Different RPM readings

[Tyranade]

So I have reconnected my case fans to my Motherboard and the Gigabyte software is reporting that both my AF 120 fans running at 60% have 2 different RPM readings. Surely if 2 of the exact same fan where running at 60% they would be running at the same RPM ? Their 3 pin fans BTW.

 

One fan was running at 660RPM the other was at 700RPM surely they should be closer than that or is voltage control just iffy at best?

[WoodenMarker]

Are they connected to different fan headers?

[Tyranade]

3 minutes ago, WoodenMarker said:

Are they connected to different fan headers?

Yes they are.

[WoodenMarker]

Just now, Tyranade said:

Yes they are.

Which headers? What motherboard do you have?

[Tyranade]

Just now, WoodenMarker said:

Which headers? What motherboard do you have?

The Gigabyte GA-Z170X-Designare and System Fan 1 and CPU_Opt simply because of fan cable length.

[WoodenMarker]

1 minute ago, Tyranade said:

The Gigabyte GA-Z170X-Designare and System Fan 1 and CPU_Opt simply because of fan cable length.

CPU_OPT mirrors the CPU_FAN header settings. If you want the fans to act similarly, use SYS_FAN headers for both.

[Tyranade]

Just now, WoodenMarker said:

CPU_OPT mirrors the CPU_FAN header settings. If you want the fans to act similarly, use SYS_FAN headers for both.

But I can control both of them completely independently in the software so I do not believe it does.

 

 

I have control other both fans in SIV.

[Tyranade]

Like I was saying I have 2x AF 120 Fans connected to System Fan 1 and the other connected to CPU Optional Header and when both set to 60% they have different RPM readings. My CPU Fan header is running at 1800RPM so they are independent.

[WoodenMarker]

Just now, Tyranade said:

But I can control both of them completely independently in the software so I do not believe it does.

I have control other both fans in SIV.

Oh, alright. 

Both are wired for pwm along with sys_fan2_pump. 

To control fans using DC, use headers sys_fan1 and sys_fan3. 

[Tyranade]

1 minute ago, WoodenMarker said:

Oh, alright. 

Both are wired for pwm along with sys_fan2_pump. 

To control fans using DC, use headers sys_fan1 and sys_fan3. 

I can control the fan using DC on CPU_OPT_PUMP I'm doing it now down from 1200RPM to 600ish but what I want to know is WHY my 2x AF120 fans are reporting 2 different speeds while both set to 60%

[WoodenMarker]

3 minutes ago, Tyranade said:

I can control the fan using DC on CPU_OPT_PUMP I'm doing it now down from 1200RPM to 600ish but what I want to know is WHY my 2x AF120 fans are reporting 2 different speeds while both set to 60%

They're wired differently. If you want them to run the same way, use sys_fan1 and sys_fan3. 

[SageOfSpice]

I'd say pwm control is just like that. I experienced the same thing when I was trying to sync some of my fans. Ended up having to set 1 fan 15% higher than the other to achieve the same speed.

[Tyranade]

Just now, SageOfSpice said:

I'd say pwm control is just like that. I experienced the same thing when I was trying to sync some of my fans. Ended up having to set 1 fan 15% higher than the other to achieve the same speed.

All my fans right now are 3-pin DC fans not PWM. Until I get my hands on some Corsair ML fans.

[Tyranade]

1 minute ago, WoodenMarker said:

They're wired differently. If you want them to run the same way, use sys_fan1 and sys_fan3. 

I can't because I have my H100i V2 Fans connected to Sys_fan_3 with a fan splitter cable.

[WoodenMarker]

3 minutes ago, Tyranade said:

I can't because I have my H100i V2 Fans connected to Sys_fan_3 with a fan splitter cable.

Connect your SP120L's to cpu_fan instead.

[SageOfSpice]

4 minutes ago, Tyranade said:

All my fans right now are 3-pin DC fans not PWM. Until I get my hands on some Corsair ML fans.

Should be the same deal. No two fans are ever really going to be the same, so treating them the same and dumping the exact same voltage into them isn't going to result in the precisely the same RPM.

 

Hell, proximity to other objects can affect RPM, as can heat. It doesn't take much to slow down a little DC fan.

[Tyranade]

Just now, WoodenMarker said:

Connect your SP120L's to cpu_fan instead.

I can't because I am using the NZXT S340 so the cooler is mounted in the front and the SP 120 Quiet Edition fans I am using have very short cables and they don't reach.

[WoodenMarker]

Just now, Tyranade said:

I can't because I am using the NZXT S340 so the cooler is mounted in the front and the SP 120 Quiet Edition fans I am using have very short cables and they don't reach.

So you're using SP120 QE's instead of the stock SP120L's? If so, are they DC or PWM?

[Tyranade]

8 minutes ago, WoodenMarker said:

So you're using SP120 QE's instead of the stock SP120L's? If so, are they DC or PWM?

They are 3 Pin DC fans. 

 

I would of wired the fans into the cooler itself but it doesn't allow 3 Pin Voltage Control on the cooler and the SP120L fans sound like freaking chainsaws and look nasty too. I am going to be swapping to a Kraken x61 with ML 140 Fans which are 4 pin and will be powered off the Kraken itself but until then I am going to be stuck with my H100i fans connected to System Fan 3.

 

Can you explain to me the need for motherboard manufacturers to wire their bloody fan headers differently it is a massive inconvenience. I was using the Grid + V2 before but in preparation for the ML Fans I need PWM control really for those.

 

Maybe I am over-thinking it and it might be due to variance in the fans. I had to set SYS_FAN_1 to 54% Voltage to match the RPM count of the fan connected to CPU_OPT_PUMP which is at  60% which doesn't sound like a lot.

 

EDIT: Also on this motherboard I did find out you can not control the CPU_FAN with Voltage I tried and even set to 0 volts it wouldn't turn off so I am assuming that is a PWM control ONLY header. Mainly because CPU_FAN is the only one with Speed Control on Pin 4 which my fan did not have but all the other headers it is on pin 2 with the "Pump" headers have it on 2 and 4.

[WoodenMarker]

41 minutes ago, Tyranade said:

They are 3 Pin DC fans. 

 

Can you explain to me the need for motherboard manufacturers to wire their bloody fan headers differently it is a massive inconvenience. 

 

Maybe I am over-thinking it and it might be due to variance in the fans. I had to set SYS_FAN_1 to 54% Voltage to match the RPM count of the fan connected to CPU_OPT_PUMP which is at  60% which doesn't sound like a lot.

In that case, you might just go with another splitter for the case fans. 

They're wired that way to save on cost. 

Variance in the fans is a plausible explanation. 

[Tyranade]

Just now, WoodenMarker said:

In that case, you might just go with another splitter for the case fans. 

They're wired that way to save on cost. 

Variance in the fans is a plausible explanation. 

As I will be going with the Corsair MagLev fans which it is recommended you use PWM control due to the bearings in the fan not working properly if it goes below 9 volts I should connect them to either CPU, or PUMP 1 or PUMP 2 right as they are PWM? 

 

But why does the Pump headers have Speed Control on Pin 2 unlike the CPU fan which has +12v There?

[Tyranade]

I think I may just get one of these https://www.scan.co.uk/products/phobya-pwm-8x-4pin-splitter-box-with-molex-pwm-adapter-y-cable to power 2x of the ML Fans off the CPU PUMP 2 Header as it is PWM as its near the bottom of the case run 2 of them that way and the other 2 off the Kraken x61.

[WoodenMarker]

56 minutes ago, Tyranade said:

As I will be going with the Corsair MagLev fans which it is recommended you use PWM control due to the bearings in the fan not working properly if it goes below 9 volts I should connect them to either CPU, or PUMP 1 or PUMP 2 right as they are PWM? 

But why does the Pump headers have Speed Control on Pin 2 unlike the CPU fan which has +12v There?

CPU_FAN is the most reliable header for pwm. 

Speed control should mean 12v. The second pin being 12v is for DC and the fourth pin is for pwm. 

50 minutes ago, Tyranade said:

I think I may just get one of these https://www.scan.co.uk/products/phobya-pwm-8x-4pin-splitter-box-with-molex-pwm-adapter-y-cable 

That works.