First, using my own formulas and method then compared it to the standard method and formulas. Porsche claims a 198 mph top speed. Using these specs and parameters, it calculates to 204.25 mph using standard formulas. Way off. Now, my formulas and method calculated it at 197.82 mph — right there! I used 45.0 psi with the corresponding 0.0392 rolling coefficient for the speed and tire pressure, based on Porsche's recommended tire pressure:

https://tirepressure.com/porsche-911-tire-pressure#2021

https://www.caranddriver.com/reviews/a36164987/2022-porsche-911-gt3-drive/

Hc = (0.00000556517pAfCdS^3+ 0.0026667CrSWt)/Pf -> my formula

Pf = 5,252Hc/EpTp -> my formula

2022 Porsche 911 GT3

Where:

Hc = Horsepower 502 (509 PS)

EP = 8,400 rpm

Tp = 346 lb-ft @6,100 rpm -> 469 Nm

p = 1.204 kg/m^3

Af = 21.85 sq ft -> 2.03 sq mt

Cd = 0.34

S = 197.82 mph @45.0 psi

Wt = 3,222 (car); 165 (driver) = 3,387 lbs -> 1,536 kgs

Pf = 0.90714

Cr = 0.0392 @45.0 psi

P = 374,341 watts

n = 0.090

502 = (0.00000556517x1.204x21.85x0.34x197.82^3 + 0.0026667x0.0392x197.82x3,387)/0.90714

Using the standard power equation:

Pn = [0.5pCdAV^2+ Cr(M+Df)g]V, with 0.90 drivetrain efficiency and 0.015 rolling coefficient, the top speed translates to 204.25 mph.

374,341x0.090 = (0.5x1.204x0.34x2.03x91.31^2 + 0.015x1,536x9.8067)91.31

336,907 = (3,464 + 226)91.31

336,907 ≈ 336,934

However, if you substitute my "powertrain factor" of 0.90714 and rolling coefficient of 0.0392 to the standard equation, the top speed would be the same 197.82 mph — just as the manufacturer's claim! How can you get any better than this? ;-)

374,341x0.90714 = (0.5x1.204x0.34x2.03x88.44^2 + 0.0392x1,536x9.8067)88.44

= (3,250 + 590)88.44

339,580 ≈ 339,610 watts