Editing Restrictor plate (section)

=== Reason for restrictor plates ===
[[NASCAR]] used restrictor plates first in 1970 as part of a phased transition from the {{convert|7|litre|cuin|adj=on|spell=in|abbr=off}} era to the {{convert|6|litre|cuin|adj=on|spell=in|abbr=off}} era engine that would be in effect at the end of the 1973 season. Following testing and input from drivers such as [[David Pearson (NASCAR driver)|David Pearson]], [[Bobby Isaac]], and [[Bobby Allison]], NASCAR mandated the use of a restrictor plate for the big block seven-litre engines. Small block engines, in the 358 cubic inch range (which is still used today in NASCAR), were exempt from the plates; the first car to race with a small block engine was [[Dick Brooks]] at the [[1971 Daytona 500]], where he ran a 1969 [[Dodge Daytona]] with a five-litre engine (to be exact, 305 CID).  The transition period lasted until 1974, when the current 358 cubic inch (5870cc) limit was imposed.  As the early 1970s use of restrictor plates was considered a transitional process, and as not every car used restrictor plates, this is not what most fans call "restrictor plate racing".{{Citation needed|date=March 2010}}  This is similar to the [[2006 Formula One season]], where teams using V10 engines were run with air restrictors and rev limiters while teams running V8 engines were not.

The second use came following the crash of [[Bobby Allison]] at the [[1987 Winston 500]] at [[Talladega Superspeedway]]. Allison's [[Buick LeSabre]] blew a tire going into the tri-oval at {{convert|200|mi/h|km/h|abbr=on}}, spun around and became airborne, flying tail-first into the catch fencing.<ref>[http://www.popularmechanics.com/cars/news/vintage-speed/4280752?page=7 "Top 10 NASCAR Crashes That Changed Racing (With Videos!)"], ''Popular Mechanics'' (retrieved 10 Aug 2010)</ref> While the car did not enter the grandstands it tore down nearly 100 feet of fencing and flying debris injured several spectators. After a summer where the two subsequent superspeedway races were run with smaller [[carburetors]] (390 cubic feet per minute (cfm) instead of 830 cfm) proved to be inadequate to sufficiently slow the cars, NASCAR imposed restrictor plates again, this time at the two fastest circuits, both [[superspeedway]]s: [[Daytona International Speedway|Daytona]] for all NASCAR-sanctioned races and [[Talladega Superspeedway|Talladega]] for Cup races. The [[Automobile Racing Club of America]] also enforced restrictor plates at their events at the two tracks. In 1992, when the [[Xfinity Series|Busch Grand National]] series began racing at Talladega, the plates were implemented, in keeping with their use at Daytona.{{Citation needed|date=March 2010}}

NASCAR's concerns with speeds because of [[power-to-weight ratio]]s result in restrictor plates at other tracks. The [[Goody's Dash Series]] (known now as the ISCARS series with its new ownership) used restrictor plates at [[Bristol Motor Speedway|Bristol]] during at least the last years of the series' existence when the cars were using six-cylinder engines (compared to the traditional four cylinder engines), in addition to their Daytona races.{{Citation needed|date=March 2010}}

However, restrictor plates were not initially used for [[Camping World Truck Series]] trucks. Rather, aerodynamic air intake reduction through the use of a 390 cfm carburetor, and eventually a tapered carburetor spacer were implemented for those races. Combined with the aerodynamic disadvantage of the trucks, this allowed NASCAR to avoid the use of such equipment for the trucks until 2008.{{Citation needed|date=March 2010}} In 2008, the Nationwide Series (now known as Xfinity Series) and Truck Series began implementation of tapered spacers in the engines to restrict power compared to Sprint Cup cars at all 35 (NNS) and 25 (NCTS) races. Both these NASCAR series now use a restrictor plate and tapered spacer at the two tracks.

The third use came in 2000. Following fatal crashes of [[Adam Petty]] and [[Kenny Irwin Jr.]] at the [[New Hampshire International Speedway]] during the May [[Xfinity Series|Busch Series]] and July [[Sprint Cup Series|Winston Cup Series]] races, respectively, NASCAR adopted a one-inch (2.54&nbsp;cm) restrictor plate to slow the cars headed towards the tight turns as part of a series of reforms to alleviate stuck throttle problems which were alleged to have caused both fatal crashes. For the Winston Cup race, it was used just once at the [[2000 Dura Lube 300]]. [[Jeff Burton]] led all 300 laps in the ensuing race, despite a 23-car two-abreast battle in the first ten laps, a dramatic charge past 22 cars in 100 laps by [[John Andretti]] (who finished seventh), and two charges by [[Bobby Labonte]] in the final 50 laps where he took the lead but Burton beat him back to the stripe. The use of restrictor plates, intended as an emergency measure pending a more permanent replacement in any event, was discontinued at New Hampshire for the following race for Cup only. However, the Modifieds still use a restrictor plate because the speeds are too great for that class of racecar without them. The track has since been changed with SAFER Barriers to improve racing safety.{{Citation needed|date=March 2010}} Restrictor plates remain a permanent fixture on the Modifieds and the racing has often broken 20 official lead changes for 100–125 laps of competition.

[[Rusty Wallace]] tested a car at [[Talladega Superspeedway]] without a restrictor plate in 2004, reaching a top speed of {{convert|240|mi/h|km/h|abbr=on}} in the backstretch and a one-lap average of {{convert|221|mi/h|km/h|abbr=on}}.<ref name="rwdega">[http://www.nascar.com/2004/news/headlines/cup/06/10/rwallace_talladega/index.html NASCAR.com&nbsp;– Rusty Wallace hits 240mph in Talladega trial&nbsp;– June 10, 2004<!-- Bot generated title -->]</ref> While admitting excitement at the achievement, Wallace also conceded, "There's no way we could be out there racing at those speeds... it would be insane to think we could have a pack of cars out there doing that."<ref name="rwdega" />

In 2016, following a series of uncompetitive races at [[Indianapolis Motor Speedway]], NASCAR began a series of tests for the Xfinity Series using a smaller restrictor plate than used at Daytona and Talladega and aerodynamic aids. After the tests were successful, the rules package was imposed for the 2017 race at Indianapolis. For 2018, the package is being used at Indianapolis, Michigan, and Pocono for the Xfinity Series and in the All-Star Race in the Cup Series.