Summary of Software

ProECU software has been introduced to allow reprogramming of the factory ECU in order to tune the necessary components of the calibration in order to allow for modifications and increases in power.  This is not a standalone repalcement ECU so you shouldn't run into the associated issues or disadvantages of setting up a purpose-built ECU and control system from scratch.

The software allows easy control over most factory parameters including:

• Boost Targets and wastegate control

• Target AFR

• Ignition Timing

• Fuel Delivery including fuel pump calibration (using the same style pump as OEM)

• Airflow Measurement and fuel compensation

Supplemental Content

Platform Specific

General

• ECU Programming Overview

• Software Help and How-To

• EcuTek Knowledge Base

Programming

For information on how to program as well as flash recovery, check out.

• ECU Programming Overview

• How to Recover an ECU
  
  

For more software guides check out:

• Software Help and How-To

Tuning Guide

Always Take a Baseline

Before performing any tuning or hardware modifications, take a baseline log (and dyno run if possible) of the car’s current performance. DeltaDash may be used to log parameters such as ignition timing, knock correction, injector duty, boost pressure, EGT and engine RPM.

Once a baseline reading has been taken, subsequent modifications may be measured against the original.

Before embarking on any modifications to engine or ECU, satisfy yourself that the car has no faults or problem to begin with. Check for diagnostic trouble codes using DeltaDash and ensure any prior modifications are compatible with the work that you have been asked to carry out. E.g. If a customer has requested that a larger turbo be fitted and tuned, but the up-pipe catalytic converter is still present, then it will not be safe to carry out this work.

Tuning for Power

For a given engine configuration, there are a number of tuning techniques that allow more power to be produced.

Increase Air Flow

There are a number of ways to increase the air flow through the engine:

Exhaust Systems

By making the exhaust system less restrictive, air flow may be increased.

Boost Pressure

Increasing the boost pressure that the turbo produces will force more air through the system.

Bigger Turbo

Larger turbo are capable of flowing more air, with less exhaust gas restriction, at the expense of greater lag and lower torque at low revs.

Up-rated Intercoolers

Intercoolers that raise the density of the charge (by reducing temperatures) or decrease the pressure differential across them (by being freer flowing) increase air flow.

Induction Kits

Induction kits that are less restrictive than standard will allow more air to flow. However, many induction kits upset air flow metering and require careful handling.

Advance Ignition Timing

The more ignition advance that can be applied without detonation, the more power will be produced. This is why the ECU runs highly active ignition timing that always attempts to run on the point of detonation.

Most mechanical changes made will have an influence on the amount of advance that can be applied. Extensive use of live map access to monitor ignition timing can yield good results.

The richer the fuel mixture, the more ignition timing can be run. Ignition timing and fuel mixture are interrelated, so be careful when altering one – monitor the other. High RON/MON fuel will also allow more ignition advance.

Optimise Air Fuel Ratios

Maximum power is produced at an AFR of 12.5:1, approximately. Richer mixtures than this provide cylinder cooling and lower EGTs. Leaner mixtures are more economical but raise EGTs and are more susceptible to detonation.

Modification List

Results of changes to mechanical configurations of the engine must be optimised by ECU tuning. In some circumstances, the fitting of high performance parts will reduce engine power until compensated for in the ECU – a very common example of this is induction kits. Fitting of an induction kit with no ECU compensation mapping often results in poor turbo spool up, hesitation, and lean mixtures and in extreme circumstances engine failure. However with the same kit fitted, but with the ECU correctly mapped, will produce worthwhile power improvements with none of the problems detailed above.

In the following sections, a number of common modifications are listed. Under each heading, the parameters that may need attention are described. This data is provided to assist the tuner when ECU tuning to account for hardware modifications.

The ECU changes suggested are to compensate for the mechanical changes. In order to produce further power, the tuner should refer to the standard power tuning rules above.

Under each mechanical modification heading below, the parameters to modify are split into two sections:

The ‘Compensation’ section details what must be changed for correct operation. For example, changing an exhaust downpipe will cause the boost pressure to become unstable. Alteration of the wastegate duty cycle map will bring this back under control The ‘Tuning for Power’ section details what else may also be modified in order to attain further power increases. For example, when changing the up-pipe, there will no longer be a cat between the engine and turbo. This then allows the fuel mixtures to be leaned out slightly, since there is no longer a cat whose temperature must be safeguarded.

Exhaust Backbox(Muffler)/Centre Section/Downpipe Change

Compensation

Turbo Wastegate Duty Cycle

Freer flowing exhausts require lower wastegate duties to produce the same level of boost.

Load Scaling of Ignition & Fuel Maps

Higher loads will be produced with a better exhaust. Fuel and ignition maps may need to be rescaled for higher loads.

Tuning for Power

After this modification, standard techniques of raising boost and advancing ignition may be used.

Up-Pipe

Compensation

Turbo Wastegate Duty Cycle

Freer flowing exhausts require lower wastegate duties to produce the same level of boost.

Load Scaling of Ignition & Fuel Maps

Higher loads will be produced with a better exhaust. Fuel and ignition maps may need to be rescaled for higher loads.

Tuning for Power

Fuelling

Once the up-pipe cat has been removed, the fuelling may be leaned out slightly, since there is no temperature sensitive catalyst to protect.

After this modification, standard techniques of raising boost and advancing ignition may be used.

Induction Kits & Intake Pipes

Compensation

Air Flow Sensor Scaling / Fuel Mapping

The correct way to compensate for an induction kit is to modify the air flow sensor scaling to correctly relate air flow sensor voltage to mass air flow. However this technique requires precise measurement of the air flow of the new induction kit. Whilst not ideal, a similar result may be obtained by filling in any holes in the fuel map by watching lambda colouring.

Turbo Wastegate Duty Cycle

A freer flowing induction system will allow the turbo to spool more quickly. Wastegate duty cycles may need to be decreased to keep boost pressures under control.

Tuning for Power

After this modification, standard techniques of raising boost and advancing ignition may be used.

Turbo

Compensation

Turbo Wastegate Duty Cycle

The relationship between boost pressure and duty cycle required are different for each model of turbo and actuator. Duty cycles may need significant alteration to produce the desired results

Load Scaling of Ignition & Fuel Maps

With the higher loads produced by the increased air flow of the turbo, the fuel and ignition maps will need to be rescaled.

Tuning for Power

Boost Pressure

A higher flow turbo will be capable of higher boost pressure

Ignition Timing

Ignition timing may be advanced, since the turbo will cause less exhaust gas restriction, decreasing EGTs.

Fuelling

Because of the lower EGTs for a given air flow, fuelling may be able to be leaned out slightly.

Injector Change

Compensation

Injector Scaling

Tuning for Power

Boost Pressure

Once more fuelling capacity is available, boost pressure may be increased without compromising desired fuel mixtures.

Intercooler

Compensation

Turbo Wastegate Duty Cycle

Freer flowing intercoolers require lower wastegate duties to produce the same level of boost, since the pressure drop across the intercooler is lower.

Tuning for Power

Boost Pressure

Boost pressure may be increased, since a larger capacity intercooler will be more able to reduce the higher charge temperatures produced by the turbo.

Ignition Timing

This may be advanced since charge temperatures will be lower with a larger intercooler.

Major Engine Internal Modifications

When altering the capacity, strength or cams of the engine, several parameters may need to be modified.

Rev Limit

Boost Pressure

Turbo Wastegate Duty Cycle

Ignition Timing Fuelling

Related Parameters

The sections below describe ECU parameters which are interrelated. For example under the boost pressure heading are listed all the parameters that should be considered when altering boost.

Boost Pressure

When choosing the desired boost pressure, the specification of the turbo and other components should be considered, so as not to over speed or overheat the turbo.

Boost Limit

When altering the desired boost pressure, ensure that the boost limit is set high enough so that fuel cut does not occur under normal circumstances. Set the boost limit a minimum of 3 PSI (0.2 bar) above the highest desired boost pressure.

Turbo Wastegate Duty Cycle

Max Duty Cycle

Turbo Dynamics

Ignition Timing

Main Ignition Map

Ignition Advance Map

Fuelling

Lo Det Fuel Map

Hi Det Fuel Map

Boost Control

Initial Wastegate Duty

The initial duty cycle values to achieve ‘Desired Boost’. This map references both RPM and throttle position. The wastegate duty chosen from this map is then altered by compensation maps for atmospheric pressure, temperature and turbo dynamics, before being applied to the actuator. It is recommended that the Wastegate Initial map values are always set about 10% below that of the corresponding Max Wastegate values.

It can be helpful to use lesser duty cycles values as throttle position decreases to make the car ‘more linear’ in relation to throttle input (Be sure to scale all related maps accordingly).

Maximum Wastegate Duty

This map controls the maximum wastegate duty that the ECU can use for a given RPM and throttle position. The values in this map must be great enough to permit the required boost to be achieved, but low enough so as not to allow overboost to occur.

Depending on ECU version, there may be one or two copies of this map. If so, both maps should be set the same by copying and pasting their contents.

Desired Boost

This map controls the amount of boost pressure that the ECU tries to attain, based on RPM and throttle position. It is wise to tail off boost at high RPMs to preserve engine reliability.

Depending on ECU version, there may be one or two copies of this map. If so, both maps should be set the same by copying and pasting their contents.

Boost Limit

Determines the boost limit based on current atmospheric pressure. This is necessary since all boost pressure values are absolute, not atmospheric relative. When altering this map, ensure that all values are altered i.e. to add 0.1bar to the boost limit, add 0.1bar to all values in the map.

If the boost limiting is triggered, fuel cut will occur to protect the engine.

Boost limiting is triggered when the boost pressure exceeds the boost limit for a short period. To prevent fuel cut, the boost pressure must quickly drop to 0.13 bar (2 PSI) below the boost limit. This effectively allows a brief spike to occur without fuel cut, with fuel cut occurring if this high level is sustained. Because of this, the boost limit set must be at least 0.15 bar above the maximum sustained boost pressure to prevent fuel cut.

Boost Solenoid CEL MAP Threshold

This map determines the absolute manifold pressure at which the turbocharger wastegate solenoid check engine light is triggered.

If the boost limit is raised, the values in this map should be increased accordingly.

Turbo Dynamics

These maps control the rate at which the wastegate duty cycle is altered in order to produce the desired level of boost. These maps determine the percentage of wastegate duty that is added or subtracted from the current duty, based on the magnitude of error between actual boost and desired boost.

Small values in these maps will cause the boost to build very slowly, but are very safe, since there will be no over boost. Higher values in these maps will causes boost to rise more aggressively, but must be carefully set to ensure that over boost and oscillation do not occur.

Proportional Burst

Initial values of compensation are taken from this map to give a burst of duty when stamping on the throttle for example.

Larger values can be helpful for increasing the response with larger turbochargers.

Proportional Continuous

Subsequent compensation values are taken from this map. Values in the continuous map tend to be smaller than in the burst map.

Modifying this map can be useful when the wastegate duty maps have been properly scaled, and excessive surging is occurring.

Integral Positive & Negative

These maps add or subtract duty cycle depending on how long the boost error has persisted for, as well as how large the error is. The values in these maps are small, but help to maintain faster responding control of boost. Also, there may be two integral maps, split into positive and negative regions. One is used when boost is too high (the negative compensation map); the other is used when boost is too low (the positive compensation map).

When using a different turbocharger or more boost, it may be helpful to modify these maps to achieve proper boost correction without surging.

RPM below Which Turbo Dynamics are reset

Below this RPM, the ‘Turbo Dynamics’ trims will be reset.

MAP Below Which Turbo Dynamics are reset

Below the Load, the ‘Turbo Dynamics’ trims will be reset

Minimum / Maximum Turbo Dynamics Integral

The Minimum and Maximum Wastegate Duty compensation the ECU is allowed to add or subtract to Primary Wastegate duty.

If (for example) the Initial Wastegate Duty map is filled with 70% and the Maximum Wastegate Duty set to 90% (assuming Minimum = -50% and Maximum = +10%) then the maximum wastegate duty that can ever be seen would be 80% (Initial 70%+Max Integral Compensation of 10%) assuming there is a negative boost error.

Compensation

Desired Boost

Coolant Temperature Compensation

Controls how the desired boost pressure is scaled according to the current coolant temperature of the engine. This may be used to protect the engine from damage at very high/low temperatures by dropping the boost away.

Atmospheric Pressure Compensation

Controls how desired boost pressure is scaled depending on the current atmospheric pressure.

Air Temperature / RPM Compensation

Controls how desired boost pressure is altered depending on current atmospheric pressure.

Primary Wastegate Duty

Atmospheric Pressure Comp.

Controls how the duty cycle is scaled, according to the current atmospheric pressure. E.g At high atmospheric pressures, it is easier for the turbo to build boost, since the air it is compressing is denser. This means that a lower duty cycle is required at sea level for example, when compared with higher altitudes, in order to achieve the same boost pressure.

Air Intake Temperature Comp. (AIT)

Controls how the duty cycle is scaled according to the current air temperature, as measured at the air intake of the car. At low temperatures, air is denser, meaning that a lower duty cycle is required in order to produce a given level of boost.

Coolant Temperature Comp.

Controls how the duty cycle is scaled according to the current coolant temperature of the engine. This may be used to protect the engine from damage at very high/low temperatures by dropping the boost away.

Drivetrain Based Boost Controls

These maps allow adjustment of boost parameters for each gear. These values apply to manual transmission cars only. Some ECUs do not have this feature, whilst some ECUs only have one of the two maps below.

Per Gear Based Control

Boost Compensation

This map allows the desired boost for each gear to be adjusted.

Wastegate Duty Compensation 

This map allows the wastegate duty to be adjusted for each gear. For example, lower gears require a higher wastegate duty in order to produce the same level of boost. This map could be used to address this.

Disable Speed

This is the vehicle speed at which per gear compensation is switched off. This may need altering before the above maps will take effect.

Boost Based Speed Limiting

Allows a very soft limiting of vehicle speed by controlling boost pressure – the boost pressure gradually drops away to spring tension (e.g. 7 or 8 PSI on a WRX) as the upper limit is approached. Values are in km/h. Multiply by 5/8 for MPH.

This feature is very useful, but is set very high on the standard ECU. Many independent tests have shown that the standard top mount intercooler receives little air flow at high vehicle speeds and charge temperatures rise rapidly – just watch the knock correction as the car is driven hard in 4^th & 5^th gear for confirmation. This feature may be used to restrict boost pressure at very high speeds, and could save an engine from damage.

If there is a positive boost error (I.E. Desired Boost is 2.0bar and actual boost is 2.4bar) then the Primary Wastegate Duty can be reduced by up to 50% until Desired Boost pressure is achieved.  This is why it is important to keep the Initial Wastegate Duty tables about 10% less than the corresponding values in the Max Wastegate Duty Tables.

Camshaft Timing

VVT – Intake Cam Advance Angle

Specifies the intake cam advance, based on engine RPM and load.

Careful dyno testing and data logging is required for effective alteration of this map. Timing changes will affect turbo spool up, peak torque and power.

This map is only available on cars with variable valve timing – generally STIs and some JDM WRXs.

Fuelling

The fuel maps contain AFR data, based on RPM and calculated engine load. Values that are leaner than stoichiometric (for gasoline this is 14.7 parts air to 1 part fuel) cannot be specified. When altering fuel maps, bear in mind that the AFR numbers are theoretical. What this means is that this number is dependent on several calibration maps (Air Flow Scaling, Injector Size, Temperature Compensations… just to name a few). For this reason, blindly changing the AFR data in the table to match real world numbers can be catastrophic. We recommend making several ‘baseline’ pulls while data logging to see where the fuelling (among other parameters) is. Then make small changes as necessary.

Depending on the ECU version, there may be multiple fuel maps. Make sure that ‘like’ maps are kept constant (i.e. if there are two ‘Lo Det’ maps, they must always be identical).  A quick way to make changes would be to modify one map and then copy the entire map into the other map(s). This is achieved by following these steps: Under ‘Edit’ menu, use the ‘Copy Entire Map to Clipboard’ and ‘Paste Entire Map from Clipboard’ function.

Fuel Strategies

There are five strategies used in Subaru ECUs, these control when the maps are used. Diagrams of these strategies can be found in the appendix. Each of the maps has a suffix at the end of the name which corresponds to the strategy type E.g. Fuel Map S1 would be Strategy 1, Fuel Map Hi Det #1 S5 would be Strategy 5

Fueling Strategy 1

Target AFR = Fuel Map Base S1 + ( Advance Multiplier * Fuel Map Enrichment S1 )

This strategy uses two maps, Fuel Map Base which contains the target AFR and Fuel Map Enrichment, which provides an enrichment value based on the amount of knock the ECU has detected. As the Advance Multiplier increases from 0 to 1 the greater the enrichment value from the Fuel Enrichment Map will be applied.

Tuning

Tune the base map to be your ideal AFR target, and fill the values in the enrichment map to ensure the engine has enough fuel when knock is detected.

Fueling Strategy 2

IF Advance Multiplier < Fuel Map Advance Multipler Threshold THEN Target AFR = Fuel Map Lo Det

IF Advance Multiplier > Fuel Map Advance Multiplier Threshold THEN Target AFR = Fuel Map Hi Det

This strategy uses two maps, Fuel Map Hi Det and Fuel Map Lo Det. The ECU will use one of the two maps based on the amount of knock the ECU has detected. The Advance Multiplier is used to switch between the two maps, once it has exceeded the 1D value Fuel Map Advance Multiplier Threshold, the ECU will switch from Fuel Map Lo Det to Fuel Map Hi Det.

Tuning

Tune the Hi Det map to be richer than the Lo Det map to make sure the engine gets enough fuel when knock is detected.

Fueling Strategy 3

IF Advance Multipler < Fuel Map Advance Multiplier Threshold

THEN Target AFR = ( Fuel Map Base * Interpolation Factor ) + ( Fuel Map Lo Det * ( 1 – Interpolation Factor ) )

IF Advance Multiplier > Fuel Map Advance Multiplier Threshold

THEN Target AFR = ( Fuel Map Base * Interpolation Factor ) + ( Fuel Map Hi Det * ( 1 – Interpolation Factor ) )

This strategy has 3 maps, Fuel Map Base, Fuel Map Lo Det and Fuel Map Hi Det. The ECU always uses the Fuel Map Base in calculation and will interpolate towards Fuel Map Lo Det and Fuel Map Hi Det. The

Advance Multiplier is used to switch between which map is being used and will switch between the Fuel Map Lo Det and Fuel Map Hi Det once it has exceeded the 1D value Fuel Map Advance Multiplier Threshold.

Tuning

Set the base map to be similar to the Lo Det map. The values in the Lo Det and the Base map should be your ideal ignition timing targets. Set the values in the Hi Det map to be lower than those in the Base map to ensure ignition retard when the ECU detects knock.

FuelingStrategy 4

IF previous values of Fuel Map Hi Det > Fuel Map Lo Det THEN Target AFR = Fuel Map Hi Det

IF previous values of Fuel Map Hi Det < Fuel Map Lo Det THEN Target AFR = ( Fuel Map Lo Det * Interpolation Factor ) + ( Fuel Map Hi Det * ( 1 – Interpolation Factor ) )

This strategy has 2 maps, Fuel Map Lo Det and Fuel Map Hi Det. If the value in Fuel Map Lo Det is richer than that in the Fuel Map Hi Det then the ECU will use just the Fuel Map Lo Det, otherwise it will interpolate between Fuel Map Lo Det and Fuel Map Hi Det based on the Advance Multiplier.

Tuning

Tune the Hi Det map to be richer than the Lo Det map to make sure the engine gets enough fuel when knock is detected.

Fueling Strategy 5

IF Advance Multipler < Fuel Map Advance Multiplier Threshold THEN Target AFR = ( Fuel Map Lo Det ECO * Interpolation Factor ) + ( Fuel Map Lo Det * ( 1 – Interpolation Factor ) )

IF Advance Multipler > Fuel Map Advance Multiplier Threshold THEN Target AFR = ( Fuel Map Hi Det ECO * Interpolation Factor ) + ( Fuel Map Hi Det * ( 1 – Interpolation Factor ) )

This strategy is also used in vehicles without the ECO mode. In these instances the Fuel Map ECO maps will be omitted and it will revert to Strategy 2

This strategy has 4 maps, Fuel Map Lo Det #1, Fuel Map Lo Det #2, Fuel Map Hi Det #1 and Fuel Map Hi Det #2. The ECU interpolates between the Lo Det Maps or the Hi Det Maps separately, and will switch between them when the Advance Multiplier exceeds the 1D value Fuel Map Advance Multiplier Threshold.

The Interpolation factor between #1 and #2 is based on the Subaru ECO mode. When the car is in ECO mode it will use map #1 (previously named Fuel Map ECO mode), but as you increase engine load and speed it will begin interpolating towards #2. 

This strategy is also used in vehicles without ECO mode, in these instances Fuel Map Lo Det #1 and Fuel Map Hi Det #1 are not listed as they are not used in calculation. For these vehicles, tune the ECU in the same ways as strategy 4.

Tuning

Tune the Hi Det map to be richer than the Lo Det map to make sure the engine gets enough fuel when knock is detected. The ECO mode can be set leaner than the Hi Det or Lo Det maps to ensure the engine is running as economically as possible, when the engine goes into open loop mode it will begin interpolating to the richer maps.

Lo Detonation  

Lo Detonation map(s) is the main active fuel map under normal engine operation, this map is the base for all fuelling changes. Note that the actual injection time is varied depending on ‘calibration’ maps that are described later in this section. When tuning a car, be sure to scale the Load and RPM data sites as necessary to facilitate the added (or subtracted) airflow values/RPM that you will be using. If either of these values is exceed, the computer will retain the value on the last cell (either Load or RPM, which ever has been exceeded or both).  This can be detrimental as there is no longer active fuel control.

This map is used when the engine ‘Advance Multiplier’ is higher than the value in ‘Fuel Map Knock Switch Threshold’ Map.

For most applications, modifying the ‘Lo Det’ fuel map is where most of your ‘fuel tuning’ time will be spent.

Hi Detonation 

Lo Detonation map(s) is the main active fuel map under abnormal engine operation, this map is the base for all fuelling changes when severe Detonation has occurred. The cause of which can be due to poor tuning, lower octane fuel than recommended, etc. This map should have similar scaling to the ‘Lo Det’ fuel map(s).

This map is used when the engine ‘Advance Multiplier’ is lower than the value in ‘Fuel Map Knock Switch Threshold’ Map.

For the average tuning, there is not much of a need to modify these values, but you should always check to insure that theses values are ‘richer’ in the higher load/RPM sites than the ‘Lo Det’ map(s).

Idle

Fuelling Engine is idling, which is dictated by two throttle position based maps. 

These two maps are located in the ‘Other Maps’ section.

Fuel Map Knock Switch Threshold  -  Data Values

Determines when the ECU will switch between the fuel maps (‘Hi Det’ and ‘Lo Det’) dependent on the ‘Advance Multiplier’ value.

For standard applications, this map will not need to be changed.

Overrun Fuel 

Engine deceleration fuelling controls

Cut-Off Delay

The amount of delay before fuel injectors are ‘switched off’ after throttle is released. At lower RPM and load, this delay time is higher to prevent ‘jerkiness’ at small throttle percentages.

If you are having issue with poor on-off-on throttle response, making these values larger can help smooth the response. As the delay times become larger, fuel consumption will go up (more fuel being used, due to injectors remaining on for longer periods).

Fuelling Restore RPM

RPM at which the fuel injectors are switched back on in relation to coolant temperature. The colder the engine is the more likely it is to stall. To prevent this, the injectors will need to be switched on earlier (higher RPM) to prevent ‘flame out’ as coolant temperature decreases.

Due to low airspeed at idle, coolant temperature is a good indicator of ‘in cylinder’ air temperature.

Fuel Injector Sizing

One or more of these will likely need changing when a larger or non-standard injector is used

Injector Flow Scaling   -  Data Values

Allows the flow rate of the fuel injectors used to be specified. Due to the amount of variables that calculate actual fuel injector opening time (at the injector) this number does not always equal the actual injector size. It is also important to reduce the Delayed Open Loop Fueling Load Threshold values as these are Injector m/s and will have to be reduced when bigger Injectors are fitted to ensure Open Loop operation is correct.

When changing from standard WRX injectors to ‘pink’ STI injectors, the scaling should be changed from 380cc to 500cc to compensate for the higher flow rate of the injectors. If this is done correctly, then virtually no adjustment of the fuelling maps will be required.

Injector Battery Voltage Compensation  -  2D Map

This map controls the injector opening time compensation for battery voltage. Each injector type has different mechanical characteristics, which alters the amount of time that it takes for the injector to open at a given voltage. This map allows the injector lag time to be adjusted when using a non-standard injector.

When changing to non-Subaru injectors, it is quite common to change the ‘lag time’ for the injector to operate properly. EcuTK has set up several dealer forums that are a good resource for finding out Battery Voltage Compensations for most injectors.

Start-up Fuelling

Fuel compensations for starting and warm up periods. It is unlikely that these will need to be changed if the ‘Air Flow Scaling’ and Injector parameters have been set up properly. 

Modification of these parameters should only be undertaken when ‘base’ fuelling parameters have been adjusted.

Cranking Fuel

In order for an engine to start, there needs to be enough fuel added to achieve proper atomization.

If the injectors and air flow sensor have been properly scaled, you will not need to make any changes in these maps.

RPM/Cool Temp (AT/MT)

Amount of fuel added by coolant temperature and rpm.

Lower air speeds make it difficult for the fuel to remain suspended in the air stream when the engine temperatures are low.

MAP Component

Amount of fuel added dependent on manifold pressure (absolute).

Throttle Component

Amount of fuel added in relation to throttle position.

There will be less fuel at higher throttle position to facilitate starting when the engine becomes flooded.

Coolant

Amount of fuel added in relation to coolant temperature.

Post Start Enrichment – ‘Warm Up Enrichment’

Amount of extra fuel added after car is started. To prevent stalling after initial start up, extra fuel is injected for a determined ‘time limit’. As this ‘time limit’ comes to an end, additional fuel is reduced. 

When this time has expired, the closed loop lambda control is started (if minimum coolant temperature for closed loop has been met).

Throttle Based Acceleration Enrichments (Delta)

Commonly known as ‘Accelerator Enrichments’

Delta

The enrichment factor applied dependent on the delta of throttle movement (%). If the throttle is increased from 15% to 40% (delta is 25%), an enrichment factor will be calculated from the lookup value next to the 25% column. Less fuel will be injected at lower percentages of throttle movement, because the rate of ‘instant’ air flow increase is low, at higher throttle movement percentages, the increase in fuel will need to be much higher, due to the larger amount of air change (which in turn, requires more fuel). The MAF is not able to compensate for the ‘quick in time large air volume’ change that occurs with instantaneous throttle movements.

Too much fuel added to this will ‘bog’ the car when the throttle is depressed, too little will cause the car to ‘buck’.

RPM

The enrichment added at a given RPM. Engine speed based fuelling enrichment/enleanment that is not affected by changes in engine load. This will apply a ‘global’ fuelling change at a given RPM (interpolated) regardless of engine load.

Boost Error

The enrichment applied to the amount of ‘Boost Error’. If desired boost is 2.20bar and actual boost pressure is only 1.5bar (boost error of 0.7bar), then extra enrichment/enleanment may be applied.

Coolant Temperature

The percentage of fuel added during warm up.

Lambda Control

Open Loop will ONLY commence once ‘Delayed Open Loop Throttle Threshold’, ‘Delayed Open Loop Load Threshold’, ‘Maximum Closed Loop Vehicle Speed’, ‘Maximum Closed Loop RPM’, or ‘Maximum Closed Loop EGT’ values have been met/exceeded. Then the time before switchover is determined by the ‘Engine Operation Period Thresholds’ map which determines the value to be used for time delay from the ‘Delayed Open Loop Fuelling’ map.

Engine Operation Period Thresholds

The values on this map represent the amount of time that the engine has been running. These values are used to determine which one of the four sets of values in the ‘Engine Operation Period Thresholds’ is activated. This map is referenced once the other related closed to open loop parameters have been met (Throttle Position, Coolant, Load, Etc…).

For ECUs that are staying in closed loop for extended periods of time when in higher loads (e.g. positive manifold pressures), it is best to modify the map below to speed the ‘switchover time’ and leave the ‘Engine Operation Period Thresholds’ map alone.

Open Loop Delay Period

Determine the elapsed time before the ECU switches to open loop fuelling. There are four sets of values, each one of these sets contains four values. These values are: AT High Altitude, MT High Altitude, AT Sea Level, and MT Sea Level. Which set is chosen is determined by the ‘Engine Operation Period Thresholds’ map, then which value is determined by the transmission type and altitude.

On the USA 2004/2005 WRX, the delay period can be reduced (or set to 0) to speed the time in which open loop is activated. These cars have a much longer delay set to reduce emissions. If large values are left in this table then you may find you have Closed Loop (14.7:1 AFR) on full power for a one or two seconds which will cause detonation and high EGT!

Closed Loop

Closed loop fuelling control allows the ECU to make positive or negative changes to the fuel injection time (trim) to keep the air to fuel mixture at 14.7:1, which for unleaded gasoline is the ‘perfect burn’, creating only carbon dioxide and water as by products. This actual air to fuel ratio will change as the type of fuel is changed, but it is always referred to as stoichiometric regardless of the fuel being burnt.

All of the other maps trigger a time cycle that is determined by the ‘Engine Operation Period Thresholds’ map and ‘Open Loop Delay Period’ maps before switching to open loop (or ‘unregulated’ fuelling control).

Fuel Map Result before Ramping Instead of Jumping

The transitional AFR value used between fast changing Closed to Open Loop. If the engine is held at higher engine speed with low load (Closed Loop – Lambda 1) and then full throttle is suddenly applied the AFR can change from 14.7:1 (Lambda 1) to possibly 10:1 AFR (Lambda 0.70) very quickly. So a transition value of 0.10 Lambda from Lambda 1 will be 0.9 lambda = 13.2:1 AFR.

Max Closed Loop Vehicle Speed 

The maximum speed allowed for closed loop control, above this speed the ECU will switch to open loop.

Max Closed Loop EGT

The Maximum EGT allowed for closed loop control, when this EGT is exceeded the ECU will switch to Open Loop.

Not all models are fitted with EGT but it is good practise to reduce these values even if an EGT sensor is absent.

Max RPM

The Maximum RPM the ECU is allowed to use closed loop.

This map can be helpful for obtaining better highway fuel economy at lighter loads. Be sure to monitor EGTs when modifying this parameter. This can also be helpful for disabling the closed loop control of the ECU for Motorsports applications.