A shifter kart requires a particular driving style. World champion Marijn Kremers and runner-up Riccardo Longhi explain the extent to which a kart’s set-up can be adapted to the driver’s preferences
Riccardo Longhi: “On non-shifter karts, the goal of the driving style is to maintain a trajectory that allows you the highest possible speed in the centre of a bend. It is an obligatory choice when there is a single ratio and you cannot select a gear that gives you extra torque immediately. If that were not the case, once you accelerated again, it would be difficult to increase engine speed and, therefore, you would struggle in the subsequent acceleration phase. A KZ kart, on the other hand, has different characteristics: it is equipped with front brakes, an engine with more horsepower and a 6-speed gearbox. Therefore, you need to exploit them: instead of excessively round trajectories, the greater braking power allows you to take a quicker route, compensating lower speed at the centre of the bend with the ability to drop down the gears and having torque available even when trying to accelerate at slower speeds.”
Marijn Kremers and Riccardo Longhi are the two works drivers of the Birel ART Racing team who finished the FIA Karting 2019 KZ World Championship in first and second place. The Dutchman and the Italian, born in 1998 and 1994, respectively, have two quite different driving styles and adopt different technical solutions for their KZ karts. However, both are very fast and effective: a perfect “driving pair” to understand how to best drive a shifter kart and how the vehicle’s set-up can be adapted to the driving characteristics of the individual driver.
BRAKE, BUT DON’T STOP
Longhi: “Therefore, the general idea is that in a KZ you need to brake harder and when the kart is straight. However, braking should only slow down the kart, not stop it! The speed needs to be reduced as late as possible. So, my advice for effective throttle-off braking is to use the brake a lot, drop down a few gears, but wait until the last second to engage the bottom gear, which is the one you use in the acceleration phase. This means there isn’t an exaggerated use of the engine brake, which would slow down the kart suddenly and too soon, causing you to lose up to two metres to your rival in an instant. Basically, you need to maintain speed for as long as possible and slow down abruptly only when you near the centre of the curve”
DROPPING DOWN THE GEARS
Longhi: “During throttle-off braking, always pay particular attention to the use of the gearbox: exaggerated use could compromise the reliability of the engine. When I watch amateur drivers, I often hear dangerous over-revving during braking: it’s usually a sign of incorrect behaviour. To prevent this mistake, remember to start throttle-off braking using your brakes. Only then can you use the shifter lever to drop down the gears. Be careful not to drop down the gears too quickly, especially the bottom one, so that you maintain an acceptable engine speed, say between 15300 and 15500 revs. Above that you risk subjecting the engine components to excessive stress.”
Marijn Kremers: “This aspect is really important, especially for those trying to develop a smoother driving style. Excessive engine speed when dropping down the gears during braking can lead to instability just as you’re trying to prepare yourself for the bend to maintain speed. It’s undoubtedly far from ideal and, although there are some drivers who use the engine brake very aggressively, I avoid doing so”.
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