Several requests, one output
From the torque-controlled EDC Bosch introduced with EDC16, the pedal is one demand among others. Cruise control and the vehicle-speed limiter are selected with it as a propulsive torque. Traction control and stability control can raise or lower that demand. An automatic gearbox states a torque requirement during the shift, both to reduce the load on the gearbox and to make the shift smooth. The air conditioner, alternator and power-steering pump add their own torque so the driver does not feel those loads as a step. Only after that selection do idle control and surge damping act, and only then does torque limitation cut the internal demand to prevent mechanical damage or excessive smoke. The fuel quantity is calculated from the torque that survives, using the current combustion efficiency, and a protective function can limit it again, for example against overheating. Smooth-running control may still trim individual cylinders. Bosch, torque-controlled EDC, printed pages 75–77.
Earlier EDC still limits the quantity directly. The reasons Bosch gives are the same family: excessive emissions and soot, mechanical overload from torque or engine speed, thermal overload of exhaust, coolant, oil or the turbocharger, and thermal overload of the solenoid valves if they are held on too long. Inputs named for that limit include intake-air quantity, engine speed and coolant temperature. Bosch, injected-fuel-quantity limit.
The number in the pedal map is the start of this chain. It is not the torque at the wheels.
How to tell which one you are feeling
| What it feels like | Question the log has to answer | Where it is documented |
|---|---|---|
| Hesitation as the pedal goes down, then smoke or a sudden arrival of torque | Did fuel wait for measured air, or did fuel lead the air? | Diesel smoke limits and turbo response |
| A shunt or a rocking delay after a pedal step | Did the torque request itself rise as a ramp? | Pedal response and surge damping |
| Power falls only in one gear, or only as the gearbox shifts | Did a transmission request replace the driver request for that moment? | Bosch gearbox torque demand during a shift, cited above. The gearbox pages on this wiki are identification catalogues, not shift calibrations. |
| Power falls when a wheel slips, or the car will not pull away on a wet surface | Did traction or stability control reduce the engine demand? | Bosch TCS and ESP intervention, cited above |
| Acceleration stops at a road speed while engine speed is not at the rev limit | Is the vehicle-speed limiter holding fuel? | Pedal response |
| The engine goes flat when hot, with high coolant, oil or exhaust temperature | Is a temperature protection or a substitute value active? | Quantity and torque limitation, cited above |
| A petrol engine pulls, then ignition drops and the torque sags | Was the reduction a knock correction or a torque intervention through spark? | ME7 ignition and knock and ME7 torque and boost |
Petrol ECUs use the same idea with a different actuator. ME7 turns a permitted torque into a load and then into throttle and boost, and it can cut torque quickly with ignition. Simos examples separate a fast path, ignition and fuel, from a slow path, air charge and the turbo. A spark cut and a boost target that was never reached are different faults that feel similar if you only watch the road. See Simos 18 and Simos 19 and MG1.
Aftertreatment and faults are requests too
Where a particulate filter or NOx system is fitted, the ECU can change injection and boost for that mode. EDC17's documented BMW coverage includes different boost-control data for regeneration, and the Audi 2.0 TDI examples include the filter hardware. A weak pull that appears only in that mode is not the driver-wish map. See EDC17 torque and fuel. This page does not describe how to disable that equipment. A road vehicle has to remain within the law that applies where it is used.
A failed sensor does not always drop the engine to an obvious limp. Bosch keeps the last valid value for a time, then can substitute. The fuel-temperature substitute is explicitly chosen to avoid soot and can cost power. Log faults and substitute-value flags with the torque trace before treating a flat spot as a map.
The useful comparison
Write down four quantities, in this order: what the driver asked for, what the coordinators allowed, what the engine was estimated to deliver, and what the air and the combustion actually did. If the first and second differ, the limit is outside the pedal map. If the second and third differ, the torque model or a fast intervention is involved. If the third and the road disagree, look at the clutch, the converter, the gear and the measurement, not at another torque table. The checklist is logging a drivability complaint.
Sources
- Bosch Electronic Diesel Control (EDC), 2001, independent PDF mirror. Quantity limits and torque coordination, including gearbox, traction, auxiliary loads, smoke and thermal protection. Printed pages 50–54 and 75–77. Accessed 2026-11-11.
- EDC16, EDC17, ME7 and Simos pages on this wiki. Family-specific chains.