The victory came courtesy of a Theo Walcott goal just 20 seconds in and it lifted Arsenal, who have won six and drawn two of their last eight league games, two points ahead of Spurs and Chelsea. The three London clubs are engaged in a battle royal for the last two Champions League places.
With Arsenal and Spurs both winning, all eyes now turn to Chelsea and Sunday's trip to Manchester United, and Wenger said: "We are up for it. We are ready for a fight and the team is highly focused to do it. We are on a very strong run."
He added: "We definitely have a momentum, if you look at the points we have made compared to two months ago. We are going for it and we make the points. Away from home recently we have won everywhere - at Fulham, at Sunderland, at Swansea, at QPR. Derbies are difficult to win."
Asked how much pressure Arsenal's triumph now places on Chelsea, Wenger said: "I don't know how much but it puts you under pressure because you have to make a result."
Walcott's goal, his 20th of the campaign, was the quickest by an Arsenal player in the history of the Premier League and the fastest by anyone in the league this season.
The England international struck the post soon after but QPR competed well and in the end Arsenal had goalkeeper Wojciech Szczesny to thank for the win after he brilliantly denied Loic Remy.
QPR manager Harry Redknapp was proud of the spirit his relegated side showed in pushing Arsenal so close, and he said: "It was an awful start to go 1-0 down within a minute but I thought we showed fantastic spirit.
"There was nothing in the game. I always felt we were going to get something out of the game and their keeper's pulled off a world-class save late on. I couldn't have asked for more from them. Their heads could have dropped after that start and we could have been beaten by five or six.
"But we didn't. We got after them, we worked them and I thought it was an excellent performance. I was delighted with the players."