Basically, a narrow version of the rear wing off a Formula One car, then.
Either magnets are involved, or the cars are going fast enough (scale speed must be 1000 mph) that they generate massive downforce.
Given what the page quoted below is saying, you slightly underestimated the lower end of the scale speed:
Known as wing cars, they race on a 1:24 scale track that has steep banks and runs approximately 47 m (155 ft) long by eight lanes wide.
The wing cars can hit speeds of 80-160 km/h (50 - 100 mph) clocking lap times from 1.5 to 3.0 seconds. 0-100 km/h (62 mph) takes less than 0.3 seconds while the tuned electric motors are calculated to rev up to 300,000 RPM at 16 volts!
https://www.motor1.com/news/29368/competition-slot-cars-go-0-62-mph-in-less-than-03-seconds-video/A 1:24 scale slot car circulating round a track at 50-100 mph equates to a full-size car doing 1,200-2,400 mph - that's 1.58-3.15 times the speed of sound at sea level. Mind you, the visual effect in the video suggests that they are travelling and scale speeds closer to plaid.
At 1:24 scale, the acceleration figure of 0-62 mph in 0.3 seconds equates to 0-1488 mph in 0.3 seconds, or 226.1g
To put the performance of slot wing cars into perspective, Bloodhound SSC is designed to reach "only" 1,050 mph, and although some racing drivers have survived massive g-loads*, anything over 50g is likely to cause death or serious injury.
*
David Purley (best known for his attempts to save Roger Williamson at the 1973 Dutch GP) survived an estimated 178g when the throttle of his car stuck open and he hit a wall at Brands Hatch Silverstone in 1977 and Kenny Bräck survived an IndyCar crash in 2003 in which an impact of 214g was recorded.