Boxster 986 Aerodynamics @180km/hr

[steved0x]

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

[truegearhead]

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

Originally Posted by Nine8Six

hmmm, well spotted





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)

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

[PaulE]

Originally Posted by truegearhead

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.

[JayG]

Originally Posted by PaulE

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

[steved0x]

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.

[WorkInProgressK]

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

[Fintro11]

Originally Posted by steved0x

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.

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

[Nine8Six]

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

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).

[Nine8Six]

Originally Posted by 78F350

Or do I have to just make my own locally?

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:

[BIGJake111]

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

[Nine8Six]

^ Wroom-wroom! You are welcome Sir

[Timco]

Originally Posted by BIGJake111

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

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

What he said.

Thanks. Great stuff!!

[JayG]

Hey thanks Fred.

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

[78F350]

Originally Posted by Nine8Six

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:

I Like the angle in your original image. ...a little scaling and add a bit of text.


I still want a Procshe shirt, but this is not the one to do it on.

[Nine8Six]

^ Nice!! (less the PROCHE one, funny)

Originally Posted by JayG

Hey thanks Fred.

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

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?

[steved0x]

Originally Posted by Fintro11

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

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

[The Radium King]

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 ...

[Nine8Six]

Originally Posted by steved0x

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

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

[Nine8Six]

Originally Posted by The Radium King

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 ...

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

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

[The Radium King]

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.