Create a circuit

4ACE generates a circuit from one lap of logged vehicle telemetry. Only closed circuits are supported, where the lap starts and finishes at the same place. Point-to-point courses such as hill climbs or rally stages, where start and finish are in different places, cannot be uploaded. At a minimum the file needs time, distance, speed, and lateral acceleration. Every extra column you provide, such as friction, banking, or altitude, makes the circuit model and the viewer richer.

The upload accepts CSV files only. This page explains how to build the file, what every column means, how the upload works, and how 4ACE turns the file into a circuit.

Before you start

• Select the correct team.
• You need module create permission to add a circuit. New is hidden without it.
• Log one clean lap on a closed circuit. The file must cover a single lap from the start line back to the same start line, not several laps and not a point-to-point course.
• Download a template so your columns are in the right order.
• Choose a name and a short name of at most 7 characters.
• Optionally prepare a PNG or JPEG picture up to 5 MB. If you skip it, 4ACE generates a 2D snapshot of the track.

Download a template

Both templates contain a full example lap with all 25 supported columns in the exact order 4ACE expects, a header row with column names, and a units row. Each file is about 20 MB. The Excel workbook itself cannot be uploaded.

Build the CSV file

1. Start from the template and keep row 1 (column names) and row 2 (units). Row 1 lets the Verify preview label your channels.
2. Paste your lap samples from row 3 onward, one sample per row, sorted by time.
3. Keep the columns in template order. 4ACE reads columns by position, not by name. Remove unused columns only from the right-hand end of the file.
4. If a middle column is not logged but you need a column to its right, keep the column and fill it with a constant inside its valid range, for example 1 for Friction, 0 for Banking, or 0 for VehAccZ.
5. Fill every cell in every kept column. Empty cells, NaN, and text are rejected.
6. Make sure Time increases on every row and Dist starts at 0 and never decreases.
7. Use . as the decimal separator and a comma or semicolon as the column separator.
8. Check that every row has the same number of columns and that no row ends with a trailing separator.

Column reference

Column positions are fixed. The first four columns are mandatory. Any further columns must follow this order without gaps, because 4ACE identifies a column by its position and ignores the header text.

Category meanings:

• Mandatory: the four columns 4ACE needs to build the track shape. The upload is rejected without them.
• Highly recommended: surface grip, banking, and elevation. They are stored with the circuit, shown in the 3D viewer, and used by simulations.
• Optional: geolocation, vertical acceleration, and suspension travel. Stored with the circuit for reference.
• Reference: driver and vehicle channels that are plotted in the circuit viewer. They do not change the track shape.

File rules

Upload the circuit

1. Open Circuits from the sidebar.
2. Select New. The Add Circuit sheet opens on the General step.
3. Enter Name.
4. Enter Short Name. Short name is limited to 7 characters.
5. Add Notes and Tags when useful for event, track version, or source tracking.
6. Optionally upload a Picture in PNG, JPEG, or JPG format up to 5 MB.
7. Upload the Circuit File in CSV format.
8. Continue to Verify. The step becomes available when name, short name, and file are valid and the file contains at least one data row.
9. Review the 3D track preview and the Telemetry charts. Use the channel selector to color the track by a channel, and Flat to hide elevation and banking in the map.
10. Adjust Start Angle with the slider or the number field. Use a whole number from -180 to 180. The map rotates live so you can match the orientation your team expects.
11. Select Save. A progress bar shows upload and processing progress.

After the save finishes, the circuit appears in the Circuits table, can be selected in FastSim setup, and can be opened in the viewer. Start angle can only be set during upload. To change it later, delete the circuit and upload the file again.

Circuit fields

How 4ACE processes your file

The whole pipeline runs while the progress bar is shown. In plain terms, 4ACE takes these steps:

1. Validate the data. Every cell is checked against the ranges in the column reference. Time must increase and distance must never decrease.
2. Detect the logging rate from the time column.
3. Smooth speed and lateral acceleration with a low-pass filter to remove sensor noise. Other channels are not filtered.
4. Calculate curvature at every sample from lateral acceleration and speed. Curvature describes how tightly the track turns at that point.
5. Build the map. The data is resampled to a fixed 1 kHz grid, and the X and Y coordinates of the track are integrated step by step from speed and curvature.
6. Close the lap. Real telemetry never ends exactly where it started, so 4ACE assumes a closed circuit and forces the lap to close. It first applies a small lateral acceleration offset so the lap turns exactly one full circle, then distributes the remaining position error along the lap so the start and finish lines coincide.
7. Store the circuit. Apexes are detected, the full data set is stored together with the calculated curvature and coordinates, and a slim outline (X, Y, Z, and distance) is stored for lightweight map drawing.

Good to know:

• Track length is the last Dist value in the file. Average lap time is an estimate based on track length.
• Friction, banking, altitude, GPS, and reference channels are stored as they are. They are shown in the viewer and used by simulations, but they do not change the track shape.
• Start angle is stored as metadata and only rotates how the map is displayed.

Troubleshooting

Next steps

• Analyze a circuit
• Run a FastSim simulation
• Review units and conventions
• Look up glossary terms