403:; 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.
25:
577:, 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.
382:, 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
122:
559:
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.
518:
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.
585:
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
558:
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
446:
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
349:
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
517:
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
386:
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
569:
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
541:
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
607:
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;
470:
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
395:
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
345:
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
390:
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
612:
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.
377:
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
421:
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
434:, 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
616:
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
286:
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).
640:
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
590:
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
621:, 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
309:
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.
475:(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
510:
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.
682:
648:
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
241:
256:
141:
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
244:
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
550:
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
668:
749:
298:
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
145:, to limit top speed to provide equal level of competition, and to lower costs; insurance purposes have also factored in for motorsports.
240:
cars were outlawed from rallying because they were too powerful (rumored to have reached 600 hp), too fast and too dangerous, the
157:
limit only the displacement and air intake mouth dimension. However, in 2006 air restrictors (as well as rev limiters) were used by
679:
699:
89:
225:; LMP1-categorized cars use a 5% smaller air restrictor compared to LMP2- categorized cars to balance performance in the races
61:
530:
214:
451:, where teams using V10 engines were run with air restrictors and rev limiters while teams running V8 engines were not.
68:
608:
the plates were singled out as impeding ability to pass, a criticism contradicted by the use of restrictor plates in a
488:
108:
42:
781:
392:
359:
75:
722:
649:
804:
604:
480:
326:
46:
609:
423:
57:
600:
180:
762:
574:
283:
799:
514:
190:
495:
series began racing at Talladega, the plates were implemented, in keeping with their use at Daytona.
387:
teams mastered the nuances of this kind of racing and improved their cars (and drivers) accordingly.
210:
have restrictors based on precalculated tables depending on the type and size of the engine and fuel
194:
410:
because of concerns over speed after the circuit was repaved and reconfigured to 28 degree banking.
587:
566:
484:
463:
448:
330:
203:
35:
507:
503:
407:
82:
499:
379:
363:
8:
727:
592:
218:
186:
158:
337:
for Cup Series only. The plates were put into use in 1988 as a result of a wreck in the
543:
306:
538:
491:
also enforced restrictor plates at their events at the two tracks. In 1992, when the
318:
199:
142:
782:
NASCAR.com – Rusty Wallace hits 228 mph in Talladega trial – June 10, 2004
618:
459:
439:
400:
338:
334:
506:(known now as the ISCARS series with its new ownership) used restrictor plates at
750:"Monster Energy Series to forgo restrictor plates at Daytona, 'Dega | NASCAR.com"
686:
626:
526:
366:
that were far higher than registered on restrictor plate tracks. Drivers such as
295:
268:
248:
534:
492:
355:
351:
322:
207:
793:
622:
596:
570:
would be insane to think we could have a pack of cars out there doing that."
562:
555:
551:
476:
467:
455:
443:
431:
367:
342:
222:
121:
723:"NASCAR's change to fuel injection won't mean the end of restrictor plates"
630:
264:
260:
634:
547:
472:
435:
427:
383:
299:
174:
154:
217:
combines both LMP1 and LMP2 into a single LMP class on all races except
522:
580:
371:
168:
680:
IMSA/ALMS Competitor Bulletin #10-01: Technical Specifications, 2010
24:
251:
had about 250 hp in 1987). But with development in the 1990s,
276:
272:
252:
245:
237:
418:
374:
used on the cars cannot keep them on the ground above 204 mph.
291:
138:
255:
cars were rumored to have reached 405 hp or more. So the
16:
Device installed at the intake of an engine to limit its power
595:
had 88 lead changes, but the 88th – the race-winning pass by
447:
fans call "restrictor plate racing". This is similar to the
763:"Top 10 NASCAR Crashes That Changed Racing (With Videos!)"
652:
broke 35 official lead changes in both of its 1971 races.
399:
The last race with the original restrictor plates was the
471:
two subsequent superspeedway races were run with smaller
164:
Many other racing series use additional air restrictors.
521:
The third use came in 2000. Following fatal crashes of
513:
However, restrictor plates were not initially used for
406:
Starting in 2022, restrictor plate rules were used for
302:
the torque drops and the power does not increase much.
573:
In 2016, following a series of uncompetitive races at
161:
to facilitate the transition to a new engine formula.
700:"NASCAR takes 'really big step' with fuel injection"
282:
This means that the rally version of a car like the
49:. Unsourced material may be challenged and removed.
581:The competitive quality of restrictor plate racing
396:sits in the same place as the former carburetors.
502:result in restrictor plates at other tracks. The
791:
599:– was on the last lap of the third attempt at a
413:
325:have mandated the use of restrictor plates at
125:Artist rendering of a NASCAR restrictor plate
554:(who finished seventh), and two charges by
454:The second use came following the crash of
498:NASCAR's concerns with speeds because of
109:Learn how and when to remove this message
777:
775:
120:
720:
792:
341:at Talladega that involved the car of
772:
531:New Hampshire International Speedway
483:for all NASCAR-sanctioned races and
47:adding citations to reliable sources
18:
586:increase in positional passing; at
13:
721:Demmons, Doug (October 23, 2011).
697:
14:
816:
489:Automobile Racing Club of America
370:have cited data showing that the
346:plate at the end of the season.
148:
23:
650:Michigan International Speedway
177:, 710cc, 20 mm restrictor.
34:needs additional citations for
756:
742:
714:
691:
673:
662:
605:Daytona International Speedway
327:Daytona International Speedway
1:
655:
137:is a device installed at the
601:green-white-checkered finish
414:Reason for restrictor plates
181:Deutsche Tourenwagen Masters
7:
669:Formula SAE Rules 2019 v1.0
575:Indianapolis Motor Speedway
284:Mitsubishi Lancer Evolution
267:engines in all categories (
231:
10:
821:
515:Camping World Truck Series
333:since 1988, and until the
191:FIA GT1 World Championship
312:
259:mandated restrictors for
193:) and other series using
769:(retrieved 10 Aug 2010)
588:Talladega Superspeedway
567:Talladega Superspeedway
464:Talladega Superspeedway
449:2006 Formula One season
331:Talladega Superspeedway
290:It also means that the
204:American Le Mans Series
153:A few top classes like
500:power-to-weight ratios
442:, where he ran a 1969
408:Atlanta Motor Speedway
126:
805:Auto racing equipment
183:, 4000cc, 470 hp
171:, 2000cc, 215 hp
124:
645:his way around me."
493:Busch Grand National
364:Texas Motor Speedway
43:improve this article
728:The Birmingham News
504:Goody's Dash Series
487:for Cup races. The
249:Lancia Delta HF 4WD
219:12 Hours of Sebring
187:FIA GT Championship
159:Scuderia Toro Rosso
685:2010-12-05 at the
544:2000 Dura Lube 300
539:Winston Cup Series
307:Toyota Team Europe
200:Le Mans Prototypes
195:FIA GT regulations
127:
58:"Restrictor plate"
800:Engine technology
767:Popular Mechanics
319:NASCAR Cup Series
143:automobile racing
119:
118:
111:
93:
812:
784:
779:
770:
760:
754:
753:
746:
740:
739:
737:
735:
718:
712:
711:
709:
707:
695:
689:
677:
671:
666:
619:1988 Daytona 500
593:2010 Aaron's 499
565:tested a car at
460:1987 Winston 500
440:1971 Daytona 500
401:2019 Daytona 500
360:Michael McDowell
339:1987 Winston 500
335:2019 Daytona 500
213:The ALMS in the
131:restrictor plate
114:
107:
103:
100:
94:
92:
51:
27:
19:
820:
819:
815:
814:
813:
811:
810:
809:
790:
789:
788:
787:
780:
773:
761:
757:
748:
747:
743:
733:
731:
719:
715:
705:
703:
696:
692:
687:Wayback Machine
678:
674:
667:
663:
658:
627:Darrell Waltrip
583:
533:during the May
527:Kenny Irwin Jr.
416:
315:
269:World Rally Car
234:
151:
115:
104:
98:
95:
52:
50:
40:
28:
17:
12:
11:
5:
818:
808:
807:
802:
786:
785:
771:
755:
741:
713:
698:Aumann, Mark.
690:
672:
660:
659:
657:
654:
582:
579:
477:superspeedways
415:
412:
393:IndyCar Racing
356:Pocono Raceway
352:Elliott Sadler
323:Xfinity Series
314:
311:
233:
230:
229:
228:
227:
226:
208:Le Mans Series
197:
184:
178:
172:
150:
147:
135:air restrictor
117:
116:
31:
29:
22:
15:
9:
6:
4:
3:
2:
817:
806:
803:
801:
798:
797:
795:
783:
778:
776:
768:
764:
759:
751:
745:
730:
729:
724:
717:
701:
694:
688:
684:
681:
676:
670:
665:
661:
653:
651:
646:
644:
638:
636:
632:
628:
624:
623:Bobby Allison
620:
614:
611:
606:
602:
598:
597:Kevin Harvick
594:
589:
578:
576:
571:
568:
564:
563:Rusty Wallace
560:
557:
556:Bobby Labonte
553:
552:John Andretti
549:
545:
540:
536:
532:
528:
524:
519:
516:
511:
509:
505:
501:
496:
494:
490:
486:
482:
478:
474:
469:
468:Buick LeSabre
465:
461:
457:
456:Bobby Allison
452:
450:
445:
444:Dodge Daytona
441:
437:
433:
432:Bobby Allison
429:
425:
424:David Pearson
420:
411:
409:
404:
402:
397:
394:
388:
385:
381:
380:"the Big One"
375:
373:
369:
368:Rusty Wallace
365:
361:
357:
353:
347:
344:
343:Bobby Allison
340:
336:
332:
328:
324:
320:
310:
308:
303:
301:
297:
293:
288:
285:
280:
278:
274:
270:
266:
262:
258:
254:
250:
247:
243:
239:
224:
223:Petit Le Mans
220:
216:
212:
211:
209:
205:
201:
198:
196:
192:
188:
185:
182:
179:
176:
173:
170:
167:
166:
165:
162:
160:
156:
149:Racing series
146:
144:
140:
136:
132:
123:
113:
110:
102:
91:
88:
84:
81:
77:
74:
70:
67:
63:
60: –
59:
55:
54:Find sources:
48:
44:
38:
37:
32:This article
30:
26:
21:
20:
766:
758:
744:
734:February 16,
732:. Retrieved
726:
716:
704:. Retrieved
693:
675:
664:
647:
642:
639:
631:Neil Bonnett
615:
584:
572:
561:
535:Busch Series
520:
512:
497:
466:. Allison's
453:
417:
405:
398:
389:
376:
348:
316:
304:
289:
281:
265:turbocharged
261:supercharged
235:
163:
152:
134:
130:
128:
105:
96:
86:
79:
72:
65:
53:
41:Please help
36:verification
33:
635:Buddy Baker
610:Busch North
548:Jeff Burton
473:carburetors
436:Dick Brooks
428:Bobby Isaac
384:Daytona 500
300:rev limiter
215:2010 season
175:Formula SAE
155:Formula One
99:August 2010
794:Categories
706:30 January
656:References
523:Adam Petty
372:roof flaps
69:newspapers
537:and July
485:Talladega
169:Formula 3
702:. NASCAR
683:Archived
350:such as
305:In 1995
232:Rallying
202:used in
529:at the
508:Bristol
481:Daytona
458:at the
438:at the
277:Group N
273:Group A
253:Group A
246:Group A
238:Group B
83:scholar
633:, and
430:, and
419:NASCAR
313:NASCAR
292:torque
236:After
139:intake
85:
78:
71:
64:
56:
643:drive
296:power
189:(now
90:JSTOR
76:books
736:2013
708:2012
542:the
525:and
358:and
329:and
321:and
317:The
294:and
275:and
263:and
242:FISA
221:and
206:and
62:news
603:).
462:at
362:at
354:at
279:).
257:FIA
133:or
45:by
796::
774:^
765:,
725:.
637:.
629:,
625:,
546:.
479::
426:,
271:,
129:A
752:.
738:.
710:.
112:)
106:(
101:)
97:(
87:·
80:·
73:·
66:·
39:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.