The below testing was performed using stressberry. If you want to try them yourself, instructions are below:

To run stressberry on your computer, simply install it with

[sudo] apt install stress pip3 install stressberry --user

and run it with

stressberry-run out.dat stressberry-plot out.dat -o out.png

(Use MPLBACKEND=Agg stressberry-plot out.dat -o out.png if you’re running the script on the Raspberry Pi itself.)

The run lets the CPU idle for a bit, then stresses it with maximum load for 5 minutes, and lets it cool down afterwards. The entire process takes 10 minutes. The resulting data is displayed to a screen or, if specified, written to a PNG file.

The first test (blue) was performed with the Pi4 simply sitting on the desk, with no cooling done. It quickly hit the 80c thermal throttle cap, and stayed there for the majority of the test.

The second test (orange) was performed with a simple computer fan plugged into the gpio, facing the Pi as pictured below. You can see that it never throttled, and it hit a peak of 63c.

The third test (green) was performed with the world-famous Flirc case. The Flirc case costs $13, and is a completely passive cooling solution. The case acts as a heatsink for the Pi.

As shown, the Flirc case was able to compete with the active cooling solution. Just as with the Pi3, the Flirc case is AMAZING and hands-down the best passive cooling solution for your Pi4!

Below are images as tested: