Budget Racecar Aero?
11-04-2014, 05:47 PM
#32
Three Wheelin'
Patrick, thanks for the photos of the "inner works". Some serious development there. I will be working on my aero package this winter along with a few detail changes. Thinking about a flat bottom like the current Corvette race cars. I spoke with Ernie Jakubowski at Mid Ohio and looked at the 951 he had in the wind tunnel.
Ernie 951 (stock body):
1. High pressure air ducted from the trans axle tunnel behind the rear seat, vented via brake duct tubing to the quarter windows.
2. High pressure relief vents at the top of the front fenders abaft the wheel opening.
3. 997 cup style splitter with under tray extending to the engine cross brace. His own design that he sells.
That is all I can remember, Ernie was very generous with his time discussing the work in the wind tunnel.
Ernie 951 (stock body):
1. High pressure air ducted from the trans axle tunnel behind the rear seat, vented via brake duct tubing to the quarter windows.
2. High pressure relief vents at the top of the front fenders abaft the wheel opening.
3. 997 cup style splitter with under tray extending to the engine cross brace. His own design that he sells.
That is all I can remember, Ernie was very generous with his time discussing the work in the wind tunnel.
11-04-2014, 06:53 PM
#33
Rennlist Member
Thanks Steve. Wish we could get track insurance down here. Not sure if it's just a numbers game due to population size, but if you mention T.I. down here people just look at you strange!
Jim, there's a bit more underneath than I've shown but it has seriously helped us drop major chunks of time in our car.
I'm a bit confused when trying to picture the first point? Was he saying that some high pressure air from the trans tunnel around the gearbox is ducted up and out of the 1/4 windows? Be good to see some tuft test video on that?
Definitely on the 2nd point. Even the profile of the vents is important or at least has greater or lesser effect. The ones we have aren't perfect and I wanted to have them remodeled so that the first of the louvres is taller, sharper and steeper. You can see the 'first draft' of the new one as is.
I had a quick look on Ernie's site (Mantis?) and saw what I assume is the splitter he sells. Perhaps it's an optical illusion but it appears as if the small diffusers actually protrude downwards towards the road surface? Unless that's just a cutout area for the wheels during movement?
Patrick, thanks for the photos of the "inner works". Some serious development there. I will be working on my aero package this winter along with a few detail changes. Thinking about a flat bottom like the current Corvette race cars. I spoke with Ernie Jakubowski at Mid Ohio and looked at the 951 he had in the wind tunnel.
Ernie 951 (stock body):
1. High pressure air ducted from the trans axle tunnel behind the rear seat, vented via brake duct tubing to the quarter windows.
2. High pressure relief vents at the top of the front fenders abaft the wheel opening.
3. 997 cup style splitter with under tray extending to the engine cross brace. His own design that he sells.
That is all I can remember, Ernie was very generous with his time discussing the work in the wind tunnel.
Ernie 951 (stock body):
1. High pressure air ducted from the trans axle tunnel behind the rear seat, vented via brake duct tubing to the quarter windows.
2. High pressure relief vents at the top of the front fenders abaft the wheel opening.
3. 997 cup style splitter with under tray extending to the engine cross brace. His own design that he sells.
That is all I can remember, Ernie was very generous with his time discussing the work in the wind tunnel.
I'm a bit confused when trying to picture the first point? Was he saying that some high pressure air from the trans tunnel around the gearbox is ducted up and out of the 1/4 windows? Be good to see some tuft test video on that?
Definitely on the 2nd point. Even the profile of the vents is important or at least has greater or lesser effect. The ones we have aren't perfect and I wanted to have them remodeled so that the first of the louvres is taller, sharper and steeper. You can see the 'first draft' of the new one as is.
I had a quick look on Ernie's site (Mantis?) and saw what I assume is the splitter he sells. Perhaps it's an optical illusion but it appears as if the small diffusers actually protrude downwards towards the road surface? Unless that's just a cutout area for the wheels during movement?
11-04-2014, 09:23 PM
#34
Rennlist Member
Agreed Mark but what you may not have seen as the pic wasn't perfectly clear, we now have no openings in the front bar or bumper/nose panels for air to get into our engine bay at all. The only opening is the aforementioned ducted cooling cores and the two small round openings on the LHS which leads to a sealed box where the air filter is housed. In general 1/3rd of a car's drag is due to the cooling cores in the front bar. As you mention, the more air that goes into an engine bay, the more likely it is that it finds it's escape route under the car. Imagine having a full flat floor car with no upper body ventilation. That would be a massive drag inducer. In our class we can't run a full flat floor. Only allowed to run to each axle line respectively. Hence, we actually raised our side rocker height from the legal limit. No point in keeping the air running under the car if it hits the oem chassis between the axles and gets all dirty. So we've encouraged it out the sides with the angled fronts to the rockers and of course very large fender and door openings.
Strategic positioning of hood and fender vents is highly beneficial. Even the shape of the vents is important. Ours are not ideal. We worked to get some improved vents made but left it too late for a few weeks ago. It's always good to know there is more to be gained.
Strategic positioning of hood and fender vents is highly beneficial. Even the shape of the vents is important. Ours are not ideal. We worked to get some improved vents made but left it too late for a few weeks ago. It's always good to know there is more to be gained.
when I cut my hood vent, I used the wind tunnel data to find the lowest pressure point on the hood. it was a narrow range. many have ball parked it before (and sadly after this data was used) and all they end up getttng is a vent to get more air under the car!
sticks straight up at speed out of the hood vent!
I used the factor wind tunnel charts and verified it with tufts... the yarn
11-04-2014, 11:33 PM
#35
Rennlist Member
Yes, the hood vent is usually best fairly forward on there, but it depends on what you want to evacuate. For us we had to have it located to work with the ducted outlet.
With regards to more air being vented under the car were you saying this is due to poor placement of the vent...or?
Interesting to see the 928 pressure charts. The first one shows with the original rubber rear spoiler where the coloured ones show with the later GT/S rear wing. Be interesting to see what happens at the rear with the old rubber lip spoiler by comparison.
With regards to more air being vented under the car were you saying this is due to poor placement of the vent...or?
Interesting to see the 928 pressure charts. The first one shows with the original rubber rear spoiler where the coloured ones show with the later GT/S rear wing. Be interesting to see what happens at the rear with the old rubber lip spoiler by comparison.
11-05-2014, 10:17 AM
#36
Three Wheelin'
Ernie explained that there is a high pressure area at junction of the drive shaft tunnel just as it widens into the transaxle area (between the rear seat buckets. He had cut holes there and used brake tubing to evacuate/relieve that high pressure area to holes cut into a plexi quarter window.
Unsure about those end plates. The splitter can improved upon for custom applications like ours but it's a nice part for a stock body outline.
I plan to track down a friend who is an expert in CFD to give me a hand. His last job before he returned to the US was in Woking, England.
Unsure about those end plates. The splitter can improved upon for custom applications like ours but it's a nice part for a stock body outline.
I plan to track down a friend who is an expert in CFD to give me a hand. His last job before he returned to the US was in Woking, England.
11-05-2014, 07:01 PM
#37
Rennlist Member
Ernie explained that there is a high pressure area at junction of the drive shaft tunnel just as it widens into the transaxle area (between the rear seat buckets. He had cut holes there and used brake tubing to evacuate/relieve that high pressure area to holes cut into a plexi quarter window.
Unsure about those end plates. The splitter can improved upon for custom applications like ours but it's a nice part for a stock body outline.
I plan to track down a friend who is an expert in CFD to give me a hand. His last job before he returned to the US was in Woking, England.
Unsure about those end plates. The splitter can improved upon for custom applications like ours but it's a nice part for a stock body outline.
I plan to track down a friend who is an expert in CFD to give me a hand. His last job before he returned to the US was in Woking, England.
Yes the splitter is a fine addition, I just wasn't sure about those indentations?
Woking...lots of interesting stuff goes on in that little Villiage!
11-05-2014, 07:09 PM
#38
Rennlist Member
Thread Starter
A) Other than the listed exceptions, every Production vehicle must retain its unmodified:
1) OEM frame rails/rear frame cross beam, and/or Unibody, and Sub-frames/
suspension cross-members (in their OEM locations)
2) Strut/shock towers
3) Inner/inboard side of the fender wells (any non-horizontal aspect)
4) Rocker panels
5) Transmission tunnel
6) Floor pan
7) Windshield frame location
11-06-2014, 03:16 AM
#39
Rennlist Member
Not sure that you're flounting the rules as you're keeping the original trans tunnel and in the same place. You just happen to be cutting a couple of holes in there. We have what would appear a similar setup but in actual fact it's for ducting cool air into the car, not the other way. For the trans oil cooler/fan. Maybe you could say you're using it for cooling purposes? (Some older pics)
11-06-2014, 08:21 AM
#40
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I have a 60" predator wing I will sell.
https://www.gt-racing.com/products-p...e-predator-60/
I have about 1300 in it with uprights and custom fabbed aluminum adjusters (not avail from gt). Will sell for 600 firm plus shipping. Not the best quality stuff, but decent aero on the cheap. I would repaint it.
https://www.gt-racing.com/products-p...e-predator-60/
I have about 1300 in it with uprights and custom fabbed aluminum adjusters (not avail from gt). Will sell for 600 firm plus shipping. Not the best quality stuff, but decent aero on the cheap. I would repaint it.
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11-06-2014, 03:16 PM
#41
Rennlist Member
Thread Starter
Thanks, this definitely along the lines I was looking.
I assume this is for the fiberglass version, not the carbon one, correct?
I am in negotiations on the same wing off of a 968 that has uprights to fit my car. If that does not work out, I might be interested, though I likely wouldn't be able to use the uprights as is.
I assume this is for the fiberglass version, not the carbon one, correct?
I am in negotiations on the same wing off of a 968 that has uprights to fit my car. If that does not work out, I might be interested, though I likely wouldn't be able to use the uprights as is.
11-06-2014, 03:28 PM
#42
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Thanks, this definitely along the lines I was looking.
I assume this is for the fiberglass version, not the carbon one, correct?
I am in negotiations on the same wing off of a 968 that has uprights to fit my car. If that does not work out, I might be interested, though I likely wouldn't be able to use the uprights as is.
I assume this is for the fiberglass version, not the carbon one, correct?
I am in negotiations on the same wing off of a 968 that has uprights to fit my car. If that does not work out, I might be interested, though I likely wouldn't be able to use the uprights as is.
11-06-2014, 05:30 PM
#43
Rennlist Member
Thread Starter
OK, I'll let you know.
On a separate note, I finally found some extended, bullnose, splined studs for the 944 from this place: http://www.msiracingproducts.com/products.html
I know there were some threads in the past about trying to find bullnose studs for the 944. Nice guys, too.
On a separate note, I finally found some extended, bullnose, splined studs for the 944 from this place: http://www.msiracingproducts.com/products.html
I know there were some threads in the past about trying to find bullnose studs for the 944. Nice guys, too.
11-06-2014, 05:51 PM
#44
Rennlist Member
Patrick, I all the mods look First Class all the way.
Just curious , why the trans tunnel vent tube to the side of the rear quarter panel?
Ive done a lot of pressure measurement all over and under the car and I didn't find any pressure build up underneath the car. most all of the measurements were 0. however, lots of vacuum pockets on top of the car, and most of the side areas were 0 as well. I would think that if you want to get some of the air out of the under car flow, you could vent it to the roof behind the driver.
Just curious , why the trans tunnel vent tube to the side of the rear quarter panel?
Ive done a lot of pressure measurement all over and under the car and I didn't find any pressure build up underneath the car. most all of the measurements were 0. however, lots of vacuum pockets on top of the car, and most of the side areas were 0 as well. I would think that if you want to get some of the air out of the under car flow, you could vent it to the roof behind the driver.
11-06-2014, 05:55 PM
#45
Rennlist Member
That's why I was curious too Mark. My venting is clearly into the car, not out. I wondered even if there is some high pressure buildup around the trans how it would duct upwards and possibly a little forwards (?) to go out the 1/4 window....but Ernie has done Windtunnel tests with a 944 so I guess something must be going on there. I'm not sure what mods were done to that 944 that they measured though? Was it a stock car at stock ride height (for reference)? Therefore how much difference would there be if you lower the car or run a splitter and even more, run diffusers in the splitter and vent out of hood/fenders etc. Pretty sure this would reduce that high pressure zone also. Still, it's all fun and interesting stuff! I know of a few more super builds of 944/968 turbo cars in Australia and Sweden. These will have some pretty high end Aero going on also. Amazing to see how these transaxles are still being developed to extemes considering their roots and what great results are being recorded now and promise for the future!