Ian Thorpe was a happy man after blitzing the open 200 metres freestyle field with his fastest time in the lead-up to a major championship at the NSW state swimming titles at the Sydney Aquatic Centre.

Thorpe qualified for the open final after winning the 19 and over final on Wednesday night in, what was for him, a leisurely time of 1min:50.23sec.

But he put the afterburners on in his full bodysuit to eclipse that time by almost four seconds, finishing in 1:46.65.

The 21-year-old's world record is a little more than two seconds faster (1:44.06) and even he was surprised at the fast time.

"I've done my full program coming into here, I haven't really dropped off anything and to do a time like that...," he said.

"I don't think I've done a time that fast in the lead-up to a competition before, I'm usually pretty slow at these meets, so I'm pleased with that."

Thorpe's time was exactly the same Grant Hackett swam last week at the Queensland state titles.

"That's good because that'll mean he'll swim pretty quick at trials as well hopefully," he said, referring to March's national titles in Sydney which double as Olympic selection trials.

Thorpe had looked disinterested on Wednesday night and said he swam only because his coach Tracey Menzies wanted him to compete and on Thursday she even made him don his full bodysuit.

"Tracey wanted me to do it, I wasn't too fussed whether I wore a suit or not," he said.

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