Before installing a tuning box, remap or other performance upgrade, it is smart to check the engine’s super-knock history. This is especially important on turbocharged BMW engines such as the N20, B38, B48 and B58.
Super knock is not the same as normal engine knock. It is an uncontrolled combustion event that can create extremely high cylinder pressure. In serious cases, it may damage pistons, spark plugs or other internal engine parts.
The BMW DME records these events, allowing you to check the history with Tool32.
What Is Super Knock?
Super knock happens when the air-fuel mixture burns too early and too violently inside the cylinder. It can be triggered by hot spots, carbon deposits, poor fuel quality or excessive cylinder pressure after tuning.
Unlike normal knock, changing ignition timing may not prevent super knock. When the DME detects a serious event, it can reduce engine power and temporarily stop fuel injection on the affected cylinder for several combustion cycles.
A stored super-knock event should never be ignored, especially if the car has been modified.
Important Safety Step
Always connect a suitable battery charger before using Tool32 or carrying out coding and diagnostic work.
Low battery voltage can interrupt communication with the vehicle and may cause additional problems during programming or module access.
Correct PRG Files
Use the PRG file that matches the engine and DME:
- B32, B36, B38, B42, B46 and B48: dme_bx8.prg
- B46, B48 and B58: dme8ff_r.prg
- Mini Cooper S with the B48 engine: usually dme_bx8.prg
- MEVD1724: use the matching PRG file for that DME version
PRG files are commonly found in:
C:\EDIABAS\ECU\
Newer files may also be located inside the Rheingold or ISTA ECU data folders.
How to Check Super Knock with Tool32
- Connect the car using an ENET cable.
- Connect a battery charger to the vehicle.
- Open Tool32.
- Load the correct PRG file.
- Select the job status_lesen.
- Enter the argument: ARG;SUPERKLOPFER
- Press F5 to read the stored values.
The DME will display the recorded super-knock information for the engine.
Values You Should Check
If the engine has no recorded super-knock problems, these values should normally be zero:
- STAT_INFOBSK_0_VALUE through STAT_INFOBSK_19_VALUE
- STAT_INFOBSSK_0_VALUE through STAT_INFOBSSK_19_VALUE
A value greater than zero does not automatically prove that the engine is damaged, but it is a warning sign. The vehicle should be inspected before adding more boost or increasing ignition and fueling demands.
Other useful data may include:
- Engine speed
- Engine load
- Cylinder number
- Engine temperature
- Charge-air temperature
- Boost pressure
- Fuel quality estimation
- Lambda readings
- Ignition angle
- Misfire counter
- Smooth-running values
- Knock signals for each cylinder
For example, Tool32 may show values such as STAT_MOTORSPEED_VALUE, STAT_SUSPENSION_PIPE_PRESSURE_VALUE, STAT_AIR_MASS_VALUE and cylinder-specific knock or misfire data.
Why Tuning Can Increase the Risk
A performance tune raises cylinder pressure, combustion temperature or both. If the fuel quality is poor, the intake temperature is high or the engine already has carbon deposits, the risk can become higher.
A tuning box may also increase boost without fully considering the engine’s condition. That is why checking the DME history before and after tuning is good practice.
If super knock is recorded, inspect the following:
- Spark plugs
- Ignition coils
- Fuel quality
- Injectors
- Intake temperature
- Boost leaks
- Carbon deposits
- Engine software and tuning calibration
Tool32 gives valuable information, but the results should be interpreted alongside live data, fault memory and a proper mechanical inspection. Do not clear the counter and assume the problem is solved.
For a healthy tuned BMW, use quality fuel, maintain sensible intake temperatures and make sure the calibration matches the engine’s hardware. A few minutes checking super-knock history can help prevent a very expensive piston or engine repair.
Always confirm the correct PRG file and DME procedure for your exact BMW model before carrying out diagnostic work.