Boxster 986 Aerodynamics @180km/hr
 

Air Flow analysis on the mighty Porsche Boxster 986 running down at 180km/hr in the Shanghai Industrial Park (at night, cops sleeping and all!).

Just leaving this here for you guys to enjoy ;)

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Very cool.......Lots of red over the roof.
Quite interesting.

I'd like to see it with the spoiler up

Yes, I thought the same! :)

Lots of little internet lawyers on this board these days. Gotta be careful with these things :D

That was actually what started me. Quickly modeled the 'aircraft style wing' I got on the back of my Boxster and ran lift & drag on the whole assembly to find out I have the rear lifting up starting at 80km/hr (flying, just like an aircraft, how fun lol). You don't want to see this at 180km/hr trust me (embarrassing).

The stuff you find on eBay these days huh LOLLL Certainly looking good, Go Go Ricer Go!!!

The brick wall stocker is not entirely better... it badly loosen up the front past 150km/hr but does actually provide amazing down-force on the rear-end. Also trying to find out what's the best staggered wheel setup for my Boxster. Seeing a lot of drag on the front's 245, the flow then close and over-pressurize right on the rear 265. Trying to find a tire width/setup so that pressure ends up to be as close as to atmospheric as possible both on the fronts and rears. Fascinating stuff for sure!

Enjoy the top wallpaper in a meantime ;)

Passenger NOT allowed until further notice :D

Great little city-car other than that - if kept <100km/hr LOLLL

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Fred you need to submit this [edit: the first pic] to Blipshift for printing onto a black shirt, I would buy one for everyone in my family. Awesome!!!!

PS Better submit it now before someone steals the graphic and submits it anyway, happened to a guy on Rennlist that had some turbo design that is now sold in several placed without his consent...

By all means, I'd only feel flattered bud, not robbed. Do they print colors? jeez can't be cheap, no?

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Nastran?
You love playing for CFD, don't you LOL

Why do I get the feeling I'm bothering you guys LOL

Hey we have our own dedicated 986 forum's Virtual Wind Tunnel man! Want to know exactly where to place your Ram Air Intake on your Boxster?!

As silly looking as this is, it is indeed Nastran w/ TMG thermal/flow solvers (Simcenter3D). Should have bought the new 718 as company car instead right?

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this is airspeed, yes? so we are seeing the air accelerating over the roof and can assume some venturi effect (lift) as a result? also some acceleration along the side creating negative pressure at the air intake?

Using velocity here, correct (dynamic pressure). Haven't posted the lift & drag plots fearing to be blasted by the anti-geak community LOL

Wallpaper purposes but can upload if you need anything specific ;) Anything for you man

So... who is going to start the thread for a group buy of the T-shirts?
Or do I have to just make my own locally?

Luccia, you could stock these at Pelican, Black T-Shirts with the first wind tunnel image and a Pelican Parts/986Forum logo. We will buy them.

Please make it a good one like Gildan or Hanes Beefy T

Go with BlipShift

I think it would get wider distribution that way too...

Also please add a 3rd radiator if it is a Boxster S :)

Can you re-run the aerodynamics with your new center caps? I just know they will improve things. :cheers: Just kidding, I am a big fan of your work. I was also surprised to see that your wing creates lift, just goes to show that you can't eyeball aerodynamic effects, the wing looks like it would create downforce.

Picky bastard :rolleyes:

That just proves what I and others have said about putting untested aero on your car.
Just because it looks like it will be beneficial, doesn't mean it will be

Fred, can you do a run with the top down and see how it differs from top up?

hmmm, well spotted :o

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I'm also dying to see this. Hard job tho as the model needs to be a water-tight solid body. But I'll try for sure.

Paul - can't do that. Those caps create such a violent vortex the team at Porsche studio will need to recall all those GT3. See it on the bright side though; so violent that the brake dust is sucked off the wheel (self-cleaning wheel) :D

Re wing: does not create any downforce or let's say nothing like the stock slab (tombstone?) that Porsche designed. The CFD I ran was based on my actual set-up (the wing + slab up). The Ricer in me said that the more wings you have the better. Results were so 'lifty' that I'm sure I would have killed myself if I'd ever ran this car on the circuit here (thank god I never did). City car only and I can't drive faster than 80km/h anywhere without murdering 1.4billion other drivers in front of me anyway :/

Those eBay sellers should really warn idiots (like myself) about the risks LOL

Would be interesting to see how the air dam with duck tail stands up :)

Oh yeah, this could be useful for modeling front splitters, 3rd party wings and spoilers, etc... Fred you are in for it now...

I would also love to see the top down results since I have with the top down on the track (most of us do).

Is that HDPE or some other kind of track event where you can run with the top down? I'm just curious because my region of PCA is NNJR, and I think their rules for HDPE require convertibles to run top up unless they have a full roll cage.

Same in Zone 8 out in in the southwest
Top up is required, or if you have no top, arm restraints
Roll cage is not required for a Boxster unless you have a lot of performance points

PCA is top up but a lot of other groups let you drive top down, I did it once and didn't really like it, of course it was hot as $%&* that day.

Do you mind sharing the model? I would like to see if I could design a spliter to balance the rear spoiler.

Depends on the region, PCA minimum de standards allow top down

Topless as requested Jay! Just took me 4hrs just to sew and stitch those cabin surfaces LOL. You've done so much good e.g. leaving multiple kind msg on RL on my behalf, that I think I owe you more than a few visuals bud :cheers:

RE Air Flow on the Topless boxster; to me it appears that the spoiler becomes redundant as there is absolutely no friction for the air to drag onto above your head. I'm not a professional but it appears to me that you are going to go so much faster at the track with the top down LOL You'll certainly have cheaper gas bills that's for sure ;)

Velocity only - same speed (180km). No lift & drag figures in fear to get sued by Porsche if I ever try to go that far! Not my car after all and the CAD model may differ from specs (i.e it would be pretty unfair to them).


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I think Steve wants to do some. His idea really and I can't recommend it more. I'll buy one! Need some creativity but sure Steve is all geared up for that. Use original visual as-is or modify as you wish Steve.

Preview - surely look better up close:

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This thread is fantastic, as usual I have to pass a huge thanks for nine8six for the contributions provided to this forum.

^ Wroom-wroom! You are welcome Sir :cheers:

This says it best, so I'll just quote him.

What he said.

Thanks. Great stuff!!

Hey thanks Fred.

I may be reading the flow wrong, but is the airflow smoother with the top down?

I Like the angle in your original image. ...a little scaling and add a bit of text.
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I still want a Procshe shirt, but this is not the one to do it on.
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^ Nice!! (less the PROCHE one, funny)

The input velocity is set 50,000mm/sec (180km, or 112mph). Judge from the side scale!

My observations are that topless delete all friction and the air flow is more linear (better, less drag, eliminating extra lift potentially also). This seems to cancel the spoiler purpose and downforce however. Compared to the w/ roof where the air drops down on your clam shell, creating more drag due to friction BUT offer much better downforce.

Roof/no roof; which is better in a stock setup I have no no bloody idea man. You guess is as good as mine. Sure the track guys will chime in having obviously better knowledge on this subject than me.

TRK, hello?

Interesting, next time it is cool I may try to do a top down :) Especially if I am going to be much faster according to the recent diagram :)

w the roof the air is forced to follow the roofline which is a longer distance than the air travelling under the car (a curve vs a straight line). conservation of mass and all that says that the air traveling over the roof has to get to the back of the car the same time as the air under the car. since it is a longer distance over the top it has to travel faster (red vs green) to get to the back at the same time as the underneath air. the faster air is less dense, which creates a pressure differential btw top and bottom of the car - this is lift. the purpose of the rear spoiler is not downforce (otherwise it would be a wing) but rather to 'spoil' the airflow over the top to kill the lifting effect (the spoiler creates a pocket of turbulent air which causes the airflow to delaminate from the roof further forward than it would otherwise, forcing it to travel straight back instead of along the car - shortening the path).

w/o the roof then the curved path is gone and the spoiler not as necessary. replaced by a big pocket of turbulent air - less lift, but it takes work to make air turbulent, so increased air resistance.

the soln is to keep the roof (less air resistance) but kill airflow under the car to reduce lifting effect - front lip, side skirts. add a rear diffuser which effectively extends the length of the underside of the car so that the travel distance is the same under as over and no lift effect. stop those frigging radiators from venting air down and under the car. all that kills lift.

next step is to add downforce - wings, front canards, vent the radiators upwards. vent the wheel wells (wheel wells accumulate air with a high pressure point at the top of the wheel just forward of the wheel centre line - vent the wheel wells up and you convert lift to downforce). beware downforce - the faster you go the better it works - chicken out and slow down and you lose downforce which means you lose traction ...

WARNING (teenagers!)
 

For sure faster (less drag) but possibly flying also! Maybe flying is a bit apocalyptic-ally said but I'm convinced your rear-end will be dancing a little more than let's say "with the roof closed". But then who doesn't like a little bit of dancing right :D

Thanks for that TRK. Knew you'd save the show

What is this? dual-purpose? (serious question)

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i think so, yes. the tailbase spoils lift (and grabs air to cool the engine) while the wing sits up in the clean air to create downforce.