When tuning a turbocharged petrol engine, maximum horsepower is only part of the story. Torque delivery across the usable RPM range plays an equally important role in how a car feels during everyday driving. A well-developed Stage 1 ECU calibration can therefore improve engine response without pursuing the highest possible peak power figure.

At AutoChip, we carried out Stage 1 tuning on a 2018 BMW 5 Series G31 equipped with a 2.0-litre turbocharged petrol engine and Bosch MG1CS003 ECU. The engine's factory rating is 252 HP and 350 Nm. Before modifying the software, the vehicle underwent a dynamometer test. A second test and diagnostic data logging followed the ECU calibration.

The measured result was an increase from 255 to 275 HP, while peak torque rose from 347.4 to 426 Nm. That represents a gain of 20 HP and approximately 79 Nm, achieved with a deliberately moderate Stage 1 setup.

Baseline dyno test: how close was the BMW to its factory specification?

Before remapping an engine, it is important to establish the vehicle's actual performance in its original configuration. This provides a meaningful baseline against which the results of software changes can be evaluated.

The BMW G31 was placed on the AutoChip dynamometer and tested with its original ECU calibration.

The manufacturer's stated engine figures were:

• Factory power: 252 HP.
• Factory torque: 350 Nm.

The initial dynamometer measurement showed 255 HP and 347.4 Nm. Power was therefore 3 HP above the stated factory output, while torque was 2.6 Nm below the nominal specification.

These relatively small differences showed that, under the conditions of this test, the car was performing very close to its factory-rated figures.

This provided a useful starting point for evaluating the Stage 1 calibration. However, a close match between factory and measured output in one test does not prove absolute dynamometer accuracy under all conditions. Vehicle condition, testing procedures and environmental factors can affect the results.

Bosch MG1CS003: Stage 1 calibration for a turbocharged petrol engine

This BMW uses a Bosch MG1CS003 engine control unit. The ECU coordinates fuel injection, ignition, turbocharger operation, torque management and other functions required for the engine to operate correctly.

Modern petrol engine management relies on interconnected control strategies. Requested torque must be coordinated with boost pressure, fuel delivery, ignition control and the engine's operating limits.

For that reason, professional Stage 1 tuning involves more than simply increasing a boost target. The relevant calibration functions must work together to deliver the desired engine characteristics.

AutoChip selected a moderate Stage 1 calibration for this BMW. The technician explained that a more aggressive tune could potentially produce higher output, but the goal was not to extract the maximum possible horsepower.

Instead, the chosen calibration retained a degree of performance headroom while delivering a useful improvement in torque and power.

Stage 1 dyno results: 275 HP and 426 Nm

After modifying the ECU software, the BMW returned to the dynamometer for another power measurement.

The results showed a clear improvement compared with the original calibration:

• Power before Stage 1: 255 HP.
• Power after Stage 1: 275 HP.
• Power increase: +20 HP.
• Torque before Stage 1: 347.4 Nm.
• Torque after Stage 1: 426 Nm.
• Torque increase: approximately +79 Nm.

The power gain was relatively modest, but the increase in peak torque was considerably more pronounced.

The technician displayed the two dynamometer curves for comparison. The blue curve represented the original calibration, while the red curve showed the modified AutoChip Stage 1 result.

This comparison made it possible to examine the change in engine output rather than relying on claimed performance figures alone.

The measured values apply to this specific vehicle and should not be treated as guaranteed results for every BMW using a similar engine.

Why does an additional 79 Nm matter?

Horsepower and torque describe related but different aspects of engine performance. Torque represents the engine's twisting moment, while power depends on both torque and rotational speed.

In this case, peak torque increased from 347.4 to 426 Nm — a difference of 78.6 Nm.

An increase of this size can potentially make a noticeable difference during acceleration, especially if the additional torque is available in the RPM range commonly used during normal driving.

For example, stronger torque delivery may allow the engine to respond more confidently without requiring as much increase in engine speed. Depending on the transmission and driving conditions, it may also reduce the need for downshifts.

However, the peak torque figure alone does not describe the complete driving experience. The shape of the torque curve, the RPM range in which additional torque is available and the transmission's behaviour all affect how the improvement is delivered.

This is why comparing full dyno curves is more informative than looking only at the maximum horsepower and torque numbers.

Diagnostic data logging after Stage 1

Following the ECU software modifications, AutoChip also recorded diagnostic data logs from the BMW's engine management system.

A dynamometer measures the resulting output, while data logging helps technicians examine the electronic control systems that produce that output.

During the video, the technician showed several groups of available parameters:

• Engine speed: engine RPM during the test.
• Accelerator pedal position: the driver's acceleration request.
• Selected gear: transmission operating information.
• Ambient pressure: atmospheric pressure information relevant to operating conditions.
• Air and turbocharger systems: parameters associated with airflow and boost control.
• Fuel injection: information about fuel delivery and injection operation.
• Ignition: ignition control parameters.
• Engine torque: calculated and requested torque-related data.
• Temperatures: engine and related system temperature measurements.

Reviewing these parameters helps technicians understand how the engine management system responds under load and whether the available data reveals inconsistencies that require further attention.

This is particularly useful after remapping a turbocharged petrol engine, where changes in one control strategy can affect several other functions.

The video does not provide specific boost pressure values, ignition corrections, fuel trims or operating temperatures. Therefore, no particular numerical values or confirmed operating margins can be attributed to the data log review.

What is documented is that diagnostic logs were collected and demonstrated as part of the tuning process.

Why did AutoChip avoid a more aggressive tune?

The technician explained that a more powerful ECU calibration could potentially have been developed for this petrol turbo engine.

However, AutoChip deliberately chose not to pursue maximum possible output. The completed Stage 1 was intended to provide a worthwhile performance improvement without pushing the calibration unnecessarily hard.

This approach matters because increasing engine output also affects the demands placed on the powertrain. The appropriate level of tuning depends on the vehicle's technical condition, intended use and the operating characteristics of its engine and transmission.

With peak torque already increased by almost 79 Nm, the calibration offered a substantial change in the engine's available torque potential without a particularly large increase in maximum horsepower.

The technician expected the BMW to feel noticeably more responsive on the road. However, the video does not document a separate acceleration test or long-term driving evaluation. Improved road behaviour therefore remains an expectation based on the tuning result rather than an independently measured road-test outcome.

Why verify ECU tuning on a dynamometer?

Testing a powerful vehicle at high loads on public roads can be dangerous, particularly when the test requires sustained acceleration or high speeds.

A dynamometer provides a more controlled testing environment in which power and torque can be measured and recorded. It also makes it possible to compare results before and after ECU calibration using the same type of test.

For this BMW G31, AutoChip first established the original output, then carried out Stage 1 programming and measured the vehicle again.

This approach provides more objective evidence than relying only on how fast or responsive the car feels to the driver.

Diagnostic data logging can also complement dyno testing by recording engine management parameters during the measurement. Road data logging may be useful in some circumstances, but an ordinary road test is not a direct replacement for a properly conducted dynamometer power measurement.

BMW G31 Stage 1 ECU remapping at AutoChip

This 2018 BMW G31 demonstrates how a moderate Stage 1 calibration can produce a substantial increase in peak torque while keeping the horsepower gain relatively modest.

The original dyno test recorded 255 HP and 347.4 Nm. After Bosch MG1CS003 ECU remapping, the BMW produced 275 HP and 426 Nm. Diagnostic data logs were also collected, and the technician explained the decision to retain performance headroom rather than pursue a more aggressive calibration.

AutoChip provides individual Stage 1 ECU remapping, engine diagnostics, control unit programming and dynamometer testing for petrol and diesel vehicles. The appropriate calibration is selected according to the engine, the vehicle's technical condition and the intended performance goals.

The accompanying video shows the BMW G31's original and tuned dyno curves, the available diagnostic data and the technician's explanation of the final Stage 1 result.