The Z/28’s lap is actually four seconds faster than the Camaro ZL1. It even beats published times for the Porsche 911 Carrera S and Lamborghini Murcielago LP640.
"One of the challenges of testing at the 'Ring is that the track is so long that conditions can change radically in a single lap," said Al Oppenheiser, Camaro chief engineer. "Adam Dean, the development driver for Z/28, did a heroic job driving in deteriorating conditions. Based on telemetry data from our test sessions, we know the Z/28 can be as much as six seconds faster on a dry track."
Source: General Motors