The Superbikes were second out on track, which was still damp in patches after overnight rain, and although BMW rider Todd led the way in the early stages, times were down on Wednesday’s opener, which took place in sunny, dry conditions.
However, as the sun came out at the end of the session, Irwin smashed the unofficial lap record by going two seconds faster than the lap he set on Wednesday.
Todd, who recorded the fastest speed on the run down to University corner with 209.8mph, also improved but was 2.230 seconds down on Irwin, while Dunlop continued his solid start with third place, 2.270 seconds down on the Yorkshire rider.
Running Superstock machines, the Honda of Dean Harrison and BMW rider Peter Hickman rounded out the top five.
Irwin has won the last eight Superbike races and can equal the record for wins in the class set by Michael Rutter and the late Joey Dunlop if he wins Thursday’s opener.
“I love this place and it’s really nice to have that tag,” Irwin said on his unofficial lap record.
“I expect a strong challenge in the race. Davey is riding really well, Michael, Peter and Dean are tough characters and resilient. They are top riders.”
