, cooking and other uses * Combustion, an exothermic chemical reaction between a fuel and an oxidant * Fusion ignition, the point at which a ...
control). The abbreviations "SPi" and "MPi" refer to the single-point and multi-point injection configurations, respectively. In 1985, Rover Group made the decision to develop a new electronic engine management system in-house, and from its inception, the system was intended to be flexible enough for use with future engine designs. It was also intended to improve quality and reliability and to consume less power and occupy less underbonnet space than previous engine management systems. The system first became available in 1989, when it was fitted to the
Austin Montego The Austin Montego is a British family car that was produced by British Leyland from 1984 until 1988, and then by Rover Group from 1988 until 1995. The Montego was the replacement for both the rear-wheel drive Morris Ital and the front-wheel dri ...
2.0L. Over the next seven years, the system appeared on cars across Rover's model lineup, including the Mk VI and Mk VII
Mini The Mini is a small, two-door, four-seat car, developed as ADO15, and produced by the British Motor Corporation (BMC) and its successors, from 1959 through 2000. Minus a brief hiatus, original Minis were built for four decades and sold during ...
and the
MG F / MG TF The MG F and MG TF are mid-engined, rear wheel drive roadster cars that were sold under the MG marque by three manufacturers between 1995 and 2011. The MG F was the first new model designed as an MG since the MGB that was produced from 1962 ...
. It was also paired with Rover engines used by other marques, such as the
Lotus Elise The Lotus Elise is a two-seat, rear-wheel drive, mid-engined roadster conceived in early 1994 and released in September 1996 by the British manufacturer Lotus Cars. The Elise has a fibreglass body shell atop its bonded extruded aluminium chass ...
and several
Caterham Caterham () is a town in the Tandridge District of Surrey, England. The town is administratively divided into two: Caterham on the Hill, and Caterham Valley, which includes the main town centre in the middle of a dry valley but rises to equa ...
models using the
Rover K-series engine The Rover K-series engine is a series of internal combustion engines built by Powertrain Ltd, a sister company of MG Rover. The engine was a straight-four cylinder built in two forms, SOHC and DOHC, ranging from . Design history The K seri ...
.


Hardware

The ECU design was a joint venture between Rover and
Motorola Motorola, Inc. () was an American multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent public companies, Motorola ...
Automotive and Industrial Electronics Group (AIEG), who were responsible for the ECU manufacturing. The software run on the ECU was designed and written by Rover Group engineers. The "Modular" characteristic of the ECU was represented in the hardware design, which featured a common core with multiple optional add-on modules. In 1990, these modular features included the following: * Base programmed ignition * Single fuel injector * Second fuel injector * Batch-fired (bank) fuel injectors *
Automatic transmission An automatic transmission (sometimes abbreviated to auto or AT) is a multi-speed transmission (mechanics), transmission used in internal combustion engine-based motor vehicles that does not require any input from the driver to change forward gea ...
control * Pulse air *
Exhaust gas recirculation In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide () emissions reduction technique used in petrol/gasoline, diesel engines and some hydrogen engines. EGR works by recirculating a portion of an engine's exhaust ...
* Purge valve control * Knock sensing *
Air conditioning Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling ...
control *
Oxygen sensor An oxygen sensor (or lambda sensor, where lambda refers to air–fuel equivalence ratio, usually denoted by λ) or probe or sond, is an electronic device that measures the proportion of oxygen (O2) in the gas or liquid being analysed. It was d ...
(s) The processor in the ECU is an Intel 8096 running at 12 MHz and featuring 8KB of on-chip ROM for storage of code and data and 232 bytes of general-purpose RAM. The main connector is a 36-pin
TE Connectivity TE Connectivity is an American Swiss-domiciled technology company that designs and manufactures connectors and sensors for several industries, such as automotive, industrial equipment, data communication systems, aerospace, defense, medical, o ...
344108 ("Econoseal"), and its mating connector (used in the wiring harness) is a TE Connectivity 344111. On earlier versions of the system, a
MAP sensor The manifold absolute pressure sensor (MAP sensor) is one of the sensors used in an internal combustion engine's electronic control system. Engines that use a MAP sensor are typically fuel injected. The manifold absolute pressure sensor provid ...
was internal to the ECU, requiring that an
inlet manifold In automotive engineering, an inlet manifold or intake manifold (in American English) is the part of an engine that supplies the fuel/ air mixture to the cylinders. The word ''manifold'' comes from the Old English word ''manigfeald'' (from th ...
vacuum line be run to the ECU enclosure. In MEMS 1.6, this MAP sensor is the Motorola 5141550T02, and the vacuum line feeding it passes through a vapor trap to prevent admission of fuel vapor into the ECU. An analogous system for engines with a
Carburettor A carburetor (also spelled carburettor) is a device used by an internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the venturi tube in the main meteri ...
was developed at the same time as MEMS. This system was known as "ERIC", which stands for "Electronically Regulated Ignition and Carburetion". The development of the MEMS and ERIC systems became the first in-house units for ignition and fuel-control, areas which had previously been undertaken by Lucas Engine Management Systems, a division of Lucas Industries. While the development of MEMS and ERIC occurred at the same time, there was no commonality between the two systems - while MEMS used an Intel micro-controller, the ERIC system used the
Motorola 68HC11 The 68HC11 (6811 or HC11 for short) is an 8-bit microcontroller (µC) family introduced by Motorola in 1984. Now produced by NXP Semiconductors, it descended from the Motorola 6800 microprocessor by way of the 6801. The 68HC11 devices are more p ...
device; the development of MEMS used a PC based toolset, while that of ERIC used a Unix based toolset; the two teams working on MEMS and ERIC were totally independent.


Function

Like other electronic engine management systems, MEMS reads data from a number of sensors and computes an appropriate fueling rate and ignition advance/retard. The ECU samples engine speed, manifold absolute pressure, coolant temperature, intake air temperature, throttle position, and battery voltage. Base values for the fueling and ignition timing are each retrieved from a three-dimensional map, and certain sensor values are applied as correction factors, for example, to enrich fueling during wide-throttle acceleration or on cold startup. The MEMS firmware also features a limp-home capability (referred to in the literature as "limited operating strategy") that will substitute a nominal value for any non-operative sensor. Crankshaft position and speed are determined by input signals generated by poles in a
magnetic reluctance Magnetic reluctance, or magnetic resistance, is a concept used in the analysis of magnetic circuits. It is defined as the ratio of magnetomotive force (mmf) to magnetic flux. It represents the opposition to magnetic flux, and depends on the geom ...
disc. The system may be run in either open-loop or closed-loop mode (with the latter requiring a lambda sensor). Additional features include an engine speed limiter, overrun fuel cut-off, startup fuel enrichment (both during cranking and after startup), and fueling compensation for battery voltage. Some operating parameters are learned by the ECU over time, such as the optimal IAC valve position for a stable idle. This accommodates slight differences in engine wear and tune between different engines. Among the different revisions of MEMS were the following: *1.2: First version to enter production. Not designed for use in vehicles with
catalytic converter A catalytic converter is an exhaust emission control device that converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters are usuall ...
s. ECU has single 36-pin connector. *1.3: Designed with capability to control emissions-related equipment. ECU has two connectors (one 36-pin and one 18-pin). *1.6: Finned aluminum enclosure normally with single 36-pin connector, some have a 36-pin and 18-pin connector. *1.9 Introduced in mid-1994, version 1.9 of the system uses a redesigned mechanism for idle air control and supports multipoint injection. *2J: Supports sequential injection (with a fallback to batch-fired injectors in the event of a cam position sensor failure.) Also supports variable valve timing control in the form of Rover VVC. *3: Supports EOBD3 (European On Board Diagnostics version 3)


Diagnostics

Because it was designed before industry-wide
on-board diagnostics On-board diagnostics (OBD) is a term referring to a vehicle's self-diagnostic and reporting capability. OBD systems give the vehicle owner or repair technician access to the status of the various vehicle sub-systems. The amount of diagnostic inf ...
were standardized, early versions of MEMS use a proprietary diagnostics protocol and signaling scheme. This protocol is known as ROSCO, which is an abbreviation for Rover Service Communications. On earlier cars, the diagnostic port used a circular three-pin connector (type 172202 manufactured by TE Connectivity), where later cars switched to the standardized 16-pin ISO J1962 connector type. When the system detects a fault, a corresponding fault code is stored in the ECU's nonvolatile memory. Fault codes may only be cleared by commanding the ECU via the diagnostic port. Testing of MEMS equipped cars was originally possible with the "COBEST", "Microcheck", and "Microtune" test equipment provided to Rover dealerships and service centers. The Rover TestBook system later became available to provide similar functionality as well. There are now various open and closed source applications for PC and mobile phones in order to interact with these ECUs, rather than having to purchase an old Testbook tool.


External links


MGF TF MEMS ECU Motorola (MEMS 1.9)

Rover MEMS diagnostic protocol

3-pin diagnostic cable

16-pin diagnostic cable


References

{{reflist Fuel injection systems Engine components