The Ruf's full name, SCR 4.2, gives a hint as to just what’s hiding under that whale-tail wing: a 4.2-litre flat-six. But rather than a bored-and-stroked air-cooled 993 engine, the SCR is ...

Steps to replacing advanced exhaust gas recirculation with Cummins SCR complicated by reliance ... to the systems all other heavy-duty truck engine makers have certified to 2010 exhaust standards.