The results of our testing can be seen in this table as well as in the following diagram:
As you can see, the NZXT Kraken X40, unlike the majority of compact liquid cooling systems we tested earlier, looks very good even in its default configuration with one 140mm fan. The large radiator and high-performance pump make it competitive against the Phanteks PH-TC14PE as well as the Corsair H100i Extreme Performance. With its 140mm fan working at 1870 RPM, the NZXT Kraken X40 turned out to be more efficient than its opponents, beating the air super-cooler by 3°C in terms of peak CPU temperature. At 1200 and 1000 RPM the Kraken X40 is also efficient, competing with the Phanteks PH-TC14PE and easily beating the Corsair H100i when the latter’s two fans work at 1200 RPM or lower. However, when the speed of the Kraken X40’s fan is reduced to 800 RPM, the CPU temperature grows by 5°C, so the air super-cooler looks preferable (at its 750 RPM). The Kraken X40 is ahead of the Corsair H100i at the minimum speed of the fan, though.
It is after we install an additional 140mm fan on the Kraken X40’s radiator that it delivers truly impressive performance. It has no rivals in this case, especially at 800 RPM when the second fan helps lower the temperature by 7°C! Take note that the Corsair H100i can deliver the same 71°C only at 1600 RPM. Just an excellent result!
Then we checked out the NZXT Kraken X40 with our CPU overclocked to 4.5 GHz at a voltage of 1.435 volts. Here's a table with results and a diagram too:
The Kraken X40 couldn't cope with the overclocked CPU in the default configuration with one fan rotating at 1000 and 800 RPM. The Corsair H100i Extreme Performance also failed at 800 RPM. The overall picture is the same, though. The standard Kraken X40 is somewhat better than the Phanteks PH-TC14PE and comparable to the Corsair H100i. The additional 140mm fan improves the Kraken X40’s performance dramatically, making it superior to the Corsair H100i, which is the best ready-made liquid cooling system, in the speed range of 800-1200 RPM, notwithstanding its smaller size and lower price. The 140mm radiator and fan(s) are an advantage indeed.
We tried to check out the Kraken X40 at the highest frequency of our CPU (4.625 GHz at 1.49 volts) but our attempts were futile even when we installed a second fan on it. We always got an error message in the end:
So, we finished our performance tests and proceeded to measure noise.