Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community - FT86CLUB - Interesting aerodynamics differences between USDM, JDM, etc.

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- - Interesting aerodynamics differences between USDM, JDM, etc. (https://www.ft86club.com/forums/showthread.php?t=9913)

Interesting aerodynamics differences between USDM, JDM, etc.

Data:
US Scion website says coefficient of drag for FR-S: .27
US Subaru website: .29 for premium .28 for limited
Subaru development video says .27 for BRZ in euro market
US FR-S and US BRZ don't get underbody aero package that is standard in Japan and possibly Europe.

Conclusions:
*The scion website datapoint of .27 might be not of the FR-S, but really for the JDM FT-86. The FR-S's number is probably the same as the premium BRZ at .29, but maybe not due to front end differences.

*The little wing on the limited BRZ might bring down the coefficient of friction from .29 to .28 since it's the only aero difference from the premium BRZ (maybe not, but look up parasitic drag on wikipedia before naysaying)

*The JDM underbody aero parts are probably needed to get to .27

Not important for auto-x, but could increase top speed and high speed stability and reduce fuel consumption.

From my knowledge the GT86 high spec was the one rated at cd 0.27, while the lesser models were cd 0.28. Never saw .29 until you pointed it out.

The FR-S may have a slight aerodynamic advantage over the BRZ based on the front bumper profile.

Overall im still willing to bet that the US spec FR-S does come in .27-.28

I believe it was the Australian 'wheels' mag (posted recently as a .pdf here) that had a breakdown on the drag.

IIRC, the .27 listed was for the GT86, equipped with rear spoiler - without spoiler was .29 - I expect the FR-S is the same.

I agree with WoW on this

are the differences in drag big enough for anyone to notice?

I just spoke with Tom Selleck, he confirms that his giant mustache increases his drag coefficient. So there's your answer right there.

Quote:

Originally Posted by mechaghost (Post 280446)

are the differences in drag big enough for anyone to notice?

i think it depends. if you were one to value that number enough to talk about how great this car was six months ago and how it was groundbreaking, yes. if you are a rational human being, not really. you might even know that drag is how you generate downforce

Quote:

Originally Posted by WingsofWar (Post 280346)

Quote:

Originally Posted by fatoni (Post 281187)

this was also dicussed

down force isnt a direct result of drag
CoD is how smooth the airflow is around the car(reducing turbulent air)
Down force has to do with airspeed over the car and under it, the closer you can get (how close you can get to press against the car and how little air you can get under the car to suck it to the ground)

for example a teardrop has almost the same CoD as a sphere but a sphere has mor turbulent air behind it, which causes a suction in the opposite direction of movement. The teardrops tail gives a path for the air to follow completely eliminating the turbulent air behind it

this is a simple way of describing drag vs down force

Quote:

Originally Posted by carbonBLUE (Post 281225)

FR-S .28
GT-86 (with full under body panels) .27
GT-86 (with spoiler +) .26
FR-S (five axis spoiler) .28, aerodynamics dont increase but down force is up by a couple percent
real number dieerence between the FR-S and FR-S with five axis spioler was like .283 vs .279(with spoiler)

i cant seem to find the 2-3 threads it was discussed over but i do remember the numbers
this was noted in a thread in early march from what i remember and discussed aswell

this was also dicussed

down force isnt a direct result of drag
CoD is how smooth the airflow is around the car(reducing turbulent air)
Down force has to do with airspeed over the car and under it, the closer you can get (how close you can get to press against the car and how little air you can get under the car to suck it to the ground)

for example a teardrop has almost the same CoD as a sphere but a sphere has mor turbulent air behind it, which causes a suction in the opposite direction of movement. The teardrops tail gives a path for the air to follow completely eliminating the turbulent air behind it

this is a simple way of describing drag vs down force

i know. im not saying they have a direct relationship. im just saying they have a relationship. i guess my point is that it isnt a big deal in the grand scheme of things.

Quote:

Originally Posted by fatoni (Post 281329)

i know. im not saying they have a direct relationship. im just saying they have a relationship. i guess my point is that it isnt a big deal in the grand scheme of things.

it is a small factor but it is nice to know where the starting point is and the available improvements

Guys when u say GT86 with spoiler r u meaning the aero spoiler? http://brzpost.com/forums/picture.ph...6&pictureid=92

If not does anyone have the data on coefficent of drag with this.....

I hate that spoiler, it looks very similar to the STi spoiler, could actually be it but I really don't know and don't care. It looks so wrong on the frs/brz/86.

Quote:

Originally Posted by carbonBLUE (Post 281225)

FR-S .28
for example a teardrop has almost the same CoD as a sphere

Not really...

Quote:

but a sphere has mor turbulent air behind it, which causes a suction in the opposite direction of movement.

i.e., drag

Quote:

The teardrops tail gives a path for the air to follow completely eliminating the turbulent air behind it

And giving it a MUCH lower drag coefficient! Highly dependent on Reynold's number and surface roughness, but similar vs. similar, teardrop wins by a HUGE margin.

Regarding drag and downforce, drag doesn't give you downforce, but lift or downforce induces drag.

Most production cars produce some lift. Minimizing lift minimizes drag, so win/win. When you start adding downforce, you begin adding drag again.

For a 200-hp FR-S/BRZ, zero lift/downforce and minimal drag makes a lot of sense. For much higher-horsepower cars, adding dowforce at the cost of drag makes sense.

Quote:

Originally Posted by mechaghost (Post 280446)

are the differences in drag big enough for anyone to notice?

I'm guessing that with that small of a difference, likely no, unless you are constantly doing top speed runs or frequently cruise at triple-digit speeds.