Cooling System & Radiator Sizing Calculator
Calculate the heat rejection your engine produces and size a radiator for track use based on horsepower, thermal efficiency, and ambient conditions.
NA: 25-33% · Turbo: 30-38%
Typical: 30-40% of waste heat
Sizing Note
These are minimum requirements for sustained track use. Oversize by 20-30% for safety margin, especially in hot climates or turbo applications. A thicker core (2-3 row) can offset smaller face area.
Cooling System Variables
Radiator sizing depends on variables beyond this calculator:
- Core thickness, fin density, and tube design
- Airflow velocity through the core (speed-dependent)
- Ducting efficiency and radiator placement
- Fan shrouding and pull-through vs push configuration
- Coolant mixture ratio (water wetter vs glycol vs pure water)
Methodology
Waste heat: HP ÷ thermal_efficiency × 2545.46 BTU/hr - (HP × 2545.46)
Coolant load: waste_heat × coolant_percentage
Radiator area: coolant_BTU ÷ (heat_transfer_coeff × ΔT)
Coolant rise: Q ÷ (mass_flow × Cp_coolant)
Frequently Asked Questions
Why does my car overheat on track but not on the street?
Track driving produces 3-5× more sustained heat than street driving. On the street, you rarely exceed 50% throttle for more than seconds. On track, you're at 80-100% throttle continuously on straights — the radiator must reject far more heat per hour.
Is a bigger radiator always better?
For track use, generally yes — up to a point. The limiting factor becomes airflow. A massive radiator with poor ducting will underperform a smaller, well-ducted one. Ensure air flows THROUGH the core, not around it.
Should I use Water Wetter or full glycol on track?
Pure water transfers heat ~15% better than 50/50 glycol. Many tracks require glycol-free coolant (spills are slippery). Use distilled water + Water Wetter for best heat transfer. Check your sanctioning body's rules.
Disclaimer & Legal Notice
All tools and calculators provided by Lapsite are for informational and educational purposes only. While we strive for mathematical precision, these results are approximations and should not be used as the sole basis for critical engineering, financial, or safety decisions. Lapsite Ltd and its creators provide no warranty, express or implied, regarding the accuracy or fitness of these calculations for any specific use.Always double-check calculations independently, especially for safety-critical components such as brakes, suspension, or structural changes. By using these tools, you agree that Lapsite Ltd is not liable for any mechanical failure, financial loss, or injury resulting from the use of this data.
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