GR86/BRZ Aerodynamics

[Jianlun]

I didnt yet see a thread on aero for the new twins. I hope the experts here (and companies... looking at you Verus Engineering...) can help comment, with the idea of letting everyone understand the aero details/benefits/shortfalls/improvement potential.

I am no CFD expert. I do dabble a little in my line of work for internal flows etc (internal cooling, circulation etc), but not these complicated flows. I hope the community can enlighten/correct me.

Based on what I can find from here:

No doubt heavily censored and desensitised. But I am writing this with the interest of seeing what I can infer with regards to the stock car. Not so interested in what the GR parts do to the car. Besides, other than the ducktail and maybe the front splitter (which are really low hanging fruits that no doubt will have many options soon/already), the CFD plots didn't really "sell" the benefits of the other GR parts.

Cps = Coefficient of Static Pressure. Usually shown on physical surface. Denotes the static pressure acting on that surface, as if you put a pressure probe there, versus the equivalent static pressure of freestream.

Cpt = Coefficient of Total Pressure. Basically the sum of Static pressure and Dynamic pressure. Kinda like how "tired" (amount of energy) the air is compared to untouched air (not involved with the car ie at freestream). Usually shown in "x ray" slices.

On the Cps plot of the backside. Looks like quite little base drag, seeing how the pressure on the bumpers are actually not too low (colours are warm ie higher pressure, unlike the back of the side mirrors which is super low pressure ie a lot of base drag). Maybe cos of the effective infill of air from the sides past the tail lamps (see the streamline image where the paths of the air turn abrupt inwards when they move past the tail lamps, to fill up the volume behind the car).

On the Cps plot of the underneath. Quite strong suction at the metal undertray area, and that rectangular part in front of it (hmmm downward facing oil cooler ala Revolution anyone...). And the area behind the rear wheels beg for a proper diffuser (looking at you again Verus) cos it's doing f all now. Interesting somewhat low pressure area behind the rear wheels, outboard of the muffler, where that "half diffuser" with vanes are. Guess toyota did what they could. Unless one puts a HKS Spec L2 with the two cans instead of the big ass center muffler box, just saying...

On the Cps plot of the iso view. Note low pressure (colder colours) at the bonnet. That's where the hood/fender louvers should be!!

On the Cpt plot, side view. centerline slice of car. Underfloor flow looks nicely undisturbed (underfloor of car does not disrupt it/cause turbulence). Seeing this with the Cpt plot, rear view, shows that the disruption is mainly around the centerline of the car (maybe from the cooling air from the engine bay that exits from around the transmission/center resonator area). With flows either side of the centerline generally undisturbed. Red means air that never saw the car/didn't know it existed. Efficient, good floor!

On the Cpt plot, iso view. Both slices show minimal "outwash" (hahah duh, its not an F1 car...) which I guess is good cos low drag. Interesting vortex caused by the side window visors I guess.

[Spuds]

Kind of useless without knowing the scale. All 3 Cps images have different scaling, and it is unknown if it is a linear scale, or even where ambient pressure is.

Same goes for the Cpt images. If these are really showing total pressure, it's really just an image of how much energy has been taken out of the air at any given point, not directly related to how the air has been moved.

One thing I can say is the lower radiator shroud seems to be able to use some additional sealing lol.

[Dake]

Interesting. So is this a case where vortex generators (properly installed) might actually help maintain the airflow to the base of the rear window?

[PBR]

This seems like marketing guff to justify a fashion accessory body kit. 19 inch wheels also. That doesn't exactly telegraph function over form. This is all for style imo.

[zze86]