Page organisation in this revision
- Page type
- Technical article
- Subject
- Tuning
- Parent
- Section level
- Applies to
- No ECU-specific applicability
- Tool groups
- None
- Manufacturers
- None
Changes from revision 1 to revision 1
Removed text is struck through; added text is highlighted.
Overrun is a different operating mode
When the pedal is closed and the engine is being driven by the wheels, a diesel calibration can stop injection. Bosch's needle-motion sensor cannot confirm the start of injection in that condition, because there is no injection to see, so that particular timing loop is open. On the VP30 and VP44 the start-of-delivery control still runs from the pump angle signal during overrun, which lets the timing device sit at the position the next injection will need. Bosch, start of injection during overrun.
Where a lambda sensor is fitted, Bosch also describes a check for combustion that should not be happening on the overrun. If the sensor falls below a calculated threshold, the source says the engine can be stopped by closing a control flap and the EGR valve. That is a safeguard in the 2001 description, not a map to copy onto a later ECU. Bosch, undesirable combustion on overrun.
A petrol engine commonly cuts fuel on a closed throttle as well. The documented ME7 side of the return to fuel is the wall-film and warm-up correction: fuel that has condensed, or that will condense as airflow returns, is not the steady-state injector time. See ME7 fuelling and MAF calibration. The cut thresholds themselves are software-specific and are not listed here.
What the driver feels when the pedal comes back
The complaint is rarely the cut itself. It is the moment fuel, air and timing have to start again.
A stumble or a puff as the pedal reopens on a diesel is the smoke limit, the turbo and the injection timing meeting a request that has just come back from zero. The timing device may already be in place, as on the VP44 case above, while the air is not. See diesel smoke limits.
A shunt as the drivetrain takes up is the same torque step that surge damping is there to filter. Coming off overrun is one of the largest steps the filter sees. See pedal response and surge damping.
A petrol hesitation off idle or off overrun belongs with the transient fuel correction and the lambda request, not with the wide-open-throttle table. If the mixture is learned at cruise and then the cut returns, also read adaptations and calibration drift.
Popping or a misfire on a closed throttle needs the question of whether injection was supposed to be zero. Combustion on a diesel overrun is the condition Bosch treats as undesirable. On a petrol engine, the same noise can be fuel that was not fully cut, or ignition that is still firing a cut mixture. Log injected quantity or pulse width, lambda and throttle together before treating it as a feature of the exhaust.
Engine braking and a speed ramp
Bosch's engine-brake function, described for a truck, reduces injected quantity to zero or to the idle quantity when the engine-brake switch is on. That is a separate switch input, not the normal passenger-car overrun. The maximum-rpm controller is also separate: above the rated-power point it reduces fuel on a ramp until, just past the maximum speed, injection stops. The ramp is there so the engine does not surge. A rev limiter that feels like a series of hits, and an overrun that feels like engine braking, are different functions even when both end in less fuel. Bosch, maximum-rpm control and the engine-brake function.
What to record
Log the pedal, clutch and brake, engine speed and vehicle speed, injected quantity or pulse width, lambda if it exists, requested and actual boost, and the start-of-injection or spark value through the cut and through the return. A trace that starts only once the car is pulling again misses the mode change. The wider list is logging a drivability complaint.
Sources
Bosch Electronic Diesel Control (EDC), 2001, independent PDF mirror. Overrun with no injection, start-of-delivery control during overrun, undesirable combustion, maximum-rpm ramp and the engine-brake function. Printed pages 50–54 and 60–62. Accessed 2026-11-11.
ME7 fuelling and MAF calibration. Wall-film and warm-up corrections used when petrol airflow is changing.
Rendered revisions
Open each version to inspect formatting, tables and photographs.
Revision 1: Overrun and return to throttle
Overrun is a different operating mode
When the pedal is closed and the engine is being driven by the wheels, a diesel calibration can stop injection. Bosch's needle-motion sensor cannot confirm the start of injection in that condition, because there is no injection to see, so that particular timing loop is open. On the VP30 and VP44 the start-of-delivery control still runs from the pump angle signal during overrun, which lets the timing device sit at the position the next injection will need. Bosch, start of injection during overrun.
Where a lambda sensor is fitted, Bosch also describes a check for combustion that should not be happening on the overrun. If the sensor falls below a calculated threshold, the source says the engine can be stopped by closing a control flap and the EGR valve. That is a safeguard in the 2001 description, not a map to copy onto a later ECU. Bosch, undesirable combustion on overrun.
A petrol engine commonly cuts fuel on a closed throttle as well. The documented ME7 side of the return to fuel is the wall-film and warm-up correction: fuel that has condensed, or that will condense as airflow returns, is not the steady-state injector time. See ME7 fuelling and MAF calibration. The cut thresholds themselves are software-specific and are not listed here.
What the driver feels when the pedal comes back
The complaint is rarely the cut itself. It is the moment fuel, air and timing have to start again.
- A stumble or a puff as the pedal reopens on a diesel is the smoke limit, the turbo and the injection timing meeting a request that has just come back from zero. The timing device may already be in place, as on the VP44 case above, while the air is not. See diesel smoke limits.
- A shunt as the drivetrain takes up is the same torque step that surge damping is there to filter. Coming off overrun is one of the largest steps the filter sees. See pedal response and surge damping.
- A petrol hesitation off idle or off overrun belongs with the transient fuel correction and the lambda request, not with the wide-open-throttle table. If the mixture is learned at cruise and then the cut returns, also read adaptations and calibration drift.
- Popping or a misfire on a closed throttle needs the question of whether injection was supposed to be zero. Combustion on a diesel overrun is the condition Bosch treats as undesirable. On a petrol engine, the same noise can be fuel that was not fully cut, or ignition that is still firing a cut mixture. Log injected quantity or pulse width, lambda and throttle together before treating it as a feature of the exhaust.
Engine braking and a speed ramp
Bosch's engine-brake function, described for a truck, reduces injected quantity to zero or to the idle quantity when the engine-brake switch is on. That is a separate switch input, not the normal passenger-car overrun. The maximum-rpm controller is also separate: above the rated-power point it reduces fuel on a ramp until, just past the maximum speed, injection stops. The ramp is there so the engine does not surge. A rev limiter that feels like a series of hits, and an overrun that feels like engine braking, are different functions even when both end in less fuel. Bosch, maximum-rpm control and the engine-brake function.
What to record
Log the pedal, clutch and brake, engine speed and vehicle speed, injected quantity or pulse width, lambda if it exists, requested and actual boost, and the start-of-injection or spark value through the cut and through the return. A trace that starts only once the car is pulling again misses the mode change. The wider list is logging a drivability complaint.
Sources
- Bosch Electronic Diesel Control (EDC), 2001, independent PDF mirror. Overrun with no injection, start-of-delivery control during overrun, undesirable combustion, maximum-rpm ramp and the engine-brake function. Printed pages 50–54 and 60–62. Accessed 2026-11-11.
- ME7 fuelling and MAF calibration. Wall-film and warm-up corrections used when petrol airflow is changing.
Revision 1: Overrun and return to throttle
Overrun is a different operating mode
When the pedal is closed and the engine is being driven by the wheels, a diesel calibration can stop injection. Bosch's needle-motion sensor cannot confirm the start of injection in that condition, because there is no injection to see, so that particular timing loop is open. On the VP30 and VP44 the start-of-delivery control still runs from the pump angle signal during overrun, which lets the timing device sit at the position the next injection will need. Bosch, start of injection during overrun.
Where a lambda sensor is fitted, Bosch also describes a check for combustion that should not be happening on the overrun. If the sensor falls below a calculated threshold, the source says the engine can be stopped by closing a control flap and the EGR valve. That is a safeguard in the 2001 description, not a map to copy onto a later ECU. Bosch, undesirable combustion on overrun.
A petrol engine commonly cuts fuel on a closed throttle as well. The documented ME7 side of the return to fuel is the wall-film and warm-up correction: fuel that has condensed, or that will condense as airflow returns, is not the steady-state injector time. See ME7 fuelling and MAF calibration. The cut thresholds themselves are software-specific and are not listed here.
What the driver feels when the pedal comes back
The complaint is rarely the cut itself. It is the moment fuel, air and timing have to start again.
- A stumble or a puff as the pedal reopens on a diesel is the smoke limit, the turbo and the injection timing meeting a request that has just come back from zero. The timing device may already be in place, as on the VP44 case above, while the air is not. See diesel smoke limits.
- A shunt as the drivetrain takes up is the same torque step that surge damping is there to filter. Coming off overrun is one of the largest steps the filter sees. See pedal response and surge damping.
- A petrol hesitation off idle or off overrun belongs with the transient fuel correction and the lambda request, not with the wide-open-throttle table. If the mixture is learned at cruise and then the cut returns, also read adaptations and calibration drift.
- Popping or a misfire on a closed throttle needs the question of whether injection was supposed to be zero. Combustion on a diesel overrun is the condition Bosch treats as undesirable. On a petrol engine, the same noise can be fuel that was not fully cut, or ignition that is still firing a cut mixture. Log injected quantity or pulse width, lambda and throttle together before treating it as a feature of the exhaust.
Engine braking and a speed ramp
Bosch's engine-brake function, described for a truck, reduces injected quantity to zero or to the idle quantity when the engine-brake switch is on. That is a separate switch input, not the normal passenger-car overrun. The maximum-rpm controller is also separate: above the rated-power point it reduces fuel on a ramp until, just past the maximum speed, injection stops. The ramp is there so the engine does not surge. A rev limiter that feels like a series of hits, and an overrun that feels like engine braking, are different functions even when both end in less fuel. Bosch, maximum-rpm control and the engine-brake function.
What to record
Log the pedal, clutch and brake, engine speed and vehicle speed, injected quantity or pulse width, lambda if it exists, requested and actual boost, and the start-of-injection or spark value through the cut and through the return. A trace that starts only once the car is pulling again misses the mode change. The wider list is logging a drivability complaint.
Sources
- Bosch Electronic Diesel Control (EDC), 2001, independent PDF mirror. Overrun with no injection, start-of-delivery control during overrun, undesirable combustion, maximum-rpm ramp and the engine-brake function. Printed pages 50–54 and 60–62. Accessed 2026-11-11.
- ME7 fuelling and MAF calibration. Wall-film and warm-up corrections used when petrol airflow is changing.