'Project Aerodynamic' - Because everyone else just gives up

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NWZ - The storm is here
May 22, 2016
Pilbara Region Western Australia
So apart from the obvious title , i thought I'd share my little project that i have been working on since 'VX reborn' rose from the dust cave and has undergone a few of the standard modifications from stock.

Now this is not about reshaping, cutting or anything major with the 80. I am talking simply about the basic mods and add ons that anyone can do to maximize the aerodynamic efficiency of these blocks of beauty. We all know what is possible and whats not possible with mileage on these beasts but where things go wrong in my opinion is where we claim to lose 1mpg or 1L/100km here and there for every little modification. 99% of the time can be attributed towards a loss of aerodynamic and an increase in drag.

The myth of added weight (relative to the vehicle) = mpg loss in a vehicle only plays a small role compared to aerodynamics, so what if we can recover these losses by adding it back without stripping the accessories and mods that we put on in the first place. Or for those running stock even improve the efficiency?

Well it just so happens to be that is exactly what I have been doing and continuing to do, whilst at the same time being mindful of turning the beast into an eye sore or spending more than what you will recover in saved gas/fuel.

To date my car has some typical mods and like all 80s the obvious wind-drag hotspots:
- Roof rack: steel with no perspex or alloy visor (this is on the way)
- 2" lift
- 275/75/16 (not really a mod but aggressive A/T tread)
- Original Bull bar: steel with spotties
- Spare wheel underneath
- Aftermarket alloy bash plate

now here are the aero mods that i have started so far:
- Sunroof visor that meets the same width as the roof rack and lowered the rack as low to the roof as possible to meet the top of the visor without interfering with the tilt up on the sunroof.
- Alloy aero shaped bash plate
- Window visors for the four main side windows (not the rear slides)
- Bonnet visor
- Boot/roof visor (could almost be called a rear spoiler)
Total bill $320

So doesnt seem like a lot does it? but actually is it?
Well according to some patient data covering regular driving, different conditions and averages then comparing them to the stock efficiency i used to average before any mods, have been able to recoup a fair amount of that loss without breaking the bank.
Here are my figures so far:

Stock average - 16L/100km or 17.5mpg
Mods average - 18.5L/100km or 15mpg
Mods with aero adjust - 17L/100km or 16.5mpg

to only lose 1mpg with a lift and roof rack on is not what i was expecting, Now im fully aware these will differ by vehicle so i can only tell you what i have observed on my truck over much patient and unbiased testing with my commutes and routine rarely altering at all and very consistent weather where i live.

Needless to say i was very happy with this result as over a short period of driving i can recoup the money i spent on the extras. When i'm finished i will post photos of how it looks. One thing i forgot to mention earlier in the post is a mechanical designer friend of mine was saying the diffs and joints on the 80s are the biggest drag factors underneath so anyway of deflecting or streaming wind down there is going to assist particularly with the lift exposing them more.

More to come with further adjustments and testing (no i wont give up till i maximize efficiency so negative nancys say what you will but maths dont lie) :)
Not sure if serious or playing a game here ...

*** waits for math about hitting a kangaroo ***
As streamline as I can get with everything I need to live out of my 80. Very little wind drag and good MPG.

And photogenic
Actually, he is fairly accurate on his assessment of things. And YES, the undercarriage has a MUCH higher drag the higher it is lifted. Every tie rod, drag link, shock, and bolt that is exposed to the air in the front is increased drag on the truck.

Actually, an air dam in the front will help the most. I should be made of a semi-rigid plastic in order to allow SOME flexibility for rock crawling, snow drifts, tall grass, medium sized wetland creatures, and other items you will continue to drive over.

This is precisely why the "older" cars thoughts on aerodynamics was to get the front end up in the air to "get it off the ground" backfired and caused cars to start lifting at speed made the handling worse.

That's why race cars are slammed and have aerodynamics to create areas of low pressure under the car to keep it on the ground. It's all about surface area. Install an air dam on the front to push the air out of the way and around the front tires, then the same down the sides (look at the recent additions to all the semi-trailers!). It takes less total HP to push the air out on the way ONCE rather than across EVERY piece f the truck underneath.

Unfortunately, adding the "ground effects" kits are quite detrimental to the idea of rock crawling, mudding, or general off-roading. If you can come up with a setup that goes up and down like a curtain when needed.....THEN you'd really have something.

Look at the mid 1970's through 1980's Chevy 4x4's. They added an air dam in front about 4" tall to push the air around some of the front suspension components. I have thought about this a lot as well, it just wasn't the financial priority for me. I was going to do this on my old 69 Chevy K10 because at the time, I had a 235 CID 6 cylinder in it and with a tiny bit of wind I could barely hold 55 MPH. Yes, waxing it made a noticeable difference, it was THAT under powered. I never did it because I added a 350 bored 0.060" over, ported, polished, balanced, Mild cam, Holley 650 double pumper, so I ended up with about 375 HP to overcome the excess drag caused by a 6" lift and 6 lights on a roll bar and a bull bar in the front with 4 more lights...........
Keeping it simple and near stock with the 80 is the best solution. Start hanging stuff on it and jacking it up and no amount of streamlining gets around the basic aerodynamics of drag.

That's the route I've taken, helped along by a limited budget and low (6'6") garage door opening. Our truck never had a roof rack or running boards (yeah!) so no need to take them off. OPld age and the low door mean an expedition grade roof rack weren't in the mix anyway. I did compromise by adding the ARB, but needed a place for the winch and like the protection (saved my beans in a major way at least once.) While the ARB isn't that aerodynamic, it does help smooth the flow as much as it can.

Also stuck with skinnies instead of 285s when I upgraded to 33" tires. Again, you could go lower, but I like taking advantage of not needing the lift and wanting to maximize stock off road performance. Other than that, a few antennas add drag, but the stock AM/FM still retracts to do its small part.

It gets 17 mpg on the highway, but still the standard 10 mpg around town where the low speeds cancel most help in this area anyway.
One thing i forgot to mention earlier in the post is a mechanical designer friend of mine was saying the diffs and joints on the 80s are the biggest drag factors underneath so anyway of deflecting or streaming wind down there is going to assist particularly with the lift exposing them more.

I've been wondering about the role of the undercarriage. Obviously, anything that sticks out is adding drag, but what about all of the pockets underneath? Like the area between the rocker panel and the frame, then between the frame and the transmission? Would smoothing the whole undercarriage with an aluminum skid plate (well, one-time-use skid plate :D ) make a difference?

Here's a page on aerodynamic improvements in heavy trucks and buses:

Review of Aerodynamic Drag Reduction Devices for Heavy Trucks and Buses - Transport Canada

I've also wondered about the boat tail (as described in the above link) for the rear of a Land Cruiser, particularly when hanging a spare and other stuff off the back. I seem to recall reading years ago that you only need something like 1/3 of a teardrop tail to get nearly the full aerodynamic benefit of the full teardrop shape.
This is on a new F-350.

Lift and aero cannot really go together. Every inch of air that passes under the vehicle has a detrimental effect.

Go over to Ecomodders forum. Those guys take advantage of hundreds of tricks/hacks or whatever you want to call them. They do have some good reads with fairly well documented data.
I've been wondering about the role of the undercarriage. Obviously, anything that sticks out is adding drag, but what about all of the pockets underneath?

When my 105 series was stock, it had a lot of plastic belly pans from front bumper to engine, under the trans and under the transfer.
They are long gone due to damage or due to being a PITA for maintenance so I can't remember exactly where they were.
I figured they were partly to reduce drag, partly to reduce NVH as they were all insulated. Even the space between engine block and the dust cover for the flywheel was chocked full with a foam pad.
Some valid points here, i have already proven that small gains are possible without compromising your mods. I imagine they are in the states aswell but the bull bars designed here such as ARB and TJM are far better streamlined and angle the wind from the front end around the wheel arches and even have there own bash plates with angled edges to assist with the downwards movement of air.

Of course noone expects to turn these into F1 cars and i have no intention of leading myself into the idea of achieving an aerodynamic 80. Gotta keep this in context and just maximize what you can without compromising your mods. Even if you can just streamline air around 10% of your biggest drag locations you are going to improve things by 10%. To get an understand this i ask anyone of you to drive 60mph down the highway with your roof rack on and sunrof closed. Tilt up the sunroof and feel what happens to the handling of the car. If you have a rack that creates drag then i almost guarantee your truck will sway a bit initially until the air stream adjusts itself and the car grips down to the road a tad better. I have tested this multiple times hence i went with the permanent solution of using a roof to rack sunroof visor so that airflow is constant. Further improved with a visor around the front of the rack. It has made a lot of difference which has equated to better mileage, just the same way as packing your roof with camping equip and spare fuel will drag your efficiency down. Not to mention the reduction ind wind roar through the sunroof which is deafening at hwy speeds.

The exposed diffs and steering gear is dealt with by using the aftermarket angled bash plates like the one i have. The rear of the car helps if you remove the underneath spare tyre and mount it on the back. Who wants to remove their lift for mileage when you can simply do this?
** UPDATE ** HG blown....

Just kidding although i shouldn't kid around i probably just jinxed myself... Doh!

SO testing stage 2 is in and results are mixed. Using the co efficiency drag rule to measure what add ons are responsible for the most drag, well Rack and lift are the definite killers above all. Many claim wide tires but they infact are on the lower scheme for some strange reason but this does depend on the vehicle and flare protection you have i suppose. Each mod seemed to equate to about 0.2mpg increased co-efficient drag with big racks, square bull bars and lifts equating to about 0.5mpg each at the worst end. This is pretty accurate given my mileage before mods was around 19mpg

Worst figures were 14 MPG with no aero adjustments
Stage 2 average with top half of the vehicle adjustments 15.7mpg (Hey thats something!)
Stage 3 will be bottom half adjustments including spats, belly plates/aftermarket bash plate and underneath spare wheel removal

More to come with stage 3
I added this mod to improve my MPG, and doubled it, not one plastic wind diffuser , air dam or any other attachments I get 20 mpg happy , and I can pass people without tail wind or downhill :flipoff2:

Did you do the diesel conversion yourself? Not something i could do and the only people that can do that nearby will only to the 6.5 chevvy v8 which i have no interest in and the cost is about 20K
I added this mod to improve my MPG, and doubled it, not one plastic wind diffuser , air dam or any other attachments I get 20 mpg happy , and I can pass people without tail wind or downhill :flipoff2:

View attachment 1575150

What air box are you using, looks factory?

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