Now this is an hilarious way to test the functioning of an aftermarket radiator: just place Tarzan inside a bathtub and see if the water is too cold or too hot!
Human radiator testing!
Don’t worry, the NSFW parts have been blurred out!

Watch the video below:

Okay, they were cheating a slight bit: they were revving the S15 engine much higher with the stock radiator.

Direct link to video: ラーマン山田 の 人体実験 ラジエター 編~ラーマン山田の 肌で温度をチェック の巻~