414:; after that race, the cars moved to a variable-sized tapered spacer already used at all other tracks, with the exception that the spacer would have smaller holes than the ones used at the smaller tracks, to ensure speeds stay under 200 mph. The shape of the spacer helps a car funnel more air smoothly into the manifold, increasing fuel performance, while ensuring airflow is still restricted. With that change, NASCAR also mandated the use of larger rear spoilers, larger front splitters, and specially-placed front end aero ducts. The combination of those features increased drag on the cars, counteracting the increased horsepower, keeping the cars close to the speeds they were running prior to the switch to the tapered spacer. While the racing quality noticeably improved, and passing was made easier with larger horsepower and bigger runs, speeds also noticeably increased past 200 mph, and even into 205 mph ranges.
36:
588:, 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.
393:, as cars rarely become separated. Talladega has been considered the more likely track for these instances to occur as the track is incredibly wide, enough to have three to four distinct lines of cars running side by side. With the new pavement at Daytona, three-wide racing became far easier, and multi-car wrecks became more common. The 2011
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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. 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.
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2008. 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.
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A frequent criticism of restrictor plates is the enormous size of packs in the racing, with "Big One" wrecks as noted above singled out for condemnation despite the greater violence of "smaller" crashes on unrestricted tracks. In restrictor plate racing the packs have brought about an often-enormous
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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
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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
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The restrictions are in the interest of driver and fan safety because speeds higher than the 190 mph range used for
Daytona and Talladega risk cars turning over through sheer aerodynamic forces alone. The severity of crashes at higher speeds is also much greater, shown by telemetry readings of wrecks
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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
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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
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without a restrictor plate in 2004, reaching a top speed of 228 mph (367 km/h) in the backstretch and a one-lap average of 221 mph (356 km/h). While admitting excitement at the achievement, Wallace also conceded, "There's no way we could be out there racing at those speeds... it
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races, respectively, NASCAR adopted a one-inch (2.54 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
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has generally been less competitive because the age of the asphalt (the track was repaved in 1978 and again in 2010) has reduced grip for the cars and thus handling has impeded passing ability to a significant extent. The 2000 New
Hampshire race was condemned because Jeff Burton led wire to wire;
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blew a tire going into the tri-oval at 200 mph (320 km/h), spun around and became airborne, flying tail-first into the catch fencing. 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
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and other motorsports series; the EFI system that NASCAR put into use was compatible with the old restrictor plates, allowing NASCAR to continue to use them to keep the speeds lower at the superspeedways and save costs for race teams. The restrictor plates were bolted beneath a throttle body that
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crashing into the frontstretch catch fence at a high enough speed to destroy almost 100 feet of the fence and put the race under a red flag condition for two hours. The following race at
Talladega that year would be run with a smaller carburetor, however, NASCAR mandated the use of the restrictor
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The 2011 Sprint Cup season was the last complete Cup season with carbureted engines; at the end of the 2011 season, NASCAR announced that it would change to an electronic fuel injection system for the 2012 racing season. The injection system used by NASCAR is a different system from that used in
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support race the day before where the lead changed seven times in 100 laps and by the highly competitive nature of restrictor plated
Modified races; as noted above the 300 also saw a 23-car battle for third in the first ten laps and a burst by 22 cars from John Andretti.
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The drawback to the use of the restrictor plates has been the increased size of packs of cars caused by the decreased power coupled with the drag the vehicles naturally produce. At
Daytona and Talladega, most races are marred by at least one wreck, usually referred to as
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used restrictor plates first in 1970 as part of a phased transition from the seven-litre era (427 cubic inch) to the six-litre era (358 cubic inch) engine that would be in effect at the end of the 1973 season. Following testing and input from drivers such as
445:, 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
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The criticism stems from reduction in throttle response brought by the restriction. The reduction in throttle response, however, has never been shown to have impeded ability to pass; the criticism was shot down in the first "modern" plate race, the
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may have less power than the street version (the "280" hp Evo VII was believed to have more than 300 hp, and in some markets the FQ-320, FQ-340, FQ-360, FQ-400 versions were sold, with the number representing the total horsepower).
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Said
Waltrip before the race, "I feel, as a driver, now I can do more than I could before (the plates). Now, instead of a car just blasting by me with a burst of speed and a lot of horsepower, he's got to think his way, he got to
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the Sprint Cup cars have surpassed 40 official lead changes sixteen times from 1988 onward, including both 2010 Sprint Cup races at Talladega, which had 87 official lead changes in the regulation 188 laps. (The
632:, as the lead changed 25 times officially and saw several bursts where the lead changed several times a lap and also several bursts of sustained side-by-side racing, notably in the final 50 laps between
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used an illegal device to bypass the restrictor (allowing an estimated extra 50 hp). Due to this the team lost their results in the 1995 season and was banned from rallying until the end of 1996.
486:(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
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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.
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In the transitional years (1971–76) where the seven-litre engines (430 cu in) had restrictor plates, Daytona and Talladega broke 40 official lead changes six times, while
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of an engine to limit its power. This kind of system is occasionally used in road vehicles (e.g., motorcycles) for insurance purposes, but mainly in
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decided that rally cars should not have more than 300 hp (220 kW). For a while no special restrictions were needed for that (e.g. the
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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
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curves of the engine are unusual. The engine produces peak torque and almost maximum power at a relatively low RPM, and from there to the
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cars were outlawed from rallying because they were too powerful (rumored to have reached 600 hp), too fast and too dangerous, the
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limit only the displacement and air intake mouth dimension. However, in 2006 air restrictors (as well as rev limiters) were used by
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the plates were singled out as impeding ability to pass, a criticism contradicted by the use of restrictor plates in a
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series began racing at Talladega, the plates were implemented, in keeping with their use at Daytona.
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have restrictors based on precalculated tables depending on the type and size of the engine and fuel
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because of concerns over speed after the circuit was repaved and reconfigured to 28 degree banking.
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also enforced restrictor plates at their events at the two tracks. In 1992, when the
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NASCAR.com – Rusty Wallace hits 228 mph in Talladega trial – June 10, 2004
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517:(known now as the ISCARS series with its new ownership) used restrictor plates at
761:"Monster Energy Series to forgo restrictor plates at Daytona, 'Dega | NASCAR.com"
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that were far higher than registered on restrictor plate tracks. Drivers such as
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would be insane to think we could have a pack of cars out there doing that."
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734:"NASCAR's change to fuel injection won't mean the end of restrictor plates"
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combines both LMP1 and LMP2 into a single LMP class on all races except
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IMSA/ALMS Competitor Bulletin #10-01: Technical Specifications, 2010
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had about 250 hp in 1987). But with development in the 1990s,
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used on the cars cannot keep them on the ground above 204 mph.
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cars were rumored to have reached 405 hp or more. So the
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Device installed at the intake of an engine to limit its power
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had 88 lead changes, but the 88th – the race-winning pass by
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fans call "restrictor plate racing". This is similar to the
774:"Top 10 NASCAR Crashes That Changed Racing (With Videos!)"
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broke 35 official lead changes in both of its 1971 races.
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The last race with the original restrictor plates was the
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two subsequent superspeedway races were run with smaller
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Many other racing series use additional air restrictors.
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The third use came in 2000. Following fatal crashes of
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However, restrictor plates were not initially used for
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Starting in 2022, restrictor plate rules were used for
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the torque drops and the power does not increase much.
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In 2016, following a series of uncompetitive races at
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to facilitate the transition to a new engine formula.
711:"NASCAR takes 'really big step' with fuel injection"
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This means that the rally version of a car like the
60:. Unsourced material may be challenged and removed.
592:The competitive quality of restrictor plate racing
407:sits in the same place as the former carburetors.
513:result in restrictor plates at other tracks. The
610:– was on the last lap of the third attempt at a
336:have mandated the use of restrictor plates at
136:Artist rendering of a NASCAR restrictor plate
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565:(who finished seventh), and two charges by
465:The second use came following the crash of
509:NASCAR's concerns with speeds because of
120:Learn how and when to remove this message
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352:at Talladega that involved the car of
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542:New Hampshire International Speedway
494:for all NASCAR-sanctioned races and
58:adding citations to reliable sources
597:increase in positional passing; at
732:Demmons, Doug (October 23, 2011).
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500:Automobile Racing Club of America
381:have cited data showing that the
357:plate at the end of the season.
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661:Michigan International Speedway
188:, 710cc, 20 mm restrictor.
45:needs additional citations for
616:Daytona International Speedway
338:Daytona International Speedway
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148:is a device installed at the
612:green-white-checkered finish
425:Reason for restrictor plates
192:Deutsche Tourenwagen Masters
680:Formula SAE Rules 2019 v1.0
586:Indianapolis Motor Speedway
295:Mitsubishi Lancer Evolution
278:engines in all categories (
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526:Camping World Truck Series
344:since 1988, and until the
202:FIA GT1 World Championship
270:mandated restrictors for
204:) and other series using
780:(retrieved 10 Aug 2010)
599:Talladega Superspeedway
578:Talladega Superspeedway
475:Talladega Superspeedway
460:2006 Formula One season
342:Talladega Superspeedway
301:It also means that the
215:American Le Mans Series
164:A few top classes like
511:power-to-weight ratios
453:, where he ran a 1969
419:Atlanta Motor Speedway
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816:Auto racing equipment
194:, 4000cc, 470 hp
182:, 2000cc, 215 hp
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656:his way around me."
504:Busch Grand National
375:Texas Motor Speedway
54:improve this article
739:The Birmingham News
515:Goody's Dash Series
498:for Cup races. The
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230:12 Hours of Sebring
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696:2010-12-05 at the
555:2000 Dura Lube 300
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69:"Restrictor plate"
811:Engine technology
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330:NASCAR Cup Series
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383:roof flaps
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180:Formula 3
713:. NASCAR
694:Archived
361:such as
316:In 1995
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492:Daytona
469:at the
449:at the
288:Group N
284:Group A
264:Group A
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249:Group B
94:scholar
644:, and
441:, and
430:NASCAR
324:NASCAR
303:torque
247:After
150:intake
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654:drive
307:power
200:(now
101:JSTOR
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747:2013
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328:The
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