The London club's fans stuck by Redknapp during a difficult start to the season and have been rewarded with improved performances in recent weeks.
The vocal away support was noticeable last Saturday, when Chelsea boss Jose Mourinho commented on it to Redknapp following the leaders' 2-1 win at Stamford Bridge.
"He came up to me during the game and he said they were fantastic," Redknapp said. "They have stuck behind the team and that's all we can ask.
"They made a lot of noise last week and that's really good. The fans can make or break a team."
Such support at Loftus Road will be valued on Saturday as Redknapp targets an upset against a City side reeling from Wednesday's crushing 2-1 home UEFA Champions League loss to CSKA Moscow.
That defeat cranked up the pressure on City, for whom a derby success over Manchester United on Sunday was their only triumph in their last five games in all competitions.
Redknapp, whose side are second bottom, added: "Whenever you play City, it is a difficult game. They have a fantastic squad.
"It will certainly be a tough game. We did well at Chelsea last week, but we need to show the same commitment if we are going to get anything out of the game.
"You don't become a bad team overnight. They are the Premier League champions and we will be playing a top team."
Adding to Redknapp's confidence is the uncertainty surrounding City skipper Vincent Kompany, who is struggling with a calf problem.
David Silva and Aleksandar Kolarov are certain to miss out through knee and calf injuries respectively, while Frank Lampard should be available despite a thigh concern. Samir Nasri is pushing for a first start since returning from a groin issue.
Rio Ferdinand will miss out for QPR as he serves a three-match suspension for comments made on Twitter.
But that is one of few concerns for Redknapp, who has Joey Barton, Niko Kranjcar, Jordon Mutch and Nedum Onuoha available for selection.
Redknapp said: "Touchwood, we've got a clean bill of health – everybody's fit, probably for the first time since I've been at QPR! That's great.
"It's nice to have too many good players, as opposed to not enough. It's great to have a full squad. All players should be available for selection at the weekend."
The last meeting between the two sides was a damp squib, with City and QPR playing out a goalless draw at Loftus Road in January 2013.