TLDR: from W220 Mercedes, it drops right in and fits perfect. In fact it's silly. But you will need a controller and bigger electrical system.

VIDEO of PWM test. At full song, it is absolutely howling, but it gets there so gracefully lol.

Like many of my modifications, when I looked into the light, I couldn't look away. It's completely unnecessary. The stock fan was actually just fine for me. I just felt like it. If you think stock fan is better, that's great, there are other posts that discuss that.

I was looking at Mercedes fans because many have an embedded MOSFET unit to drive PWM which is necessary for variable speed and PID. MOSFET necessary even if you build the logic, because variable speed duty cycles high current at steady voltage which needs a big heat sink for the solid state switching. So I compared spec sheets on radiator sizes and decided to give a 2006 S65 AMG a try. It's 850 watts which is cartoonishly big, but with PWM you only use a portion of it (hopefully), and with good logic, only when you need it.

OEM replacement fan will give you sticker shock. I bought aftermarket on AMZN prime for $254. You may have luck at the wrecking yards.

Snug as a bug. Upper shroud is perfect at top of core and check out how nice the arch fits between filler neck and upper hose. Opened up a ton of room in front of motor too:


Psgr side looking down. Check out the shroud lip. It is perfect:


Driver side looking down. If you look down low, you can see that the Mercedes fan has a rubber tit to sit in a bracket on both sides. The weight of the fan sits in those and they bolted in stock location and they pinch the shroud lip against radiator frame:


Lower mounting... Here's a pic of zinc plated bracket, unmodified from McMaster. You can sort of see here how it pinches the shroud lip against radiator frame so the bracket gap you can see looking down is moot because fan shroud is clamped against radiator. Brackets cannot rotate because it's up against shoulder of fan shroud. Super snug:


Upper mounting... The upper holes ALMOST landed on target. They are perfect height and right size, but just a couple mm outboard. I have them zip tied in right now. I might use metal core zip ties, or I might hog out the hole, not sure yet.




Bottom of fan and shroud leaves a few inch gap, but the shroud is very close to core so I really don't think there will be any pressure losses inside shrouding, and it covers 90% already.


I've got 120amp alternator and 'big3' completed. 8 awg to the fan power and 80 amp fuse lol. Circuit breaker over the fuses is charge wire from alt. Actually, with proper cooling system maintenance, it's hard to imagine this fan will ever pull more than 30-40% in the worst conditions? Guess I'll find out.


I had another thread started few months back when I shared the controller I'm building, but I started this thread because I just wanted to share fan fitment on it's own. Zero fabrication or modifications to the fan or 4runner. It fastened into stock location and fit perfect. I just had to laugh.

I've got a few angles going right now on my truck so I'll prob be a couple weeks before getting back on road. Arduino will have an LCD screen, show upper and lower radiator temps, ambient temps, AC condenser temps, interface with OBD (even though my 98 only has like 2 outputs lol), it will read, display, and clear codes, and with properly tuned PID algorithm, I will be able to select desired engine temp and it will find perfect fan speed and adjust for any disturbances to temp to stay on target. Again... the fan drops right in, but not so easy to control right and fill in all the features.

I like it! Is it overkill? Maybe, but sometimes overkill is awesome. What I really like is that this is something new (at least to me anyway). Very nice to see people come up with ideas.

What's the total amp draw of the fan though? If you are wheeling, you'll see crazy high temps that might actually see the full amp draw. Even with a 120 amp alternator, that might not be enough.

I have a 16" SPAL fan that struggled to keep up cooling my 4Runner wheeling in the hot summer, was in the 210's and it draws up to 25 amps. Sloppy math puts that fan at 70 amps...

Your math isn't so sloppy. That's the reason for the 80 amp fuse. Wiring is set up so I can put in a bigger alternator if I actually use all that fan. I have a CS144 already installed so there are a lot of solid options to swap for bigger alt if necessary.

The most important thing with a fan is creating a pressure differential on the face of the core. The actual speed of air flow through a radiator is very slow and it's a function of pressure differential rather than CFM ratings. This is why shrouding is so important and was the number one priority when I was looking for a fan. I didn't expect to end up with such a powerful rated fan, but the shroud fit is perfect so I anticipate that it will be very efficient at low duty cycles and will leave most that power in the back pocket, and the real magic in PWM. I'm real interested to find out and I'll update here. I'm headed to Moab in a few weeks and will put it through the paces.

My DC current clamp was throwing fits today so I couldn't get a good measurement.

what battery terminals are those? can you post a pic of what they look like without the covers on?

AMZN $20

That's awesome. I want to see you swap in the engine from the S65 too!

Yeah even I had to put in a CS144 for mine. Tried on the stock alternator and it died.

I do have to say, that fan fits insanely well. Unless you say something, it almost looks like the fan was some sort of e-fan factory option.

It totally looks factory!

I took a look at current without motor running (coolant still drained). I can’t post scope pic from my phone, will update with scope shot after I have data w motor running, but at 1.25 millisecond cycles, you can see current through each coil winding ramps from 45a to 80a 70% and then back down to 45a for the rest of 30% cycle. Avg looks about 60a (slight curve). Without alternator, Voltage drops to avg 11.0v through that. Importantly, with MOSFET, there is zero current rush at fan start.

It's not hot weather yet, but I thought it would be interesting to share a couple notes...

The current draw from this fan rises exponentially:

FAN RPM / % full fan RPM / Current

680 / 32% / 1.4 amps (lowest setting)
760 / 36% / 2.3a
840 / 40% / 3.3
940 / 45% / 4.4
1050 / 50% / 6.0
1140 / 54% / 8.1
1230 / 59% / 10.5
1350 / 64% / 13.0

2100 / 100% / 60 (full blast)

Weather has been cool (< 60°), but so far, the fan has never been on more than lowest setting. When coolant hits 200°, fan comes on at 1.4 amps for 30 seconds and knocks the temps down 12° to thermostat level. Then truck sits at 188° thermostat level (Toyota OEM 180) for a couple minutes and slowly rises to 200° again for another 30 second cool. About 30 seconds on / 3 minutes off at idle.

Fan does not come on when driving because frontal air flow. It is SO nice not to have a fan strapped to front of motor anymore.

I've got a handful of things to sort on the algorithm to drive the fan, but the install is done and it's all systems go to dial everything in.

When I flushed my cooling system, I pulled the thermostat out and just wanted to see what the fan would do at full blast. It was pulling 60 amps, I had HID head lights on, LED spot lights on, rear defroster on, fan full blast on cool, and stereo amp/sub pulling whatever it could. There was a voltage drop from 14.2v to 13.2v at idle. Rev to about 950 RPM brought it back to 14.2v.

But more amazing, is how much and how fast it pulled temps out when thermostat was removed. Starting at 206° coolant temp, in 60 seconds it pulled out 45° to 161°. 200 seconds it pulled more than 80° out to 125° and still dropping.

I'm a nerd, and thermal is what I do so that's why I did the swap. The real surprise has been how little of the fan has been required and how little amperage it draws when only enough PWM is sent that is necessary.

When weather gets hot enough, I just *might* compare this set up and stock setup in A/B test and compare injector opening times as a matter of understanding efficiency gains (and HP estimate) to determine how much a mechanical fan is spinning when it's not needed (even with clutch disengaged it saps, especially at highway RPM).

When the PID algos get dialed in, I may design this as a product for aftermarket so that enthusiasts can send PWM to stock OEM fans with built in MOSFET units like this one. Compatible with multiple OEM fans and sensors. When an embedded MOSFET fan is used, the controller circuitry is basic and low cost instead of the controllers on the market now that are huge and expensive units and have limited current capacity. Flexible OEM integration is such a great way to go for enthusiasts. I have some experience with product manufacturing, check out my patent pending thermometer cooler drain plug that fits your Yeti/RTIC/Cabellas/Orca/Others cooler. I'm not sure who to contact, but I'd consider a group buy and a great deal on customized T4R Maluna coolers. I did custom badged coolers for Minnesota Overlanders, they were stoked on them. Great coolers, I did loads of lab tests to prove their performance.

Sorry if you're offended by my product plug above ^^... mods feel free to delete, but I thought it was relevant to the thread and I'm serious about the discounted group buy on T4R coolers, just not sure who to contact or if there's interest.

Very nice work. I'm far more of an info collector than wanting to do anything remotely like this yet curious do your numbers include any overhead the PMW or other devices along the way in your cooling setup?

Enjoy the runner.

What do you mean overhead? Current? Computing only draws like 25mA. That’s tiny but I’m not sure that’s what you were asking?

Any update on the fan / PWM design? I’d be keen to chat and learn more about the controller you were putting together - electromechanical is my jam, happy to contribute.

I’m new to the 4runner community but not working on trucks (coming from a 1997 FZJ80).

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