Rear window air-flow deflector?

[NevadaGeo]

I also wonder how well a deflector mounted UNDER the rear bumper might work.....I found this illustration:

Here's a CFD pic, comparing a NASCAR spoiler (top) to a NASCAR wing (bottom). These were both designed by competent people. Blue is turbulence. You can see how the red laminar airstream avoids the spoiler, but hugs the wing:

View attachment 19766

Interesting comparisons. The wing definitely shows more laminar flow and elevates the vacuum under the rear of the vehicle. Turbulence is what I would call slip stream vacuum. Unfortunately, a deflector under the rear bumper for me would be torn off on some of the off road work I do. Great for the highway, but not for off road.

 

[jeff kushner]

Yup, just good mental exercise.....we used to go through the same gyrations when we were road racing bikes. You wouldn't think so but 2mph at 160mph or more on a track is a huge difference in a race. I mainly did the engine building but my partner who actually put up the $$ and owned the bike would come up with some pretty imaginative stuff....and some of it worked! We moved the fuel into a 3.2 gallon fuel-safe container and fit it behind the engine below the air filters then left the factory fuel tank in place. We weren't breaking the rule as long as we didn't exceed the factory volume of the tank. Moving nearly 20 pounds of fuel closer to the center of gravity does wonders for the handling of a 73 H2 kaw...but the real benefit was that the handling didn't change as the fuel level lowered as with the stock location. Yup, our H2 handled like crap ALL THE TIME<LOL>!

That's one of the reasons we switched to a GT750 Zuk!

jeff

 

[powerboatr]

i agree totally with air flow up from the bottom, my 13 f150 top of bumper would get dirty real fast, as does the expy.
and a source to redirect or influence airflow from the bottom valance could be done without changing the aesthetics dramatically.
i need to follow an expy at highway speeds and watch .

a small deflector, talking about 1" might be enough to move the burble of air back far enough to loose its dirty throwing onto the glass.
in fact the flimsy lower valance may just need some areo slicking or support from underneath to stop the buffeting if it wiggles like the escalades or navigators do
maybe bleed air holes in the plastic bumper cover to blow under car air up?
took a few days off the web and you guys may have solved the problem

 

[jeff kushner]

Don't know if anything is solved PB but it's fun to kick crap around sometimes. The dead-air zone is so large behind these trucks compared to other passenger cars that it's a pretty tough nut to crack.

Creating a "air-wash" for the rear window is a good idea but because the boundary layer is so thick at the rear, the deflector would have to stand off the surface several inches and wouldn't necessarily be aesthetically pleasing to the eye.

The new Suburbans have a tapered rear end much like the '18 Expy's and I've been looking for a dirty new Suburban to see if it's "dirtier" on the rear than the sides but the only one in my neighborhood is washed all the time.

jeff

 

[powerboatr]

this is funny
i to have started really paying attention to dirty suvs
driving dirty
we may end up at the same spot, as in no deflector. but dam our brains are getting a workout

 

[NevadaGeo]

this is funny
i to have started really paying attention to dirty suvs
driving dirty
we may end up at the same spot, as in no deflector. but dam our brains are getting a workout

PB, didn't your mother warn you about dirty SUVs??

 

[powerboatr]

PB, didn't your mother warn you about dirty SUVs??

hilarious

i did find this afternoon surveying the under side rear valance that this approach would most likely far exceed cost versus actual returns, to much to clean up and then air would have to flow forwards .

i did find the rear valance attachments points on the frame, there are two little plastic push pins to hold it from wiggling, i replaced those with a nuts and bolts and large washers, to restrict the over 1/2" of play the plastic pins allowed. Might further cure some noise from out back

 

[ExpeditionAndy]

I have a car wash membership for a local car wash. I pay monthly and I have unlimited access I can get it washed everyday if I wanted. I typically wash it 1 - 2 times per week. I do notice the most dirt when it is raining that mist that comes from the wheel wells just covers the rear window. But then I do use my rear wiper. I understand Nevada's issue with not wanting to scratch the rear glass.

 

[jeff kushner]

PB, didn't your mother warn you about dirty SUVs??

Yeah buddy.....we be "ridin dirty"!

Gee, now I'll have to go back to my girlfriend and re-explain what that means!

jeff

 

[NevadaGeo]

Yeah buddy.....we be "ridin dirty"!

Gee, now I'll have to go back to my girlfriend and re-explain what that means!

jeff

If she is dating you, does that really need re-explaining??