Is 1600 RPM too high for fans?

No, that's fine.

What is the difference between the idle and gamming temp's...? Personally I might kick it up a little higher if the temps were still going above 75C.

FWIW I still have an Early 2006 Core Duo iMac that has been on SMCfancontrol for 8+ years and it has never had a hardware failure. Contrary to what others say here. I say that, controlling the temp's has made all my Mac's last years longer.

I agree.

1600 RPMs for the iMac fans is probably as far as I would set these.

It's a temperature sensing diode built into the Graphics Processing Unit chip.

Gaming usually = more use of GPU, so it gets hotter.

What are the temps at 1,600, while gaming? Which fan is that? Is this one of the newer Macs with only one fan?

If you don't have some kind of temperature software, get

http://www.bresink.com/osx/0TemperatureMonitor/download.php

And post the temps.

If the default is 1,400, if needed, I think you could probably go even a bit higher, as Den said. My defaults are 1,000, 1,100 and 1,200 ODD, HDD, CPU. There I wouldn't push anything faster than around 1,600, not at least for a prolonged period.

I am not sure what this is, either, but it is usually the hottest element in my iMac, too and I do not game.

Whenever I am doing a moderate amount of work, my GPU Diode is usually around 60-70 ° C.

I agree and andy is spot on.

Sounds like you have pretty much found the sweet spot. If it was going over 75C, I would go to 1700 rpm to see if that helped.

Everyone has their own preferences for manually setting the iMac's fans.

That is why I only advise a max range for the fans for people setting the IMac fan speeds, manually.

I run the three fans in my 2009 iMac in the 1200-1500 RPM range.

Plus, I run a small, portable desktop fan from behind blowing on the back and toward the top of my iMac, too!

That is why I only advise a max range for the fans for people setting the IMac fan speeds, manually.

But you cannot advise a max speed in isolation, as you have. It all depends on the default speed. 1,400->1,600 is only +200, while my default HDD at 1,100, which I may push up to 1,600 is + 500.

Anyway, it's mostly guesswork. No one really can say how fast is too fast. And no one's going to do any trials to find out at what speeds and for how long running at those speeds will premature aging of a fan motor likely begin.

And there's also the tradeoff of increased dust input from higher fan speeds to consider.

I have a window fan that's 40+ years old and still going strong (cheap shaft bearing), mainly because I have an electronic variable speed control which allows me to set it at the lowest necessary speed, plus I oil it periodically--something you can't do with an iMac fan.

In general there is no reason to set the fan speed: the mac takes care of itself. The fan speeds are different for different macs: my mbp's for example start at 1900-2000RPM as a minimum, and get u to 6000RPM as a maximum when the GPU diode is over 80°C.

In general there is no reason to set the fan speed: the mac takes care of itself.

No, sounds good in theory, but not in practice. The fans in the iMacs are set for quiet running, not for longevity of the hardware. The fans will not ramp up quickly enough or at all to deal with higher temps. Heat kills hardware, especially drives.