Electric fans on a 3/4 or 1 Ton... Maybe as an auxiliary pusher fan. Let me kill this "Bad Idea" D-E-A-D. I have some numbers...
Cliffs Notes: Electric Fans (aka 2 fans) make 5000 CFM freestanding. Clutch fans make over 10,000 CFM in place with radiator restrictions. 10,000 CFM is NOT enough to keep a 1993 6.5 Turbo Diesel (200HP 400 TQ) cool. So a electric fan does not make enough CFM to keep your Cummins cool pulling a grade at max GCWR.
The electronic fan clutch on the Cummins is worth the cost when it can turn on just for the AC before the engine warms up. It eliminates ALL the delays an obsolete thermal spring system has before the spring sees "hot air" and can get the s l o w fan clutch to start locking in. Thermostat opens up delay, heat radiator delay, heat thermal spring delay, move the working fluid in clutch delay... all while the ECT rises uncontrolled with no fan.
Electric Fan equipped vehicles mean Light Duty, period. Oh, you are going to tow: "Good Luck With That!" They do have their place in MPG econo boxes or bringing home the groceries. And this includes GM's 1/2 ton gas pickups "Mark Of Mediocrity" where GM's cooling systems can't cash the power check their engines write. Especially GM Diesel engines. The Eco Diesel has Light Duty GM garbage cooling design written all over it with that electric fan choice.
As part of a aftermarket product development I did some CFM measuring of a cooling fan in a Chevy Trailblazer SS. The measurements came first then as a result a thicker all aluminum radiator built by Ron Davis was developed so it could use all the CFM the fan generated. With the fan locked up the OEM radiator was stuck at 208 ECT. The thicker one allowed me to close a 170 degree T-Stat. Lower ECT before a run means less detonation and better 1/4 mile track times. There is an art to cooling it down and then getting the fan kicked out before the track run.
Rant: A real bailing wire and duct tape "Let's shove this 6.0L V8 engine in here quick". If you could keep the transmission from literally exploding. Loose a sprag and the input drum is now doing 2x the 6500 engine redline RPM and the shrapnel blows the top of the transmission off at 13,000 RPM.
Aftermarket found a way to shove a 4L80E in it as even built transmissions wouldn't live. The mechanical cooling fan was a few inches above the top of the radiator resulting in erratic airflow from the shroud. The Duramax LLY 90 degree to turbo intake elbow and this shroud design are some clear examples that NO ONE at GM has any idea about smooth airflow. The oil pickup was at the front of the oil pan starving the rear rod bearings of oil during a hard launch at the track. GM used the wrong oil in the diff causing the posi clutch packs to fail. A real Blazer with several wiring problems that would burn it to the ground. If you could keep it out of the damn repair shop it was a real rocket to drive.
/ Rant Off.
First prototype radiator with the EV fan clutch for a Trailblazer SS.
The Trailblazer SS was equipped with a electronic cooling fan like the newer the Dodge/RAM Cummins (Except the last years GM went cheap and back to obsolete thermal spring clutches and GM went Bankrupt anyway. GM delayed the needed modern electronic fan clutch on the Duramax as well as it was promised for 2008 model years.) Anyway I was able to manually lock up the Trailblazer fan clutch in via a "tune" and measure it at specific RPM's.
Aftermarket cooling fans are rated in "Freestanding CFM". This means in free air: no radiators, no engine, no closed hood. Typical ratings were 5000 CFM "freestanding" for a pair of fans. This means the CFM goes down with restrictions.
Equipped with a Nielsen-Kellerman Kestrel 4000 Pocket Wind Meter I pulled the Trailblazer SS grille and warmed up the engine hood closed with 99% fan in the tune for all ECT temp values.
I then revved the engine over 2000 RPM for 2 minutes and verified full clutch lockup via HPTuners RPM readings.
I then took 28 separate airflow, in MPH, readings.
Radiator divided in two by center grille support and bumper is also a factor. So 9 readings each in the two upper sections (18 total), 2 readings behind the grille support, 6 readings under the bumper, and 2 readings at the bottom. I averaged the MPH and came up with the CFM from the MPH readings.
These tests are nearly full restriction with the radiators in place and hood closed - the grille was removed and it can be a restriction. All tests : parked front in garage to eliminate wind.
Front opening through condenser:
~18" TALL
~27" WIDE
OEM Fan Diameter 21” (Wow!)
9.75” of the center wasted due to clutch and fan center blockage.
No free air space between blades. (High suction ability for restrictive radiator stacks.)
18.75” shroud Diameter – rest used for double ridge air seal and noise control I guess.
13.5” from bottom to upper restriction on shroud. Upper shroud restriction is 3” from fan. This is from fan center being too high for radiator location. Top of fan circle is over the top of the stack.
Operating RPM ~300 – 6800 (Code sets over 6800 RPM)
Observed 768 Fan RPM at ~600 RPM idle. I run into the EV fan system limit at a little over 4000 FAN RPM, the belt noisily reaches it's limit at 5300 RPM. 4000 fan is ~3500 engine RPM. Possible road speed and airflow would raise this limit. Note engine RPM math has to include 90% max lockup of clutch.
LS1 type replacement fans
12 LBS assembly plus any brackets and relays.
4"-5.25" deep. (Tips of motors)
18.3" tall
28" Wide.
2 electric fans
6 blades per fan
2.5” Fixed blade length
1” blade depth.
12.25” Fan dia (24.5 total fan area) Rest is blocked off.
4.25” Motor dia blockage center of fan
Lots of free space between blades.
First test OEM Clutch Fan: 'idle'
600 ENGINE RPM
768 FAN RPM
6.94 MPH avg airflow
2050 CFM
Second test
~1200 ENGINE RPM (Fast as HPTuners can command)
1472-1504 FAN RPM
14.62 MPH avg airflow
4350 CFM
Third quick test
800 ENGINE RPM
9 measurements all are +3 MPH over 600 RPM
10 MPH rounded up .06
2975 CFM.
Last test
~3024 ENGINE RPM (helper on throttle)
3424 FAN RPM
35.46 MPH avg airflow
10,500 CFM
Free standing, no radiator resistance for the Electric Fan test:
2400 RPM on battery voltage.
(2500 RPM in reverse oops!)
4925 freestanding CFM on battery power: avg 16.6 MPH. Installed CFM was not tested, that is radiator and hood down restrictions that lower the CFM of any fan. Not worth the pain to test in place.
Conclusions:
So getting 10LBS of rotating mass off the engine will get you better track times. The electrics have an RPM advantage at idle.
I used the Trailblazer SS 21" cooling fan on my 1993 6.5TD and then hauled a 24' trailer full of auto parts and tires to Lake Havasu. I neglected that the blade pitch was too shallow and the 6.5TD ran hot. I picked up a 1998 steel OEM 9 blade 6.5TD fan that had more blade pitch and thus would move more than 10,000 CFM and ran cool towing from there on out. Thus a diesel needs more than 10,000 CFM for cooling and that's 2x what the electrics can do.
Why didn't they make it in 2 halves so you could lift the top half out?
The old shroud of yours has become hard and brittle. Use a sawsall to remove it in 2-3 parts. The new one should be flexible enough to go in without removing the coolant overflow ... at least on the 2003 I had.
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