Available programs:
- ADAMS - Powerful and complex. Full vehicle dynamics
- Lotus - Simple and effective. Awkward interface.
- WinGeo3 - Simple and effective. Akward interface.
- SolidWorks + Cosmos - Powerful and complex. Takes alot of work to get meaningful results.
- Optimum K - Never used it.
- SuspensionAnalyzer - Never Used it.
- DIY Excel - Hardcore Mode. Requires alot of brains and time.
The goal would be to analyze the stock package and look at how various aftermarket options would perform. Since each person has a different goal (autocross, street, rally, drift, etc) their interest will push the project in that direction. I'll be pushing the limits of SCCA street tire.
The Facts (in 'Murika units and Sissy units):
Curb Weight (FR-S, no spare/tools/mats, minimal gas) = 2645 lbs or 1200 kg LINK
Corner Weights:
LF = 823 lbs (701 ideal) or 373.3 kg (318.0 ideal) or 3660.9 N (3118.2 ideal)
RF = 684 lbs (701 ideal) or 310.3 kg (318.0 ideal) or 3042.6 N (3118.2 ideal)
LR = 513 lbs (622 ideal) or 232.7 kg (282.1 ideal) or 2281.9 N (2766.8 ideal)
RR = 625 lbs (622 ideal) or 283.5 kg (282.1 ideal) or 2780.1 N (2766.8 ideal)Unsprung Weight: (best guess - LINK )
83 lbs or 37.6 kg or 369.2 N per cornerSprung Weight:
LF = 740 lbs (618 ideal) or 335.7 kg (280.4 ideal) or 3291.7 N (2749 ideal)
RF = 601 lbs (618 ideal) or 272.4 kg (280.4 ideal) or 2673.4 N (2749 ideal)
LR = 430 lbs (539 ideal) or 195.1 kg (244.5 ideal) or 1912.7 N (2397.6 ideal)
RR = 542 lbs (539 ideal) or 245.9 kg (244.5 ideal) or 2410.9 N (2397.6 ideal)Dampers = SHOWA non-inverted, twin-tube, low-pressure Nitrogen, conventional strut
Shock Dyno:
Suspension Spring Rates: LINK
Front = 131 lbs/in or or 22970 N/m
Rear = 211 lbs/in or 36998 N/m
Spring Dimensions: Link to Bordom.is.me's post
FRONT:
- External Diameter = 4.625"
- Internal Coil Diameter = 3.625"
- Wire Diameter = .5"
- Free Length = 11.625"
- Active Coils = 5 (excluding grinding of bottom coil)
REAR:Tire Spring Rates: (FSAE guru states 350 N/mm for passenger tires at passenger pressures. I concur.)
- External Diameter = 4.125"
- Internal Coil Diameter = 3.125"
- Wire Diameter = .5"
- Free Length = 10.5"
- Active Coils = 4 (excluding grinding of bottom coil)
30 psi = 6500 lbs/in or 114000 kg/m
45 psi = ~10000 lbs/in or 175000 kg/mSway Bar Spring Rate:
Front = 141 lbs/in or 2467 kg/mEffective Wheel Rate (in roll, including sway bar):
Rear = 113 lbs/in or 1978 kg/m
Front (FR-S) = 373 lbs/in or 6528 kg/m (70% from sway bar)
Front (BRZ) = 410 lbs/in or 7175 kg/m (64% from sway bar)
Rear (FR-S) = 212 lbs/in or 3710 kg/m (37% from sway bar)
Rear (BRZ) = 200 lbs/in or 3500 kg/m (39% from sway bar)Caster Angle: Link
Front = -5.937 degRoll Center Height: Link
Front = 3.140" (stock height) --> ground plane (1" of compression)Spring Angle:
Front = 15.5 degSpring Motion Ratio:
Rear = 4 deg
Front = 1.050 (2.5" compression) --> 0.997 (1.5" compression) --> 0.95 (OEM height) LinkSway Bar Motion Ratio:
Rear = 0.768 (2" compression) --> 0.763 (OEM height) --> 0.758 (2" rebound) LINK
Front = 0.92Natural Frequency (in ride):
Rear = 0.59
Front (FR-S) = 1.24 Hz
Front (BRZ) = 1.43 Hz
Rear (FR-S) = 1.54 HzNatural Frequency (in roll):
Rear (BRZ) = 1.47 Hz
Front (FR-S) = 2.27 Hz
Front (BRZ) = 2.38 Hz
Rear (FR-S) = 1.95 HzTire Info:
Rear (BRZ) = 1.89 Hz
215/45-17 Michelin Primacy HP LINK
Section Width = 8.46 in or 0.215 m
Contact Width = 7.5 in or 0.1905 m via TireRack measurement
Contact Length (at 60 mph and stock pressure) = ~5.71 in or 0.145 m
Overall Diameter = 24.7 in or 0.6274 m
Load Rating = 87W SL (168 mph or or 270 kph)
UTQG = 240 A A (hmm... A?)
Max Load (at rated pressure) = 1201 lbs or 545 kg
Max Rated Pressure = 51 psi
Tread Depth = 9.5/32 in
Material = Green X - Low Rolling ResistanceWheel Info:
Wheel Diameter = 17 in or 0.432 m
Wheel Width = 7 in or 0.178 m
Wheel Offset = +48 mm or 1.89 in or 0.048 mTrack Width: LINK
Front = 59.8 in or 1.51m
Rear = 60.6 in or 1.54mRoll Bar Diameter: LINK
Front = 0.71 in or 0.018m
Rear = 0.55 in or 0.014mCenter of Gravity Height = 18.1 in or 0.46 m LINK
Roll Center Height:
Front = 2.1 in
Rear = 3.8 inWheelbase = 101.2 in or 2.5705 m LINK
Suspension Travel:
Bump Travel = 2.5 in or 0.1 m
Rebound Travel = 3.5 in or 0.15 m
Max Roll Angle = +/- 2.3 deg
Max Pitch Angle = 0.9 deg (braking)
Roll Resistance on Front: 61%
Braking on Front = 60%
Anti-dive Under Braking: 5% (front)
Anti-lift Under Braking: 196% (rear)
Anti-squat Under Acceleration: 64% (rear)
Steering Ratio: 14.3 (on center) - 14.4 (at 90 deg)
Distance (axial) between lower strut bolts = 2.4" (or 60.5 mm)
Thickness of lower flange = 1 in (or 25.4 mm)
Distance (radial) from strut center to lower bolt = 2.4 in (or 60.7 mm)
Distance (axial) from AST's lower bolt to hat mount = 15.4 in (or 392 mm)
Upper strut thread:
- AST = M12x1.25-25, with 1 mm of thread relief, 5 mm long (for camber plate)
- KW = M14x1.5-30, with 0 mm of thread relief, 10 mm long (for camber plate)
Length of AST's spring = 7.1 in (or 181 mm)
Distance (axial) from lower bolt to sway bar mount = 4.5 in (or 115 mm)
Distance (radial) from strut axis to sway bar mount = 1.97 in (or 50 mm)
Diameter of sway bar mount hole = 0.4 in (or 10.2 mm)
Here's a cool MATLAB function that helps you simulate shock dyno graphs:
function y=critdamp(cwlbs,srppi,spmr,shmr,lsd,knee,hsd)
%cwlbs=corner weight, lbs minus unsprung for more accuracy
%srppi=spring rate, lbs per inch
%spmr=spring motion ratio
%shmr=shock motion ratio
%lsd=low speed damping, percentage of critical
%hsd=high speed damping, percentage of critical
%knee=location of knee, in inch per second
lbf2n=4.448; % 1 lbf = 4.448 newtons
m2i=39.37; % 1 meter = 39.37 inch
p2kg=0.4536; % 1 lb=0.453 kg
if (spmr>1)+(shmr>1)
disp('Motion ratios must be less than 1, but I''ll convert it for you')
spmr=1/spmr;shmr=1/shmr;
end
wheelratestandard=srppi*spmr^2
wheelratemetric=wheelratestandard*lbf2n*m2i
cd=2*sqrt(wheelratemetric*cwlbs*p2kg)/lbf2n/m2i/shmr^2
vel=(0:0.1:20);
damp=lsd*cd*(0:0.1:knee);
hispeed=damp(end)+(0:0.1:20-knee)*cd*hsd;
damp=[damp hispeed(2:end)];
plot(vel,damp,'r','linewidth',2,'displayname',['LS:' num2str(lsd*100) '% Knee:' num2str(knee) ' ips HS:' num2str(hsd*100) '%'])
legend('off');legend('show','location','east')
Still looking for accurate suspension geometry coordinates (X,Y,Z). The current "best guess" is housed in a Google Docs spreadsheet: LINK
Special Thanks to MLA163, Wepeel, and Boredom.is.me for contributing measurements and discussion.
Thanks to Shankenstein