The Pole will drive a Citroen DS3 RRC in the WRC2 category, competing for the first time on gravel. Kubica finished fifth on last Saturday's Fafe Rally Sprint, but he still feels short on loose-surface mileage.
"In total, in my life, I have done around 400 kilometres [250 miles, on gravel]," Kubica told AUTOSPORT. It's better than nothing, but it's not so impressive.
"When I came here I wasn't so confident, it's a very different technique to drive on this surface, but after the first day of the recce I feel more confident and after the second day of the recce I feel more confident again."
The Faro-based event will be the longest rally Kubica has tackled and there were concerns over his physical fitness following the injuries he sustained to his right arm in his crash in 2011.
Sunday's Almodovar stage at 32 miles is expected to provide a particularly tough test.
"I like that stage after the recce," Kubica added. "It's a really interesting stage with lots of different aspects.
"This event will be a good physical test for me. There is less grip, so the steering wheel will be lighter, but you do more corrections on the wheel on gravel than asphalt.
"The good thing about the long stage is that it's near the end of the rally, so I will also have more experience of the car. I'm hoping Portugal will give me a lot of positive answers.
"I am really looking forward to the event and the experiences of driving on gravel.
"You hear many stories - but you need to have the experiences and go through the experiences. I would give everything to have these experiences already."
- Sports & Recreation