Most modern dyno testers are capable of doing that all by themselves, calculating how much of the engine's power is wasted by the gearbox and prop shafts to within a 1% error. So when French tuning firm Digiservices says the Clio 4 RS actually makes 181.4 PS, not the 200 PS claimed by the manufacturer, we presume that they didn't make any mistakes.
In any case, the same dynamometer has been used by many other cars this year, and most of them didn't fall short of expectations. The Audi S1's 2.0 TFSI engine was tested at 248 PS instead of the official 231 PS, the Leon 2.0 TDI put out 154 PS instead of 150 PS and the BMW X1 18d produced exactly 143 PS like it was supposed to.
It's not even a problem of the Clio RS being French, as Renault's dCi 110 and dCi 160 diesel engines do what they say on the box.
There are two possibilities here. The first is that Renault built a lemon that actually delivers the same amount of power as its rival, the Fiesta ST. We've seen tests of the previous generation Clio RS and its 2.0-liter engine also suffered from being overrated, with dynos showing around 175 PS.
The other idea we have is that there's something wrong with the engine on this car. Either way, it's not pleasant seeing how 10% of the ponies have escaped.