Brushless Radiator Fan Success

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Noah Levreau
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Joined: Fri Aug 19, 2022 2:35 pm

Brushless Radiator Fan Success

Post by Noah Levreau »

Hello. I decided to upgrade to a brushless radiator fan on my 1990 Miata, since the stock one went out, and the ecu has PWM outputs. Here is how I did everything:

I went with Flyin' Miata's stage 2 fan kit which came with: a 14 inch Spal fan, a breaker, and a wiring harness.

What I like about these fans is that they can start off slow then speed up, so it doesn't have a large startup surge. These fans need a PWM output to be controlled, so you will not be able to use the original plug for the fan or on/off controls. They will need a separate power source from the alternator or battery since it does not reuse the original plugs. The sensor wire will be wired to the Radiator Fan or Fan Relay pin on the ecu.

Now to program it, you can use the General Purpose PWM under advanced settings; make sure to use an unused PWM chart. The X-axis is RPM values (which can not be changed). Set the y-axis to Coolant temp and change the values to the coolant temps you want the fans to spin and not to spin at. Now the boxes inside the chart are going to be duty% (how fast the fans spin). In the fan that I am using, the values are inversed. 100 means 0% of full speed, 75 means 25% of full speed, etc. However, the values of 5-10 are treated as 100% of full speed and anything lower than 5 turns the fans off. You will also be able change the duty% for the rpms. You will need to use this to set the fans to be off at 0 rpm so they will not turn on when the engine is off.

Here is a picture of my GPPWM chart below:
radfanPWM.png (37.82 KiB) Viewed 1975 times
At 15% on is more than enough to cool my stock engine at idle.

Important note: make sure to deselect the radiator fan in the Fan Settings under Base Engine.
Fanset.png (35.68 KiB) Viewed 1975 times
I forgot to do this the first try and got a bunch of error messages.

Here is a link to my tune:

If you have any question, feel free to ask. I will do my best to answer.
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Re: Brushless Radiator Fan Success

Post by AndreyB »

Thank you for the write up.
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