ECU Sensors, Inputs and Outputs
Sensors used by the VR4 ECU
The VR4 ECU has a number of sensors it uses to allow safe operation of the engine.
| Sensor | Acronym | Purpose | Type | Location | Notes |
|---|---|---|---|---|---|
| Crank Position Sensor | CPS/CKP | Measures rotational speed of the engine | 3-wire 5V PWM | Behind Crank Pulley | This is not a notched sensor. TDC can only be detected via combination of this signal and the cam pulse signal |
| CAM Position Sensor | Triggers Top Dead Center of cylinders | 3-wire 5V PWM | Behind Front exhaust cam sprocket | ||
| Mass Airflow Sensor | MAF | Measures airflow into the engine | 5V PWM on 5-wire connector | Just past airbox | Primary airflow and boost control mechanism |
| Intake Air Temperature Sensor | IAT | Measures intake air temperature (before turbos) | 5V analogue on 5-wire connector | Inside MAF assembly | Used as part of airflow calculations |
| Barometric Air Sensor | BARO | Measures intake air pressure | 5V analogue on 5-wire connector | Inside MAF Assembly | Used as part of airflow calculations |
| Engine Coolant Temperature Sensor | ECT | Measures engine coolant temperature | 2-wire 5V analogue | Screwed into thermostat housing | This sensor is not used to drive the dashboard temperature gauge. That is handled via a separate 1-wire sensor mounted next to the ECT sensor. |
| Knock Sensor | Knock | Detects engine detonation (knock/ping/pre-ignition) | One-wire piezo-electric microphone | Screwed into top of block, between "V" of engine (underneath intake runners) | Critical to avoid engine damage. If the ECU detects knock, it will retard the ignition and add fuel based on how much knock it detects. Knock Detection is fairly complex and uses an algorithm to convert the anologue sound signal into a digital rating between 1 and 35. |
| Throttle Position Sensor | TPS | Used to measure the position of the throttle plate in a percentage of how open or closed the throttle is | 3-wire 5V analogue | Mounted on the side of the throttle plate | The TPS can be used as a backup airflow metering system (aka "Alpha-N" airflow measurement) if the MAF fails, however this is essentially a limp mode. The TPS is also used to detect the rate of change of the throttle position, so that extra fuel can be added to the engine to avoid transient lean conditions and therefore provide better throttle response. This process is analagous to an accelerator pump on a carburetor. |
| Speed Sensor | VSS | Measures vehicle speed | 3-wire 5V PWM | Screwed into the top of the gearbox (connected to the gearbox output shaft) | Vehicle speed is data seen by the ECU, with the pulses also sent to the speedometer in the dashboard cluster. Vehicle speed is used in the custom ROM files that use launch control (two-step), available from Transformance Mechanical Engineering. |
Sensors NOT used on the VR4
Whilst being a turbocharged car, the VR4 does not use a Manifold Absolute Pressure (MAP) sensor. Boost control is performed via a "target airflow" table in the ECU map. This map is used to dictate control over the wastegate control solenoid which controls the wastegates on the front and rear turbos together.
This is likely the same way that the Lancer Evolution of the same generation manages boost pressure, however as those cars have boost gauges, a MAP sensor is needed from factory.
Outputs from the VR4 ECU
Based on data collected from sensors, the VR4 ECU controls the engine via a number of outputs.
| Output | Purpose | Type | Location | Notes | |
|---|---|---|---|---|---|
| Injectors (x6) | Injects fuel into each cylinder | 2-wire ground-switched 12V | Inserted into the intake runners | There are six individual injectors, one for each cylinder. The ECU uses sequential injection, only firing each injector in one pulse for each intake stroke of the relevant cylinder. | |
| Coils (x3) | Connects to spark plugs and ignites the air/fuel mixture in each cylinder | 3-wire 5V triggered | On top of the front cylinder bank | The stock coil setup on the VR4 is three coils with each coil driving two separate spark plugs/cylinders. This is a "wasted spark" or "batch fire" ignition setup where each spark plug fires on the compression stroke and on the exhaust stroke (e.g. "wasted"). Coil on Plug (CoP) kits add an additional three coils so that each cylinder has its own coil, but if using the stock ECU the setup still uses a wasted spark model. |
Sensors NOT used on the VR4
Whilst being a turbocharged car, the VR4 does not use a Manifold Absolute Pressure (MAP) sensor. Boost control is performed via a "target airflow" table in the ECU map. This map is used to dictate control over the wastegate control solenoid which controls the wastegates on the front and rear turbos together.
This is likely the same way that the Lancer Evolution of the same generation manages boost pressure, however as those cars have boost gauges, a MAP sensor is needed from factory.
Sensor pinout
The following image was taken from Merlin's VR4 tuning guide and will be replaced with a text table.
