passively variable angle VG; fixes crosswinds

[4drviper]

That was a lot better than "I don't know any VG working IRL so no".

Thank you for that.

[freebeard]

I Thanked him for you.

[4drviper]

Originally Posted by aerohead

What you're observing could be explained simply as a styling gimmick.
A perfect belly pan would be required for the diffuser to work in the first place. Failing that, it wouldn't matter what the diffuser looked like, it would be submerged in turbulence either way.

I had to bring a picture to make sure I'm not being treated like a complete idiot because I still cannot believe a manufacturer driven for profit would put this kind of "styling gimmick" at that location.




For the past 5 years I was able to spot these under many Toyota/Lexus on the road like Corolla, Camry, ES350, RX, just to name the ones I've seen a lot.

I understand manufacturers put styling diffusers on the bottom of rear bumper but not under the trunk.

And I mean the 4 "strakes" on the plastic piece covering spare tire bulge not the trailer hitch for those just looking to pick a fight.

[4drviper]

Are these really just RICE??
(race-inspired cosmetic enhancements)


This is corolla. I only see 2 to the very left of the picture.



This one looks like the back one is probably cosmetic but the under one??

anyone who wishes to see more can google "undercarriage + [model]" themselves.

[MeteorGray]

Interesting four-wheel alignment on that car, or is it the wide-angle lens distorting things?

[Vman455]

Originally Posted by 4drviper

Are these really just RICE??
(race-inspired cosmetic enhancements)

Of course not. They're completely invisible to anyone looking at the car unless they kneel and peer under it, yet most if not all manufacturers of passenger vehicles today use rear diffuser panels or, as is becoming more common in the last 2-3 years, a centrally-mounted muffler shaped to function as a diffuser panel. Toyota uses straightening vanes on all its cars since the 2010 Prius was introduced.

The idea that one has to have a full, smooth belly pan before even considering a rear diffuser is bogus. You can glean as much from Hucho's book; in particular the discussion of the Opel Calibra's front air dam cutout and rear diffuser (p. 189-90 in the 4th edition), where he writes:

Finally, the central cutout in the spoiler may improve the flow at the end of the underbody (Fig. 4.82(d)), so that a diffuser can work more effectively.

(emphasis added)

As well as from the example of nearly every current production car (and a fair number of SUVs/crossovers) in the world.

[4drviper]

Originally Posted by MeteorGray

Interesting four-wheel alignment on that car, or is it the wide-angle lens distorting things?

Not funny or constructive. This is exactly why I give zero credibility to post count #s like your car's odometer is rarely an indicator of how good or fast of a driver you are.

Originally Posted by Vman455

Of course not. They're completely invisible to anyone looking at the car unless they kneel and peer under it, yet most if not all manufacturers of passenger vehicles today use rear diffuser panels or, as is becoming more common in the last 2-3 years, a centrally-mounted muffler shaped to function as a diffuser panel. Toyota uses straightening vanes on all its cars since the 2010 Prius was introduced.

I guess I should have posted a picture instead of assuming everyone who wants to talk about car aero could Google for 5 seconds instead of side tracking and posting completely unrelated study from its grave because I mentioned it as a side note.. Glad it's back on track now.

Originally Posted by Vman455

The idea that one has to have a full, smooth belly pan before even considering a rear diffuser is bogus. You can glean as much from Hucho's book; in particular the discussion of the Opel Calibra's front air dam cutout and rear diffuser (p. 189-90 in the 4th edition), where he writes:
(emphasis added)
As well as from the example of nearly every current production car (and a fair number of SUVs/crossovers) in the world.

I don't know how you remember which pages to quote but thanks a lot. I was thinking the exact same thing but what does a 20-post-count kid know? lol


This is the best I can do to add for anyone thinking one needs a full belly pan before diffuser, yeah he's just a youtuber so take it or leave it.

https://www.youtube.com/watch?v=Mi5NgRyAqt4

I recommend you focus on the parts where he explains how the air from mid section of the car goes into the diffuser, not the diffuser itself.
For cars without smooth belly pan, a diffuser design used on full belly pan cars would be considered "poor diffuser design". Not "no diffuser will work without smooth belly pan". So Toyota made the design suitable for each car they put it on as you can obviously see some differences between models.


from
https://www.semanticscholar.org/pape...e956edbe2955f7
Doesn't this resemble the one used under Camry? (the one with trailer hitch) VGs don't have to be paper thin to be efficient. Actually bump VGs are less draggy IIRC.

But since I have no ability or superficial hourly expense to verify my idea/question scientifically, I look at pictures like these. (for you wind-tunnel fanatics, there are also studies showing significant difference between wind tunnel vs real life and concluding road test is mandatory to optimize airflow around a car)


I can't tuft-test those and I don't have a Toyota. So now I'm really curious if they are straightening strakes and/or variable angle VG (to crosswind). Also I want to know why they have some thickness to it as opposed to tire spoilers which are just a panel of plastic.

What would the angle of attack on those underbody strakes do? Since there is always some crosswind IRL and cars don't always drive in straight line??

A tube-fed version of those who don't understand why I posted the video in #1.

https://www.youtube.com/watch?v=kYa0pP9kxmc

Now that I think we cleaned up that the idea I got from Toyota wasn't from a "styling gimmick" I hope it continues in constructive direction trying to suppress flow detachment on the downside of crosswind over the A pillar and roof line.

Originally Posted by JulianEdgar

...
2. Separated flow on the downwind side of the car will, however also cause instability
...

https://ecomodder.com/forum/showthre...tml#post626011
in this post he tested them on the side of A pillar's curvature so I plan to test them on the front side of A pillar, parallel to tufts I will attach to the very outer edge of windshield when the they dance over and around A pillar. I don't have those equipments sadly.

[j-c-c]

Originally Posted by 4drviper

Also I want to know why they have some thickness to it as opposed to tire spoilers which are just a panel of plastic.

Not sure if your comparison has a strong merit to your original question here, but I'm also wondering, if its an aero concern, or something else at play regarding the thickness we observe on the "strakes".

[freebeard]

And JulianEdgar's Edgarwidget. The airfoil section would just try to pull it off the car.

F1 front airfoils have a constant chord[, apparently].

[4drviper]

Originally Posted by MeteorGray

Interesting four-wheel alignment on that car, or is it the wide-angle lens distorting things?

Originally Posted by j-c-c

Not sure if your comparison has a strong merit to your original question here, but I'm also wondering, if its an aero concern, or something else at play regarding the thickness we observe on the "strakes".

Ah, I wish I added question marks at the end of the title but oh well.

Yes they are relevant because,, originally I was thinking I don't care where they go. But if they were to go in the front part of the car they'd be the clear "flexible" ones as I already have some airtabs on my spare tire belly pan. I guess I raved too hard about the new VGs I found so I was focusing there since Mr. Edgar was providing some tests results as well but I repeat, it is not limited to A pillar or hood. I don't care anywhere.

The airtabs i installed anywhere behind the rear wheel of my sedan(by that I just mean it's pretty downstream, rooftop, Cpillar, tail lamp, and undertray), OBD2 fuel consumption testing showed about up to ~0.5% fuel economy decrease PER PAIR of airtabs installed in repeated tests (1 to 6 pairs then back down to 1 and back up to 3 to confirm the numbers then I left it alone) so I was looking for options that will not trip vortices in relatively straight wind, but become VGs when wind blows sideways, like the plane engine nacelle strake. And the Toyota ones just came to my mind so yeah.

I might need to check the numbers it was several years back but the decrease in MPG was very small but they did stack.

When I said I don't care about FE, I meant when the VGs are in action, not ALL the time like the airtabs I run now for the time being.