Here we’ll give a brief breakdown on how a Bosch EDC15P+ ecu works. The example below is taken from an early 2004 Skoda Fabia vRS fitted with the ASZ 1.9 TDI PD130.
Their are many more maps within this ecu but below gives you an idea on how this particular ecu works and also whats needed to extract the Hidden-Power.
This map determines how much injection quantity (IQ) in mg per stroke is requested for a given RPM based on the throttle position.
Example, 70mg of fuel is injected at wide open throttle (WOT) between 0-2499rpm.
This map limits injection quantity (IQ) in mg per stoke against RPM and atmosphere pressure. Example, 51mg of fuel is the maximum that can be injected at 3000rpm.
There are two smoke limiters in the Bosch EDC15P+ ecu. One is based on airflow through the MAF sensor. The second is based on boost pressure through the MAP sensor. Only one of these maps are ever used at one time. There are switches elsewhere in the file that tells the ecu which smoke map to use.
The Skoda Fabia vRS with the ASZ 1.9 TDI PD130 uses the map based on the MAF sensor. Some later BLT engines are based on the MAP sensor.
Based on MAF
This map limited injection quantity in mg per stoke against RPM and airflow through the MAF sensor.
Example, a maximum of 53.9mg is injected when airflow is 925 at 2001rpm.
So three maps…
The three maps above all relate to how much fuel is to be injected at a given RPM. All three have different values, so which one takes effect?
The lowest value.
Example. If the drivers wish says inject 70mg at wide open throttle at 2500rpm, it then goes to the torque limiter. The torque limiter then checks the 2500rpm value but finds that the limiter is set to 60mg. It now goes to the smoke map. The smoke map then checks if there’s enough air to meet the 60mg demand. If the smoke map value is higher, then the 60mg value is then use. If the smoke map says only 55mg can be injected due to the amount of air through the MAF sensor,then the 55mg value is used.
The duration maps are calibration maps that tell the ecu how long the injectors have to stay open to meet a given injection quantity. The duration is measured in degrees of crank rotation.
Example. To inject 25mg of fuel at 3800rpm, the injector needs to stay open for 10.73 degrees of engine rotation.
In the Skoda Fabia vRS, there are six duration maps. The ecu selects each one of these maps based on the start of injection.
Start of Injection
The start of injection map(s) tell the Bosch EDC15P+ ecu when to start injecting fuel. This is measured in degrees before top dead center (TDC) Example. If 60mg has been requested at 4250rpm, then the injector will begin injecting fuel at 23.51 degrees before top dead center.
In the Skoda Fabia vRS, there are 10 start of injection maps. The ecu selects each one of these maps based on coolant tempurature.
This is the requested boost pressure map. This is calculated by taking the requested injection quantity against engine speed.
Example. When 50mg is requested at 2499rpm. 1.35 bar of boost is requested. The values in the map include atmosphere pressure.
This map controls the N75 valve. The N75 is used to control the actuator on the turbo which in turn controls the VNT part of the turbo.
At low RPM the VNT vanes are in a closed position to help speed up the turbo. As engine speed increases, the VNT vanes open up to prevent over boost.