Karting 101 Fast Motorsports & Cloud 9 Racing Jeff Cloud Erik Frank
Karting 101
Fast Motorsports & Cloud 9 Racing
Jeff Cloud Erik Frank
Types of karts
• Sprint kart– Sit up– Weight ~ 350 lbs – Engines - 2 or 4 stroke
• 100cc Yamaha, Rotax• 80 – 125cc dirt bike • Briggs & Stratton
– HP - 8 ~ 40+– Top speed ~ 100 mph
125cc Shifter Kart
Types of karts
• Enduro kart– Laydown– Road racing only– Engines - 2 stroke
• Piston port (KT100 Yamaha, TKM)• Reed/Rotary (DAP, Parilla, Komet, PCR)
– Top speed >100 mph
Laydown Enduro Kart
Types of karts
• Super kart– Wings– Weight ~ 450 lbs – Engines - 2 stroke
• Rotax 257• Motocross bike (CR 250, YZ 250)• 250cc Twin: Rotax 256, Yamaha TZ-250 (G.P.
derived)
– HP - 65+ (singles) 90+ (twins)– Top speed ~ 150 mph
Super karts @ Laguna Seca
Kart Engines 101
Yamaha KT100 100cc Reed
CR-125 YZ-125 Rotax 257 SGM F/E(Rotax 256)
Rotax Max FR125
Racing Formats
• Sprint Racing– Tight, twisty tracks < 1 mile long– Speeds limited to <75 mph– Short races (typically 10-20 laps)– Very quick pace– Very physical– Texas Sprint Tracks:
• Hill Country Kart Club (New Braunfels)
• North Texas Karters (Denton)• Gulf Coast Karters (Houston)• Waco
NTK – Denton, TX
Racing Formats
• Road Racing– Run on large road racing
courses– Longer races (usually 30
minutes)– High speeds - over 100
mph for some classes– Large fields– Regional Road Race
Tracks:• Texas World Speedway (College
Station)• Motorsport Ranch (Cresson)• Oak Hill Raceway (Henderson)• Hallet Motor Racing Circuit (Oklahoma)
Oak Hill – Henderson, TX
Typical 125cc Grid
Kart Racing Organizations
Kart vs. race car handling
Karts• Very quick steering response• Short wheelbase and wide track • Direct acting steering linkage (typ. 1/3 turn lock-
to-lock)• Must be smooth to achieve quick lap times
Cars• Slower steering response • Longer wheelbase vs. track• Heavier• Smooth is still fast
Kart vs. race car handling
• Brakes – Sprint kart brakes only on rear– 125cc Shifter karts and Super karts
also have front wheel brakes– Approx. ~2G deceleration is possible
Front Brake assy (Brembo) Rear brake assy (Brembo)
• Must lift inside rear tire to go around corner– Solid axle wants to go straight
– King Pin Inclination (KPI) and caster cause inside front wheel to drop and outside front wheel to rise which tilts kart to outside of turn and lifts inside rear wheel (Jacking Effect)
– Caster and front track width (offset) alter jacking effect
Kart chassis setup
• Kart setup seems to be contrary to conventional auto practice
– Stiffen chassis and increase weight transfer for low grip track
– Soften chassis and decrease weight transfer for high grip track
Kart Cornering 101
Look!
• Karts will never have zero caster, typically negative 15 degrees• Karts typically run +/-1 degree camber (will go more negative as chassis flexes)
Camber/Caster Orientation
Kart Chassis Setup
• Center of Gravity– Driver is largest mass
• Location has critical effect on handling
– Raising driver increases weight transfer • Low grip track - higher seat position
• High grip track - lower seat position
– Raising ride height also increases weight transfer
Kart Chassis Setup
•Tire Pressure
•Track Width Adjustments
–Increase Rear track: (decreases rear grip)
–Increase Front track: (increases weight transfer)
Up to a point!
–Higher pressures
Increases temperatures
Increases grip
Safety
• Helmet• Gloves• Racing shoes• Neck Collar• Suit or heavy jacket and long pants
– Not fireproof, abrasion resistant– Typically made of Cordura/Nylon
Safety is Important!
Measured parameters•Lap time•Sector times•RPM•Speed•Water temp•Exhaust gas temp•Lateral / longitudinal G•Steering position•Throttle position•Tire Temps•Etc…
Data Acquisition
Aim Sportsystems EVO 3
Data Acquisition
• Analysis software versatility:
Alfano Pro D/A–Handling evaluation•Oversteer/Understeer (driver or kart induced)
–Engine performance•Engine tuning aid•Horsepower calculation
–Driver training / consistency•Lap time comparisons•Kart behavior at specific locations on track
–Eliminate guessing •Solid foundation for setup changes
AIM Sportsystems Race Studio
AIM Sportsystems Race Studio
Kart Engine Tuning Overview
• Intake • Cylinder porting• Ignition • Exhaust
Kart Engine Tuning - Intake
• Mixture setting is critical– Carburetor adjustments:
• Main Jet• Needle• Fuel system (delivery)
– Reed cage setup• reed material• aftermarket options
Keihin PWK Carb
V-Force Reed Cage
Kart Engine Tuning - Porting
• Exhaust Port timing is important– Higher ports “More top end”– Lower ports “More torque”
• Compromise between port area and piston/cylinder life
Auxiliary “Boost” Ports
Transfer Ports
Inlet Ports(piston port)
Exhaust Ports
Kart Engine Tuning - Ignition
• Static Advance – Stator setting on crankshaft
• Dynamic Advance– Achieved by CDI box (on shifter engines)– Digital Programmable systems available
CDI Box
Coil
Rotor/Stator
Harness
Spark Plug Boot
Kart Engine Tuning Overview
• Exhaust – Pipe Selection– Determines Operating Powerband
Experimental Pipe setup – YZ 125
Dyno Testing
• Optimization of YZ-125 for Roadracing
– Porting– Cylinder head– Piston– Intake– Ignition– Exhaust
Dyno Testing
Road Atlanta - Nov. 2002
• 12 turns – 2.54 miles• Substantial elevation
changes• 5000 ft. Long
“straight”• 250cc Super kart lap
time: 1:34 (97.2 mph avg!)
Wrap-Up
• Questions?
• Show and Tell