Should the speed of a card's fan directly affect performance?

[abblem]

I have a 9800 GT and I have documented in a handful of games I own that by using Rivatuner to directly control the speed of the fan and increase it the card seems to produce better results, averaging about a 1 extra fps per every 5% increase of speed and 1 less for 5% decrease. Should this be happening? It doesn't seem to directly be a heat issue, as the the card's temperature doesn't vary much, if at all. Would it be harmful to the card to run the fan at 100% during game playing?

 

[xaira]

are you shure its the fan speed and not the core clock

 

[abblem]

are you shure its the fan speed and not the core clock

I'm not really sure how the two could be mixed up but yeah I'm sure. I don't mess with the clocking.