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Default Sensor AiO's in iCue.


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Ok, to keep it as simple and short as possible. Since an half year, I am year a "proud" owner of the Capellix H100i but from the start I was wondering why this cooler, although performing, was overmastered by coolers like for example a Fuma 2. I even ordered the new AM4 retention kit, with my regards to your costumer support for the great actions they have taken, to get rid off that dreadful & weak hook mounting system. Yet, the performance remained weak of this AiO. Till yesterday, when I dived into the settings of the iCue software and wondered why the fan speed of my cooler was stuck around 300 rpm even in Balanced mode. Fiddled a bit around, read some reddit and forum posts and came up with an important question for the devs of the iCue software: What is the most important sensor needed when cooling a CPU? Is that the Coolant temperature, CPU temperature, VRM temperature, Motherboard temperature and why is the default sensor been set on the Coolant? 

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Coolant temperature is the correct control variable for the fans on the radiator.  Their purpose to reduce the coolant temperature.  They do not cool the CPU directly.  Heat is removed from the CPU by conduction between the CPU lid or heat spreader and the "cold plate" that makes contact with it on the cooling apparatus.  This is true whether you have an air or water cooler.  If you take a CPU and run a stress test with several different cooler brand/types, they will all yield the same CPU temp for the first few seconds.  It's the waste heat removal next phase that differentiates one cooler from another. 


Once conducted away, you have to do something with the waste heat.  Air coolers blow it off.  Water coolers transport it to the radiator where the fans help dissipate the heat via the cooling fins.  Typically water coolers have a higher heat capacity than an air cooler.  This means they do not need to be as responsive or run the fans as hard to dissipate the heat.  It's effective a larger trash can.  You can fill it up more before you need to take it out and dump it. 


For each +1C to coolant temp, CPU temp will increase +1C as well.  The same is true in reverse for cooling.  This allows to measure the relative value of more fan speed.  If you coolant is 34C with the fans at 1000 rpm and decreases to 32C at 1500 rpm, you have reduced CPU temp by 2C in exchange for 500 rpm worth of noise.  Generally speaking, you can't overheat a water cooling system by running fans super slow, but there is a large penalty for doing so.  Most water cooling systems are very effective at moderate fan speed, with gains at high speed hard to come by except with specialized equipment designed for that sole purpose.  I am not sure why the fans are stuck at 300 rpm, but that is too low for almost all applications.  That puts you into the poor results, but not overheating.  Most 120mm fans have a minimum effective level around 700 rpm on radiator with a user specific sweet spot vs noise somewhere between 1000-1500 rpm.  


What I suggest to almost everyone is to make your own curve.  If you go to the cooling tab and +, it will create a graph below the field.  Change the sensor to "H100i Elite Temp" (coolant temperature).  Go to the 4 shape tools in the corner and pick one of the 4 choices.  These are copies of the Quiet/Balanced/Extreme presets, except now you can see the data points and what the speed should be at a specific coolant temperature.  Make sure you back to the fans above and change their setting to the new Custom 1 preset.  If the fans are still not changing speed, then we need to investigate further.  They should not have been stuck at 300 rpm for any of the presets.  

Edited by c-attack
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@c-attack: Yeah, Quiet & Balanced profile keeps the fans spinning at an avarage of 300 rpm. They don't ramp up to provide more cooling. 


But that's beside the question. If I can run my CPU at a lower temperature with a costume setting on the CPU sensor then when that profile is controled by the coolant sensor, then what is more effective in your opinion? Especially when the difference is about 10 °C in favour of using the CPU sensor. I am currently running Star Trek Online, while typing this and with the sensor on coolant, the CPU hits 67° max and with the sensor on CPU, it hits only 58° Max. And no matter what you think of a CPU overheating or not, in my opinion hitting sometimes temperatures between 75 & 80°C is way too much for a cooler that costs 150 Euros.


Besides that, I wonder why, if this explanation of yours is the wonder solution, it hasn't been adapted by others. Most, if not all, are using the simple CPU sensor for fan speed and a fixed pump speed. Yet, they manage to run circles around Corsair AiO's at a more silent operation. Instead of providing a gimmick, which for non savvy user may cause concerns and unneeded issues, keep it simple: default on CPU sensor, leave to choice to switch to other sensors over to hardcore enthousiasts. I wouldn't mind it if I could pick for example the balanced profile and set the sensor on VRM, which a lot are doing to have a good cooling without too much noise.


And if noise of the fans are a concern with the operation of your AiO's at full speed or elevated speed., maybe, just maybe it's time to put finances and development into more performant, less noisy fans or fans that can deliver the same perfomance at a lower speed. Sad, that this complaint by many users is never picked up by Corsair. 


TBH, after all this research into why my cooler didn't perform better as said Fuma 2 (and no, I can't place a tower aircooler in the current case (139mm max cooler height)) and by the lack of a serious explanation into the operation of iCue and this AiO aka lack of manual (which can put you legal troubles in certain countries as it seems that iCue is an essential part in the operation of the AiO), but yet managed to make this cooler to perform as desired, I can't say I am pleased with it. Too much hassle, especially for non tech savvy people who want simply performance out of the box. 

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Well, the fact is controlling the fan speed by CPU temp is just a sound nuisance with zero performance benefits.

The problem Corsair has is those 3 fan curves, quiet, balanced and extreme, that are absolute garbage with water coolers.

That's why everyone should make their own fan curve, and that's why you can't have good performance out of the box too unfortunately. Same goes for those making a $$$ custom loop watercooling system and using those fan curves. the temperatures are just bad.


When you use the CPU temp as variable, lets say you start gaming, the CPU warms up instantly, your fans speed up... but they dissipate nothing since the water is not warm yet. they make noise while doing nothing.

If the CPU load varies a lot as is often the case in games, the fan speed will move up and down, despite the water temperature varying very slowly.

Ideally you want to make a fan curve controlled by the water temperature, to only speed up the fans when there is heat to evacuate.

300 RPM is way too slow, so you end up with warm water at idle, and a hotter CPU than with an aircooler.

When you game, they accelerate too late, and you end up with a warmer CPU than it should be, as you saw.

That's why those 3 default curves absolutely suck and should be replaced by your own. They can't make an universal one because ambient temperature changes from user to user. Well, there are 3 universal fan curves but you saw how they perform 😛


A fan curve is really easy to make, as he suggested. just match a temperature with a fan speed and you can make the PC as cool, or as silent as you like. And with the fans controlled by water temp, you won't have to bear with those constant accelerations and decelerations of the fans that serve no purpose when you use watercooling.

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I think both don't understand the issue: Most important use of an AiO is too cool the CPU, so the sensor on the CPU should dictates the "performance" of the presets. What use the has the costumer of the fact that the coolant is registing 30 to 35°C while your CPU is hitting 80°C. Most of the users don't care about the coolant temperature, but about the CPU temperature. So, if you expect your users to have a silent, correct performance of these coolers, I have already offered the solution, instead of this useless mumbojumbo of coolant temperature: start fixing the years long complaint of having too noisy fans, invest in that or I'll put those ML fans in the trash and replace them with some BeQuiet Silent Wings.

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what we're trying to explain is that the fans don't cool the CPU but the water ^^' It sounds silly but that's the one reason why controlling by CPU temp makes way less sense.

when your CPU gets to 80 on cold water, when you start to load it, guess what your fans do ramping up to 2000 RPM, forcing ambient air through a cold radiator? They make noise, and that's about it, because they dissipate no heat YET.

Radiator efficiency goes up as the difference between water temp and ambient air increases.

The warmer the water, the easier they dissipate. So as long as the water is cool there is absolutely no need to speed up the fans.

As water gently warms up, the fans should also start to accelerate (that's what iCue's default presets don't do well)


In the end when your water has reached some equilibrium while you play, using CPU or water makes very little difference. The fans need to run faster, so that's okay.


Now when you stop, same deal as when you start.. the water is hot. the CPU cools down instantly when you stop playing and the fans slow down.. but they should keep running since water is hot. it basically kills cooling headroom for when the CPU will be loaded next, and keep the CPU 15 - 20° hotter at idle for way longer.


in the end using either variable will get you by, but using CPU will be a lot noisier with those speed variations. There's nothing wrong using the cooler the way you do, it's just more noisy and less efficient. that's why we were trying to help.

Ah and the silent wings aren't stellar when installed on radiators

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46 minutes ago, Reddorki said:

I think both don't understand the issue: Most important use of an AiO is too cool the CPU, so the sensor on the CPU should dictates the "performance" of the presets

No, because the fans are not capable of cooling the CPU.  That's not what they do.  CPU cooling is conductive.  If you have any doubts about that, detach the cold plate from the CPU on any cooler and try and boot up.  You can put a really big fan to blow on the whole motherboard if you like, but then you are going to need to go buy a new CPU.  


If you really want to maximize your cooling potential, set the fans to 100% and leave it.  Done.  You are now at the maximum possible dissipation rate at all times, needed or not.  The alternative is to use a control variable to lower the fans when certain conditions are met, in the interest of avoiding a prolonged headache.  CPU temp=X is not it.  Go ahead and use it if you like, but it is likely to create an unpleasant and useless fan response.  


Your fans on the AIO should not be capable of running 300 rpm and most Corsair fans cannot be forced into that low speed.  The cooling presets should not be passing on a 300 rpm command.  Something is wrong.  If you want help with this, we need to see the control graph and the fans running at 300 rpm when they graph shows they should be at 1000 rpm or whatever.  Be cautious about running additional full spectrum monitoring programs like Aida or HWiNFO at the same time as CUE.  These can cause a loss of fan control and typically also produce garbage data points for both programs.  

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