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Brushless Fans for LS Swaps DIY - Let's get out of the stone age
As more and more brushless fans become available in the aftermarket and junk yard, many are discovering that these fans can move way more air, are very flat, have soft start and have variable speed capabilities built in. Those if you who want to buy the entire brushless solution from a vendor, go right ahead, there are probably some good solutions out there and you won't need this thread.
Many who see the benefit of the new generation of brushless fans but don't know how to control them with their existing ECMs, BCMs or even aftermarket like Holley or whatever, and also like a little DIY, stick around.
I'd like this thread to be about identifying brushless fans out there as more and more become available in junkyards and aftermarket as well as controlling them. I'm going to propose some methods of controlling these brushless fans. There are lots of ways, some a bit more complicated and some surprisingly simple. I test as much of what I propose as possible, but can't test all versions. I'll let you know what I've tested and what I haven't. I'm not in business so I make no money from this and provide no promises or warranties.
The first setup I'd like to propose is brushless fans in the most common LS swap, replacing the two speed relay setups in GM ECMs and BCMs to run brushless fans with 2 speeds. I'm drawing up the diagram for this now. Most will be amazed how simple this is.
Based on what I've seen in my threads before, some vendors will begin to package up some of these ideas for controls and wiring harnesses for profit. I'm ok with that, some people are not into doing any of their own wiring.
I'm going to add other methods as time goes by. Hint, hint, I really like Arduinos. Some of these have already been discussed on my DIY Fan thread in the Forced Induction section, but I'd like to keep this thread to brushless fans only.
If you're going to introduce Brushless fans to this discussion that we don't know about yet, please also provide information on dimensions and what the control strategy is for that fan.
I opted for new C7 Fan - PWM module is integrated and it was less than $250 new
It has worked flawlessly in my twin turbo with AC I drive pretty regular and race.
19368655 - GM Connector
84486698 - Fan Z51 (600 watt)
Forget the actual dimensions but it is mounted on my stand up radiator in 2002 Trans Am
Griffin Radiator 1-58241-XLS - 27.5X15.5
I use Holley Dominator to control via an MSD SSR Relay
For those of you who only have a PCM with two speed relay and want the benefit of Brushless, here is a wiring I propose. Instead of using 3 relays like you've seen a thousand times, One relay and 2 PWM Modules (example only) instead. I haven't tested the 2 speed setup, but I have been running a single speed one in my Turbo Minivan project.
You can set the PWM on each of the PWM modules to whatever you feel should be the low or high setting. The setting is remembered from that point on, even when power is removed. Most will find that full speed is way more than most cars need, so they may dial back the full speed PWM module to conserve amps.
Most brushless PWM fans I know about like 100 to 128 hz.
I opted for new C7 Fan - PWM module is integrated and it was less than $250 new
It has worked flawlessly in my twin turbo with AC I drive pretty regular and race.
19368655 - GM Connector
84486698 - Fan Z51 (600 watt)
Forget the actual dimensions but it is mounted on my stand up radiator in 2002 Trans Am
Griffin Radiator 1-58241-XLS - 27.5X15.5
I use Holley Dominator to control via an MSD SSR Relay
Thanks for the model number, connector info and dimensions.
I assume this is a brushless, PWM controlled fan. Why do you need an MSD SSR instead of going right to the Holley PWM- ?
I was at the junkyard picking up an L33 engine for my BMW project and went to check out their pile of radiator fans just for the hell of it. Cost me $10. Instead of going into the BMW project, it went into the C3 Vette.
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The shroud is 24 x 17.5 and the entire assembly is 4" thick. Basically it has a heavy Ground and +12 wire that goes to the battery and a small PWM control wire. The pwm wire has an internal pullup to 12V so all you need to drive this is a PWM- style or ground signal PWM.
It worked fine with a PWM frequency between 100 and 312 hz. Anything out of that range, it shut down. I would guess 128hz that is being used by other fans would be good.
Full power was at 7-10% duty and low speed was 90%. anywhere outside that range it shuts off, so 0% or 100% duty are off. Anywhere between 10 and 90% the fan varies speed with smooth transitions, always with a soft start.
At full blast, this fan drew about 45 amps. This thing really throws air. It just about hovered on the workbench.
Fans it replaced. modified the plastic shroud to fit my Aluminum Radiator:
Cut out all the excess plastic and mounted on the radiator. Moved the power connector outside the fan and sealed up any holes.
Even though the fan is flatter overall than my old fans, the blades are further away from the radiator and the shroud has more room. I've dialed in my cruising temps to 195 and temps at the track to 180.
ForecFed86 posted this BMW 335I fan. he thinks it's about 16" but I think it's bigger. I own a 335I, I didn't even know this was in there. I'll measure it.
I used relay as I assumed it was safer than risking any issues with damage to dominator.. and I had the ssr already for transbrake
I can't see any downside except cost and complexity. Definitely gives you a warm and fuzzy safe isolation feeling. The SSR can go up to about 1000hz so no harm done there. On the other hand, I believe thee are hundreds of millions of direct connections between ECMs and PWM inputs out there.
if you're running a transbrake solenoid from the Holley or other controller, then absolutely yes, you need to isolate that.
I also use a volvo brushless fan in my Turbo 5spd MTX minivan. I needed a flat fan to make room for the Air to Water intercooler. This ECM only has an on and off fan output, so I run the PWM generator instead of the original fan relay. PWM generator is set to about half speed and that's all this needs to keep cool.
The amazing thing was that I found this Volvo fan in a flooded car. You could see that the silt was covering lots of parts in the car including the fan. I took a chance on it anyway, brought it home, cleaned the sand out and it works perfectly. A testament to hardiness of these fans.
For those of you who only have a PCM with two speed relay and want the benefit of Brushless, here is a wiring I propose. Instead of using 3 relays like you've seen a thousand times, One relay and 2 PWM Modules (example only) instead. I haven't tested the 2 speed setup, but I have been running a single speed one in my Turbo Minivan project.
You can set the PWM on each of the PWM modules to whatever you feel should be the low or high setting. The setting is remembered from that point on, even when power is removed. Most will find that full speed is way more than most cars need, so they may dial back the full speed PWM module to conserve amps.
Most brushless PWM fans I know about like 100 to 128 hz.
forgive my ignorance here...when using these to convert a ls pcm (2 or 3 relay setup), will these ramp up to the chosen pwm value? i would guess thats where the "soft start" benefit comes from but haven't seen this type of setup in action before. the voltage spikes with the 2 or 3 relay setup is pretty brutal.
forgive my ignorance here...when using these to convert a ls pcm (2 or 3 relay setup), will these ramp up to the chosen pwm value? i would guess thats where the "soft start" benefit comes from but haven't seen this type of setup in action before. the voltage spikes with the 2 or 3 relay setup is pretty brutal.
Yes, they ramp up with no spikes. It's all handled by the integrated controller.
09-20-2022, 10:34 AM
Brushless Fans for LS Swaps DIY - Let's get out of the stone age 
