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