Herne blasted a 1:18.0456s in Practice 2, edging out Joey Mawson who lapped a 1:18.0740s in Practice 2, while Aaron Cameron was third in that session with a 1:18.3312s.
The sub-1:19s laps arrived despite the S5000 field running with restricted horsepower at the Adelaide Parklands Circuit, to meet the mandated weight-power ratio for Category II vehicles at a Grade 3 circuit.
Mawson topped Practice 1 with the two-time Australian Drivers' Champion setting a 1:18.4275s, finishing the session ahead of Aaron Cameron (1:18.7044s), and Cooper Webster (1:19.3323s).
Mawson and Cameron traded times over the course of the session, which was red-flagged after debutant Brad Gartner crashed at Turn 1.
When the session resumed, Cameron went to the top on his sixth lap with a 1:20.7701s, before he was shelved by Mawson who returned to the top with a 1:20.6770s to be ahead by 0.0931s.
Three-time Formula 1 race winner Giancarlo Fisichella went to second with a 1:20.6054s on his seventh lap, displacing Cameron to third.
Cameron responded with a 1:19.1450s to go to the top of the timesheets on his eighth lap, over 1.2372s ahead of Webster, with a 1:20.3822s, also on his eighth circulation.
Mawson went to the top on his with a 1:18.4275s on his 10th lap, over 0.2769s ahead of Cameron.
Herne was fourth with a 1:19.6540s, 0.1537s ahead of Fisichella, who ended the session in fifth with a 1:19.8077s.
Jordan Boys (1:20.2318s) and Blake Purdie (1:20.2632s) finished that session in sixth and seventh respectively.
In his farewell from full-time driving, two-time Gold Star winner Tim Macrow was eighth with a (1:20.6117s), with Noah Sands (1:21.2983s) in ninth, while Supercheap Auto TCR Australia Series regular Ben Bargwanna (1:21.8189s) rounded out the top 10.
In Practice 2, Herne finished ahead of Mawson and Cameron in third in a red flag-interrupted session that was decided by late lap times.
The session was red-flagged after Mark Rosser went sideways across the kerb at the Senna Chicane complex, with Elly Morrow avoiding the #17.
Action resumed with 17 minutes on the clock, before being red-flagged for a second occasion after contact between Macrow and Sebastien Amadio resulted in the latter going into the wall at Turn 4.
After the incident was cleared, the session resumed with four-and-a-half minutes on the clock, resulting in a flurry of late times.
On his ninth lap, Herne topped the session with Mawson and Cameron recording their fastest laps on their eight circulations.
Boys was fourth-fastest with a 1:18.8630s, ahead of Ben Bargwanna in fifth with 1:18.8733s, while Sands was sixth after his 1:19.2387s.
Fisichella improved on his Practice 1 effort with a 1:19.2847s, lapping as high as fourth place before ultimately finishing the session in seventh, with Webster in eighth (1:19.3395s), while Macrow (1:20.2182s) and Purdie (1:20.7447s) rounded out the top 10.
The S5000 Tasman Series field will take to the track tomorrow for Qualifying at 10:25 local time/10:55 AEDT.