MoTeC M84 User Manual
MoTeC M84 User’s Manual
Contents
Introduction ........................................................................ 1
Additional Documentation ................................................................................... 1
Overview ............................................................................. 3
Options ............................................................................................................... 3
ECU Inputs & Outputs......................................................................................... 4
Calibration & Setup ............................................................................................. 7
ECU Functions .................................................................................................... 8
MoTeC Software ............................................................... 11
PC Requirements ............................................................................................. 11
Connecting a PC to the ECU ............................................................................ 11
Installing the Software ...................................................................................... 11
Starting the Software ........................................................................................ 12
ECU Manager Software .................................................................................... 12
Data Logging .................................................................................................... 12
Installation ........................................................................ 15
Throttle Position or MAP Load Sensing ............................................................ 15
Sensors ............................................................................................................. 15
Wiring................................................................................................................ 19
Fuel System ...................................................................................................... 21
Ignition System ................................................................................................. 25
Auxiliary Valves ................................................................................................ 27
ECU Mounting .................................................................................................. 27
ECU Cleaning ................................................................................................... 27
Initial Setup ....................................................................... 29
Main Setup ........................................................................................................ 29
Sensor Setup .................................................................................................... 30
Input / Output Functions.................................................................................... 30
Other Functions ................................................................................................ 31
Initial Calibration .............................................................. 33
Fuel Tables ....................................................................................................... 33
Ignition Tables .................................................................................................. 34
Initial Starting Procedure ................................................ 37
Pre Start Checks ............................................................................................... 37
Starting ............................................................................................................. 39
After Start Checks ............................................................................................. 40
Calibration ........................................................................ 43
Warning Alarms ................................................................................................ 43
Ensure that the engine is “On Site” ................................................................... 43
Site Tables ........................................................................................................ 43
Dyno Calibration ............................................................................................... 44
Fuel - Main Table .............................................................................................. 44
Ignition - Main Table ......................................................................................... 45
Fuel - Injection Timing ...................................................................................... 46
Fuel - Cold Start ................................................................................................ 46
Other Calibration Tables ................................................................................... 46
Data Logging & Road Testing ........................................................................... 47
ECU Manager Software .................................................... 49
Introduction ....................................................................................................... 49
Basics ............................................................................................................... 49
Calibration Files ................................................................................................ 51
Versions & Upgrading ....................................................................................... 51
Screen Layouts ................................................................................................. 53
Making Adjustments ......................................................................................... 55
View Screen ...................................................................................................... 65
Testing the ECU Outputs .................................................................................. 66
Enabling ECU Options ...................................................................................... 66
Keyboard Reference ......................................................................................... 67
Appendices ....................................................................... 69
Appendix A: General Specifications .................................................................. 69
Appendix B: Sensor Supplies ........................................................................... 70
Appendix C: Input Characteristics ..................................................................... 71
Appendix D: Auxiliary Output Characteristics ................................................... 73
Appendix E: Ignition Output Characteristics...................................................... 74
Appendix F: Injector Output Characteristics ...................................................... 75
Appendix H: Wire Specifications ....................................................................... 76
Appendix J: CAN Wiring - Multiple Devices ...................................................... 77
Appendix K: CAN Bus Wiring - Single Device ................................................... 78
Appendix L: Pin list by Function ........................................................................ 79
Appendix M: Wiring Schematic ......................................................................... 81
For racing and off highway use only
Not legal on emissions controlled vehicles unless appropriately certified
© Copyright – MoTeC Pty Ltd 2001-2010
While every effort is taken to ensure correctness, no responsibility will be taken for the consequences of any
The information in this document is subject to change without notice.
inaccuracies or omissions in this manual.
11 April, 2014
MoTeC Introduction 1
Introduction
Thank you for purchasing a MoTeC Engine Management System.
This manual will help you understand the installation and calibration
requirements of your MoTeC Engine Management System.
Additional Documentation
Additional documentation is available in the form of Drawings and Tech
Notes. These can be downloaded from the MoTeC website at
www.motec.com.au
Drawing Categories
Accessories
ECUs
Looms
Ignition Modules
Combined Module & Trigger Systems
Trigger Systems
Valves
Sensors
Miscellaneous
. They are also available on the MoTeC Resource CD.
Tech Notes
Traction Control
Boost Control
Idle Speed Control
Closed Loop Lambda Control
Wideband Lambda Sensor
Others
2 Introduction MoTeC
MoTeC Overview 3
Overview
The MoTeC M84 ECU is a powerful and compact programmable Engine
Control Unit (ECU). The M84 is characterised by the following features:
• 1, 2, 3, 4, 5, 6 and 8 Cylinder/ 2, 3 and 4 rotor operation
• 8 injector outputs
• 6 ignition outputs
• 8 Auxiliary outputs
• Waterproof plastic connector with gold plated contacts
• 512 kByte logging memory
• Single Wideband Lambda input
Data Logging
Allows logging of the ECU sensors and operating parameters to the internal
data logging memory. The logged data may then be analysed in graphical
format using the MoTeC i2 Software.
Wideband Lambda
Allows Wideband Lambda (Air Fuel Ratio) measurement, which may be used
for data logging or closed loop control of the Air Fuel Ratio. The ECU is
compatible with Bosch LSU 4.0, 4.2 and 4.9 or NTK Wideband Lambda
sensors.
Options
A number of options are available which allow the ECU to be configured for a
particular need and can also be updated later if necessary.
The options may be enabled at any time by entering an enable password.
Optional functions include:
• Traction Control
• Boost Enhancement (Anti-lag)
• Hi/Lo Injection
• Gear Change Ignition Cut
• Advanced Functions (Traction Control, Boost Enhancement (Anti-la g),
Hi/Lo Injection, Gear Change Ignition Cut)
• Dual Wideband Lambda Inputs
4 Overview MoTeC
ECU Inputs & Outputs
The ECU analyses signals from the sensors, then controls the Fuel Injectors,
Ignition System and other auxiliary devices according to the Calibration and
Setup Data which is stored in the ECU’s programmable memory.
The Inputs and Outputs are shown below.
Main Engine Sensors
The Main Engine Sensors are required for correct operation of the ECU.
The engine RPM is derived from the REF trigger sensor.
The SYNC trigger sensor is required to synchronise the Fuel and Ignition to
the correct engine cycle for sequential injection and correct firing of multicoil
ignition systems.
MoTeC Overview 5
The Throttle Position, Manifold Pressure, Air Temp and Engine Temp are
used as inputs to the various calibration tables.
Optional Sensors
The Optional Sensors are not required for basic operation of the ECU.
The Lambda Inputs may be used for Wideband air fuel ratio measurement or
Wideband or Narrowband closed loop Lambda control.
The Digital Inputs may be used for wheel speed measurement or to activate
functions such as Dual RPM Limit.
The other inputs may be used for data logging (e.g. Exhaust Gas Temp, Fuel
Pressure etc.) or for special calibration features.
Fuel Injector Outputs
Up to eight injectors may be driven fully sequentially including very low ohm
types (0.5 ohms).
Ignition Outputs
The Ignition Outputs may be used to drive many different types of ignition
systems, which are detailed in the various ignition system drawings.
Up to six ignition outputs are available for multicoil applications.
• Up to 8 coils may be driven from one Ignition Output using a MoTeC CDI8 or
MoTeC Ignition Expander.
Auxiliary Outputs
The M84 has eight Auxiliary Outputs that may be used for:
Turbo Waste Gate Control, Idle Speed Control, Gear Change Light, Driver
Warning Alarm (plus many others).
CAN Communications
The CAN Communications system is a high speed network comm unications
system that allows multiple devices to be connected and communicate with
each other.
The CAN connection is used for all communications with the PC via the ECU
Manager software which includes calibration, diagnostics checking, retrieving
the logged data, firmware upgrading and enabling options.
6 Overview MoTeC
CAN may be used to communicate with the MoTeC ADL & SDL Dash
Loggers, PLM, LTC and SLM.
RS232 Serial Communications
Used for receiving GPS data input and transmitting MoTeC Data Set 1 for use
with dash displays and loggers.
MoTeC Overview 7
Calibration & Setup
Calibration Tables
The Calibration Tables determine how the output devices should be controlled
for various sensor readings. For example, the fuel calibration table determines
the base injector pulse width for all combinations of RPM and Load. Other
calibration tables will also affect the fuel injector pulse width such as Air
Temperature compensation and Engine Temperature compensation.
The ECU determines the amount of fuel to inject by first calculating the RPM
and Load then extracting the corresponding value from the table. If the RPM
and Load do not match an RPM and LOAD point exactly then the values from
the closest sites are mathematically interpolated to arrive at an intermediate
value.
A typical 3 dimensional fuel calibration table is shown below.
The calibration tables may also be represented graphically as shown below.
8 Overview MoTeC
Setup Parameters
The Setup Parameters allow the ECU to be configured for almost any engine.
The Setup Parameters include Number of Cylinders, Ignition Type, Sensor
Types, Injector Current, Auxiliary Output Functions etc.
• The Setup Parameters must be correct before attempting to start the
engine.
ECU Functions
The ECUs can perform a large number of functions in addition to the normal
Fuel and Ignition control capabilities including; Hi /Lo injection, Individual
Cylinder tables for Fuel and Ignition, Rotary Ignition Split and various sensor
compensations
The functions are setup using ECU Manager either in the Functions menu,
the Digital Input Functions menu or the Auxiliary Output Functions menu.
Help on each function is available from within ECU Manager by pressing the
F1 key when the appropriate screen is shown.
Tech Notes are available from MoTeC on the more complicated functions such
as Traction Control.
The functions are as follows:
Functions
The following functions are setup in the Functions menu
• Boost Control **
• Warning Alarms **
• Gear Detection *
• Overrun Fuel Cut
• Ground Sped Limiting *
• Gear Change Ignition Cut *
• Boost Enhancement (Anti-lag) *
• Lambda Control
• Traction Control *
• Idle Control
* must also be setup in the Digital Input Functions
** must also be setup in the Auxiliary Output Functions
MoTeC Overview 9
Digital Input Functions
The following functions are setup in the Digital Input Functions menu
• Speed Measurement
• Period Measurement
• Pulse Measurement
• Dual RPM Limit
• Air Conditioner Request
• Ignition Switch
• Brake
• Logging Enable
• Clutch
• Overrun Boost Enhancement
• Traction Control Enable
• Ground Speed Limiting
• Power Steering
Auxiliary Output Functions
The following functions are setup in the Auxiliary Output Functions menu
• Boost Control
• Idle Speed Control
• Aux Table Controlled Output
• Tacho Signal
• Stepper Idle Speed Control
• Lambda Sensor Heater
• Fuel Pump Control
• Thermatic Fan Control
• Air Conditioner Fan Control
• Air Conditioner Clutch Control
• RPM / Load Table Output
• Gear Change Light Output
• Fuel Used Pulse Output
• Slip Warning Output
• Alternator Control
• Spray Bars Output
• Status Output
• Thermo Pump
10 Overview MoTeC
MoTeC Software 11
MoTeC Software
The following software is available for the M84 ECU.
ECU Manager: Used for calibration, setup, diagnostics, output testing,
upgrading, unloading the logged data and enabling
ECU options.
i2: Used to analyse the logged data.
PC Requirements
• IBM PC compatible
• 200 MHz Pentium or faster
• Operating System: Windows XP. Windows Vista, Windows 7
Connecting a PC to the ECU
The PC must be connected to the ECU by a MoTeC UTC or CAN Cable. Note
that the ECU must be wired with the mating connector.
MoTeC
Connected to the
Printer Port
CAN Cable
Installing the Software
The MoTeC Software must be installed on to the PC hard disk before it can
be used.
12 Software MoTeC
The main software required is the ECU Manager software, if Data Analysis is
required then the i2 software should also be installed.
The software can be downloaded from the MoTeC website at
www.motec.com.au
MoTeC is continually updating the software and newer versions may be
downloaded from the website at no charge.
To install the software after downloading from the web, double click on the
downloaded file and follow the instructions.
Note that a separate folder (directory) is automatically created for each
version of the software. Old versions are kept so that they may be used if
necessary.
• Do not change the MoTeC directory structure or move the software to a
different directory, otherwise the software will not operate correctly.
. It is available on the MoTeC Resource CD.
Starting the Software
To start the MoTeC Software double click the appropriate icon on the desktop
or select the appropriate program from the Start menu. For example: Start /
Programs / MoTeC / M84 / ECU Manager 1.0
ECU Manager Software
The ECU Manager software is covered in more detail later in this manual.
Data Logging
Data Logging allows the ECU operational data to be recorded in a memory
chip inside the ECU. The data may then be extracted for analysis on a PC.
Data logging is extremely useful for checking mixture readings, sensor
readings, diagnostics errors and other operating information.
The items to be logged and the logging rates must be setup using the MoTeC
ECU Manager software. This is done in the Data Logging Setup screens.
The ECU will remember the logged data even if the ECU power is turned off.
• If the logging memory becomes full, the oldest data is overwritten so that
the most recent data is always available.
MoTeC Software 13
Unloading the Logged Data
The logged data can be extracted by connecting the MoTeC UTC or CAN
Cable to the ECU and selecting Utilities | Get Logged Data from the ECU
Manager menu.
Data Logging Analysis
The MoTeC i2 software may be used to analyse the logged data.
The i2 software is supplied separately to the ECU Manager software.
The i2 software makes it easy to analyse mixture readings and other sensor
readings by presenting the data in various graphical formats.
Refer to the i2 help screen for more detail.
14 Software MoTeC
MoTeC Installation 15
Installation
Throttle Position or MAP Load Sensing
The load point for the fuel and ignition calibration tables may be based on any
defined load measuring sensor.
The most commonly used are the Throttle Position sensor or the MAP
(Manifold Pressure) sensor.
Turbo Charged Engines
Normally use Manifold Pressure load sensing (connect the MAP sensor to the
inlet manifold).
A Throttle Position sensor is optional and will be used for acceleration
enrichment if fitted.
Normally Aspirated Engines
Normally use Throttle Position load sensing.
The MAP sensor may be used to compensate for barometric pressure
changes by venting it to atmospheric pressure.
If Idle Speed Control is used then the MAP sensor should be connected to the
plenum or Manifold Pressure load sensing should be used. This is required so
that the fuel is varied as the idle speed control valve opens and closes.
Sensors
Throttle Position Sensor
The Throttle Position sensor must be a potentiometer type, older switch types
are not suitable. The sensor will produce a voltage proportional to the angle of
the throttle plate.
Throttle sensors generally have a dead band at either end and must be preloaded to avoid the dead band.
The Setup Parameters TPHI and TPLO must be set to indicate the fully
closed and fully open positions. These parameters must be set any time the
16 Installation MoTeC
sensor is moved or replaced. It is very important to set these parameters with
the butterfly in exactly the same place each time.
The resistance element inside the sensor may wear due to vibration in high
performance engines which can cause erratic readings. It is best to replace
the throttle position sensor periodically.
Avoid high pressure washing as this may penetrate the seals and damage the
sensor.
For wiring details refer to the appropriate MoTeC drawing.
MAP Sensor
The MAP (Manifold Absolute Pressure) sensor measures Absolute Pressure
(i.e. pressure relative to a vacuum).
0 kPa Absolute = Complete Vacuum
100 kPa = 1 Bar = 14.5 PSI
Atmospheric Pressure at sea level is approximately 100 to 102 kPa,
depending on the weather.
MAP sensors normally produce a voltage between 0 and 5V, depending on
the pressure.
The pressure sensor may be used to measure the inlet manifold pressure or
to measure the barometric pressure depending on the Load Sensing
arrangement detailed earlier.
The ECU Sensor Setup parameters must be set to indicate the type and
pressure range of the sensor.
Avoid severe vibration of the sensor as this can cause fluctuations in the
reading. Do not mount rigidly to the engine. Normally the pressure sensor is
mounted to the vehicle body.
If Used for Manifold Pressure Sensing
For normally aspirated engines use a 100 kPa sensor.
For turbo charged engines a 300 kPa absolute sensor will measure up to 200
kPa (29 psi) of boost (above Atmospheric). If higher boost will be achieved, a
sensor with a higher pressure range will be needed.
The sensor should be connected to the inlet manifold plenum via a short hose
(less than 1m). The sensor should be mounted above the level of the plenum
with the port facing down to avoid moisture accumulating on the sensor
element. The hose should run downwards all the way to the plenum.
MoTeC Installation 17
The plenum take off point should be at a position that best represents the
average manifold pressure and has minimal pressure pulsations. A small
restrictor may be needed at the manifold end of the hose to help reduce
pressure pulsations. The take off point should not be teed in with other items
such as idle speed control valves as they can affect the pressure reading.
If used for Barometric Pressure Sensing
Use a 105 kPa sensor.
Vent the sensor to the atmosphere with the port facing down.
Avoid mounting at a point where air buffeting occurs Any pressure
fluctuations will directly affect the mixture.
It may be desirable to sense the pressure at the air intake as the pressure
may vary due to aerodynamic effects.
Air Temp Sensor
The Air Temperature sensor is mainly used to correct for air density change
due to air temperature variation.
The sensor contains a temperature dependant resistor and is designed for
high speed response in an air flow.
The Air Temp sensor must be placed to measure the air temperature before
the butterfly (and after the intercooler on turbo charged engines).
Avoid placing the sensor too close to the stand-off vapour in a multi-runner
manifold as this will cool the sensor and give a false reading.
The ECU Sensor Setup parameters must be set to indicate the particular type
of sensor.
Engine Temp Sensor
The Engine Temperature sensor is mainly used for cold start enrichment.
The sensor contains a temperature dependant resistor and is designed for
water immersion.
The ECU Sensor Setup parameters must be set to indicate the particular type
of sensor.
18 Installation MoTeC
Trigger Sensors (REF & SYNC)
The trigger sensors supply the necessary timing information to the ECU so
that it knows when to fire the fuel injectors and ignition system. Normally two
sensors are used, REF and SYNC.
Many different types of trigger sensors and chopper patterns may be used.
The wiring and ECU setup information for the trigger sensors are specific to
the particular system. Refer to the appropriate MoTeC drawing.
Home made sensor systems often cause problems. Do not use Chrome molly
for chopper disks as it is a non magnetic material. Runout of the disk,
imperfections and bolt heads are also potential sources of problems. Where
possible it is best to use the manufacturer’s trigger system.
REF Sensor
Supplies the crank position information.
Some sensors supply one pulse per Top Dead Centre (4 pulses per engine
rev on a V8), others supply as many as 360 pulses per engine revolution.
The Engine RPM is derived directly from this signal.
SYNC Sensor
Used to indicate each engine cycle, which is required for sequential injection
and multicoil operation.
Generally supplies one pulse per engine cycle (i.e. once every 2 revs on a 4
stroke engine).
On some special trigger systems the ECU can be synchronised using the
REF sensor only (e.g. Ford Narrow Tooth)
REF / SYNC Alignment
Most modern distributors supply both REF and SYNC signals in which case
the alignment is pre-set.
When using separate REF and SYNC sensors the alignment of the two
sensors relative to one another is critical. Ensure that the sensors are aligned
correctly for the type of trigger system being used. Refer to the appropriate
drawing. Allow for any mechanical play in the distributor drive system if the
SYNC signal is derived from the distributor.
MoTeC Installation 19
Exhaust Gas Sensor (Lambda Sensor)
The ECU may optionally use a wideband exhaust gas sensor for data logging
or closed loop control of the Air Fuel Ratio.
The ECU is compatible with the Bosch LSU Wideband sensor and the NTK
Wideband sensor. These sensors are different to the sensors used on
previous model ECUs.
Note that the sensor heater must be connected to these sensors at all times
and must be controlled by the ECU by connecting it to one of the Auxiliary
Outputs.
The sensor should preferably be placed within 0.5 m of the collector pipe on a
normally aspirated engine or 0.5 m of the turbo on a turbo charged engine. If
placed too close to the exhaust outlet, the reading may be affected by the
outside oxygen.
The sensor can be contaminated by exhaust manifold sealant - use an
exhaust gas sensor friendly sealant.
The lifetime of the Sensor will be significantly reduced by leaded fuels.
Refer to the MoTeC Tech Notes and Drawings for more details.
Wiring
Wiring Drawings
For general wiring details refer to the following drawing; M84 Wiring.
The wiring details for the REF and SYNC Trigger Sensors and the Ignition
Module are specific to the type of sensors and Ignition system. MoTeC can
provide wiring diagrams for most Trigger Sensors and Ignition systems.
Wiring details for other sensor types are available from MoTeC.
Wiring Reliability
The wiring is critical for reliable operation of the ECU. The following points will
help to ensure that the wiring is reliable.
Ground Wiring
One of the most common wiring problems is poor ground wiring.
The ground wire must be grounded properly to the engine block. There should
be no paint or anodising between the ground wire and the engine block.
20 Installation MoTeC
Temporary wiring is likely to cause problems: use a proper eyelet terminal that
is securely crimped to the ground wire. Studs fixed in place by Loctite® can
also cause a problem as the Loctite® becomes an insulator. These comments
apply to both the ECU ground wire and the Ignition system ground wire.
2
The ground wire must be at least 12# (3.3 mm
possible.
) and must be kept as short as
Power Wiring
The power wire must be wired by the shortest path possible to the battery via
a 30 Amp relay and a 20 Amp fuse. The relay and fuse must be in good
condition and the wires must be crimped securely to the appropriate
terminals. The relay should be activated by the Ignition Switch. The ECU
power must NOT be fed directly from the Ignition switch because it probably
won’t handle the required current.
2
The power wire must be at least 12# (3.3 mm
possible.
) and must be kept as short as
Spark Plug Leads
The spark plug leads can cause interference in the ECU wiring. Keep the
ECU wires away from the plug leads wherever possible (at least 100mm). If it
is necessary to cross the plug leads, cross at right angles.
Terminal Crimping
Use the correct crimping tool for each type of terminal. Do a pull test on a
sample wire and terminal to verify that the crimp is sound. In theory the wire
should break before the wire pulls out of the crimp.
Most crimp tools are only designed for a certain range of wire sizes so be sure
to test the crimp with the particular wire size being used.
Soldering the terminal is a last resort if the correct crimping tool is not
available. Soldering will cause a stress point where the solder wicks up the
wire which is likely to fracture unless all movement is avoided. Solder flux can
also cause corrosion and may affect the contacts.
Terminal Damage
The various connector terminals are easily damaged if probes are inserted
into them. Do not insert probes of any kind into the terminals. If checking a
circuit for continuity, gently touch the side of the terminals only, or preferably
attach a mating connector.
MoTeC Installation 21
Wire Splicing
Preferably use a crimp splice. If soldering a wire splice, wire movement near
the joint must be avoided otherwise a fracture may occur at the stress point
created by the solder. Use heatshrink sleeving to insulate and provide support
to the wires.
Wire Strain
Avoid pulling the wires tight at the connectors.
Wire Movement
Avoid wire fatigue by tying the wires down close to the connectors.
Heat
Keep the ECU wires away from the exhaust system.
Fuel System
An ideal race fuel system is shown below
Lift Pump
The Lift Pump is a low pressure pump designed to lift the fuel from the fuel
tank to the swirl pot (header tank).
The Lift Pump must be capable of flowing enough fuel for full power operation.
22 Installation MoTeC
Swirl Pot
The swirl pot (header tank) maintains a reserve of fuel to avoid fuel starvation
to the engine during cornering and acceleration. Fuel starvation can also
cause damage to the pressure pump as it relies on the fuel for cooling,
lubrication and speed limiting.
The swirl pot also forms a header tank for the pressure pump since the
pressure pump is not capable of lifting the fuel from the tank if the tank is
lower than the pump. Place the swirl pot at the same level, or higher than the
pressure pump.
Pressure Pump
The Pressure Pump is a high pressure pump that must be capable of
delivering the required amount of fuel at the correct pressure at full power.
It is very important that the pump is capable of maintaining the correct fuel
pressure at full power otherwise the engine could be damaged due to a lean
mixture.
A 600 hp engine requires a flow rate of approximately 250 lb/hr for petrol or
gasoline.
Notes
• The pressure pump must be lower than the outlet of the swirl pot.
• Prime the pump with fuel before use.
• The pump’s flow capability is dependant on the required pressure, the flow
capability of the pump will be less at higher pressures. A small pump will
maintain correct pressure at light load but will not maintain correct
pressure as the flow requirement increases.
• On boosted engines the pressure required from the pump increases with
boost pressure because the regulator maintains constant pressure above
manifold pressure.
• Avoid running the pump dry as this may destroy the pump.
Filters
The filters are necessary to ensure that the fuel pump is not damaged and to
ensure that the injectors do not become blocked.
• The strainer before the pressure pump is essential to prevent the pump
from seizing. A strainer is used because the pressure pump won’t suck
through a paper filter.
MoTeC Installation 23
Fuel Lines
The fuel feed lines must be high pressure type and should be at least 8mm
(5/16 inch) diameter. The return lines should also be at least 8mm (5/16 inch)
diameter to ensure that the fuel is easily returned to the tank.
Use proper high pressure hose clamps to ensure that the lines do not blow off
under pressure.
Keep the fuel lines as cool as possible to avoid fuel vaporisation. The
temperature of the fuel will also affect the mixture due to the change in fuel
density.
Avoid fire risk by ensuring that all hoses and fittings are in good condition and
installed correctly.
Fuel Rails
The fuel rails must be free of any debris that could block the injectors. Welded
fuel rails can often cause a problem unless they have been properly treated to
remove all scale and debris and even then they may corrode and cause
problems. Aluminium fuel rails mounted directly on the injectors are
recommended as they do not suffer these problems.
The fuel rails must have sufficient volume to minimise fuel pressure pulsation
and resonance problems.
Fuel Pressure Regulator
The fuel pressure regulator maintains constant fuel pressure to the injectors
which is necessary to ensure constant metering of the fuel. Any variation in
the fuel pressure will cause a corresponding mixture change.
The fuel pressure regulator should be mounted at the end of the fuel rail so
that fuel is always flowing through the rail. This helps to avoid vapour locks.
Adjustable pressure regulators are available.
If Using Manifold Pressure Load Sensing
Connect the regulator port to the plenum as this ensures that constant
pressure is maintained across the injectors.
Note that this will cause the fuel pressure required from the pump to increase
as the manifold pressure increases.
24 Installation MoTeC
If Using Throttle Position Load Sensing
Leave the regulator port open to the atmosphere, unless the MAP sensor is
connected to the manifold as is recommended when using idle speed control,
in which case the regulator port should be connected to the manifold.
Fuel Injectors
The fuel injectors meter the fuel by opening for a short but defined time once
per engine cycle (sequential operation).
The injectors must be wired in the firing order of the engine.
Sizing
The size of the injector determines the maximum amount of fuel that can be
delivered to the engine.
As a rule of thumb the engine will require about 5 cc per minute per horse
power for petrol or gasoline. For alcohol a higher flow rate is required.
For example: A 600 hp V8 will require each injector to flow at least
600 hp x 5 cc/min/hp/8 injectors = 600 x 5/8 = 275 cc/min.
Note that the flow rate of any particular injector is dependant on the fuel
pressure applied to it.
Sometimes oversize injectors are used to maintain lower duty cycles, since
high duty cycles reduce the effect of sequential injection, because the
injectors are turned on for most of the time. However this can affect idle
fuelling as the injector may have trouble delivering small amounts of fuel.
Flow Rate Matching
The flow rate of injectors can vary between injectors of the same type. It is
advisable to match the flow rates of injectors by testing each injector on a flow
bench.
Fuel Pressure
The fuel pressure applied to the injector will directly affect the amount of fuel
that the injector delivers. Doubling the pressure however only increases the
fuel flow by about 1.4 times.
Most injectors will only operate correctly over a certain range of fuel
pressures. If the pressure is too low then the fuel may not atomise properly. If
the pressure is too high then the injectors may not turn off fully. Many injectors
Loading...