In the form of his life, left-handed Fazal hit his third successive century of the season with a sublime 142 (22x4), while Ramaswamy gave fine support at the other end with a patient 117 (14x4).
Ramaswamy was unbeaten with senior pro Wasim Jaffer (18) when bad light stopped play after 83 overs on day one.
Bengal captain Manoj Tiwary's decision to bowl after winning the toss backfired as the Vidarbha openers put up a solid 259-run opening partnership on a frustrating day for the home team bowlers.
Fresh from his 125 and 136 against Chhattisgarh and Services respectively, Fazal carried on from where he left off.
Both Fazal and Ramaswamy anchored the innings and completed their half-centuries in the first session.
The duo then completed their triple-figure milestones on either side of the tea-break with Fazal first to get to the mark in 184 balls, his 14th first-class century.
Ramaswamy took 191 balls for his third firstclass century as the duo continued to frustrate Tiwary who himself was made to bowl three overs.
Bengal sorely missed the services of India pacer Mohammed Shami who did not get the Board's clearance, even as the other Test cap Wriddhiman Saha featured in their lineup.
It was only in the 73rd over of the day, Ashok Dinda (1/62) gave the breakthrough when he trapped Fazal.
Brief Scores In Kalyani: Vidarbha 285/1; 83 overs (Faiz Fazal 142, Sanjay Ramaswamy 117 batting) vs Bengal.
In Dharamsala: Himachal Pradesh 175; 44.2 overs (Pankaj Rao 3/52, Sumit Ruikar 3/20). Chhattisgarh 91/1; 34 overs (Rishabh Tiwari 46 batting, Ashutosh Singh 40 batting).
In Delhi: Services 228/8; 90 overs (Nakul Verma 64, Vikas Yadav 61; Heramb Parab 3/35) vs Goa.
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