ich glaube, ich habe es:
"A turbocharger essentially compresses the air going into the engine in order to force more air than it would be possible using the atmospheric pressure. More air into the engine means, automatically, that more fuel has to be injected in order to maintain the appropriate stoechiometric value of the air/fuel ratio (around 14:1). More air and fuel into the engine leads to more power. However by compressing the inlet air the turbocharger also heats it. Higher air temperatures lead to thinner air and therefore an altered stoechiometric ratio which results to richer mixtures."