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11-22-2008, 08:26 AM | #1 |
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Drives: 2008 Yaris Join Date: Oct 2008
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Observations on LB turbulence
Noticed on the way home that my rear window gets dirty very fast. I'd be willing to speculate that the laminar air flow over the car does not recombine near the tail, leading to vortices just behind the hatch.
Wonder whether some sort of base bleed or disruption of flow near the hatch might improve drag characteristics? Gene |
11-22-2008, 08:30 AM | #2 |
vroom vroom
Drives: lil red 5-door Join Date: Sep 2006
Location: Bangkok, Thailand
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several people have messed around with vortex generators but I have no idea if they did any actual aerodynamic testing
Due to the sudden dropoff of the rear hatch, we can't expect great aerodynamics back there sadly, it is one of the drawbacks of the hatchback form factor. Spoilers can only help so much, I have one but the rear glass still turns to a mess real fast...
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11-22-2008, 09:14 AM | #3 |
Super Moderator
Drives: Absolutely red Liftback Join Date: Oct 2008
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It's a Yaris man. How much of your driving is done above 55mph? The DCOE really doesn't matter that much for in town driving. To clear your back window of excess debris you could add a downward facing wind deflectoe similar to that used on an SUV.
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11-23-2008, 12:45 AM | #4 |
On Friday I did some driving in some light snow and I saw a little bit of a swirl back there. I guess if a spoiler could be extended to keep the air attached, it could help keep the window clean.
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11-23-2008, 03:39 AM | #5 | |
MetalShark
Drives: 2008 Yaris LB Join Date: Oct 2008
Location: Mesa, AZ
Posts: 104
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LB aerodynamics
Quote:
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Absolutely red, Drawtite hitch, CAI, Insulated Header, Amsoil 5w-30, Mag-drain plug, Red-Line MT-90 tranny oil, Scotch-Guard, Window Tint, Dash rug, Custom short throw shifter, Lowered OEM arm rest, Super-Turbo muffler/w chrome slash cut tip., TRD rear sway bar, sticky pads, front shock tower bar, RS grill badge, VVT-i emblems, Second tire set from Tirerack.com, DISABLED DAY TIME RUNNING LIGHTS, platform- style locking custom bike rack. 86K miles so far. 5 years use now on ceramic wrapped insulated stainless-steel header. |
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11-23-2008, 12:01 PM | #6 |
Drives: Blazing Blue Liftback Join Date: Oct 2008
Location: Port Angeles, Wa
Posts: 385
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I noticed a slight improvement when I added the lip spoiler, but the back window still gets pretty dirty.
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11-23-2008, 12:37 PM | #7 |
Steals terrorist's lunch
Drives: 2007 Yaris Liftback Join Date: Mar 2007
Location: Reno, Nevada, USA
Posts: 1,299
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I cut roughly half of the accumulation on and half of the misting behind my LB simply by adding on the OEM mud flaps. That means that much of the turbulence comes from underneath the car.
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11-23-2008, 05:13 PM | #8 | |
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Drives: 2008 Yaris Join Date: Oct 2008
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Quote:
Could also mean that most of the crap comes from the rear wheels, which when you vent it downwards doesn't contaminate the rear glass. Gene |
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11-25-2008, 09:05 AM | #9 | |
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I have the small (tiny) factory lip spoiler and that seems to take the brunt of the dirt (where the rain does not hit). It is a vacuum back there. I have noticed when I do a complete glass cleaning that the dirt from the back window is blackened from the exhaust fumes. Just one of those things we have to endure....... until you report back on the reverse drivinf technique!
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11-25-2008, 11:56 AM | #10 |
Steals terrorist's lunch
Drives: 2007 Yaris Liftback Join Date: Mar 2007
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No, there is no irony there. I did not expect that kind of result from adding the mud flaps but I got it.
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- Brian Share the Road I often carry 2 carpool passengers and mountain bikes or snowboards/skis over a 4,500 foot elevation difference. Click the graphic above to see my detailed mileage logs. |
11-26-2008, 12:59 AM | #11 | ||
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Drives: 2008 Yaris Join Date: Oct 2008
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Quote:
Think I'll pass on seeing whether Toyota considering driving backwards for long periods of time to be "abuse" under the warranty. Quote:
Gene |
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11-26-2008, 12:14 PM | #12 |
Drives: 07 Yaris sedan Join Date: Jun 2007
Location: Keremeos BC
Posts: 986
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Agreed, but be careful. Belly pans can play their own mean tricks to the aerodynamics of a car!
"Filling in" that vacuum can be accomplished in a few ways, but smooth air is mandatory for the best results. I contend that the good mileage I get is because of the shape of our sedan: the extra length ("... 20' long...") and slope of the back is better streamlining than the blunt rear on the hatch. The rear window doesn't get dirty for the same reasons. So the chore becomes, making the air think you are driving a sedan, and I really think it takes a wind tunnel to do that properly, rather than with the wannabe aerodynamic packages available now. |
11-26-2008, 12:25 PM | #13 |
それを吸ってください
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I use this handy dandy doohicky. I get amazing results and sometimes a compliment or two
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11-27-2008, 04:53 AM | #14 |
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Drives: 2008 Yaris Join Date: Oct 2008
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I have a wiper. I thought that the deposit of road gunk - mainly calcium chloride and sodium chloride that also eats Yaris - was an artifact of drag.
Thanks to TLyttle about the word on belly pans. I had forgotten that nasty thing called "Ground Effect". That's all I need, to have the damn thing float! Gene |
11-27-2008, 11:47 AM | #15 |
Drives: 07 Yaris sedan Join Date: Jun 2007
Location: Keremeos BC
Posts: 986
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Funny thing about vacuum: it doesn't really care where the air comes from, and under the car is as good a place as any, hence the accumulation on the back window. Decades ago, I had an old Volvo wagon whose roof design didn't allow for a deflector over the rear door, so I used two small aftermarket deflectors, one each side, to infill the rear window. It certainly created some weird mud patterns, but it did keep the window relatively clear.
The mudflaps also change the air patterns in a positive way, but I am not sure how much drag that would add. You just know that someone will think, "Whut's good, more's better", and add a full-width mudflap; it might just work. Like I said, a tunnel would tell all. And "floating" can be very disturbing alright! I built an aluminum duner in the 60s, and the front fenders had a tendency to lighten up the car at ~75mph. First hint was the steering being ineffective. Nerve wracking.... |
11-28-2008, 04:11 PM | #16 |
resident senior
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Use the poor mans wind tunnel . Use surveyors tape to make streamers . Of course you will have to elevate the streamers about 1 " from the surface . Then follow your car while videoing the sequence .
I've thought about using CF canards right in front of the tail lights to create more downforce , but you could easily redirect .
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11-28-2008, 07:29 PM | #17 |
Drives: 2008 Silver Hatchback Join Date: Oct 2008
Location: Pickering, Ontario, Canada
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I have had many a hatchback including a VW Rabbit, AMC Gremiln, smart car and Yaris. All of them have pulled the road moisture onto the back window. The wiper is the best solution.
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11-28-2008, 09:04 PM | #18 |
JuicyCoutureGirl
Drives: 2009 Blazing Blue LB Join Date: Nov 2008
Location: South Carolina
Posts: 14
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I do have to use the wiper on the back window quite a bit.
I didn't realize that all Yari (yep, I say the plural for Yaris is Yari) don't have wipers on the back. |
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