Quick answer: keep a Boost value (0 to 1) that rises with RPM and throttle and lags behind them. Drive a looping whine’s pitch and volume from Boost, and when the throttle snaps shut with Boost above 0.5, play a blow-off sound and drop Boost to zero.
You need a looping turbo whine (a steady high whistle, 2 to 4 seconds) and one or two blow-off recordings.
Step 1: Simulate boost
In your vehicle Blueprint, add a float Boost. On Event Tick:
- Read Get Engine Rotation Speed and Get Throttle Input from the Chaos movement component.
- Work out the target:
Throttle × Clamp((RPM − 2000) ÷ 2000, 0, 1). No boost below 2000 RPM, full boost from 4000. - Set
Boostto FInterp To from Boost to the target, Interp Speed 2. That gives a realistic half-second of lag.
Step 2: The whine
- Add an Audio component with your whine loop, set to auto-activate and loop.
- Each tick, call Set Pitch Multiplier with
0.6 + 1.2 × Boostand Set Volume Multiplier withBoost × 0.5.
Keep the whine quiet. On a real car it sits under the engine; too loud and it sounds like a jet.
Step 3: The blow-off
- Keep
LastThrottlefrom the previous tick. - If
LastThrottle > 0.5,Throttle < 0.2andBoost > 0.5, call Spawn Sound Attached with your blow-off sound at the engine, with its volume scaled by Boost. - Then set
Boostto 0, so the whine drops away and the turbo has to spool up again.
| Problem | Fix |
|---|---|
| Blow-off fires on every gear change | Only fire it when Boost > 0.5, and ignore lifts shorter than 0.1 s |
| Whine sounds detached from the engine | Route it through the same attenuation and play it from the engine’s position |
| Turbo spools instantly | Lower the FInterp To speed |
A blow-off valve and turbo flutter are different sounds. A valve vents the pressure (“pssh”). Without one, air surges back through the compressor and stutters (“stu-tu-tu”). Pick the one that matches your car.
We do this in our Any Car Engine plugin.
FAQ
Does a supercharger work the same way? No lag and no blow-off: its whine is locked to engine RPM. Drive the whine’s pitch straight from RPM instead of Boost.
Should boost affect the engine sound too? Ideally yes: more load makes the exhaust louder and rougher. Raise the engine volume slightly with Boost.
Can players hear it from outside the car? Yes, but quieter. Lower the whine volume when the camera is outside.