TRK - I place 1mm plates under the tires to measure lift and downforce. They are essentially sensor preset at -1N/mm2 and I then solve those transient with accelerating air flow. How legal is it to publish/plot this online? let's say I'd do the full analysis of the Porsche Boxster 986 (as per model you've seen here). To your knowledge is this scope for potential attacks?!

To me this is what you guys would need, not the effect of a windy day in BoxsterTown lollll Although you must agree it does great wallpaper and t-shirts!

Also, your take on Ram Air Intake. Given that amazing dynamic pressure over the 986, any scope for a hard roof retrofit? instead of wasting our time doing bigger plenums and all the fuss behind them. No?

You can check out the DE standards on the PCA website, that being said those are minimum and each region can be more strict. Send a email the national de chair, he's a great guy and always open to chatting about de.


* had faster autocross times with the top down*

no idea on legality, but the pressure info would be excellent. even just seeing the airspeed info is interesting. in your initial post, the blue air behind the cockpit is slower than the incoming air so is the turbulent area i was speaking of. am i correct in assuming that the model with the car on an angle has the spoiler up, while the top/side models do not? if so, note how the red 'lift' area is reduced, replaced by the blue turbulent flow.

re ram air, i think grab the fastest air you can - somewhere on the roof in this case? this appears to reflect real world practice as well.

I'll be honest I have no recollection of what model/angle was what. I have about 30 more screen grabs here with and without the spoiler, wings etc and just picked up the best looking one I had (my current mobby's wallpaper!).

I'll see if I can get an answer from the ppl I know at P but doubt they will be helpful 'anything legal', hence why I was asking you. The problem is the model is so bloody realistic (and scaled also) that I'm sure someone will hit me behind the head if I go too far. I'll ask, never know. In a meantime there is no problem to PM if you need any data on whatever.... given of course it doesn't take me more than a day or two to solve ;)

ps. I had the TMG solvers included in the advanced sim package we got for the Co back in 2016 (mainly for structural). So going through all the online training that actually came with the deal. We only have 4 months left on the maintenance and tough Mrs Boxster was a good candidate to get tings squared for CFD. Let me know if you need anything bud

Oh anyone reading and have a spare hard top, please retrofit and go kill some 911 cars with it ;)

Good car shapes... natural air compressor lolll

I have a hardtop but I haven't been running it on track because of the extra 55 pounds...

I'll take it with me next time, and hopefully the temp and other conditions will be similar, and I'll post a comparison.

Unfortunately there will be another change at the same time between the two runs, I have sold my Beluga Exhaust and putting my original exhaust back on, but with the Fister mod. With the Beluga I was consistently getting to 126/127 with two times of 128 on the front straight at RRR (vs 122 with the stocker). Some of this is technique but I am not coming through turn 9 6 mph faster so some is the car. Will be interesting to see what happens with the Fister. I may do some runs with the hard top off and then add it back on for a comparison, that way we can do both on the same day.

Gut it man, toss the useless weight away and install this with ducts running to your air intake (testing your fabrication skills haha). You'll get something like +35% compressed air on the 986. See first few plots.

Always wondered why the roof area was used by the performance guys (ruff, mirage cgt, etc). It just never made any sense to me (roof?!?) until I saw why like you guys did.

http://986forum.com/forums/uploads02...1486494497.jpg

There you go, found it finally. Let me know when you've grabbed/saved it locally so I can delete it from my flickr (click to dwload the high resolution 2550*1350).

https://c1.staticflickr.com/1/535/32...8d96ac38_c.jpg

And forget those $500 side vents (aka ram-air intake). Another bloody eBay scam that doesn't work. The air is pressured off the car sides on the 986 (see plots again)

Yea that's my car, who else's LOL
http://986forum.com/forums/uploads02...1486496127.jpg

Thanks, got the image. ...I really need to get some good fonts.
Here's a layout put together with Gimp:
https://c1.staticflickr.com/1/547/32...222c26b8_z.jpg
or a little busier.

Just a tiny little change --> 986 (printed or even better as a badge, would need a little scare box around it) on the arm side.
Right in the center is a little too prominent for my taste :cheers:
http://986forum.com/forums/uploads02...1486499682.jpg

One thing to keep in mind are that most functioning spoilers don't create downforce, they kill lift. The retractable spoilers found on our 986s and Audi TTs are there for a reason, the factory did air tunnel tests and actual road tests, and found that they made the car more stable by killing rear-lift. The factory wants a car that has more lift at the front of the car than the rear, because that makes for a much more stable and forgiving car.

The software shown in this thread is amazing, but it doesn't replace air tunnel testing. If you were to see photos from air tunnel testing, the smoke plumes would show that there is a dramatic increase in turbulence around the top of the car with the top down. Turbulence = drag. My guess is that a 986 is faster with the top up than down, because of the increased drag. The top speed on my Miata was about 5 - 8 mph slower with the top down. The car shapes are different, but the top shape is pretty similar. A Boxster is about 30 mph + faster than a first generation Miata, so the drag differences between top up and top down would be even more dramatic.

Wow,
What a great design. Put me down for one. Size = XL.

@Fred - I wish I had your toys. I always enjoyed CFD when I was modelling furnaces for heat treatment. Sadly retirement took those toys away. Great rasters Fred! :cool:

I want it! Maybe with two channels - the other to feed an air to oil cooler :)

I saw a 2nd gen MR Turbo with a roof scoop like this and it was sweet!

here you go ...

https://scontent-sea1-1.xx.fbcdn.net...21&oe=58FD4030

or

http://4.bp.blogspot.com/-I7rDhChWaA...ed+boxster.jpg

or just build your own ...

GTM Roof Scoop - Factory Five Parts Catalog

CTR3...
http://986forum.com/forums/uploads02...1486503305.jpg

Butt dyno says hardtop off is faster.

Ok, I want a t-shirt too. Who ever put this up please link up the "Buy Now" button (Jon?)

Wow, surprised, me did not know that, Don!

Yea you should see what's available to us today in terms of problem solving you'd freak out. 'Dynamic-anything' throughout the whole study domain. Toys indeed :cool:

The only difference today (from your time I'm guessing) is the abilities to coupled any of the CFD data fields with thermal and/or structural problem solving (PLM suite). Friggin scary when you start thinking about it (lets just hope only kind & honest ppl have access to these tools I tell ya).

Hope you are well there buddy, my regards to you and your family as always :cheers:

Submitted it to Blipshift for you Fred

and then what, they offer the designing work and then they'll email you back the link for us buy them? Let us see let us see

If they accept the artwork, they will create the shirt with lots of options (short sleeve, long sleeve, sweatshirt, etc) and post it on their website. They make them all limited editions and are only available for a few days.

They have great quality and good pricing. If they accept it, Ill order one for you:cheers:

You-Are-a-Top-Man!!! Fingers crossed in that case :cheers:

Keep us posted, I'll go spray the Boxster S with more air in a meantime (tell me when you had enough loll)

I'm in for one in XL too.

deleted. I'll re-post the 'correct' viz in a bit :/

One tiny detail, and you should only care if you're really anal about these things - which I am.
The picture is not of a Boxster S.

https://c1.staticflickr.com/1/581/32...97416a9a_b.jpg
https://c1.staticflickr.com/1/382/31...c24f3ea8_b.jpg

Hm, i don't know. There must be something wrong with the calculations. :D Because the top speed of the car is faster with the top closed than with the top open.

Maybe you can recalculate at 260 Km/h? :D

Regards, Markus

PS:

Great - i need 1 2:

http://986forum.com/forums/uploads02...1486478752.jpg

Markus, we'll never be able to make friend if you continue your rampage man LOL
************************************************** *****************


Here goes the real deal. Same: 180km/hr. Enough 'wallpapers' and 'streamlines' otherwise it all leads to confusions and members mocking up the mighty Boxster's science-of-winds!

Those familiar with CFD, I'm using using the K-Epsilon turbulence model here so this is as accurate/advanced as real-life as it possibly can be. Commercially available to us anyway. Hopefully next week when all have recovered from seeing green & yellow I'll push those same but with the topless boxster (same format/grid, so to de-comfuse Markus).

Have fun (TRK!)


Air Velocity

https://c1.staticflickr.com/1/568/32...d04540d2_b.jpg


Air Density

https://c1.staticflickr.com/1/659/32...c806dfdf_b.jpg


Total Pressure

https://c1.staticflickr.com/1/643/32...c623a98f_b.jpg


Static Pressure

https://c1.staticflickr.com/1/445/32...9e762a08_b.jpg


Turbulence Energy

https://c1.staticflickr.com/1/639/32...800eab8a_b.jpg


Turbulence Dissipation

https://c1.staticflickr.com/1/726/32...e9ca3140_b.jpg

What? :D

Man, now i know what happened. You've used a cheap chinese 3D model for you calculations. :D

Just compare the silhouette of the real car with your 3D CAD car. ;) No wonder, that the top down is faster than the top closed. :D

http://image.superstreetonline.com/f...bside_view.jpg

Regards, Markus :cheers:

Silly me. I'll contact Dr Yang Procshe to get this fixed right away. Totally (totally) unacceptable and unreasonable.

Jeez don't they know who I am and where I'm from?

Wroom wroom!

Topless version (ignore the title in the plots)
 

So I went to Dr Yang Proshche to complain but came back emptied hands.

Even the part when I told him where my ancestors comes from had-no-effect whatsoever. He asked WHY you need this model so perfectly accurate then? So I shown him what I do and he suddenly became all agitated and started acting all weird. Not very used with this type of f'ed up behavior so I quickly left and did those for you guys - nonetheless ;)

Fascinating comparaisons


Air Velocity

https://c1.staticflickr.com/4/3704/3...1e290db3_b.jpg


Air density

https://c1.staticflickr.com/3/2124/3...be0bf0b8_b.jpg


Total Pressure

https://c1.staticflickr.com/3/2363/3...fcb7dc50_b.jpg


Static Pressure

https://c1.staticflickr.com/3/2139/3...7432d20b_b.jpg


Turbulence Energy

https://c1.staticflickr.com/3/2085/3...aa020924_b.jpg


Turbulence Dissipation

https://c1.staticflickr.com/3/2663/3...eb8d1fed_b.jpg

Huh, apart from some drag, I'm not seeing much down force effect at the spoiler.

Perhaps Boxsters need whale tails :p

Fascinating results though, thanks for posting them.

You are very welcome Sir :cheers:

That spoiler thing does somehow get cancelled at speed, for some reason. Boxster wasn't necessarily designed for racing I think.

Me think you are 100% correct about the requirement for a wing on the "track only" 986. But again, not a 'car mosport' professional at all here. Just leaving those here for you guys to judge

Dear Sir Mr. Nine8six,

could you please ask Dr. Yang Proshche if there is a mistake in the pictures. Because besides the text the picture looks the same, whereas at the open top pictures they look different.

Honestly, your how can we be rampage friends guy.

That's because a spoiler does not create down force, it reduces lift
aerodynamics 101

Deleted - misleading grid.

if Jay doesn't understand it I don't think many will.

^^^^^^
OK Fred, what does all that mean????

Edit: you know what bud, I've delete this grid because this will be interpreted wrongly by ppl... you can imagine what could happen next.

Better be safer than sorry lolll Let's just look at the pretty pics... not real-life but at least we have something to compare with.

There you go, special for you Markus. Took a snapshoot of my super duper Virtual Boxster Z in "perspective" mode just like your friend's did with his camera lens. Those simulation plots weren't screen-captured in perspective mode (and a bit dark) but if you want them like that next time, hey man, me-can-do-special-fo-yu :cool:

Wroooooom!

http://986forum.com/forums/uploads02...1486612308.jpg

Markus Markus Markus... they are everywhere on my hard drives here, all in CAD, class A&B surfaces, G2/3 curve continuity and all man. Markus.... its crazy, I have a Virtual Porsche Inventory. Which is faster on a windy day you think?! the Carrera or GT4?

(lolll I think I win a price for the most picture intensive thread page ever recorded)


http://986forum.com/forums/uploads02...1486614743.jpg


http://986forum.com/forums/uploads02...1486614751.jpg


http://986forum.com/forums/uploads02/GT41486614758.jpg

I was wondering if the major difference in those profile shots (aside from perspective) was that yours was a center-line cross section. No display of fender contours?