DRS EFI Engine Control Support nEditor Support Article

This document is written for the purposes as a software interpretation guide, not as an engine calibration guide.

Fuel Injection

The fuel map is used for calibrating the amount of fuel the engine requires within various load sites. The fuel map can be viewed in either a numeric table or in 3D graphic mode. Either method allows for real-time editing. The value fond in the load site is the injection pulse width (or amount of time the injector is open for a given pulse). Load is typically measured in Hg for forced induction engines, whereas for naturally-aspirated engines it is typically favored to use the throttle sensor as a load reference. For any engine that is fitted with large duration camshafts it is favorable to default to use the throttle sensor for load (typically referred to Alpha N), as this will offer the highest resolution. Large duration camshafts will usually reduce the amount of vacuum available for a MAP sensor to measure from closed throttle to atmosphere, therefore reducing the accuracy of the sensor as a load calculator. MAF sensors also will work less effectively in these conditions as pulsations in the air stream will act as disturbances. While adjusting the fuel map the user can make small or large changes in a given load site, such as while using the Active Cursor function, or across a large section of the map by highlighting with the cursor. See "Interpolation" and "hot keys" in your EFI Help File as a reference as well. Note that the injection value in a given load site is the raw value before any corrections are applied. See Corrections Tables for applicable offsets. The actual injection value in Data Controls represents the summation of any corrections applied. Corrections for altitude (density) and temperature will aid in determining the final injection value at any given time. These corrections as well as other corrections will be discussed in more detail later.

Injection Phase

This map is used for adjusting while the injection event occurs relative to crank angle in degrees after top dead center (ATDC). This map is also configured to be used in numeric or 3D graphic mode, with load, rpm, and degrees as the units in the load sites. This map offers a fine tuning aspect that is best to explore after most of the fuel map is calibrated. It is advised, in my experience, to not enter drastic differences in degrees between immediate load sites, as this is usually "unnatural" for most engines fuel requirements. It is also advised that tuning this map is done with a very controllable dyno that can produce Hp and Torque in real-time while the engine is "held" at a given amount of load. In experienced users should leave this table where the base map values are. See Corrections Tables for applicable offsets. The actual spark value in Data Controls represents the summation of any corrections applied.

Injection Bias

This map is not used for the Lotus systems and therefore will not be explained in depth. In summation, it allows for the "blending" of injection banks, such if 2 injectors were to be used per cylinder.

Injection f (Battery)

This is a preset calibration for injection pulse width as a function of battery voltage. As battery voltage decreases the raw injection time will increase per the curve in the map.

Cylinder Trims

This table allows for the trim (increase or decrease in %) for a given cylinder. The system supports up to 16 cylinders by default.

Fuel Constants

These calibrations are set up for typical values in all Lotus base maps. Some engines will require slight changes to the cranking pulse value in extreme conditions. Also note that some high octane fuels will exhibit different cold start characteristics. The fuel rev limiter can be set in this section as well. Most Lotus maps are pre-set for a fuel limit to exceed the spark limit. This is generally less abusive to the engine in most circumstances, and is less likely to create a lean condition. It is never advised to hold the engine at a limiter for any significant length of time. Other settings in the Fuel Constants section will be covered at a later time.

Spark Advance

The spark map is used for calibrating the spark event in units of degrees before top dead center (BTDC). The spark map can be viewed in either a numeric table or in 3D graphic mode. Either method allows for real-time editing. Load is typically measured in Hg for forced induction engines, whereas for naturally-aspirated engines it is typically favored to use the throttle sensor as a load reference. Note that the spark value in a given load site is the raw value before any corrections are applied. See Corrections Tables for applicable offsets. The actual spark value in Data Controls represents the summation of any corrections applied.
Dwell f (Battery)

This table is pre-calibrated specifically for the coils fitted to the 2ZZ engine and should not be altered. A change to this calibration could result in damage to the coil or performance degrade of the ignition.

Cylinder Trims

This table allows for the trim (increase or decrease in units of degrees BTDC) for a given cylinder. The system supports up to 16 cylinders by default.

Spark Constants

Settings in this section are advised to be unchanged as they are specific to the Lotus 2ZZ configuration, with the exception of the spark limiter if one needs to adjust maximum revs.

Boost Control

This section is functional in the software however currently not enabled for the Lotus system. This feature can be added and it is advised to contact a DRS Representative for tech support.

Boost Curves

This section provides 5 unique boost curves that can be calibrated by the end user for a target boost. By default, each boost curve is assigned to a gear (gears 5 and 6 will share the same curve). The boost curves can be viewed in either graphic or numeric mode, load v. rpm.

Boost Constants

These calibrations are typical values for the applicable base map. For forced induction engines it is advised to set the boost limiter to not exceed a boost level the engine can safely run at (measured in Hg).

Lambda Control

Lambda is defined as a ratio relative to stoicheometric. For example, Lambda 1.00 = 14.67 Air-to-fuel ratio. Any value below 1.00 is richer than stoich and conversely any ratio above 1.00 is leaner than stoich. The Lambda setpoints can be edited in either numeric or 3D mode.

The Lambda setpoint is relative to the engine being mapped. Typical forced induction engines will favor a Lambda ratio of ~ .810 to .820 (depending on the amount of boost and fuel octane rating). It is advised that a secondary wideband Lambda on a dyno is used as a reference during engine mapping if your system is fitted with a narrowband Lambda.
Systems with wideband Lambda sensors can benefit from the inherent response and accuracy. While running in closed-loop mode the max and min % is the limit in which the fuel map will be modified if the actual Lambda measured deviates from the Lambda setpoint.

Recommended channels to monitor in Data Controls are Lambda 1 (typically for narrowband) or Lambda 2 (typically used for wideband), Lambda Cor 1 (correction measured in %) and Lambda Setpoint.

Refer to Lambda Constants 1 setting to adjust the correction parameters and enabling parameters. The failed ratios are also adjustable and designed to allow the fuel map to ignore the Lambda in an event that the sensor reads incorrectly (i.e. a failed sensor or damaged wiring).

Lambda Constants 2 settings are preset with typical values for the PID function. It is advised that these settings are left unchanged if you are a novice with engine mapping. PID functions are also explained in the EFI Tech helpfile.

Currently supported Lambda sensors:

Bosch 4 wire

Innovate LC1

AEM wideband

NGK AFX wideband

DynoJet wideband

NGK (NTK) wideband via EFI NGK module


Idle Speed

The system is designed to adjust the OEM IAC (idle-air-control) fitted to all 2ZZ non-drive by wire engines. The settings in the Idle Constants are pre-calibrated (i.e. 400 Hz for the base frequency is advised to be left as such). However, the proportional and integral gain can be modified to accommodate specific idle behavior. For example, some engines fitted with light weight flywheels and/or larger duration cams may require adjustments to the gains. Typically less gain will result in a higher idle speed.

It is very important to make sure the Throttle limit is set at least 1 to 2 degrees above fully closed throttle position to allow for some error upon closing throttle. Too low of a value can result in faulty IAC circuit operation. Same concept applies to RPM limit, except that value should be about 500 RPM above desired maximum RPM during idle.

Speed f (Water T) is a curve that accelerates the engine speed while the engine is cold and will typically lower the idle speed as the engine warms up.

Note: Drive-by-wire cars will not use any of the functions in the Idle Speed section. These applications will be explained later in the DC Motor section.

Sensor Calibration

All Lotus systems come with the sensors pre-calibrated. It is only required to adjust the calibration of a sensor if a sensor is to be replaced from the standard specification. For customers who intend to use oil pressure, fuel pressure, and or oil temp inputs it is advised to contact a DRS Representative for the correct sensor and/or to make sure your map is updated for these sensors.

Note: If using a sequential gearbox a system channel can be used directly for gear position instead of using the gear calculator function. Cars equipped with sequential gearboxes can also benefit from using the "no-lift-sift" function included in the software. A strain gauge sensor is necessary to enable this function. It is advised to contact a DRS Representative to set up this function.

Sensor Calibration

Naturally aspirated engines include a 1 Bar MAP sensor by default (the input is typically used as a Barometric and/or Airbox pressure sensor). In this configuration the 1 bar MAP sensor is NOT to be used to measure manifold pressure (post throttle plate). Typical installations are with a hose installed directly to the Airbox or left open to atmosphere. The calibration constants MAP Scale (In/Hg) = 0.125 for this configuration. Forced induction engines systems include a 3 bar MAP sensor. The installation of this sensor is typically directly off a vacuum/boost reference. Exige S cars require an external outlet for this, and must be post blower to measure boost. The calibration constants MAP Scale (In/Hg) = 0.375 for this configuration.

Correction Tables

These correction tables are used for correcting either fuel or spark as a function of another condition. If your system is not using a given input to provide a correction simply leave the correction inactive.

Inj f (Airbox)

This correction is used as an Airbox pressure or Barometric pressure correction in naturally aspirated configurations. This function will convert to Inj f (Throttle) when the system is set up for Speed Density mode. This type of correction is global and is applicable as a constant.

Inj f (Water T)

This correction is used to offset the fuel injection pulse width relative to water temperature. Typical settings are pre-calibrated in all Lotus maps. Some engines will require slight adjustments to this curve depending on the ambient conditions. It is typical for most engines to require a slightly richer mixture (below 1.00 Lambda) during this condition.

Inj f (Air)

This correction is used to offset the fuel injection pulse width relative to air temperate. The typical calibration for this correction derives from the PV=nRT equation. Ideal Gas laws can be further researched at sites such as this http://en.wikipedia.org/wiki/Ideal_gas_law

Inj f (Fuel P)

This correction is used to offset the injection pulse width relative to fuel pressure. In the event that fuel pressure was to decrease, the injection time will increase to the determined amount in the curve. I.E. this correction can be in percent proportional to the pressure difference.

Spark f (Airbox)

This correction is used as an Airbox pressure or Barometric pressure correction in naturally aspirated configurations. This function will convert to Spark f (Throttle) when the system is set up for Speed Density mode. This type of correction is global and is applicable as a constant.

Spark f (Water)

This correction is used to offset the spark advance relative to water temperature. Typical settings are pre-calibrated in all Lotus maps. It is typical for most engines to respond well to a slight advance during temps colder than running temp. Conversely, it is typical for spark advance to retard when engine temp increases to reduce heat generation by decreasing performance and reducing likelihood of detonation. .

Spark f (Air)

This correction is used to advance or retard the spark relative to the temperature measured by the air temp sensor. In forced-induction engines it is recommended to measure air temp after the intercooler if possible. As a safety the spark can be retarded when air temp increases and density decreases.

Spark f (Fuel P)

This correction is to control spark advance relative to fuel pressure. This correction is typically used to retard spark in the event that fuel pressure were to decrease.

Reserved Corrections are not used and will vary depending on firmware version.

Accel / Decel

This portion of the software is for acceleration calibrations only.

Accel f (Water T)

This table is used as a correction for accel enrichment as a function of water temperature. Typical settings will require more enrichment in conditions that are colder than running temp.

Accel Mult f (RPM)

This table is used as a multiplier for the accel circuit as a function of engine speed. Usually as engine speed increases less accel enrichment is required.

Accel Constants

This section is where the constants are set for which the previously mentioned accel corrections are based of. Max Accel limit = Sets the maximum throttle rate that will be used for the accel fuel calculation. Min Accel limit = Sets the minimum throttle rate to enable the accel fuel function. Accel Decay = Sets how long the accel enrichment function is active. The accel rate is reduced by this value per engine cycle until the value returns to zero. RPM Cutoff Limit = If RPM is above this value in a state of deceleration the injection time will go to a zero pulse width (Overrun function). Throt Cutoff Limit = If throttle angle (in degrees) is below this value in a state of deceleration the injection time will go to a zero pulse width (Overrun function).

In a race application (typical turbo application) it is common to disable the decel fuel cutoff by setting the RPM and Throttle values to unobtainable high values. This provides both a cooling effect for the pistons and an anti-lag for turbo engines. Tuning Anti-Lag will be discussed in more detail later.

Additional notes directly from the Helpfile

Accel Calculation
Accel Fuel = Accel Rate x 100 x Accel f(Water) x Accel f(RPM) Assuming an accel rate of 20 bits and modifiers of 1.0 and 1.2 for each of the correction tables we would calculate the accel fuel for the first engine revolution as follows : Accel Fuel = (20 x 100 x 1.0 x 1.2) = 2400 uS Notes " Negative throttle rate values are not used by the accel enrichment function. " The throttle accel rate can be logged by the ECU internal logger to help with tuning this function.

System Constants

The settings in these tables are pre-set calibrations unique to the Lotus system configuration. It is advised to not alter these settings if using a standard system. If using a sequential gearbox with a shift cut function (no-lift-shift) it is advised to contact DRS for the correct configuration.

VANOS Control (VVTi-L for Toyota Engines)

The "VANOS Control" section currently enables the control of the Toyota VVT-i system with load and RPM inputs using a setpoint for cam timing in units of degrees.

Intake Cam Deg Map
This map can be used in 3D graphic or numeric mode. This map is used for controlling cam timing (cam phase) with pulse-width modulated control. The mechanical range of cam degree movement is 40 (55 Deg is maximum retard and 15 Deg is maximum advance). Like all other maps, Breakpoints for RPM and Load can be uniquely defined.

VVL RPM Limit = The minimum RPM that enables the cam profile switch-over.

VVL TPS Limit = The minimum throttle that enables the cam profile switch-over.

Note: VVL is commonly referred to as "Cam Switch-over".

Traction Control

All Lotus systems are compatible with the EFI Technology traction control systems. These systems can use a 12 position rotary switch to control the amount of power reduction. Slip setpoint is a 3D table that uses slip values (expresses as units in ratio of the front to rear wheel speed inputs) with throttle and speed. Slip f (gear) is used to adjust the percent of slip relative to a given gear position. Slip f (Lat G) is used to adjust the percent of slip relative to measured lateral G load. TC Constants is the section where the traction control configuration, limits, and PID functions are determined.

DC Motor

Motor position is a table used for controlling an external DC Motor driver with a 3D map. An example of an application would be a variable intake runner that can be controlled with load and rpm. This table is redundant when drive-by-wire (DBW) mode is enabled.

Idle f (Water T)

This is a table specific to DBW engines. Here the idle speed can be increased when engine temp is below running temps. It is typical for gradual slope to decrease the idle speed as the engine warms up.

Pedal Position

This table is used to set the pedal position input for which the throttle plate responds to as a reference. The bits values (20 position axis) are pre-calibrated for the Lotus (2ZZ) throttle body to help simplify the process. Typical settings will call for an increased pedal position in Pos 1 relative to Pos 2; however the values thereafter are typically linear. Below is a typical calibration for this table.

Most engines favor a value of 10 to 12 degrees in Pos 1 (this is set up as a position to slightly open the throttle if the calculated position drops below the desired idle speed. This calibration is to help offset factors such as a voltage drop and/or load on the electrical system that could cause oscillations in the closed throttle position and therefore affect idle speed. Pos 2 (is calculated as the throttle position in an ideal idle) is usually set to a value of 8.5 to 9.5. Furthermore, throttle response relative to pedal movement can be tuned by adjusting the values in Pos 3 through Pos 19, Pos 20 is adjustable for wide opened throttle only. A value of 87 deg for the Pedal is typical to avoid the throttle plate from over opening beyond 90 deg if system voltage deviates during this condition. It is always recommended to visually check the operation of the throttle plate during the set up of this table before running the engine.

DC Constants

The calibrations in this section are pre-set and it is advised to not change them. In the configuration there is a safety setting enabled to disable the throttle operation if the pedal and throttle plate are not in sync. DC Constants updates will be released upon review and further testing. It is very important to note that maps for non-DBW configurations and DBW configurations are NOT interchangeable. Damage can result if this precaution is not taken. Maps can be converted from DBW spec to non-DBW spec and vice versa, but it is recommended you contact a DRS representative first.

Nitrous Functions

This section of the software is currently not enabled in the standard Lotus systems and therefore will not be discussed in detail. It can be enabled with custom software. For more information regarding the Nitrous Functions please refer to the Helpfile.

Engine Protection

The engine protection feature is designed to help reduce damage to the engine by limiting the operation of the engine or maximum revs in the event that an enabled input measures a value defined in the table.

Available inputs to be used for engine protection: Air Temp Limit Coolant Temp Limit Oil Temp Limit Fuel Temp Limit ECU Temp Limit CDI Temp Limit (N/A for Lotus OEM coils) Fuel Pressure Limit Oil Pressure Limit EGT 1 Temp Limit (custom) EGT 2 Temp Limit (custom)



Mapping tools, using the ECU Data Logger, Dash display configuration, and diagnosis strategies will be added to this article in the near future.

Last update 05/30/2009