Speed Density
Applies To:
- BE5 EJ206, EJ208 (when using single turbo firmware)
- BH5 EJ206, EJ208 (when using single turbo firmware)
- GC8 EJ207
- GF8 EJ205, EJ207
- SF5 EJ205
Speed density mode can be useful in situations where a MAF sensor is not reliable or accurate. In this mode the engine airflow is calculated using engine speed, air density, and volumetric efficiency instead of measured directly using the MAF sensor.
This patch you the option of running full-time SD fueling mode or a hybrid MAF/SD blending mode depending on airflow. The airflow is then used to calculate engine load similar to the original MAF airflow calculation. This way, the fuel and spark maps remain indexed by engine load and RPM.
We have patched in Speed Density mode for the following firmware IDs:
AF041 - GC8 EJ207 JDM
AE481 - GC8 EJ207 JDM
AE491 - GF8 EJ205 JDM
AE831 - SF5 EJ205 JDM
AG380 - SF5D EJ205 JDM
AE901 - SF5 EJ205 EDM
AG050 - SF5 EJ205 EDM
AG060 - SF5 EJ205 ADM
EDM GC8/GF8 EJ205 engines can use AE831 firmware with knock settings copied over from AE782/AE802.
Installation
Intake Air Temperature Sensor
Speed density requires an air temperature sensor to calculate the density and mass of air entering the engine. See Intake Air Temperature Sensor for details.
Dedicated MAP Sensor
The original remote-mounted MAP sensor is also used for measuring atmospheric pressure through the switching of the pressure exchange valve. If faster response, accuracy, or increased boost pressure is desired, an additional MAP sensor can be added and wired in place of the MAF sensor. The original MAP will remain place for measuring atmospheric pressure only and the pressure exchange valve can be removed. The ECU will support a maximum MAP reading of 544 kPa although boost control is currently limited to 272 kPa pending further firmware updates.
Wiring
When adding a dedicated 2nd MAP sensor, wire the MAP's pressure signal output to the ECU's 'Airflow Signal' input.
| Wire | ECU Pin | |
|---|---|---|
| Airflow Signal | B136-1 | Connect to MAP signal output |
| Sensor Ground | B136-31 | Connect to MAP ground |
| 5V Power | B136-12 | Connect to MAP power |
Conveniently, all the wires required for wiring a 2nd MAP sensor to the ECU are also available at the MAF connector.
DANGER
Be careful not to accidentally connect the 12V power wire to the MAP sensor as this may damage it. The MAP sensor's output signal should be wired to the 'Airflow Signal' wire.
Configuration
MAP Sensor
MAP Sensor - Sampling Engine Speed Minimum
May need to be decreased in SD mode to allow smoother startup after cranking the engine.
MAF Sensor Disable
Set to '1' to completely disable all code related to the MAF sensor. Allows removal of MAF when running full-time SD mode.
MAP Sensor on MAF Sensor Input
Set to '1' when a dedicated MAP sensor is installed and wired in place of the MAF sensor. When enabled, the original remote-mounted MAP sensor becomes a full-time atmospheric pressure sensor.
SD Settings
Engine Displacement
Engine displacement volume is needed for the SD airflow calculation.
MAP Sensor Filter
An exponential filter is applied to the MAP readings before it is used for any calculations. A higher number means less filtering, so faster response time but includes more signal noise.
The remote-mounted MAP is sampled every 4ms while dedicated MAPs are sampled every 2ms. With the dedicated MAP's 2x faster sample rate, a lower filter value is required to apply the same amount of filtering as a remote-mounted MAP.
Speed Density/MAF Blend Ratio
A value of 0% uses the MAF airflow while 99.6% (approximately 100%) will use the SD airflow. A blend of the two can also be applied depending on the previously calculated final airflow. Set all to 0% for MAF mode only or all to 100% for SD mode only. Blending should not be used when the MAF sensor is removed.
Charge Temperature IAT/ECT Blending Ratio
The IAT underestimates the true air temperature entering the cylinders as additional heating occurs in the intake runners and cylinder head. At lower airflow there is more time for heating to occur. This map is used to calculate air charge temperature as a blend of IAT and ECT. 0% uses IAT only while 100% uses ECT only.
Volumetric Efficiency
This represents the volumetric efficiency map of the engine. Higher values will increase the calculated SD airflow result.
Volumetric Efficiency - Throttle Compensation
THis map can be used to compensate where throttle position affects the volumetric efficiency.
Volumetric Efficiency - Atmoshperic Pressure Compensation
Use this map to compensate for changes to volumetric efficiency due to atmospheric pressure/altitude.
Datalogging
New datalogging parameters have been added to aid in tuning with Speed Density enabled.
Air Density Factor
Airflow correction factor based on air density at a reference temperature of 20 C.
Airflow (MAF)
Load (MAF)
Airflow reading and calculated load from the MAF sensor only.
Airflow (SD)
Load (SD)
SD mode calculated airflow and load.
SD Blend Ratio
The current ratio being used from the 'Speed Density/MAF Blend Ratio' map.
SD Map
The filtered MAP sensor reading used for SD calculations.
VE Base
The value from the 'Volumetric Efficiency' map currently in use.
VE Final
The final volumetric efficiency value after compensations have been applied.