Complex sentence: Boxer engines (and flat engines in general) tend to be noisier than other common engines for both intrinsic and other reasons, e.g., in cars, valve clatter from under the hood is not damped by large air filters and other components.
Split into simpler sentences: Boxer engines (and flat engines in general) tend to be noisier than other common engines for both intrinsic and other reasons. In cars, for example, valve clatter from under the hood is not damped by large air filters and other components.