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4th gen aero


boxkita

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I hear ya, but the radiator's gotta have airflow to function, right? At least as much as is pushed by the fans at full blast, probably more I'd think.

 

I'll grab a quick run w/ the radiator disabled before I go home tonight, though.

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I hear ya, but the radiator's gotta have airflow to function, right? At least as much as is pushed by the fans at full blast, probably more I'd think.

 

I'll grab a quick run w/ the radiator disabled before I go home tonight, though.

 

racing folklore says fans are useless after 35 mph. further if you don't duct the air somewhere else, you'll overheat when drafting. Lgt didn't do well running on someone's bumper.

 

The racewagon has no fans and lots of holes in the bottom pan. For airflow.

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Hm alright. Guess I was thinking that the fan is useful at low speed, and at high speed you must be pushing more air than the fans can supply, which I think lines up with what you said. I'd think sitting behind someone would cause you to overheat because you're pretty much sitting in a stagnant zone and have no dynamic pressure to motivate the flow, since the statics in front of and behind the radiator are probably pretty close.

 

Wonder if utc_pyro still has that anemometer - could stick it behind the radiator and see what the flow speed really is? I think we could use that to estimate the restriction to set for the porous radiator model.

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Here's that shot - the radiator is now entirely solid, so what you see in there is just stagnant flow recirculating. The scoop flow I double checked matches in/out, it's just very small compared to the free stream. I wonder what the value would come out to be from utc_pyro's pressure delta values - I used flow velocity to back out the mass flow here.

Capture1.PNG.38b3c8061f70e58b143f133f7a0c9c1f.PNG

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This thread is making my brain hurt because I’m not a math guy whatsoever :) really appreciate what you guys are doing tho, especially since I’m starting to play with a front splitter on the track car, (and wondering what that’s going to mean for a rear spoiler without looking absurd)
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  • 4 weeks later...

You ever get excited about trying something new and realize you've bitten off way too much? That's what happened to me lol. I don't understand 90% of this thread lol.

 

I had started working with onshape but I have a 5yo $300 chromebook. And even though onshape is offloading the work, it was still too much for my chromebook to handle.

 

Been learning very rudimentary stuff about aero though. Think I'll be purchasing the Joseph Katz book as I've seen it mentioned other places before as well.

 

 

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Ive got a bunch of theories and so far they seem to be worth exploring more. I agree the math is hard and having the right software/hardware/budget helps alot. I learned more about flow patterns on the tailgate in a few graphs than I did in 3 hours of taping yarn & gopros to Gunnar's wagon.

 

Sgt.Gator used a large wing on the roof of the wagon just behind the centerline of the rear wheels (as far forward as the rules allowed). Mostly this crushed the roof and took 4 mph off his speed on the straight, although he says it helped the cornering. The prevailing theory on rear mounted spoilers is to attach to the unsprung part of the rear suspension (trailing arm) to get the most effect. Unless you have a purpose built car this is really hard to do. So the next best spot is attaching to the rear frame as close to rear axle centerline, so it acts as a lever pushing the rear down.

 

The charts indicate the flow from rear bumper area moves up the back of the tailgate to the bottom of the spoiler, suggesting the rear spoiler is bling. Ideally you want the air flow off the top and bottom to come together behind the car in a smooth arc. The spoiler would be in this area.

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finally bot a license for windows. In the middle of ripping out my 20 year old network and upgrading to take advantage of 100mb internet. Want to try openfoam against the online servers. Figure if I bang on it enough, it'll make sense.

 

Because putting vortex generators on the top of the windshield seems nutty but looks like the biggest bang for the buck

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I thought the point of the wagons little spoiler would be just to interrupt the flow. So that it doesn't try to follow the curve down the back glass.

 

And yea attaching a wing to the unsprung mass would be difficult. I've seen a hatch wrx that had a wing built into the frame rail down by the bumper. Also there's a lot of absolutely crazy stuff in lemons. I think our Lady of perpetual downforce mounted a huge wing to the control arms and built it to articulate with the brakes.

 

I would think the best way to get a big wing on the car would be to use large curved arms attached to the lift gate.

 

I'm very curious about the flow along the side and venting the radiator. I've got a love of hood and fender vents. Probably from watching rally.

 

 

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Any thoughts on mounting a little ducktail spoiler that attaches to the last roof support? (which also is about at the centerline of the rear axle). My rag wool yarn tests show clean, consistent airflow in that area. I'm just not ready to bolt some mega hatch spoiler, (a la Nine Lives Racing big wang, similar to the one they make for the Focus RS) but wondering if a bit of aero back there would be beneficial at all. Was going to see if you could take a snap of that area in the race wagon at some point Boxkita, I'm chicken to pull my headliner to get a good look at it unless I go for fabbing one up :)
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Well for those of you who have actually gotten to track your car, are you losing grip front or rear first? I understand from the factory the car understeers but I know boxkita has actually corner balanced his so I don't know that the race wagon does the same.

 

I wonder the impact of the roof rails on the outback. It would be easy to mount something straight to them. But yea I'd think a duck tail should increase downforce. But maybe a custom diffuser and smooth under tray for the rear segment might help more though.

 

 

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Based on my current set up, its not so much that the car feels like its understeering as much as the nose feels less planted than I'd like at higher speeds, i.e. the back straight at PIR here in Portland. Also some of the high speed corners at ORP in Grass Valley. Now that my front splitter is all but done, my concern is whether its going to throw the balance of the car off just having front aero. I'm running with the Porsche club next weekend at ORP, hope to have the front rods installed and everything finished up as I'm interested to see how it changes the car.
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Any thoughts on mounting a little ducktail spoiler that attaches to the last roof support? (which also is about at the centerline of the rear axle). My rag wool yarn tests show clean, consistent airflow in that area. I'm just not ready to bolt some mega hatch spoiler, (a la Nine Lives Racing big wang, similar to the one they make for the Focus RS) but wondering if a bit of aero back there would be beneficial at all. Was going to see if you could take a snap of that area in the race wagon at some point Boxkita, I'm chicken to pull my headliner to get a good look at it unless I go for fabbing one up :)

 

Just say no. The race wagon has dents in the roof from this.

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Well for those of you who have actually gotten to track your car, are you losing grip front or rear first? I understand from the factory the car understeers but I know boxkita has actually corner balanced his so I don't know that the race wagon does the same.

 

I wonder the impact of the roof rails on the outback. It would be easy to mount something straight to them. But yea I'd think a duck tail should increase downforce. But maybe a custom diffuser and smooth under tray for the rear segment might help more though.

 

 

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rear diffuser and smooth undertray are going to be better than a roof mounted wing.

 

With regards my wagon, I did 3 rounds of corner balancing trying to get things sorted. There's too much squat post apex to keep the front end on the ground. I found myself driving a really odd line to keep rolling on power and rarely was I at full throttle by the end of the turn.

In a decreasing radius turn (ridge), the final solution was to wait for the slicks to start howling and matt the throttle creating snap throttle oversteer. In a stock interior wagon. Ymmv, but I bot a fully prepped spec miats not long after trying this.

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Based on my current set up, its not so much that the car feels like its understeering as much as the nose feels less planted than I'd like at higher speeds, i.e. the back straight at PIR here in Portland. Also some of the high speed corners at ORP in Grass Valley. Now that my front splitter is all but done, my concern is whether its going to throw the balance of the car off just having front aero. I'm running with the Porsche club next weekend at ORP, hope to have the front rods installed and everything finished up as I'm interested to see how it changes the car.

 

The viper team I worked with used stainless steel cables instead of rods. Even had adjusters built so we could adjust wing angle. The cables allowed the wing to survive if the fastest line was through the dirt. The rods snap if you try that :)

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rear diffuser and smooth undertray are going to be better than a roof mounted wing.

 

With regards my wagon, I did 3 rounds of corner balancing trying to get things sorted. There's too much squat post apex to keep the front end on the ground. I found myself driving a really odd line to keep rolling on power and rarely was I at full throttle by the end of the turn.

In a decreasing radius turn (ridge), the final solution was to wait for the slicks to start howling and matt the throttle creating snap throttle oversteer. In a stock interior wagon. Ymmv, but I bot a fully prepped spec miats not long after trying this.

 

 

How much power does the race wagon have? When I read that, it sounds to me like it's a suspension stiffness problem correct? I can't think any amount of aero that helps that.

 

The second scenario sounds like.... You'd just need more downforce everywhere. I can't really envision that scenario though.

 

And don't worry. I think I'll be getting an lo206 kart when I move so I realize there are issues getting a 3500lbs wagon around the tightest corners lol.

 

 

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The race wagon always had several tunes available, its legal max should have been in the 330hp range. My wagon was/is 310/335.

 

There's not alot of video from those sessions, but one of the problems was the body twist was affecting the handling. Having front downforce along with a front lsd would have been helpful. The front airdam/splitter on the race wagon was helpful according to Sgt.Gator.

 

I bought the race wagon so I could see what a caged wagon could do. Before I got it fixed, Kip put a 4point cage in his and let me have a few laps. It was a transformative experience, as most of the problems I had with handling went away. Listening to the cage creak was fun, as you just don't appreciate the loading otherwise.

 

There were/are so many better track platforms than a wagon. However there was real satisfaction in passing all those other cars driving a "soccer mom" car.

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Based on my current set up, its not so much that the car feels like its understeering as much as the nose feels less planted than I'd like at higher speeds, i.e. the back straight at PIR here in Portland. Also some of the high speed corners at ORP in Grass Valley. Now that my front splitter is all but done, my concern is whether its going to throw the balance of the car off just having front aero. I'm running with the Porsche club next weekend at ORP, hope to have the front rods installed and everything finished up as I'm interested to see how it changes the car.

 

Do you still run multiple cameras on your car? If so, can you do a yarn test on the front of the car? Either on the centerline? or on the side fender? If you mount a camera on the rear window you can yarn the back to see if the flow changes there. If less air is going under, you should see the flow change post rear bumper.

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