Kart Racing 101: Types, Engines, Speeds & Techniques

1. Fast Motorsports & Cloud 9 Racing Karting 101 Erik Frank Jeff Cloud

2. 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

3. 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

4. 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

5. Kart Engines 101 100cc Reed Yamaha KT100 Rotax Max FR125 SGM F/E (Rotax 256) Rotax 257 YZ-125 CR-125

6. 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

7. 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) Typical 125cc Grid Oak Hill – Henderson, TX

8. Kart Racing Organizations

9. 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

10. 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 Rear brake assy (Brembo) Front Brake assy (Brembo)

11. 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 • 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

12. Kart Cornering 101 Look!

13. Camber/Caster Orientation • Karts will never have zero caster, typically negative 15 degrees • Karts typically run +/-1 degree camber (will go more negative as chassis flexes)

14. 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

15. Kart Chassis Setup Up to a point! • Track Width Adjustments • Increase Rear track: (decreases rear grip) • Increase Front track: (increases weight transfer) • Tire Pressure • Higher pressures  Increases temperatures  Increases grip

16. Safety Safety is Important! • Helmet • Gloves • Racing shoes • Neck Collar • Suit or heavy jacket and long pants • Not fireproof, abrasion resistant • Typically made of Cordura/Nylon

17. Data Acquisition • Measured parameters • Lap time • Sector times • RPM • Speed • Water temp • Exhaust gas temp • Lateral / longitudinal G • Steering position • Throttle position • Tire Temps • Etc… Aim Sportsystems EVO 3

18. Data Acquisition • Eliminate guessing • Solid foundation for setup changes • Analysis software versatility: • Driver training / consistency • Lap time comparisons • Kart behavior at specific locations on track • Engine performance • Engine tuning aid • Horsepower calculation Alfano Pro D/A • Handling evaluation • Oversteer/Understeer (driver or kart induced)

19. AIM Sportsystems Race Studio

20. AIM Sportsystems Race Studio

21. Kart Engine Tuning Overview • Intake • Cylinder porting • Ignition • Exhaust source: http://w3.one.net/~jschust/animations.html

22. 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

23. 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 Inlet Ports (piston port) Transfer Ports Exhaust Ports

24. 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 Harness Coil Spark Plug Boot Rotor/Stator

25. Kart Engine Tuning Overview • Exhaust – Pipe Selection • Determines Operating Powerband Experimental Pipe setup – YZ 125

26. Dyno Testing • Optimization of YZ-125 for Roadracing • Porting • Cylinder head • Piston • Intake • Ignition • Exhaust

27. Dyno Testing ~3 HP gain ~10 HP gain

28. 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!)

29. Wrap-Up • Questions? • Show and Tell