Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 09-29-2022, 01:38 AM   #1 (permalink)
EcoModding Apprentice
 
Join Date: Nov 2020
Location: The Pas, Manitoba
Posts: 163
Thanks: 214
Thanked 80 Times in 56 Posts
Raising a Trunk?

Hey all,

Iíve been reading, re-reading, and reading some more of Julian Edgarís book on aero mods. In a couple different pages he mentions raising the height of the trunk lid on a car. I forget the specifics at the moment, but I believe it made for a gentler transition from the rear windshield down to the trunk on notchback-style cars, overruling the increase in wake size. I havenít seen many people do this, but I have seen it put to great use on the GM/Chevy Volt. Iím planning aero mods for my 2006 Civic Coupe (FG2), which seems to have a separation bubble at the base of the trunk lid; bottom of the windshield. If figure this could be a good remedy.

Anybody try this? Iíve seen it mentioned in various threads but havenít seen it done much.

  Reply With Quote
The Following User Says Thank You to JacobLeSann For This Useful Post:
aerohead (09-29-2022)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 09-29-2022, 07:53 AM   #2 (permalink)
マット
 
M_a_t_t's Avatar
 
Join Date: Nov 2015
Location: Indiana
Posts: 717

The Van - '95 Chevy Astro Cl V8 Swapped
Team Chevy
90 day: 7.84 mpg (US)

The new bike - '17 Kawasaki Versys X 300 abs
Motorcycle
90 day: 71.94 mpg (US)

The Mercury - '95 Mercury Tracer Trio
Team Ford
90 day: 34.35 mpg (US)

Toyota - '22 Toyota Corolla Hatchback
90 day: 40.11 mpg (US)
Thanks: 131
Thanked 258 Times in 188 Posts
Does it reconnect before final separation?
__________________
1973 Fiat 124 Special
1975 Honda Civic CVCC 4spd
1981 Kawasaki KZ750E
1981 Kawasaki KZ650 CSR
1983 Kawasaki KZ1100-A3
1986 Nissan 300zx Turbo 5 spd
1995 Chevy Astro RWD (current project)
1995 Mercury Tracer
2017 Kawasaki VersysX 300
2022 Corolla Hatchback 6MT

https://www.youtube.com/channel/UC6s...LulDUQ8HMj5VKA
  Reply With Quote
The Following User Says Thank You to M_a_t_t For This Useful Post:
JacobLeSann (09-29-2022)
Old 09-29-2022, 10:57 AM   #3 (permalink)
Master EcoModder
 
me and my metro's Avatar
 
Join Date: Jun 2008
Location: Oregon
Posts: 538

Economy Saturn - '02 Saturn L200
Thanks: 250
Thanked 192 Times in 152 Posts
This has been a common practice on circle track race cars for at least 50 years. It was done to get the rear spoiler higher in the air for more down force. They would limit the spoiler size but not the trunk lid/quarter panel configuration. People discount racing as a waste of time but there have been lots of aero in their designs.
__________________
02 Saturn L200 5 speed- 265k miles
84 Gmc 6.5 na diesel K30 4x4, TMU
2006 Lincoln Navigator, 215k miles
  Reply With Quote
The Following User Says Thank You to me and my metro For This Useful Post:
JacobLeSann (09-29-2022)
Old 09-29-2022, 12:08 PM   #4 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 14,918
Thanks: 23,050
Thanked 6,810 Times in 4,332 Posts
VOLT / CIVIC

Quote:
Originally Posted by JacobLeSann View Post
Hey all,

Iíve been reading, re-reading, and reading some more of Julian Edgarís book on aero mods. In a couple different pages he mentions raising the height of the trunk lid on a car. I forget the specifics at the moment, but I believe it made for a gentler transition from the rear windshield down to the trunk on notchback-style cars, overruling the increase in wake size. I havenít seen many people do this, but I have seen it put to great use on the GM/Chevy Volt. Iím planning aero mods for my 2006 Civic Coupe (FG2), which seems to have a separation bubble at the base of the trunk lid; bottom of the windshield. If figure this could be a good remedy.

Anybody try this? Iíve seen it mentioned in various threads but havenít seen it done much.
1) if you'll compare the original VOLT concept 'notchback', at Cd 0.42, to the production VOLT 'fastback', at Cd 0.281, it provides an insight into GM's 'solution' for the car's aerodynamic performance.
For some unspecified reason, Chevrolet Division modified the original roofline to fit the 3rd- generation aerodynamic streamlining template. Online, you can find a CFD analysis for the production VOLT, indicating for fully-attached flow until the rear of the roof. Yes, the wake IS larger, but the much-higher base pressure creates an overall pressure drag reduction, and total drag reduction.
2) for your CIVIC, you may want to compare it's roofline to that of the 2022 CIVIC, and see if HONDA hasn't followed the VOLT's lead. And if you can locate a 'blueprint' for both CIVICs, you might want to compare both to the AST-III. There's a reason why the lowest drag cars are using rooflines close to it.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
JacobLeSann (09-29-2022)
Old 09-29-2022, 02:22 PM   #5 (permalink)
EcoModding Apprentice
 
Join Date: Nov 2020
Location: The Pas, Manitoba
Posts: 163
Thanks: 214
Thanked 80 Times in 56 Posts
It looks like flow reattaches at the boot and separates cleanly off the top end of the trunk. I’ve posted some tuft-test photos here:
https://ecomodder.com/forum/showthre...tml#post675015

The 2022 civic coupe has a very neat rear end. It’s a very true-to-form fast back and has some sharp separation edges at the rear. My issue being that my rear end isn’t really like that at all. I can’t really get it to take that shape without a lot of modification, hence why I’m looking at raising the lid. The 2022 Civic sedan is a bit of a better model. You can see the progressive raising of the trunk’s height over the different model years.

I think I might go ahead and test out some prototype aero mods. I want to raise the lid toward the base of the windshield, and drop it down towards the car’s rear,, flowing out into a rear bonneville-wing type extension. I think that would work very well as a fastback substitute.
  Reply With Quote
The Following User Says Thank You to JacobLeSann For This Useful Post:
aerohead (09-29-2022)
Old 09-29-2022, 02:42 PM   #6 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 14,918
Thanks: 23,050
Thanked 6,810 Times in 4,332 Posts
reattaches

Quote:
Originally Posted by JacobLeSann View Post
It looks like flow reattaches at the boot and separates cleanly off the top end of the trunk. Iíve posted some tuft-test photos here:
https://ecomodder.com/forum/showthre...tml#post675015

The 2022 civic coupe has a very neat rear end. Itís a very true-to-form fast back and has some sharp separation edges at the rear. My issue being that my rear end isnít really like that at all. I canít really get it to take that shape without a lot of modification, hence why Iím looking at raising the lid. The 2022 Civic sedan is a bit of a better model. You can see the progressive raising of the trunkís height over the different model years.

I think I might go ahead and test out some prototype aero mods. I want to raise the lid toward the base of the windshield, and drop it down towards the carís rear,, flowing out into a rear bonneville-wing type extension. I think that would work very well as a fastback substitute.
Theoretically, the CIVIC's roofline will generate too radical of an adverse pressure gradient, jeopardizing the boundary layer.
There may be vorticity that is not revealed by the tufts, and what appears as a 'true' attached flow, is actually 'downwash,' a symptom of separation-induced longitudinal vortices of high drag.
If so, you lose the potential for pressure recovery, as much of the kinetic energy of the separation bubble is lost to heat.
The fastback moderates the rate that the flow can decelerate, avoiding the threshold for separation, allowing all the flow field to gently decelerate, and build back higher static pressure where the flow finally does separate, thereby injecting higher pressure into the wake, W.H. Hucho's near-singular mechanism for streamlining.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
JacobLeSann (09-29-2022)
Old 09-29-2022, 02:49 PM   #7 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 14,918
Thanks: 23,050
Thanked 6,810 Times in 4,332 Posts
spoiler length / angle

An option to just adding length is to also angle the spoiler up, at no more than a 30-degree angle, 'quitting' the spoiler just as in intersects the AST-III projected contour. It will allow for a shorter spoiler 'length.'
There are dozens of high-performance sports cars that have done this.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
JacobLeSann (09-29-2022)
Old 09-29-2022, 02:53 PM   #8 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 24,348
Thanks: 6,872
Thanked 7,744 Times in 6,333 Posts
I might be induced to produce a sketch, but a DALL-E prompt might be "2006 Civic Coupe (FG2), tapered hitch mount box that extends over the trunk opening, aluminum construction with rounded edges, photorealistic'.
__________________
.
.

Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster
____________________

"Stuff just keeps on getting older...." -- Graham Hancock

____________________
  Reply With Quote
The Following User Says Thank You to freebeard For This Useful Post:
JacobLeSann (09-29-2022)
Old 09-29-2022, 08:46 PM   #9 (permalink)
EcoModding Apprentice
 
Join Date: Nov 2020
Location: The Pas, Manitoba
Posts: 163
Thanks: 214
Thanked 80 Times in 56 Posts
A ducktail/lip spoiler is interesting. I see this on newer Chevy Cruze/Malibu models, Chrysler 300 models, teslas, etc. I never really did know how lip spoilers work, but seeing Aeroheadís CRX makes me wonder.

Adding a rear wing that extends the whole length of the rear into a boxed cavity (sort of like a Porsche K35 rear) is the main idea Iíve been looking at. I trialed a quick ní dirty bonneville style trunk extension on my long distance trip recently, which really did help the mileage.

The fastback is indeed a superior design, itís just that Iím trying to retain the stock practicality/aesthetics/vision. I plan to give the car to my mom once I fix up my hatchback. That one will get more radical mods. The hitch mounted tailbox is likely gonna go on that one, when traveling.

I think there is relatively stable flow down the top half of the rear glass. If you look at a side view of the FG2 chassis (as freebeard said), you can see that the transition to the rear glass is very gentle, even though itís a steep angle.
  Reply With Quote
The Following 2 Users Say Thank You to JacobLeSann For This Useful Post:
aerohead (10-03-2022), freebeard (09-29-2022)
Old 09-29-2022, 09:49 PM   #10 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 24,348
Thanks: 6,872
Thanked 7,744 Times in 6,333 Posts
IRONICK posted about the Ferrarri Purosangue at ecomodder.com/forum/showthread.php/fender-vents-separation-traps-40461-2.html#post675102



Quote:
While the suspended spoiler helps neutralise the curvature of the roof downstream of the area over the heads of the rear-seat passengers, the nolder, which is barely 7mm high, channels the wake vortices to create a slight recompression at the tail of the car.
https://www.ferrari.com/en-EN/corpor...like-any-other

Ferrari call it a 'nodler'. There are a lot of interesting details on this vehicle

__________________
.
.

Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster
____________________

"Stuff just keeps on getting older...." -- Graham Hancock

____________________
  Reply With Quote
The Following User Says Thank You to freebeard For This Useful Post:
JacobLeSann (10-01-2022)
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2022, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com