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Slipstreaming is a well-known aerodynamic technique in motorsports, allowing a trailing vehicle to reduce drag and gain speed. It’s widely used in Formula 1 and NASCAR for overtaking – but how effective is it in karting? Using Computational Fluid Dynamics (CFD) simulations, let’s analyze the impact of slipstreaming on kart performance.
1. How Slipstreaming Works
When a kart moves at high speed, it displaces air, creating a low-pressure wake behind it. A trailing kart in this wake experiences reduced air resistance, allowing it to achieve a higher top speed with less effort. CFD simulations reveal key benefits for the second kart: lower drag coefficient (Cd = 0.24 when in slipstream vs. 0.59 when driving alone). This means less aerodynamic resistance and high-pressure buildup on the front panel, improving straight-line speed. But reduced air pressure on the front panel introduces slightly positive lift (Cl = 0.02) due to decreased downforce, leading to less downforce and understeer.
First Kart Also Gains an Advantage
Although the second kart benefits the most, the leading kart isn’t left out entirely. The wake behind their kart is reduced, minimizing the vacuum effect that pulls it backward. Additionally, at just the right distance, the high-pressure zone in front of the trailing kart can create a slight pushing effect on the first kart. This principle is commonly seen in NASCAR, where drivers draft in pairs to maximize speed and break away from competitors. That also explains why it is so hard to break away alone in karting.
Slipstreaming at Greater Distances
So far, we’ve analyzed slipstreaming at close range, but what happens when the second kart follows from 10 meters behind? Even at this distance, slipstreaming remains effective, but its impact weakens. Some of the displaced air returns, increasing drag on the second kart. The drag coefficient rises (from 0.24 to 0.33) and the lift coefficient decreases (from 0.02 to -0.08), as the kart now encounters a higher volume of air. While the second kart still benefits, the effect is noticeably weaker than at closer distances.
2. The Downsides of Slipstreaming
Slipstreaming isn’t without drawbacks. The second kart must deal with dirty air, the turbulent airflow left behind the first kart. Dirty air causes reduced aerodynamic grip, making handling less predictable. It lowers the cooling efficiency, potentially causing engines to overheat. The disturbed airflow decreases stability and causes understeer, especially in corners. A prime example of the dangers of dirty air was seen in Formula 1 at the 2024 Australian Grand Prix. When Fernando Alonso decelerated early, the turbulent wake contributed to George Russell’s crash, demonstrating how dirty air can reduce handling control. What if you’re the leading driver and want to defend against slipstreaming? Your best option is to break the tow by moving off the racing line. However, sudden moves can be dangerous and may lead to penalties or crashes.
3. Conclusion
Slipstreaming is a powerful tool in karting, providing significant speed advantages for the trailing kart and some benefits for the leading kart. However, it comes with trade-offs, including reduced cooling efficiency, aerodynamic instability, and dirty air effects.
Oskar explains the concept further in the video. Follow him on YouTube!
