Aero Engineers - constant back window dirty
- Thread starter Shadytype
- Start date
Brandonium
Member
If you drive a lot with the rear window down as I do...and run a vacuum over the headliner you will see just how much shit is sucked in over time never mind the dust that settles and accumulates everywhere else that you actually see and pay attention to on a daily basis. My interior can go from immaculate new to I smoke a carton of cigs a day with the windows rolled up and don't understand the concept of cleaning a car in very short order.
Hey, me too! :cheers:
You would have to either boat-tail the rear or build some kind of spoiler that points the wind gently downwards. But that would have to be a pretty big spoiler to make any difference. I'd just try to embrace the dirty window.
DontKickTrees
New member
I just accepted it and stopped washing my car. I’m saving money on soap and the dust everywhere helps to cover up all my pin stripes and trail damage. Win-win!
DesertCanyons
New member
Back spoiler sucks dirt
I almost never open the back hatch window. I know what will happen if I do. It's known to suck exhaust into the car too because the tailpipe points straight back under the bumper. That's a good reason to have the exhaust tip turned out to the side right behind the rear wheel.
The first time I drove a dusty dirt road the bumper and tailgate hatch got covered in fine dust. It makes camping difficult with fine dirt on the bumper.
I don't know why so many SUVs have spoilers projecting out over the back window. It creates a vortex as others have noted and increases drag. I have to think it reduces fuel efficiency too. I'd like to take mine off if I could figure out what to replace it with, since it hides the wiper mechanism.
I almost never open the back hatch window. I know what will happen if I do. It's known to suck exhaust into the car too because the tailpipe points straight back under the bumper. That's a good reason to have the exhaust tip turned out to the side right behind the rear wheel.
The first time I drove a dusty dirt road the bumper and tailgate hatch got covered in fine dust. It makes camping difficult with fine dirt on the bumper.
I don't know why so many SUVs have spoilers projecting out over the back window. It creates a vortex as others have noted and increases drag. I have to think it reduces fuel efficiency too. I'd like to take mine off if I could figure out what to replace it with, since it hides the wiper mechanism.
Friggin Idiot
Senior Member
I'm no Toyota engineer, but if you're going to have a vortex behind a vehicle having a stable one and constant size is actually more aerodynamic than having many smaller ones. There's an old Mythbusters episode where they actually show a pickup truck with tailgate down, removed, up, and then add tonneau covers and have scale models in a dynamics tube. The tailgate up and tonneau cover were most efficient because they maintained a stable vortex. The main slipstream actually flowed around the vortex instead of into it.
Also having a spoiler back there keeps the sun out of the rear window. Coming from a '92 Bronco I can tell you that large piece of glass in the back can leave the inside of the truck mighty toasty!
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Yeah I'm sure Toyota put at least a little work into aerodynamics since they put those little vortex generators between the side mirrors and the door, but I suppose there's only so much you can do with a box-shaped rear end and the little spoiler is better than nothing at all. Plus it keeps the rain out if you're camping and have the rear window cracked, so that's cool...
Toffees
Member
Basically the sudden drop off in the rear creates a low pressure zone that sucks dirt and debris. This isn't exact, but gives you an idea of the airflow:
There's really not much you can do short of a large airfoil to "smooth" out the shape.
Credentials: Am Aerospace Engineer
Ok, so scraping all of my aerodynamics knowledge together (be gentle with me), but wouldn't a low pressure area create/increase drag, which decreases fuel economy? Or is this design a least bad design? Seems like if the "spoiler" were even slightly vented it would allow some air to divert down over the back window, relieving some pressure differential, reducing drag (?), and removing the dirty rear glass/exhaust smell issues as well.
I'll put my hand back down and take notes now, professor.
I think it's like you said: "least bad" design. The spoiler brings the top of the vehicle a little closer to the same distance as the furthest rear part of the bumper which would have the highest chance of allowing the flow under the car to meet the flow at the top of the car at roughly the same point behind the vehicle, reducing drag by some factor compared to not having it.
I think with everything else on modern SUVs and trucks, it's just a matter of "every little thing helps" to reach a certain drag coefficient reduction to maximize gas mileage on a giant brick going through the wind.
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Muzzle of Bees
New member
It has always been that way. My Xterra's had the same problem. The 4Runner is no better. Dirt is one thing, but sand is another. While wheeling I always pick up a lot of the Padre Island National Seashore sand. It comes out the back hatch for months. There is probably still sand in there.
:argue: just roll the back Window down if you want it to remain clean all the time
Made that mistake on a forest service road. Interior was absolutely caked!
Calif-4runner
New member
I think you just need to drive faster. Wait isn't that what the KDSS is for?
Keeps the Dang Soot from Sticking!
:behindsofa:
Keeps the Dang Soot from Sticking!
:behindsofa:
83Mule
New member
The 4Runner seems to have horrible Aero in general. I drove my Express and She drove the 4Runner and We did the same 200 mile Route together. The Van with a 4.8 and a thousand pounds of cargo got 17 mpg and the front end and windshield were almost pristine when We got home. The 4Runner got 16 mpg and was a disaster of dead bugs on the whole front end! 75 mph Freeway for the most part. About two thousand pounds more weight for the van and a bigger engine......still gets better mpg and clean has got to be the longer breadbox shape versus the high drag and shape on a lifted 4Runner.
Teamoatmealpie
New member
Can't solve the aerodynamics of the the Brick shaped 4R, but for dirt drivers -
We do a ton of offroad driving and the rear is always caked in dirt/dust, hence I keep a tiny whisk broom to clean off the rear when setting up camp. Otherwise it ends up all over me, my kids, cooking gear etc. My buddy is like what are you an Umpire. Ha, ha, ha, but it works great.
Doesn't seem to matter how many times it's washed dirt still pours out of the rear hatch drain holes. In fact the whole rig inside and out is still dust caked from last weeks camping trip.
We do a ton of offroad driving and the rear is always caked in dirt/dust, hence I keep a tiny whisk broom to clean off the rear when setting up camp. Otherwise it ends up all over me, my kids, cooking gear etc. My buddy is like what are you an Umpire. Ha, ha, ha, but it works great.
Doesn't seem to matter how many times it's washed dirt still pours out of the rear hatch drain holes. In fact the whole rig inside and out is still dust caked from last weeks camping trip.
Haha I made this same mistake had front and rear windows down for maybe 2 mi and noticed my seats were covered in dust. Didn't even notice it was happening until I stopped.
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