'08 Toyota 4Runner aero mods = 14% better fuel economy!
 

This is my '08 Toyota 4Runner, a 4,800 pound SUV with 4.7L V8 and all-the-time 4 wheel drive (meaning you can't put it in 2wd mode). With that information you can probably assume that it get's pretty poor fuel economy - and you'd be correct. I average around 14mpg 50/50 highway/city. Yeah that is remarkably bad. But what really shocked me was that the highway milage isn't much better than city. About 15mpg in winter and 16mpg in summer (75mpg). Very bad!

http://dannix.net/sites/default/file...942400_n_0.jpg

In a few weeks I'm going to drive from my home in Eastern Kansas to Portland Oregon and back, so over 4,000 miles. So I decided to do some ecomodding to the aero dynamics to see if I could improve it's highway performance.

First thing I did was delete the mud flaps, running boards, and roof rack cross bars.

http://dannix.net/sites/default/file...s/IMG_6170.jpg

For the rear mud flaps, I cut off the plastic that was extending past the body with a box cutter. I unscrewed and removed the ones in the front, then I attached them to the rear wheel openings, now they're tire spats!

http://dannix.net/sites/default/file...s/IMG_6167.jpg

http://dannix.net/sites/default/file...s/IMG_6171.jpg

Then it was time to delete the "spoiler," if you can even call it that. It's only function is to direct air onto the back window to keep it clean. Seems to me that it's a big aero drag.

http://dannix.net/sites/default/file...s/IMG_6177.jpg

http://dannix.net/sites/default/file...s/IMG_6181.jpg

It was just two bolts, some clips, and one wiring connector. I covered the holes with some gaffing tape. Gaffing tape is like duck tape that is really easy to remove and doesn't leave a residue, so like a heavy duty masking tape. It sticks really weld, holds up strong, but doesn't make a mess.

http://dannix.net/sites/default/file...s/IMG_6183.jpg

I'll have to figure out a way to get back a third brake light, for safety reasons.

Back to the front end of the vehicle, I did a partial grill block with some more gaffing tap.

http://dannix.net/sites/default/file...s/IMG_6187.jpg

http://dannix.net/sites/default/file...s/IMG_6189.jpg

I don't know if the grill block is supposed to help with aero or only help with getting the engine warmer faster, but it helps and it was easy.

[continued in next post] :turtle:

Up until now, all the aero mods have been very easy.

But there's one very important mod that I had to make, not just for aero reasons, but for protection. It's the front skid plate - the vehicle came with one from the factory but it didn't have it when I bought it. Not only does it protect against rocks, sticks, sand, snow, etc. when off-roading, but I figure that it would also help tremendously with aerodynamics.

Here's what it looked like a few days ago:

http://dannix.net/sites/default/file...s/IMG_6157.jpg

Yeah that's a lot of dirty bits.

I could buy an aftermarket one, but I had just bought a MIG welder and a large amount of sheet metal and steel (for another project), so I figured I'd make it a project and build it myself.

First thing I did was make a scaffolding out of 1/8" steel.

http://dannix.net/sites/default/file...s/IMG_6216.jpg

Then I skinned it in 18 gauge sheet metal. This will not be thick enough to drag it along boulders, but it will protect agains sticks and snow and sand. Normal duty protection.

http://dannix.net/sites/default/file...s/IMG_6219.jpg

http://dannix.net/sites/default/file...s/IMG_6222.jpg

I make it sound easy, but it took all day Sunday to make. After the seam sealer and paint dried, I hung it up today.

http://dannix.net/sites/default/file...s/IMG_6247.JPG

There was still lot of exposed dirty bits under the truck, but I was too lazy to make more stuff out of steel. So I found a political add and got some more gaffing tape and did what I could.

https://ecomodder.com/forum/attachme...1&d=1581452067

[continued on next post] :turtle:

Now for the results!

Right before starting the first mods, I did some testing to get a base score. My primary goal is to improve MPG at 75mph, so that's what I tested at.

My procedure: I live right by an interstage highway with a gas station right at the exit, so I filled up at that gas station and reset the trip meter. Drove 7 miles west, exited and turned around and drove the 7 miles back. Then I filled up at the same gas station and recorded the gas used and miles driven. I used the cruise control to keep it at exactly 75mph.

For the base score, I recorded 13.9 miles and 0.93 gallons. Which is 14.9 mpg.

Today I did it again with all the mods performed (similar weather but not exactly the same of course, but nothing else changed to the vehicle like weight or tire pressure).

I got 13.8 miles, and 0.81 gallons. That's 17mpg.

14% better!!

Yes I realize that it I should have done the test like three times for trip A and trip B but, that would have taken all day.

So for my up coming road trip to Portland, I'll be driving around 4,400 miles. Using the https://www.fueleconomy.gov/trip/ tool, it says I'll save $70. Which is great and all but I didn't really do these mods to save money. I hate burning more fuel than necessary and I saw an opportunity to improve something and I went for it.

I'd be more than curious about the rear spoiler delete, who told you all it did was keep the rear window clean?

The gaffing tape I tried one didn't hold up to water very well (wet Michigan), lasted maybe a week on my truck. Foil tape lasted much longer but was a terrible look.

Nice work, thanks for posting.

Any plans for a full belly pan?

EDIT-1

2008
Spoiler Alert: Minivans and SUVs Could Become More Fuel Efficient
https://www.treehugger.com/cars/spoi...efficient.html
https://media.treehugger.com/assets/...-efficient.jpg
https://media.treehugger.com/assets/...an-spoiler.png
I'm not sure what category your rear spoiler falls under, some A/B testing may be warranted.

EDIT-2

2017
Spoiler Alert: Audi Patents a Sliding Wing to Improve Aerodynamics
https://www.autoguide.com/auto-news/...odynamics.html
https://www.autoguide.com/blog/wp-co...le-Spoiler.png
EDIT-3

I was thinking at least a clean sharp edge for the air to release from is a consideration, similar to the below.

Bizon Truck Cab Spoiler
https://www.realtruck.com/bizon-truck-cab-spoiler/
https://c1.rt-static.com/images/prod...rodynamics.jpg
https://c1.rt-static.com/images/prod...ab-spoiler.jpg

Is there a reason not to slow down to 60? Surely that would be the simplest and by far most effective way to reduce fuel use.

Out of interest, what are the speed limits there? In Aus the highest is 110kmh or about 67mph except some roads in the Northern Territory where pretty much no one lives.

The stupidity of today’s drivers cannot be overstated. Safety, vehicle longevity & reliability are out the window. FE doesn’t matter either.

Following too closely is the worst (attended by the belief it’s is legal to travel in the passing lane; it isn’t) as under 300’ space isn’t cause for concern (it should be) and at 50’ many will travel for miles. Hell, days.

NEVER EVER allow one’s self to be surrounded by other vehicles is the key. Ever heard the phrase, “can’t fix stupid”? That’s the guy inside any crowd. For any length of time.

When the morons are trying to form up, cancel cruise and drift down about 10-mph. It’s NEVER safe to have others around. It’s reason to hit the brakes.

Firearms and drunk teenagers. That’s the EXACT risk analogy for trying to run at the upper limit. As nothing else in life has such life-changing consequences. An obese, alcoholic, chain-smoking desk dweeb will outlive the fools with firearms and bad driving.

Remember that at your funeral someone will tell the obese, alcoholic, chain-smoking desk dweeb that we are glad he’s not as stupid as was the guy we are burying.

Traffic volume determines top travel speed. Which is almost never the actual limit.

That covers risk reduction. Spacing determines set speed, and is dependent on traffic volume. Always more than 300’. At 700’, relax.



Fuel economy is in steady-state cruise. Engage cruise control on the entrance ramp. Cancel it to drop off in speed when the fools gather around one (10-mph). Re-engage on a downslope where convenient. It’s always turned on and in use until the end (except the few times when cancellation is best).

With no acceleration or braking events, and maybe passing two-three vehicles on a 600-mile or 12-hr day (the maximum daily distance) the choice of travel speed will be likely be near 65-mph or a little lower.

The needed information is in average mph. The actual time of the trip. From engine start to car parked at day’s end. Total miles divided by time. It won’t be anywhere near travel set speed.

Thus the real trick to high average mph is

1). Location, number and length of stops.

2). Time of departure.

Let’s do last first. Nationwide, traffic is lowest from 2300 to 1100. So start early. I start at around 0300. A good day for me in the Peterbilt is to have 500-miles done before noon. That happens only if everything goes well.

Planned stops. Always do this the night before. Zero unplanned stops. It’s every two hours or roughly 100-miles. A quick exit to the restroom is fine if some walking is involved.

Every four hours is a one hour break. Let this coincide with the fuel stop and/or meals.

The successful day is in knocking out those two-hour or 100-mile legs. What comes before or after is irrelevant. Skill in vehicle-handling is dependent on alertness. Fine motor skills. Without breaks as above (scientific study) those skills fall away. (Which is also accident avoidance).

Make the plan. Use Exit numbers. Stop point in the same direction of travel. No crossing major metro areas late in day. Etc.

These breaks aren’t optional. They’re built-in to the successful plan.

Again, average mph: the higher the travel set speed, the greater will be the divergence between travel set speed and average speed. And the worse the economy. (It’s not all aero problems; it’s in compounding them).

And that steering wheel corrections per 100-miles traveled is a valid FE marker, obviously lane-changing works against one. The more so in having to brake or accelerate to maintain constant speed.

I get drivers all the time on the CB complaining about slow trucks in their way. It shuts them up EVERY TIME when they’re reminded their trip plan failed. Didn’t leave early enough, either. You drive big trucks for a living and this becomes apparent right away. Every vehicle out there is constrained by safety (except in the pea brains of today’s car drivers; it was never this way until under twenty years ago).

A 4,000-mile trip is barely over a week for me. I average above 10,000-miles per month. Hit 120k for the calendar year last week. Habits and preparation are everything. Ronnie Reagan was in the White House last time I had a traffic ticket.

The miles around one’s metro area don’t count towards anything. It’s all familiar. False bravado ensues on cross-country trips. There are differences from every geographical locale and state.

What’s the real difference between running 62 or 72? The latter seems enjoyable because 90% of Americans report it as fully engaging. Any faster and the peripheral cone of vision narrows too far.

In other words, it’s work.

At 62 one arrives relaxed. There’s been no fight. One’s peripheral vision includes the scenery. It’s what vacationing is about. At either speed it’s still the rhythm of from one set point to another.

What’s the time difference? Maybe the spread from 55 to 63-mph ON AVERAGE.

In other words, not worth the trouble to stay with the racing morons all day. I sincerely assure you that’s what they are. ******* children who never had parents. No baby daddy cared enough. I’m happy to tell father & son this, to their faces. Neither is father OR son.

The relation of guns to cars is that it only takes ONCE.

Talk of skill is a laughing matter. And irrelevant.

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Just a note on gaffing tape. I'm a professional Photographer and I use gaffing tape all the time to tape down cords at events. I've also used it on my van for various mods, experiments, and temporary fixes. In the winter time, you will probably be ok with it not leaving too much of a mess. But leaving it on in higher temps and direct sunlight for long periods of time, the adhesive will degrade and leave a mess on the vehicle. I speak from experience. Lots of Goo Gone or Goof Off and elbow grease experience. ;):)

Also, keep it up and do what you feel is right for you! I know you've received some pretty strong comments and opinions here. But do what you can with what you have available and make it work. :)

Coroplast and zip ties work well. Rustoleum flat black paint works quite well and sticks to the coroplast. Or duct-tape covered cardboard painted black or use black duct tape. Worked well and handles the weather fine. Plus, as grins2go_brett said, you avoid dealing with residue issues from the tape on your car. Just a thought. :)

I believe there is a great disparity in precipitation between respective our climates.

Michigan is a whole lot wetter than Arizona.

On the other side of the coin, gaffing tape in Michigan isn't going to have the UV degradation issues of Arizona.

I'm going to guess that Lawrence, Kansas is somewhere in between.

Thanks guys!

Yeah the gaffing tape will certainly see a lot of weather between Kansas and Portland. And it will be getting us around the Portland area for 4 or 5 days, and Portland got 3" of rain in 24 hours a few days ago. I'll keep a roll of duct tape with me just in case.

The reason why I measured at 75mph and not 60mph is because 75mph is the interstate speed limit in most states these days, and that will be the speed I will go. We're making it a 3 day trip, but even then those will be long long days. Slowing down to save on fuel will not be an option. But this is not a fast speed, these days, and I'm always passed by all the other drivers except the big rigs. Even at the speed limit, I seem to be the slowest car on the road.

But for much of the drive, other vehicle on the road won't really be a factor. There will be a lot of lone, lonesome stretches, especially in Kansas, Wyoming, Idaho, Utah, and East Oregon. I hear that I-80 will be mostly truckers (just what I've read, I've never been on that road). I-70 between Denver and the ski resorts will be insane, but I should hit that stretch on Saturday afternoon, well after the crazies have all raced to the slopes. I'm thinking about taking US-50 through Colorado on the way back but I'm not sure yet.

As per the comments about the "******* children who never had parents," that was quite a rant. Do you feel better now?

When my wife is driving, she'll likely go even faster. She drives about 90 on average on her daily commute to work. I'm always telling her to slow down but she has "small car syndrome" as I call it (Toyota Yaris). She hates when another car passes her, especially if it's a SUV or truck, she feels like it's a personal threat against her because her car is small. So she "defends" herself against the bigger vehicles by driving past them as quick as possible.

If you ever want gaffing tape to come off in a hurry go to a self-serve quarter car wash and pressure wash it off.

I highly recommend not washing your car after putting the tape on it.

I recommend even more not using gaffing tape.

If you do experiment with gaffing tape, do it before the long trip, like I said mine only lasted days and you do not want failure in the middle of a long trip and lose time messing with it.

For me it was:

Gaffing tape = less than a week (in wet weather)

Foil tape (with lawn edging backer) = all winter long

You would not have experience removing gorilla tape, would you? Mine has been on my front bumper for about a year, through rain and snow storms, and it seems like it will outlast the car!

In Michigan's cold Gorilla tape does not like to hold.

Even when you use it in warm weather, when it gets cold it stops sticking.

It's garbage, I've never found a use for it.

Duct tape in the summer just melts off in the hot sun and leaves a snail like slime behind.

Foil tape is the only thing that seems to hold both summer and winter, but it has no tear strength to speak of and it's silver.

That's been my tape experiences.

I used duct tape to waterproof the first ecomods I put on my old car, and then painted it silver or black for color and further waterproofing. Held up fine to both heat and rain.

Is there a better available description of “childish” while at the wheel?

Would you “allow” a drunk 14-year-old with finger on the trigger of an automatic?

“Oh, it was an accident”.

Ha! It’s the same set of consequences.

It isn’t “defense”. It’s abstract reasoning. Visuo-spatial. Lack of ability and compensatory behavior. Seen in 99% of south of the border. Not capable in traffic above 45-mph. Not simply a constant problem for everyone else, but also a threat. (Can’t use cruise control either, right?).

Back to your vehicle. What MPG is it capable of? That’s sub-60/mph with enough miles to outweigh re-fill error percentages. 200-mile loop? Find that number to use as baseline. Then HP calculations can be made. No baseline = No appreciable results.

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4,200 mile later... I'm back.

I didn't listen and the gaffing tape fell apart after some snow in Idaho. I got some duct tape and it's holding up a little better but there's strips falling off. Should have got gorilla tape.

What MPG did you average?

Probably around 16.5 or 17 mpg. I haven't done all the math yet.

I got pretty bad performance in the high planes, it was very windy. In fact, I was worried they were going to shut down the interstate it was so windy. 35 to 40mph winds with gusts up to 70mph. Also we were going like 80mph. We felt it was worth the added expense to save time and get to our destinations as quick as possible. I don't really like giving more money than I have to to the oil and gas industry but it is what it is. I'm working on a Beetle at the moment and maybe one day I'll put an electric engine in it.

The gorilla tape on my front bumper has held up through rain and snow storms, as well as a high-pressure washer, for about a year.

How do I remove it?! :)

I'm curious; is there a reason the 4runner needed to make the trip rather than a different vehicle?

Heat gun

I was going to suggest stops in Wall and Murdo SD. Wall for Wall Drug - which seems to have expanded to about half of downtown. Get some of their fudge. :)

Murdo for the Pioneer Auto Museum, which has plenty of other non-vehicle stuff. Kinda run down but still neat stuff. Spring or fall would be the best time to hit those tourist traps. I went last summer and it was HOT, especially in Murdo.

4 runner aero mods
 

You need to remember that 4 runner is a BRICK - both inweight and aero. Tuffer than nails, but not an economy machine. Even with the V6 it's thirsty.

That said, removing the rear spoiler will in all likelihood hurt mileage.
Removing the roof rails will help - particularly at over 60mph.
Getting your baseline on a 10 or 20 mile run going by fillup volume is a little better than guessing - - - -

Using cardboard and gaffer tape when anticipating wet weather is asking for trouble. CorPlast and tie wraps are MUCH better. Make a cardboard template taped up to hit all the gaps, then cut corplast to fit. Watch the gaps at the edges. Remember to leave access for the oil change!!!

Be REAL carefull about taping up air intakes. Try to take advantage of high pressure areas and smooth out the transitions to the rad with corplast baffles behind the grille. Make sure your belly pan does not restrict air exit from the engine compartment. An overheated engine or transmission will cost youmore than a lifetime of fuel savings.
Taping over body gaps will help. A stiff transparent tape like SlickStrip applied on the edge of the hood overlapping the fenders for instance, or on the door edge or fender bridging the gap (stuck to one part - doubled to provide a slide fit over the other) will do wonders on a lot of vehicles.
The 4 runner already has flush mount glass.

If you don't go offroading run it as low as possible. Is it a Limited with air ride?If so lowering is a cinch.

As noted by others, lowering your speed even 5mph will likely do more for your milage than all your modifications, and i've found a bit lower driving speed on a long trip doesn't change the overall travel time very much. You don't get as tired and stressed and you can stretch your fuel/rest stops a bit. Every extra minute in stops is a mile and a half you need to make up. Every 5 MPH is only 5 miles every 60. - an extra maybe 10 minutes per 100 miles at best.

Not sure how much good or harm removing the mud flaps will do - they clean up the air going over the tires and ARE relatively streamlined - particularly in comparison to the tire.

Good suggestion, I've been using that method for over 50 years to get things to fit.

Just wondering: did you do the math yet ? :)


Also, for the guys saying that rear spoiler might have been better left on, I'd need to see more photos of it before making a guess. I've seen some that are clearly designed to force the airflow around the corner to keep the rear glass clean, and there's little doubt in my mind that type would increase drag.


When I saw you had removed the running boards, though, I recalled that some OEM truck designs include running boards that are drag-reducing. Dodge Ram comes to mind for some reason. Lemme see if I can find an example...

Found it!


FYI, Dodge claims their OEM "wheel-to-wheel" running board design on the new Ram offers better aero than naked.


2013 RAM 1500: New York Auto Show - AutoTrader.com