Stock Radiator Fan CFM (1 Viewer)

Joined
Sep 30, 2014
Messages
572
Visit site
I’ll just chime in with my opinion for what it’s worth...

Electric fans CAN work but it’s difficult to get right.

Firstly, although the mechanical fan may “move” like 8000cfm or whatever people have calculated their efficiency is massively reduced due to the gap around the shroud, so the actual CFM through the radiator core won’t be anywhere near that high.

Now I’m not saying mechanic is bad, obviously it works perfectly well...

For electric fans to work they need to have a correctly designed shroud and the right power to move enough air. There are electric thermofan shrouds you can retrofit from late model BMW V8s that are rated at 80amp and will EASILY move enough air (albeit that they are noisy at full tilt).

One of the issues with cooling a 4WD/80 series is the design of the front grill. Basically you want to build up high pressure in front of the radiator when moving along at speed, most cars have scoops and ducting to keep the air “contained” and run little flaps on the underside which help create low pressure in the engine bay, this in turns help move air through the rads. On my road car I can get more airflow through the rads at 45kph compared to 80am high efficiency fans... (I have actually measured this scientifically).

The solution that works best for me was to run 2 Toyota Camery “pusher” fans on the front of the a/c condenser and a pair of OEM electric fans behind the radiator (specifically from a AU falcon). They are PWM controlled based on temp (eg every degree above 80c increases fan speed by 5%) and so far I haven’t had any issues in hot Australian summers. I’ll try and post some pics up shortly....
 

SmokingRocks

I bought a Cruiser to keep miles off my Cruiser
Joined
Oct 6, 2014
Messages
3,584
Location
Colorado
Visit site
I’ll just chime in with my opinion for what it’s worth...

Electric fans CAN work but it’s difficult to get right.

Firstly, although the mechanical fan may “move” like 8000cfm or whatever people have calculated their efficiency is massively reduced due to the gap around the shroud, so the actual CFM through the radiator core won’t be anywhere near that high.

I hear what you are saying and agree with you, however, on USDM 80's all of those gaps are filled with foam. The OEM should setup is very well designed from an efficiency viewpoint. However no system is ever 100% efficient, including electric setups. Those same air gaps can easily exist with electrics, so lets say a 5500 cfm mechanical fan & shroud is 75% efficient in drawing air through the radiator, at that percent of loss its still moving 4125 cfm.

There are only a handful of high amp draw electrics that can achieve that CFM unrestricted (I'm talking about a realistic fan). So even if yo are able to find, mount and power a 4,500 CFM electric fan and you improve your efficiency to 85% you are only going to draw 3,825 CFM across the core.

I'm not dogging electric, they have their place. And if it works for you then great, I just choose to have the highest CFM fan behind my radiator and sealed shroud. This and I don't like the idea of adding a 60-80 amp fan on a vehicle that has an 80 amp alternator.
 
Last edited:
Joined
Feb 15, 2017
Messages
324
Location
Worland, WY
Visit site
I’ve been running a Flexalite 420 since I put my pile back together last year and got it on the road. It’s a 2500cfm fan. PWM module lets me control when it turns on and it runs from 60% to 100% across a 10° span. AC switch has it run 100% if the AC is on. It’s been working great. I ditched the transmission cooler too(because it was garbage and blocking airflow bigtime). Only thing in front of the AC condenser is the heat exchanger for the A/W intercooler, which also has a fan on it. I ended up with a completely different exhaust than most of the 80s in the US and now my splash guards(RAD rubber design) cover where the factory exhaust would normally be over the frame and exiting. I feel like this keeps air pressure off of the PS tire out of the engine compartment at speed and may contribute to better cooling . . .

Anyway, I didn’t build a shroud when I initially put that electric fan on and I found out that’s a very needful thing. I bolted it onto the radiator and had about an inch-ish gap all the way around. It moved air, but had to be trying to push some back through the radiator the opposite direction. It’s a new in 2019 factory radiator.

One of my other high $$$ interests is competitive shooting. PRS/NRL stuff has been my focus for the last 8 or so years. So, wind speed is important to me. I use a Kestrel to measure it and adjust my holds accordingly. I used a Kestrel to measure wind speed in front of the radiator and at the left and right hood vents. Speeds are in mph and temps are off of an autometer gauge in a pillar mounted pod and are coolant temps leaving the engine. Speed in was taken where the tranny cooler would be and the outs were taken at the middle vent.

NO SHROUD
6.1mph idling at 197° no AC
2.9 left vent
4.3 right vent

AC on 6.8mph
3.8 left vent
4.5 right vent

SHROUD
7.6mph idling at 195° w/ new shroud
4.4mph left vent
4.6mph right vent

7.2 w/ AC on @ 195°
4.0 left vent
5.2 right vent

I feel like having the engine bay more open helps move air out the drivers side more than it could with the factory fan and shroud setup(which puts most of the air movement on the ‘hot’ side of the engine bay. Idk. My set up has been working for me. I’m happy with it. Especially around town, it runs the coolest and the AC works very well.
 

zonker

SILVER Star
Joined
Mar 3, 2015
Messages
341
Location
Lonely Nevada
Website
www.willenosphotography.com
Well here is my last installment in regards to mechanical versus electrical fans and their related CFM. Since I think I am really smart and can out think Toyota engineers.. I can do the same with Ron Davis people.

I know the answer to improved cooling and that is put back in the Blue Fan Clutch.. stock fan and shroud. That will definitely happen. However in the mean time I solved the issue with the SPAL fans. It was a definitely a screw-up that belongs completely to me.

When I initially installed the RD radiator and the electric fans I had a problem with the supplied harness.. of which I documented here on MUD. It was definitely a flaw by whoever designed the harness with mini-40amp fuses. I solved the problem with ATC-40's and a slight redesign of the harness. The second part of the fans that made me crazy was the noise. The SPAL thermostatic switch turned the fans on at 185 degrees and off at 165. Obviously this meant when the thermostat opened the fans turned on and never went off during the whole engine run-time. In the winter here that kind of sucks as the engine temp barely gets more than about 185 or cools down to a little less. In my opinion that is a problem in its self since oil temp never reaches an optimum level.

SO in my infinite wisdom I decided to install a different thermostatic switch. I went with one from Painless.. on at 200 and off at 190. Since I had such a great experience with the cooling capacity of the RD radiator I felt that I would hardly ever see 200. That switch worked great until it got summer hot. Then the coolant temps started to go up. Why you ask? Heat soak. With a fan that is running constantly it was keeping the overall temperatures tamped down and consistent. Such as when using a conventional fan setup.. no opportunity for the engine and accessories to increase in heat. With the higher switch temps the engine bay was starting to accumulate heat. When the fans were running they could only drop the coolant temp to 190. Each time the fan shut off for only a short period at the 190 temp the heat soak continued. Once the coolant climbed above say 200 there was no getting heat soak reduced which then would add to an further increase in coolant temps.

One thing that bothered me thru this whole process of reconciling the issue.. I could barely but my hand on the upper plenum as it was incredibly hot. Not something I ever remember happening at prior time. Not being able to sleep a week ago and pondering the heat problem and my so called light bulb went on. First I was glad the bulb still worked! So in order to test my theory I jumpered the connector for the thermo switch and drove the same uphill route that I usually do. It was during an even warmer part of the day and coolant temp dropped a total of 24 degrees during the whole climb. From a high of 219 the other day to 195! Turned around at the same spot to come back down and shut the fan off to test air flow (no engine load of course) the temp went down to 176. So that was good. Flipped the fan switch back on for the 5 mile flat trip back home.. fans turned on at 185 and showed nothing higher than 189 all the way back to my shop.

All of this pseudo test was with the air conditioning ON.

So YES.. I screwed up as my thinking was definitely flawed. I could have skipped this whole exercise by leaving the system alone. But that is not way my mind works.. always looking for improvements. The tipping point for a change was the fan noise got to me. Hence the reason that OEM setup with a modified blue clutch is going back in.. done deal!!

Thanks for reading all my ramblings!!
 
Last edited:

Users who are viewing this thread

Top Bottom