By the end of 1972, the requisite 500 homologation cars, dubbed 911 Carrera RS 2.7, sat outside Zuffenhausen for official inspection. The flat-six engine had been bored from 2.4 to 2.7 liters, requiring a special Nikasil cylinder lining for durability. The car retained the same Bosch mechanical fuel injection system as the 2.4 S, but horsepower increased from 190 to 210, with a notable gain in torque. For the first time in production 911 history, a wider 7.0-inch rear wheel was utilized, and widened fenders allowed even larger wheels to be adequately covered for racing use. Wind-tunnel development brought forth a redesigned front air dam and rear ducktail spoiler. The spoiler reduced rear-end lift by 75 percent and became the car's signature feature. Thinner gauge glass and steel kept weight down, and the 500 homologation cars were all of lightweight (code M471) specification, meaning limited sound deadening and carpeting; non-reclining front race buckets; and no rear seats, clock, interior armrests, or passenger-side sunvisor.