Explore the world of Gear Ratios (English Accent)

[4 BANGA]

Hey y'all

I'm trying my hardest to jump into this advanced tuning stuff. But I had the same problem on Tokyo Xtreme Racer Zero. I didn't know how to tune the Gear Ratios to perform best on my car. I now have a Miata MX-5 (J) Turbo, with 265hp and a power band of 5500rpm-6800rpm. It's a pretty narrow power band. Can anyone help me out here, I want a higher top speed rather than higher accel.

 

[Katz]

If u wanna higher top speed... make sure u have the full racing transmission to get in that extra 6th gear. then setup yer gear ratios first 2 or three depending on how much excel u want sorta close together... then spread the gears apart  farther an farther to get a higher top speed. will be tuff with that narrow powerband tho

 

[Talentless]

ENGINE SIZE
CI = (bore/2)^2 * PI * stroke * cylinders

AIRFLOW
VE = CFM / (CI * RPM / 3456)
VE = Actual CFM / Calculated CFM * 100
CFM = CI / 3464 * VE * RPM * (1.2 single_plane intake OR 1.33 dual_plane)
Or if supercharged...
boost = (25.58 * BlowerCI * DriveRatio / CI) - 14.7
CFM = (CI * RPM / 3456) * (boost / 14.7 + 1)

HORSEPOWER
BHP = atmos_pres * CR * VE * CI / 5252 * RPM / 150.8
example
BHP = 14.7 * 8.5 * .8 * 355 / 5252 * 5000 / 150.8 = 224
BHP = CI * MEP * RPM / 792000
MEP = (BHP * 792000) / (RPM * CI)
or
BHP = (PLAN) / 33000
where P=MEP, L=stroke('), A=Piston area(^2), N=RPM*cyl/2 (4 cycle)
BHP loss for increase in altitude
BHP_Loss = altitude (thousands of feet) * .03 * BHP * -1
HP required for MPH in Quarter mile
HP_Req = ((.00426 * mph)^3) * weight
HP required for MPH (Aerodynamic loss)
HP_req = .0015 * CD * FA * (MPH^2)

GEARING
Tire size to Diameter conversion
tire_Diameter = Width (mm) * sidewall Height (%) / 25.4 * 2 + wheel_Diameter
Example: P205/60R15
205 * .60 / 25.4 * 2 + 15 = 24.685
MPH = tire_Diameter / 336 * rpm / gear_ratio
RPM = 336 * gear_ratio * mph / tire_Diameter
gear_ratio = tire_Diameter * rpm / 336 / mph

1/4 Mile ET / 1.54 = 1/8 Mile ET
Example: 14 / 1.54 = 9.09

KEY:
atmos_pres = Atmospheric Pressure in Pounds per Square Inch
BHP = Brake Horse Power (at flywheel)
CD = Coefficient of Drag
CFM = Cubic Feet per Minute
CI = Cubic Inch
ET = Elapsed Time (Acceleration)
FA = Frontal Area of vehicle in square feet
HP = Horse Power (Net - at wheel)
MEP = Mean Effective Pressure
PI = ~3.14159265
RPM = Revolutions Per Minute
VE = Volumetric Efficiency

If first gear is 2.88 and second gear is 1.89, than 1.89 divided by 2.88 equals 0.65625. o.65625 times the rpm at the time of the shift from first to second, let's say 7000, will give the after shift rpm. basically about how far back the needle will go. O.65625 times 7000 equals 4593.75