Aero project and tuft vids of my Z
02-07-2006, 09:12 AM
#21
Originally Posted by Chebosto
interesting. according the PDF file, the Mitsubishi engineers only reduced lift and drag by 0.006.
you'd probably get that by removing the GT3 wing, or slamming your car closer to the ground...
can you perhaps film the Flow Yarn after you remove the GT3 wing? or maybe i could find a stock Z to film it.. but it'll be interesting to see the flow characteristics over the rear hatch with out the wing..
also, put yarn on the surface of your wing, i'd be interested to see where your 'stall' speed it due to the high angle of attack your deck is at... is it adjustable?
EDIT:
i consulted the oracle (Race Car Aerodynamics Designing for Speed / Joseph Katz) this is what it states for VGs:
"...these can resemble small wing shapes or have more complex geometries as shown by thefour typical shapes (shown are: curved, delta, pyramid, and wedge tailed like the ones you got) a typical VG is a bit taller than the local boundary layer thickness, and the swirl of the cortices it creates helps to add fresh momentum (from the free air stream) into the boundary layer. if such VGs are placed near the EXPECTED SEPARATION LINE, the added momentum can DELAY flow separation. the overall effect is usually a gain in the maximum lift and a reduction in drag at the higher lift coefficient (as a result of the smaller separated flow regions) At lower lift coefficients, thought, the VGs may increase the drag. Most VGs are constructed from simple sheet metal and some are commerically avilable as a glue on-strip. "
the rest of chapter goes onto to describe the other options to delay flow seperation, including gurney flaps and built in channels into wings and surfaces.
you'd probably get that by removing the GT3 wing, or slamming your car closer to the ground...
can you perhaps film the Flow Yarn after you remove the GT3 wing? or maybe i could find a stock Z to film it.. but it'll be interesting to see the flow characteristics over the rear hatch with out the wing..
also, put yarn on the surface of your wing, i'd be interested to see where your 'stall' speed it due to the high angle of attack your deck is at... is it adjustable?
EDIT:
i consulted the oracle (Race Car Aerodynamics Designing for Speed / Joseph Katz) this is what it states for VGs:
"...these can resemble small wing shapes or have more complex geometries as shown by thefour typical shapes (shown are: curved, delta, pyramid, and wedge tailed like the ones you got) a typical VG is a bit taller than the local boundary layer thickness, and the swirl of the cortices it creates helps to add fresh momentum (from the free air stream) into the boundary layer. if such VGs are placed near the EXPECTED SEPARATION LINE, the added momentum can DELAY flow separation. the overall effect is usually a gain in the maximum lift and a reduction in drag at the higher lift coefficient (as a result of the smaller separated flow regions) At lower lift coefficients, thought, the VGs may increase the drag. Most VGs are constructed from simple sheet metal and some are commerically avilable as a glue on-strip. "
the rest of chapter goes onto to describe the other options to delay flow seperation, including gurney flaps and built in channels into wings and surfaces.
Unfortunately, the wing is not adjustable. I will do some vids of the wing soon though, good suggestion. The wing provides a lot of downforce. I felt a major difference the first time I drove it on the highway. I have a racecar which is stored about 1-1/2 hours downstate and there are a lot of roads on the way down where I can go WOT for miles. When its windy the wing hurts my terminal speed. Once I couldn't go past about 143. But last time I was down it was a calmer and I terminaled out at 159. (Downhill run). It just feels so planted at that speed with the wing. I can remember hitting top speed before without it and the car felt "floaty". I think I will miss it, but I am working on a custom carbon design which will be adjustable.
How is your rear diffuser coming along?
02-07-2006, 09:23 AM
#25
Originally Posted by zillinois
Hey Mike, I'm working on another Nav piece for you. Don't worry. At least I don't have a lot of projects. ;-)
EDIT: Or even the headlight covers...
Last edited by SinCity350Z; 02-07-2006 at 09:28 AM.
02-07-2006, 09:39 AM
#26
Originally Posted by 350ZNV
Hahaha, its no big deal. I fabbed up a crappy temporary one last night so feel free to take all the time you need. I am more interested in these aero pieces to tell you the truth...
EDIT: Or even the headlight covers...
EDIT: Or even the headlight covers...
02-07-2006, 10:03 AM
#28
Originally Posted by zillinois
How is your rear diffuser coming along?
ha. well. i still got my cutouts somewhere.. along with my other junk in my closet.. i'll dig it out. spring time is coming up so that means i'll be able to work more outside..
my thoughts:
1: plug the whole where my stock exhaust used to be.
2. attach rear diffuser to the plug.
3. cut holes in my rear bumper so airflow over the top of the diffuser can escape.
4. one piece vortex generator from the roof using your idea... btw.. that resin block, did u make that yourself? i checked that airtab place.. those might be a bit too big for us. yea it does wonders for trailing edges for BIG tracker trailers, but our rear window doesn't drop off as bad as the Evo windsheild, its actually quite even, i think smaller VGs might be ok. i mean. it needs to be slightly higher than the local boundary level, and i suspect that to be only an inch or so.. how tall are the ones you bought?
also, about your front splitter design. APR sells a giant CF sheet that you can use... or you can make one yourself, and buy the adjustable arms from like McMaster Carr
Last edited by Chebosto; 02-07-2006 at 10:22 AM.
02-07-2006, 10:14 AM
#29
Originally Posted by Chebosto
ha. well. i still got my cutouts somewhere.. along with my other junk in my closet.. i'll dig it out. spring time is coming up so that means i'll be able to work more outside..
my thoughts:
1: plug the whole where my stock exhaust used to me.
2. attach rear diffuser to the plug.
3. cut holes in my rear bumper so airflow over the top of the diffuser can escape.
4. one piece vortex generator from the roof using your idea... btw.. that resin block, did u make that yourself? i checked that airtab place.. those might be a bit too big for us. yea it does wonders for trailing edges for BIG tracker trailers, but our rear window doesn't drop off as bad as the Evo windsheild, its actually quite even, i think smaller VGs might be ok. i mean. it needs to be slightly higher than the local boundary level, and i suspect that to be only an inch or so.. how tall are the ones you bought?
also, about your front splitter design. APR sells a giant CF sheet that you can use... or you can make one yourself, and buy the adjustable arms from like McMaster Carr
my thoughts:
1: plug the whole where my stock exhaust used to me.
2. attach rear diffuser to the plug.
3. cut holes in my rear bumper so airflow over the top of the diffuser can escape.
4. one piece vortex generator from the roof using your idea... btw.. that resin block, did u make that yourself? i checked that airtab place.. those might be a bit too big for us. yea it does wonders for trailing edges for BIG tracker trailers, but our rear window doesn't drop off as bad as the Evo windsheild, its actually quite even, i think smaller VGs might be ok. i mean. it needs to be slightly higher than the local boundary level, and i suspect that to be only an inch or so.. how tall are the ones you bought?
also, about your front splitter design. APR sells a giant CF sheet that you can use... or you can make one yourself, and buy the adjustable arms from like McMaster Carr
Yes, I made and shaped the resin block myself. I have a source to make them from ABS plastic though. And am almost ready to make them. If you want one I can send you one to make molds of or whatever you want. The ones I made are 1-3/8" tall. I believe thats what the boundry layer was on the EVO. It was formed from known VG geometry equations so it shouldn't be too bad from an aero perspective. The Airtab ones are only 1" tall. They are very low profile.
I've made a blank to fill in the muffler hole. But I haven't got much further. I wanted to do more research on underbody influences first. Without being able to create that upside down wing shape underneath, rear diffusers are hard to make useful. Not impossible, but difficult.
I haven't started too much on the splitter yet. Just too many projects. But it would definitely be easier to buy some finished sheeting. I'm getting sick of wasting carbon. :-(
02-07-2006, 10:37 AM
#31
Originally Posted by zillinois
Yes, I made and shaped the resin block myself. I have a source to make them from ABS plastic though. And am almost ready to make them. If you want one I can send you one to make molds of or whatever you want. The ones I made are 1-3/8" tall. I believe thats what the boundry layer was on the EVO. It was formed from known VG geometry equations so it shouldn't be too bad from an aero perspective. The Airtab ones are only 1" tall. They are very low profile.
maybe after you're done with the mold for the ABS, send me one and i can see what i can do on my end..
I've made a blank to fill in the muffler hole. But I haven't got much further. I wanted to do more research on underbody influences first. Without being able to create that upside down wing shape underneath, rear diffusers are hard to make useful. Not impossible, but difficult.
I haven't started too much on the splitter yet. Just too many projects. But it would definitely be easier to buy some finished sheeting. I'm getting sick of wasting carbon. :-(
02-10-2006, 04:20 PM
#32
Zillinois:
i've been thinking ALOT about the VGs.. i actually got a few from AirTabs to check out and they came today,
the reason for a 'spoiler' on the back of our Zs is actually to spoil the air flowing over the rear hatch... see by having the spoiler there, it actually allows the air to seperate sooner, thus preventing the rear end from lifting... if air flows all the way over the rear back half of the bumper, it will have a tendency to lift up due to faster flowing air over it... sorta like a airplane wing's top surface.
i have an elevated wing that's up in the airstream, as do you, so we are already pushing the rear of our cars down to the ground..as stated on page 5 of the PDF, why the VGs worked so good on the Mitsubishi car is that it accelerated the air faster on the UNDERside of that wing, allowing the wing to work better..that's where the reduction of lift came from.. there's alot more red under the stock wing, indicating airflow underneath the wing was faster..
i imagine, once the removal of your GT3 wing, and if you keep the VGs you got from airtabs on there, you will actually have MORE lift than you would have if you had no VGs and stock wing due to fact air flow was attached LONGER and there fore lifting the back up....
i had this crazy idea of actually putting the airtabs on the diffusers you're making as to keep the air attached to the diffuser LONGER, and with that angle you have, it would actually keep the rear planted more so than w/o VGs..
what do you think?
i've been thinking ALOT about the VGs.. i actually got a few from AirTabs to check out and they came today,
the reason for a 'spoiler' on the back of our Zs is actually to spoil the air flowing over the rear hatch... see by having the spoiler there, it actually allows the air to seperate sooner, thus preventing the rear end from lifting... if air flows all the way over the rear back half of the bumper, it will have a tendency to lift up due to faster flowing air over it... sorta like a airplane wing's top surface.
i have an elevated wing that's up in the airstream, as do you, so we are already pushing the rear of our cars down to the ground..as stated on page 5 of the PDF, why the VGs worked so good on the Mitsubishi car is that it accelerated the air faster on the UNDERside of that wing, allowing the wing to work better..that's where the reduction of lift came from.. there's alot more red under the stock wing, indicating airflow underneath the wing was faster..
i imagine, once the removal of your GT3 wing, and if you keep the VGs you got from airtabs on there, you will actually have MORE lift than you would have if you had no VGs and stock wing due to fact air flow was attached LONGER and there fore lifting the back up....
i had this crazy idea of actually putting the airtabs on the diffusers you're making as to keep the air attached to the diffuser LONGER, and with that angle you have, it would actually keep the rear planted more so than w/o VGs..
what do you think?
02-10-2006, 04:29 PM
#33
Originally Posted by Chebosto
Zillinois:
i've been thinking ALOT about the VGs.. i actually got a few from AirTabs to check out and they came today,
the reason for a 'spoiler' on the back of our Zs is actually to spoil the air flowing over the rear hatch... see by having the spoiler there, it actually allows the air to seperate sooner, thus preventing the rear end from lifting... if air flows all the way over the rear back half of the bumper, it will have a tendency to lift up due to faster flowing air over it... sorta like a airplane wing's top surface.
i have an elevated wing that's up in the airstream, as do you, so we are already pushing the rear of our cars down to the ground..as stated on page 5 of the PDF, why the VGs worked so good on the Mitsubishi car is that it accelerated the air faster on the UNDERside of that wing, allowing the wing to work better..that's where the reduction of lift came from.. there's alot more red under the stock wing, indicating airflow underneath the wing was faster..
i imagine, once the removal of your GT3 wing, and if you keep the VGs you got from airtabs on there, you will actually have MORE lift than you would have if you had no VGs and stock wing due to fact air flow was attached LONGER and there fore lifting the back up....
i had this crazy idea of actually putting the airtabs on the diffusers you're making as to keep the air attached to the diffuser LONGER, and with that angle you have, it would actually keep the rear planted more so than w/o VGs..
what do you think?
i've been thinking ALOT about the VGs.. i actually got a few from AirTabs to check out and they came today,
the reason for a 'spoiler' on the back of our Zs is actually to spoil the air flowing over the rear hatch... see by having the spoiler there, it actually allows the air to seperate sooner, thus preventing the rear end from lifting... if air flows all the way over the rear back half of the bumper, it will have a tendency to lift up due to faster flowing air over it... sorta like a airplane wing's top surface.
i have an elevated wing that's up in the airstream, as do you, so we are already pushing the rear of our cars down to the ground..as stated on page 5 of the PDF, why the VGs worked so good on the Mitsubishi car is that it accelerated the air faster on the UNDERside of that wing, allowing the wing to work better..that's where the reduction of lift came from.. there's alot more red under the stock wing, indicating airflow underneath the wing was faster..
i imagine, once the removal of your GT3 wing, and if you keep the VGs you got from airtabs on there, you will actually have MORE lift than you would have if you had no VGs and stock wing due to fact air flow was attached LONGER and there fore lifting the back up....
i had this crazy idea of actually putting the airtabs on the diffusers you're making as to keep the air attached to the diffuser LONGER, and with that angle you have, it would actually keep the rear planted more so than w/o VGs..
what do you think?
I also agree with you assessment of more lift on the rear without a wing. I will be using a wing on the rear after the GT3 wing comes off. I just want to try and make my own. As with all things aerodynamic its the total package. That's why I started looking at airflow over the car. You have to know what you're working with before making changes. I would also like to take some video of underneath the car with tufts. I'm working on a mount for it though. Eventually I'd like to release an entire aero package that actually does something. I won't be selling everything, I'll just find the sources for the package.
Last edited by zillinois; 02-10-2006 at 04:40 PM.
02-11-2006, 09:35 PM
#34
I went to the Chicago Auto Show today and was browsing for aero stuff on the new cars. Didn't find too much, but found this diffuser on an STI. It was identical to the Rally racecar they had, but would not let me take a picture of the race on even though it was right next to the street version?? Crappy camera phone pic beware.
02-13-2006, 08:39 AM
#36
Originally Posted by zillinois
I went to the Chicago Auto Show today and was browsing for aero stuff on the new cars. Didn't find too much, but found this diffuser on an STI. It was identical to the Rally racecar they had, but would not let me take a picture of the race on even though it was right next to the street version?? Crappy camera phone pic beware.
LA auto show picts i took in 2004..
all rear diffusers..
http://www.imagestation.com/album/?id=4288096855
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