With Antti Haapala co-driving his Pirelli-equipped Škoda Fabia RS Rally2, Suninen completed the 6.41-kilometre Pendam test in a time of 3min 52.9sec.
The Finn’s performance for The Racing Factory means he will line up first on the road for today’s opening leg.
“It’s great to be able to start as the first car and some proof of the pace in tricky conditions,” said Sunninen, who holds the provisional ERC points lead after five rounds. “But we know the rally is going to be so difficult so we cannot trust that pace too much. We have to focus on what’s coming.
“I believe the feeling will be like Rallye Monte-Carlo, going into the night stages not knowing exactly the grip level because we are doing this same stage the other way round so there will be some muddy surprises. I’m a bit scared but we try to do our best.”
Michelin-shod European champion Miko Marczyk was second fastest in a time of 3min 54.4sec, with Kris Meeke – back as a points-scoring driver in the ERC for the first time in 20 years – going third quickest.
Competing in a Toyota GR Yaris Rally2, Meeke’s effort was a 3min 55.0sec, as MRF-supported Simone Tempestini and Lancia-powered Andrea Mabellini rounded out the top five on a stage made extra slippery following earlier rain.
“It’s exciting to be back and I’m not that far from home,” said Northern Irishman Meeke, who is carrying the flag of Andorra through his competition licence. “It’s a tricky rally and it is very difficult being here for the first time. I’m happy with my start. We could have run a different tyre, but it is hard to know. It will be a difficult start in the dark tonight.”
Jakub Matulka, an ERC3 category winner in Ceredigion two seasons ago, was sixth quickest followed by Meirion Evans, Erk Cais, Sam Touzel and Pierre Ragues. Max McRae was 11th following tyre damage with Master ERC contender Martin Vlček 12th fastest.
Double Rali Ceredigion winner Osian Pryce rounded out the Qualifying Stage contenders in 13th with the left-rear tyre off the rim after the Welshman clouted a bank at the water splash.
“I don't know [what happened],” he said. “There is that much muck on the road, it is one of those things. It looks like our chances of this rally are going south.”
The first of four runs through the Aberystwyth super special is next from 19:05 local time with Friday’s action concluding with the Blaenmelindwr night stage from 21:30.
Watch the action live on Rally.TV and follow all the news, stage times and results via the Live Centre.