4th gen aerodynamics - LS1TECH



Advanced Engineering Tech For the more hardcore LS1TECH residents
Sponsored by:
Sponsored by:

4th gen aerodynamics

Reply
 
Thread Tools Search this Thread
Old 11-08-2016, 04:43 AM   #1
12 Second Club
Thread Starter
iTrader: (3)
 
bufmatmuslepants's Avatar
 
Join Date: Mar 2007
Location: Warrenton, VA
Posts: 3,056
Default 4th gen aerodynamics

The cd of the 4th gen was 0.34 and now is huge compared to new cars, yet it looks like it has a slippery body. New pickups have a lower coefficient of drag. Where are the areas of improvement? The one I look at most is the tail. When I was in college working on a project called Ecocar for GM and the DOE, we met with the engineers behind the c6 Z and the hybrid Tahoe, and he gave a presentation about the backs of cars, and how chopping off the back of a car clean is more aerodynamic than rounding it off. He showed how in the 90s everyone thought the back of the car should be rounded, but they found chopping it off creates positive pressure on the back of a car instead of creating a vacuum. Notice the back pillars of the hybrid Tahoe are squared off.

For a 4th gen, has anyone tried filling in the area between the hatch and spoiler and creating a flat back? Blending the z28 spoiler down to the Berger panel, bringing the spoiler flat to the glass. I think the current design creates lift from air going under the spoiler, it's kind of shaped like the top of a wing if you follow it from the roof to the Berger. Notice prius' and other low drag cars just cut it off flat at the back, with a small lip on the top to keep that bubble pushing the back of the car. Even pickups now have a little lip on the tailgate pushing out, like the flat wing on drag cars over the chute (whatever you call it). The SS spoiler probably creates more drag than anything, my idea is blend the z28 spoiler into the glass, then blend it down into the Berger.

Other spot hurting the lt1 camaros is definitely the headlights, as well as the fog lights. For 2005, the tahoes filled in the gap around the fog lights to reduce drag, as well as changed the 3rd brake light to be like the above mentioned flat lip instead of being rounded. The overall shape of the 4th gen had a few things right, like the blended mirrors and pointed front end, but has anyone tried any real aerodynamic changes to a 4th gen and reported results?
bufmatmuslepants is online now   Reply With Quote
Old 11-08-2016, 08:16 PM   #2
Launching!
iTrader: (1)
 
SlasherVRGR's Avatar
 
Join Date: May 2013
Location: NEPA
Posts: 293
Default

The rear end you're describing sounds to me like a base firebird spoiler?
SlasherVRGR is offline   Reply With Quote
Old 11-09-2016, 03:22 AM   #3
Banned
iTrader: (32)
 
Join Date: Apr 2006
Posts: 5,136
Default

Any wind tunnel vids that actually show this pressure at the back?
Blown06 is offline   Reply With Quote
Old 11-10-2016, 05:09 AM   #4
12 Second Club
Thread Starter
iTrader: (3)
 
bufmatmuslepants's Avatar
 
Join Date: Mar 2007
Location: Warrenton, VA
Posts: 3,056
Default

The screenshots the GM engineer showed me (this was 8 years ago) used CFD showing the bubble behind the car, where the longer the bubble the more drag.







This is just an image I googled. My boss and I were talking about this and he mentioned some race team that figured this out in the 80s and when I googled the car it showed a radical cut off on the back, but I can't remember right now what the name of the car was. Basically my thought is the air is going under the spoiler now and if you closed it in, you would create the smaller bubble. The base firebird rear was too rounded at the back edges I think.
bufmatmuslepants is online now   Reply With Quote
Old 11-10-2016, 07:28 AM   #5
TECH Fanatic
 
Join Date: Feb 2012
Posts: 1,383
Default

You have drag and down force. Look into BlainFab rear lexan spoiler. That may give you some idea. Combined with a proper splitter people have reported good improvements in stability.

What are you doing this for? Road Racing? MPG's?
smitty2919 is online now   Reply With Quote
Old 11-10-2016, 11:08 AM   #6
TECH Fanatic
 
Join Date: Jul 2013
Location: Portland, Oregon
Posts: 1,808
Default

Chin splitter. Full belly pan will always help. Rear diffuser. Rear spoiler (the BlainFab is amazing). Proper heat extraction vent(s) in the hood will reduce drag by venting the turbulent air out from the engine bay. Wicker bills on the fronts of the wheel-wells. Vortex generators above the rear window.

I should note that some things increase drag in order to apply downforce to the car. Chin splitters and rear spoilers (depending on the angle of attack) in particular. For road racing, set your suspension up for 45-75mph and your aero for 75-150mph. For drag racing, undo everything and restart your build so you can use the steering wheel.
DavidBoren is offline   Reply With Quote
Old 11-10-2016, 05:04 PM   #7
12 Second Club
Thread Starter
iTrader: (3)
 
bufmatmuslepants's Avatar
 
Join Date: Mar 2007
Location: Warrenton, VA
Posts: 3,056
Default

I'm just talking about the 0.34 coefficient of drag, where do you think is causing the biggest loss? Not racecar mods, small changes GM could have made on the production car.
bufmatmuslepants is online now   Reply With Quote
Old 11-10-2016, 07:12 PM   #8
TECH Junkie
iTrader: (7)
 
HioSSilver's Avatar
 
Join Date: Aug 2002
Location: Winchester, VA
Posts: 3,802
Default

I have thought about filling in the area between the glass and spoiler. But i kinda thought some other areas should be addressed first.

I made a rear pan for mine years ago.



I've also did some front end stuff but all that is about to get revamped



Here is a little filler panel i made to address the headlight area.


Last edited by HioSSilver; 11-10-2016 at 08:44 PM.
HioSSilver is online now   Reply With Quote
Old 11-10-2016, 09:13 PM   #9
TECH Fanatic
 
Join Date: Feb 2012
Posts: 1,383
Default

Do you have a picture the leading edge of your rear pan? Does it angle up behind the differential? If it just ends, I could see that allowing air to be trapped.

Good work though. I've contemplated some of these things.
smitty2919 is online now   Reply With Quote
Old 11-10-2016, 09:54 PM   #10
TECH Junkie
iTrader: (7)
 
HioSSilver's Avatar
 
Join Date: Aug 2002
Location: Winchester, VA
Posts: 3,802
Default

Thanks.....it's sealed up to the gas tank and body.

HioSSilver is online now   Reply With Quote
Old 11-11-2016, 04:50 AM   #11
12 Second Club
Thread Starter
iTrader: (3)
 
bufmatmuslepants's Avatar
 
Join Date: Mar 2007
Location: Warrenton, VA
Posts: 3,056
Default

The rear bumper I agree is a huge parachute. That's a big area of improvement, blending it up to the underside of the tank. The headlights on an LT1 camaro can be covered with lenses, and the fog light areas need to be sealed to the lights. The radiator air dam could be full width to be all the way in front of the tires, and lower. Vents in the hood then could release the air from the engine bay rather than it going under the car. Closing in the spoiler, we talked about that. And the rear bumper is too round, if it could sweep from the Berger panel down like on a vette, that would help I think too. Your head light area and front bumper extension look great. Another is the antenna, I saw something that said only 1% of new cars have tall antennas anymore. Why did GM ever get rid of the antenna in the window like the 73-87 pickups? Those little shark fins like on Evos could stabilize the air at the back of the roof before it goes down the window.


The F body has such a slippery shape, I wonder if you did all of the above, what you could get the cd down to.

Last edited by bufmatmuslepants; 11-11-2016 at 04:55 AM.
bufmatmuslepants is online now   Reply With Quote
Old 11-11-2016, 08:44 AM   #12
TECH Junkie
iTrader: (7)
 
HioSSilver's Avatar
 
Join Date: Aug 2002
Location: Winchester, VA
Posts: 3,802
Default

I agree on the rear bumber being to round. The only way i could conceive of fixing that would be a add on piece to square it off a bit our a gurney lip type edge.

Yea if i closed off the upper part of the wing i would do the back of it also.

That front bumper wxtension i made from 2 03 mach 1 pieces. A friend wrecked his twice and i scarfed up the left overs....lol.

All of the front is getting redone with a rk sport lower. The rad air intake is getting moved to the oe holes in the front and therad air dam will be removed and the front bottom made flat.....i may put tunnels in there to. Not sure yet.

I have the whole rk sport kit actually. I will eventually wirk the rockers on to it and flat bottom the car to the tunnel area. The rear i will work into it also.

Did you notice the gurney lip on the leading edge of the front fenderwell?

I have a hood i am reworking. I got it cheap. I've closed the louvers in it up. I want to do something more like a hell cat or gt350 type of extraction opening.



Right now i am working on a over the rad cai to get rid of the lid system and hopefully produce something way more efficient. The plug is finished and i will be molding it this weekend.




Btw....i worked on a ALMS/IMSA team for about 20yrs. I made alot of widgets, aero devises, louvers, splitters and diffusers.
HioSSilver is online now   Reply With Quote
Old 11-11-2016, 09:02 AM   #13
TECH Junkie
iTrader: (7)
 
HioSSilver's Avatar
 
Join Date: Aug 2002
Location: Winchester, VA
Posts: 3,802
Default

Here is a airlid i made years ago. All the front block offs on the car is made of carbon also. I fashioned the airlid to have the most volume of any airlid on the market at the time.

HioSSilver is online now   Reply With Quote
Old 11-11-2016, 12:20 PM   #14
TECH Fanatic
 
Join Date: Feb 2012
Posts: 1,383
Default

So you are going from a bottom breather to a front breather? The LS1 SS's are easier to do that than the LT1 cars due to the convenient area to cut out on the front bumper.

You still have AC? I'm curious how you are fitting a OTR intake WITH AC lol.
smitty2919 is online now   Reply With Quote
Old 11-11-2016, 12:38 PM   #15
TECH Junkie
iTrader: (7)
 
HioSSilver's Avatar
 
Join Date: Aug 2002
Location: Winchester, VA
Posts: 3,802
Default

Yes i still have ac. That's why i wanted over the rad. The latch will have to go away but that's ok by me. At 130 or so traps I'm running i think some aero latches will be safer. The hood latch area of the hood will have to be cut out to make this work but the top skin should be fine. It's not really any higher than a lid set up.




I am converting it to a front breather. I think there is plenty of room to do that on a lt1 car to. I converted mike morris car to a front breather.







Last edited by HioSSilver; 11-11-2016 at 12:45 PM.
HioSSilver is online now   Reply With Quote
Old 11-13-2016, 02:33 AM   #16
Banned
iTrader: (32)
 
Join Date: Apr 2006
Posts: 5,136
Default

Why is my brain not understanding how the depression (low pressure area at the very back of the car) is going to provide a force to move the car forward. I don't study aero much, but conventional wisdom says that a depression would pull the car backwards, especially with the high pressure building up at the front of the car.......


What am I missing?
Blown06 is offline   Reply With Quote
Old 11-13-2016, 01:42 PM   #17
TECH Junkie
iTrader: (7)
 
HioSSilver's Avatar
 
Join Date: Aug 2002
Location: Winchester, VA
Posts: 3,802
Default

It's not propelling it forward. The low pressure is attached to the back of the car. Thus creating drag.
HioSSilver is online now   Reply With Quote
Old 11-13-2016, 02:07 PM   #18
TECH Fanatic
 
Join Date: Jul 2013
Location: Portland, Oregon
Posts: 1,808
Default

Quote:
Originally Posted by bufmatmuslepants View Post
I'm just talking about the 0.34 coefficient of drag, where do you think is causing the biggest loss? Not racecar mods, small changes GM could have made on the production car.
As for small changes GM could have made as part of production, they knew exactly how to make extremely slippery cars. The EV1 was an electric car GM produced in the late 90's was around 0.19 or 0.2, had more of a hammback profile and enclosed rear wheel wells.

Chopping off the rear overhang at the base of the rear windshield and giving it a really steep angle with a sudden cut off point, like the GM Cheetah, would have been, and still would be, greatly beneficial.


DavidBoren is offline   Reply With Quote
Old 11-13-2016, 02:11 PM   #19
TECH Fanatic
 
Join Date: Jul 2013
Location: Portland, Oregon
Posts: 1,808
Default

Like this:

DavidBoren is offline   Reply With Quote
Old 11-14-2016, 02:05 AM   #20
Banned
iTrader: (32)
 
Join Date: Apr 2006
Posts: 5,136
Default

Quote:
Originally Posted by Blown06 View Post
Why is my brain not understanding how the depression (low pressure area at the very back of the car) is going to provide a force to move the car forward. I don't study aero much, but conventional wisdom says that a depression would pull the car backwards, especially with the high pressure building up at the front of the car.......


What am I missing?
Quote:
Originally Posted by HioSSilver View Post
It's not propelling it forward. The low pressure is attached to the back of the car. Thus creating drag.
Thats what I'm saying. I agree with you. The depression creates drag.

My question is that earlier in the thread, people where saying that a complete flat chop off the rear of the car would actually product a force acting on the car in a forward direction. Thats what I don't understand. A depression or low pressure area is not going to push the car forward.
Blown06 is offline   Reply With Quote
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Revealed - 2014 Chevrolet & GMC Fullsize SUVs TriShield Automotive News, Media & Press 26 09-16-2013 10:18 PM
Revealed - 2014 Chevrolet Silverado/GMC Sierra TriShield Automotive News, Media & Press 20 12-17-2012 10:34 AM
4th gen ss wing question??? IROC403 Special Edition Vehicles 4 07-03-2008 06:12 PM
spoiler question ssfast99 Appearance & Detailing 5 02-10-2008 09:35 AM
Manta stripe idea AKidsDreamZ28 Appearance & Detailing 3 06-26-2006 04:55 AM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 12:14 PM.


 
  • Ask a Question
    Get answers from community experts
What's your question?
Send