*sits up in chair*

You are running completely without a cooling fan? Please tell us more.

 

A fan is not needed as long as you are moving, I have run mine without a fan as well.
I did have electrics installed at the time though on a manual switch.

As long as you are running more than 20 MPH and less than 65 MPH the temps will stay in a reasonable temp range even with a reasonable load on the truck.

Stoplights, very slow driving, or hard pulls on steep grades and you need a fan.
And when I usually had to run my electric fan the most, plowing snow at temps below 20 degrees.
I attribute that to lots of reverse gear, low engine speeds and a constant load on the engine going forward.
The high speed need came from heavier throttle to maintain speed and the aerodynamics of the 86 body style and 4x4.
Also driving at any speed with the plow on the truck unless the plow was almost on the ground resulted in higher engine temps.

I was running two Flexlite 16" fans for electric fans, after the third one died, I reinstalled the stock fan.
At 100 dollars each, the MPG increase was more than eaten up by the cost of buying fans.
But I also have to say that fuel was considerably cheaper, something like 1.50 a gallon when I did that.
Today it might be worthwhile with fuel over 4.20 a gallon.

NAPA had some electric fans that had a higher CFM, but at 300 dollars each I just could not bring myself to experiment with them.

 

Less than 65 MPG....hmm that won't work for me LOL

I never knew you tried electric fans, Dave. I'm looking into the lincoln/taurus electric fans right now. They are available used and the larger ones can pull 4500 CFM each. Best of all they are available from wreckers usually for under $100 each. If there is a real improvement in MPGs, I will seriously consider this mod. Would also be nice to have better A/C performance at lower speeds.

This is the one thats supposed to be 4500 CFM:
eBay Motors: Cooling fan Lincoln Mark 8 VIII electric 2 speed Ford (item 220280338028 end time Sep-18-08 11:09:36 PDT)

The ones for the taurus are 3800 CFM I think, but are small enough to use duals (same motor, smaller fan).

Being OEM ford (motors by siemens), they should last a bit better than an aftermarket.

What is the stock 6.9 fan rated for in CFM?

 

I can't say exactly what the CFM of the stock fan is, but looking at the blade pitch and size it would be a lot at higher RPM when the fan clutch locks.

At NAPA they have no electric fans that are recommended for IDI primary fan duty or at least they did not several years ago when I was looking into it.
Fan technology has increased considerably with all the front wheel drive cars on the market today with transverse mounted motors since I was experimenting.

When looking you also have to look at the amps drawn by the fan.

My main motivation was the Horton air clutch used on big rig fans.
Those puppies suck some serious HP when they locked up.
All the meat haulers wired a switch into the control circuit so we had manual control of when the fan locked up.
A double throw switch (ON OFF ON) gave you manual locked, manual unlocked and automatic.
An extra 50 HP to the ground translated to several gears we did not have to drop on the hills.

 

I also found this article, which is about the cab height to tailgate height cover.

EVWORLD FEATURE: Streamlining Light Truck Fuel Economy:PICKUP | TRUCK | STREAMLINE | TEXAS | NEW MEXICO | KNOX | TOYOTA

 

was this thread on cooling fans or mpg?? ha-ha makes sense though.
my real world mpg on my different diesel as follows
94 ext cab 7.3 idi turbo down pipe 4" exh 1 1/2 flats 4.10's 5 spd 15-16 mpg hwy up to 62 mph over 62 mph it slowly went down run 75mph it got 12-13mpg.

94 crew cab 7.3 idi turbo d/p 4" exh 1 flat e4od 4.10's 15 mpg highway 62 and under, in town driving sucked for fuel economy due to the e4od 10-12 in town

86 f-250 6.9 4 spd 3.55's all stock except for 3" exh real world on that truck was 14-16mpg in town and 17-20mpg highway

1995 ford f-250 7.3 psd all stock 3.55's e4od 13-14 in town and on a trip recently to central pa and back i got 18 mpg there and back while running 65-70 mph

1991 dodge d-250 5.9 cummins 3 spd automatic 3.07 gears 3 " exhaust and pump turned up 10% gets 15-16mpg in town and arounf 20 mpg on the highway recently i pulled a car trailer loaded to pa then came back home loaded and got 17.7mpg

these are real world #'s from some of the trucks i own and have owned. later, pete

 

I've seen that truck before, but that story was done after he got sponsors and had stickers all over the truck and some other smaller aero mods. The belly pan is something I am thinking of trying some day now that my truck doesn't leak any fluids anymore (except water from AC).

Archangel was able to run his truck with the grill blocked off and saw an improvement in MPGs. It would be so easy for me to make a decent looking aluminum panel to replace the grill, its not even be funny. This combined with hearing of improvements with the removal of the fan completely, makes me think that the cooling package could be the next place for me to attack to pick up another MPG or two. I have my doubts that I can block the grill AND remove the fan, but electric fans could certainly allow me to investigate the potential.

I have a double throw switch like you describe for my glow plugs right now. Works very well and I can certainly see using a system like that for electric fans.

 

My favorite part of that article is how it says the truck looks "exotic". I think this is a typo, they must of been trying to spell "ridiculous" and got it wrong.
I think the article is correct, though. The best gas mileage I get is when I have 2 kayaks in the back with their tips up at cab level and the tails down at the tailgate. I was wondering if a topper helps or hurts mpg.

 

Although it has been a long time, when Overdrive was doing all the aerodynamic testing one of the items they tested was a boat tail fairing on the rear of box trailers.

Instead of the square boxed back of the trailer, it sloped in from both sides and the top to smooth the air flow at the rear of the trailer, with a rather large return in MPG.

I know some people have a hard time when I say things about tractor trailers, but a pickup is just a miniture truck.
If you tow a trailer, it is a miniture tractor trailer.
The both move through the air in the same way, one is just smaller than the other.
When I retired from trucking in 1985, 5 MPG was the average for most trucks.
Today that number has increased 50+% and the legal highway speeds have increased from 55 MPH to 65 or 70 MPH.
Part of the increase came from the engines, most of it came from aerodynamics.
If you are serious about MPG, look at the big rigs.
Look at the changes they have made in the last 20 years, the scale down an incorperate as many of them as you can in your truck.
If I were back on the road driving today like I did when I retired from driving in the same truck I was running then, my fuel bill would be about 6000 a week.
A modern aerodynamic truck would cut that fuel bill by a bit over 2000 a week or 104,000 a year.
That is just one long haul truck savings, now look how many trucks are on the highway.
How about the company with 50 or 200 or 500 trucks?
500 trucks at 104,000 in savings equals 52 million a year in fuel savings.
Is there any wonder why the big truck manufacturers and companies are so serious about aerodynamics and MPG?

A cab height topper would remove the aerodynamic drag at the rear of the cab, but increase the drag at the rear of the truck.
From several people I have talked to, there is a small gain to be had from the topper so you must not add as much drag to the rear as you remove at the back of the cab.

From all of the studies I have read, on a two wheel drive road driven truck, ground effects spoilers on the front and sides will pay for themselves over time.
I guess they would even be good on a road driven 4x4, but they would limit or eliminate the off road potential of your truck.

Remember most exotic things have little real world practical value.

Look at the F40, it will hold two people and one small suitecase, goes fast enough to land you in jail in third gear.
Exotic, yes.
Practical, no.

In the end, I guess the truck was more practical then the F40, you could still get several boxes under the topper if it was movable.

 

I have not been using my truck for city driving just deliveries. I drive the same 220 mile round trip and only run 200 mile on a tank then switch tanks and then fill it. So every test is the same 200 mile route. On my last run I really topped off the tank and I was only able to add another half gallon. The mpg came out to 15.7 that was with the dually. So I gained around 2 mpg HW with no clutch fan. I made 3 trips so far with no fan and around 16 everytime. For 3 years with fan around 14. I tried to take the fan off before but couldn't. When I had changed the waterpump I just left the fan and shrould off. My first diesel an 83 F-250 the pre-owner had removed the clutch fan so it never had one while I drove it. Never had any problems

 

Aerodynamics are not only the same as other vehicles it obviously applies to anything that passes through atmosphere.
For me a good example is bullets. There is a measure of the aerodynamics of bullets called balistic coefficient, usually abbreviated B.C.
As Dave S. was talking about with the tapered trailing end of the trailer the highest B.C. bullets are Boat tails. The longer it is and the "pointier" it is at each end the longer and "flatter" it will fly given the same momentum to start with. All long-range/target/sniper bullets are of boat tail desighn.

 

Man, I really need to get the 3.55's I bought swapped in.

If only it didn't cost so much. ugh.

BTW David85- the Lincoln/Taurus fans are nice but pull big amps at startup and while running.

I have read that it's something like 90-100 amps at startup and then 50-60 amps while running. So you wouldn't want to run more than one anyway.

Are there any TRUCK dual electric fan setups that could be adapted?