Restrictor Plate - NASCAR

NASCAR

NASCAR's Sprint Cup and Nationwide Series have used restrictor plates at Daytona International Speedway and Talladega Superspeedway since 1988. They are still in use with the 2012 season introduction of McLaren Electronics engine control unit providing electronic engine management for all NASCAR races and cars with carburetors finally being phased out.

The device limits the power output of the motor, hence slowing both the acceleration and the overall top speed obtainable on the tracks where the cars are so equipped. NASCAR routinely stated that the Sprint Cup restrictor plate reduces engine power from approximately 750 hp to approximately 430 hp.

A major effect, however, is that all drivers tend to form very large "packs" of cars that run closely together for the majority of the race. In these packs drivers often run three abreast across the track, consequently there may be as little as one second separating the entire field. These large packs reduce air resistance which allows the cars to run faster and makes drafting easier.

The restrictions are in the interest of driver and fan safety because higher speeds are closer to out-of-control than the 190 MPH range used for Daytona and Talladega; the severity of crashes at higher speeds is also much greater, shown by telemetry readings of wrecks such as Jerry Nadeau at Richmond and Michael McDowell at Texas that were far higher than registered on restrictor plate tracks. Drivers such as Rusty Wallace have also cited data showing that the sport's roof flaps cannot keep cars on the ground above 204 MPH.

At Daytona and Talladega, most races are marred by at least one multi-car crash as cars rarely become separated. Talladega has been considered the more likely track for these instances to occur as the track is wide enough to have three to four distinct lines of racing. With the new pavement at Daytona, three-wide racing is now possible and multi-car wrecks could become more common. The 2011 Daytona 500 saw a record number of cautions including an early 17-car pile-up. These wrecks tend to be singled out for criticism despite multicar crashes at other tracks and the generally greater severity of impact on non-restricted tracks. In addition, the packs were far smaller in 1988 through 1990 until more teams mastered the nuances of this kind of racing and improved their cars (and drivers) accordingly.

The 2011 Sprint Cup season will be the last complete Cup season with carbureted engines. NASCAR has announced that it will change to fuel injection for the 2012 season. The injection system used by NASCAR is a different system from that used in IndyCar Racing and other motorsports series and restrictor plates are usable with the NASCAR system; they were used for January 2012 testing at Daytona. In October of 2012, a major pileup happened at Talladega, in the last lap of the race. Most blame these restrictor plates.