Lucas 14CUX
Encyclopedia
Fuel injection
Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol engines, having almost completely replaced carburetors in the late 1980s....
system developed by Lucas Industries and fitted to the Rover V8 engine
Rover V8 engine
The Rover V8 engine is a compact V8 internal combustion engine with aluminium cylinder heads and cylinder block, originally designed by General Motors and later re-designed and produced by Rover in the United Kingdom...
in Land Rover
Land Rover
Land Rover is a British car manufacturer with its headquarters in Gaydon, Warwickshire, United Kingdom which specialises in four-wheel-drive vehicles. It is owned by the Indian company Tata Motors, forming part of their Jaguar Land Rover group...
vehicles between 1990 and 1995. The system was also paired with the Rover V8 by a number of low-volume manufacturers such as TVR
TVR
thumb|right|240px|TVR No.2, the oldest surviving TVR, located at [[Lakeland Motor Museum, Newby Bridge, Cumbria]]TVR was an independent British manufacturer of sports cars. Until 2006 it was based in the English seaside town of Blackpool, Lancashire, but has since split up into several smaller...
, Marcos
Marcos (automobile)
Marcos was a British sports car manufacturer. The name was a combination of founders Jem Marsh and Frank Costin.-History:Marcos was founded in Luton, in Bedfordshire, England, in 1959 by Jem Marsh and Frank Costin. Frank Costin had earlier worked on the De Havilland Mosquito fighter-bombers and...
, Ginetta
Ginetta Cars
Ginetta Cars is a Garforth, Leeds, West Yorkshire based British specialist builder of racing and sports cars.-20th century:Ginetta was founded in 1958 by the four Walklett brothers in Woodbridge, Suffolk...
, and Morgan
Morgan Motor Company
The Morgan Motor Company is a British motor car manufacturer. The company was founded in 1910 by Harry Frederick Stanley Morgan, generally known as "HFS" and was run by him until he died, aged 77, in 1959. Peter Morgan, son of H.F.S., ran the company until a few years before his death in 2003...
.
The system is also sometimes referred to as the "Rover Hot-Wire" or "Hitachi Hot-Wire", in reference to the style of airflow sensor
Mass flow sensor
A mass air flow sensor is used to find out the mass flowrate of air entering a fuel-injected internal combustion engine. The air mass information is necessary for the engine control unit to balance and deliver the correct fuel mass to the engine. Air changes its density as it expands and contracts...
it uses (and the sensor's manufacturer, Hitachi
Hitachi
Hitachi is a multinational corporation specializing in high-technology.Hitachi may also refer to:*Hitachi, Ibaraki, Japan*Hitachi province, former province of Japan*Prince Hitachi and Princess Hitachi, members of the Japanese imperial family...
).
History
In the mid-1980s, Lucas developed the 13CU system by revising the BoschRobert Bosch GmbH
Robert Bosch GmbH is a multinational engineering and electronics company headquartered in Gerlingen, near Stuttgart, Germany. It is the world's largest supplier of automotive components...
L-Jetronic
Jetronic
Jetronic is a trade name of an fuel injection technology for automotive petrol engines, developed and marketed by Robert Bosch GmbH from the 1960s onwards. Bosch licensed the concept to many automobile manufacturers. There are several variations of the technology offering technological development...
system and adding an electronic diagnostics capability to comply with California Air Resources Board
California Air Resources Board
The California Air Resources Board, also known as CARB or ARB, is the "clean air agency" in the government of California. Established in 1967 in the Mulford-Carrell Act, combining the Bureau of Air Sanitation and the Motor Vehicle Pollution Control Board, CARB is a department within the...
requirements. The design of the 13CU also deviated from the original L-Jetronic design in that it used a hot-wire air mass sensor rather than the Jetronic's mechanical flap sensor.
The 13CU was further developed into the 14CU, which had (among other changes) an ECU that was more physically compact. The 14CU was used in US
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
-market Range Rovers in 1989. Both the 13CU and 14CU were designed for use with only the 3.5L version of the Rover V8.
The 14CUX was the final iteration of the system, and featured upgraded injectors and (for some markets) an external diagnostic display.
Hardware
The engine control unitEngine control unit
An engine control unit is a type of electronic control unit that determines the amount of fuel, ignition timing and other parameters an internal combustion engine needs to keep running...
(ECU) of the 14CUX system is run by a Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...
MC6803U4 8-bit microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
, which is an uncommon variant of the otherwise ubiquitous 6803
Motorola 6800
The 6800 was an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System that also included serial and parallel interface ICs, RAM, ROM and other support chips...
. The processor is mislabelled in the ECU, possibly to deter any reverse engineering
Reverse engineering
Reverse engineering is the process of discovering the technological principles of a device, object, or system through analysis of its structure, function, and operation...
efforts. The 14CUX determines fueling values for each bank of the V8 separately, which requires the use of two dedicated timer outputs for independent control of the fuel injectors. This requirement helped to drive the selection of the MC6803U4 part, which has three timer outputs available (in contrast to the single timer output on the standard 6803.)
The ECU got minor design updates through its life, with the earlier units given the part-number prefix "PRC" and the later units "AMR".
The code and data used by the microprocessor is stored in either a 27C128 or 27C256 EPROM
EPROM
An EPROM , or erasable programmable read only memory, is a type of memory chip that retains its data when its power supply is switched off. In other words, it is non-volatile. It is an array of floating-gate transistors individually programmed by an electronic device that supplies higher voltages...
(depending on the revision of the ECU), which is soldered in place on most PRC units and socketed in some late PRC units as well as AMR units. Only half of the 32KB PROM space is used, so the code/data image appears twice, duplicated in the upper half.
Function
In contrast to more modern engine management systems, the 14CUX controls fuelGasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
delivery only; it does not control spark ignition. On 14CUX-equipped vehicles, the spark control is done mechanically with the use of a distributor
Distributor
A distributor is a device in the ignition system of an internal combustion engine that routes high voltage from the ignition coil to the spark plugs in the correct firing order. The first reliable battery operated ignition was developed by Dayton Engineering Laboratories Co. and introduced in the...
.
When the ignition is first turned on, the ECU energizes a relay that runs the fuel pump for a short time to pressurize the fuel rail. Once the starter motor begins to turn the engine, the ECU gets a 12VDC signal that causes it to run the fuel pump again, and energize the fuel injectors. For the next several seconds, the injector pulse width is wider than normal to provide sufficient fuel for starting. Idle control is performed by adjusting a stepper-motor
Stepper motor
A stepper motor is a brushless, electric motor that can divide a full rotation into a large number of steps. The motor's position can be controlled precisely without any feedback mechanism , as long as the motor is carefully sized to the application...
-driven bypass valve in the intake plenum
Plenum chamber
A plenum chamber is a pressurised housing containing a gas or fluid at positive pressure . One function of the plenum can be to equalise pressure for more even distribution, because of irregular supply or demand...
. When the ignition is switched off, the ECU winds the bypass valve fully open to provide enough air the next time the engine is started.
To determine the amount of fuel required by the engine, the ECU reads a number of sensors measuring the following factors:
- Intake air mass
- Coolant temperature
- Engine speed
- Throttle position
- Fuel temperature
- Exhaust oxygen content (narrowband)
- Road speed
The intake air mass is measured with a "hot-wire" mass airflow sensor: drawn in by intake manifold vacuum, air moves past an electrically-heated wire filament, and the degree to which the filament is cooled indicates the mass of the airstream.
Two factors (crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
speed and engine load) are used to index into a two-dimensional matrix of numeric values known as the "fuel map". The value read from the map is offset by other environmental factors (such as coolant temperature). This corrected value is then used to meter fuel by pulse-width modulating the fuel injectors. Because each bank of the V8 feeds an exhaust line with its own oxygen sensor
Oxygen sensor
An oxygen sensor, or lambda sensor, is an electronic device that measures the proportion of oxygen in the gas or liquid being analyzed. It was developed by the Robert Bosch GmbH company during the late 1960s under the supervision of Dr. Günter Bauman...
, the air/fuel ratio can be monitored and controlled for the banks independently.
The 14CUX PROM
Programmable read-only memory
A programmable read-only memory or field programmable read-only memory or one-time programmable non-volatile memory is a form of digital memory where the setting of each bit is locked by a fuse or antifuse. Such PROMs are used to store programs permanently...
may contain up to five fuel maps, which allowed a single ROM image to contain maps for multiple target markets. In some markets, the active map is selectable by placing an external tune resistor
Resistor
A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...
on a particular pin of the ECU. This external map selection was disabled in the code for North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n specification (NAS) vehicles.
Open loop
Above a certain engine speed or throttle position, the ECU switches to "open-loop" mode; the inputs from the exhaust lambda sensors are ignored and the mixture is enriched beyond stoichiometric for higher power and decreased engine wear.In addition to engine speed and load conditions triggering open-loop mode, the selection of the fuel map also may force this mode. For certain fuel maps, the 14CUX firmware fuels in open-loop mode under all running conditions.
Diagnostics
The design of the 14CUX was done well in advance of the requirement (for the 1996 model year) that all passenger vehicles sold in the United States support OBD-II. As a result, the diagnostics information collected by the 14CUX is not accessible via an OBD-II-compliant interface. In lieu of an industry-standard diagnostic interface, the 14CUX is able to communicate over a serial link at non-standard voltage levels and baud rate. The reference clock for the UART runs at 1 MHz and the clock divisor is set to 128, which produces a data rate of 7812.5 baud. The serial interface allows reading and writing arbitrary memory locations via a simple software protocol. Because the value from a given sensor is always stored at the same location in RAMRandom-access memory
Random access memory is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order with a worst case performance of constant time. Strictly speaking, modern types of DRAM are therefore not random access, as data is read in...
, these sensor values can be read if the memory location is known.
The 14CUX is capable of storing diagnostic trouble codes in a 32-byte segment of its internal memory that is maintained (even while vehicle ignition is off) by applying 5VDC (regulated
Voltage regulator
A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components...
down from 12VDC from the vehicle's battery.) Because of this maintainer voltage, the ECU is always drawing a small amount of current. Fault codes can be cleared by disconnecting the battery for a short period of time. Diagnostic trouble codes can be retrieved from the ECU via a small electronic display referred to as the "Fault Code Display Unit". This unit contains two seven-segment display
Seven-segment display
A seven-segment display , or seven-segment indicator, is a form of electronic display device for displaying decimal numerals that is an alternative to the more complex dot-matrix displays...
s that together show a single two-digit fault code. When connected to the 14CUX wiring harness, the ECU detects its presence and reconfigures the RDATA and TDATA lines to work as an I2C link to this device.
Applications
In addition to the Land Rover DiscoveryLand Rover Discovery
The Discovery was introduced into the United Kingdom in 1989. The company code-named the vehicle "Project Jay". The new model was based on the chassis and drivetrain of the more upmarket Range Rover, but with a lower price aimed at a larger market segment and intended to compete with Japanese...
, Defender, and Range Rover, the 14CUX was used with the Rover V8 in the TVR Griffith
TVR Griffith
The TVR Griffith, later models being referred to as the Griffith 500, was a sports car designed and built by TVR starting in 1991 and ending in 2002....
and its sister car, the Chimaera
TVR Chimaera
The TVR Chimaera is a two-seater convertible sports car manufactured by TVR between 1992 and 2003. The name was derived from Chimera, the monstrous creature of Greek mythology, which was made of the parts of multiple animals...
. In the TVR applications, engines as large as 5.0L were offered; these larger displacements required the development of new fuel maps for the engine to run properly.
Between 1990 and 1993, Ginetta produced the G33 roadster, which used the 3.9L Rover V8 and 14CUX.
For model year 1996, Land Rover chose to discontinue use of the 14CUX in its products and instead used GEMS ("Generic Engine Management System"), which had been developed jointly by Lucas and SAGEM
SAGEM
SAGEM was a major French company involved in defence electronics, consumer electronics and communication systems.In 2005, Sagem merged with SNECMA to form SAFRAN...
. This was done in part due to the requirement for OBD-II in the United States market. Some automakers whose products were not exported to North America (such as TVR) continued to use the 14CUX until the later discontinuation of the Rover V8 engine.
Main connector pin assignments
The ECU interfaces with the rest of the system via a 40-pin connector. When observing the connector on the ECU box itself, with the thumb latch on the left, the numbering for the connector's pins starts at 1 in the lower left-hand corner. The pin numbering continues to the right, and then boustrophedonicallyBoustrophedon
Boustrophedon , is a type of bi-directional text, mostly seen in ancient manuscripts and other inscriptions. Every other line of writing is flipped or reversed, with reversed letters. Rather than going left-to-right as in modern English, or right-to-left as in Arabic and Hebrew, alternate lines in...
through the two other pin rows.
| Pin | Color | Name | Description/Notes |
|---|---|---|---|
| 1 | red/green | Air bypass valve | 48-58 ohms to pin 26 |
| 2 | brown/orange | MAF and main relay | Input (+12VDC) |
| 3 | yellow | Throttle position sensor | 5k ohm to pin 25 |
| 4 | black | Ground | O2 sensor heater return |
| 5 | gray/black | Tune resistor | No wire in NAS vehicles |
| 6 | yellow (or yellow/pink) | Speed transducer | To main conn (0-12V six times per revolution) |
| 7 | green/blue | Coolant temperature sensor | To brown connector |
| 8 | purple/yellow | Heated front screen | Input from main connector |
| 9 | white/light green | Diagnostic serial port | Output to 5-pin TTS connector |
| 10 | black/yellow or red | EFI warning light | Output to main conenctor |
| 11 | yellow/white | Even (right) bank injectors | Output |
| 12 | blue/red | Main relay | Output to main relay coil |
| 13 | yellow/blue | Odd (left) bank injectors | Output |
| 14 | black | Ground | - |
| 15 | brown | Ignition and main relay | Input (+12VDC always applied) |
| 16 | blue/purple | Fuel pump relay | Output to fuel pump relay coil |
| 17 | gray/yellow | Purge control valve | Output |
| 18 | white/pink | Diagnostic serial port | Input from 5-pin TTS connector |
| 19 | white/gray or white/green | Fuel pump and inertia switch | Input (+12VDC when ignition on) |
| 20 | red | Throttle potentiometer | Swings 0.29 to 5.00 VDC |
| 21 | yellow/black to yellow/green | Air conditioner compressor load | Input |
| 22 | blue/red | MAF sensor | - |
| 23 | unk | Left lambda sensor | Blue shielded |
| 24 | unk | Right lambda sensor | Blue shielded |
| 25 | red/black | MAF and ? | ? (Ground reference?) |
| 26 | green/white | Air bypass valve | 48-58 ohms to pin 1 |
| 27 | black/gray | Ground | - |
| 28 | blue/gray | Air bypass valve | 48-58 ohms to pin 29 |
| 29 | orange | Air bypass valve | 48-58 ohms to pin 28 |
| 30 | pink | Fault display data | Output to main connector |
| 31 | black/green or black/yellow | Diagnostic plug | Input |
| 32 | gray/white | Fuel temperature thermistor | Input from gray connector |
| 33 | black/gray | Heater/air conditioner cable | - |
| 34 | orange/black | Transmission neutral switch | Input from main connector |
| 35 | blue/green | MAF sensor | 0.3 to 0.6 VDC with ignition on |
| 36 | black/green | Condenser fan timer | Tall green unit (AMR 3678) |
| 37 | (n/a) | (no connection) | - |
| 38 | brown/pink | Fault display data | Output to main connector |
| 39 | white/black or white/blue | Engine speed | Output to main connector |
| 40 | black | Ground | - |
External links
- Rover 14CUX Hot Wire Mass Flow EFI: Service and Troubleshooting (www.britishv8.org)
- Reverse-engineered 14CUX ECU and serial port information
- Ginetta G33 Fuel Injection System (www.g33.co.uk)