It was a superb all-round show by Delhi as they first dismissed Bengal for a meagre 156 in 40.1 overs and then overhauled the target with 15.3 overs to spare.
Now Delhi will clash with Assam, who beat Kerala by five wickets in the other semifinal, for the title of the domestic One-day tournament.
Had it not been for a fantastic 87-run knock by Manoj Tiwary and his 73-run partnership with skipper Laxmi Ratan Shukla (30), Bengal could not have even posted a respectable total.
Pravinder Awana drew the first blood by clean bowling Wriddhiman Saha and after that Narwal and Sangwan ripped apart the Bengal middle-order.
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Sood played his part by cleaning up the tail.
Delhi also did not have a good start, losing opener Dhruv Shorey (10) early but its middle-order responded well. Unmukt Chand, who opened with Shorey scored 22 while Gambhir scored 69 off 78 balls.
Delhi lost Chand and Milind Kumar (18) while Gambhir batted superbly from the other end.