Exhaust Pops and Backfire Sounds When You Lift Off the Throttle (UE5)

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Works in Unreal Engine 5.0 to 5.8. Updated November 2026.

Quick answer: in your car’s Blueprint, detect a lift-off at high RPM (throttle was above 0.6, now below 0.1, RPM above 3000). Then, for about 1.5 seconds, play a random pop sound every 50 to 150 ms at the exhaust, with fewer pops as time goes on.

You need 4 to 8 short pop recordings (0.1 to 0.4 seconds each) and, optionally, a small Niagara flame effect.

Step 1: Detect the lift-off

In your vehicle Blueprint, add variables LastThrottle (float) and PopTimeLeft (float). On Event Tick:

  1. Read Get Throttle Input and Get Engine Rotation Speed from the Chaos movement component.
  2. If LastThrottle > 0.6, Throttle < 0.1 and RPM > 3000, set PopTimeLeft to 1.5.
  3. Set LastThrottle to the current throttle.

Step 2: Play the crackle

Still on Tick, while PopTimeLeft > 0:

  1. Subtract Get World Delta Seconds from PopTimeLeft.
  2. Count down a second timer, NextPop. When it reaches zero, play a pop and set NextPop to Random Float in Range 0.05 to 0.15, divided by PopTimeLeft รท 1.5 so the pops thin out.
  3. To play a pop, use Spawn Sound Attached with a random entry from your pop array (Random Array Item), attached to an exhaust socket. Vary Pitch Multiplier between 0.9 and 1.1.
  4. Cancel the crackle (PopTimeLeft = 0) as soon as throttle goes back above 0.3.

Step 3: Add a flame (optional)

On about one pop in five, call Spawn System Attached with your flame Niagara system on the same exhaust socket. Keep the flame short: 0.1 to 0.2 seconds.

Pops sound “pasted on”? That’s because they don’t follow the engine’s rhythm. Tie NextPop to RPM (shorter gaps at higher RPM) and run them through the same attenuation as the engine.

We drive pops from the engine simulation in our Any Car Engine plugin.

FAQ

Why do real cars pop on lift-off? Unburned fuel ignites in the hot exhaust when the throttle closes at high revs. Some cars are tuned to do it on purpose.

Should pops happen on downshifts too? Yes, a rev-matched downshift with the throttle closed often crackles. Trigger the same burst when the gear drops.

Can I use a Sound Cue for the random choice? Yes, a Random node with your pops and a Modulator for pitch does the same job.

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