Recorded engine loops replace the original synthesised engine tone. These are tuned approximations for the game's cars, not recordings of every exact make and model. Countdown, result and workshop-tool cues remain synthesised. All engine, induction and backfire layers are derived from the public recordings credited below.
Upgrade response: engine/displacement upgrades deepen the recorded note; exhaust and carburetor work open up its filtering; race cams add idle unevenness. Filtered layers of domasx2’s CC0 loop approximate Roots/Paxton whine and turbo spool with throttle lag and wind-down. These are designed approximations, not separately recorded turbochargers or exact vehicle recordings. Naturally aspirated cars receive no compressor layer.
Modifications: public high-quality MP3 previews cropped to stable idle sections, downmixed to mono, DC removed, normalized and crossfaded at loop boundaries. Playback pitch, filtering and levels change with RPM, throttle and vehicle. These recordings do not imply endorsement by the authors.