Restrictor plate
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A restrictor plate or air restrictor is a device installed at the
Racing series
A few top classes like Formula One limit only the displacement and air intake mouth dimension. However, in 2006 air restrictors (as well as rev limiters) were used by Scuderia Toro Rosso to facilitate the transition to a new engine formula.
Many other racing series use additional air restrictors.
- Formula 3, 2000cc, 215 hp
- Formula SAE, 710cc, 20 mm restrictor.[1]
- Deutsche Tourenwagen Masters, 4000cc, 470 hp
- FIA GT Championship (now FIA GT1 World Championship) and other series using FIA GT regulations
- Le Mans Serieshave restrictors based on precalculated tables depending on the type and size of the engine and fuel
- The ALMS in the 2010 season combines both LMP1 and LMP2 into a single LMP class on all races except 12 Hours of Sebring and Petit Le Mans; LMP1-categorized cars use a 5% smaller air restrictor compared to LMP2- categorized cars to balance performance in the races[2]
- The ALMS in the
Rallying
After
).This means that the rally version of a car like the Mitsubishi Lancer Evolution 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).
It also means that the torque and power 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 rev limiter the torque drops and the power does not increase much.
In 1995
NASCAR
The
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 such as
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
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 last race with the original restrictor plates was the 2019 Daytona 500; 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.[5]
Starting in 2022, restrictor plate rules were used for Atlanta Motor Speedway because of concerns over speed after the circuit was repaved and reconfigured to 28 degree banking.
Reason for restrictor plates
The second use came following the crash of
NASCAR's concerns with speeds because of
However, restrictor plates were not initially used for
The third use came in 2000. Following fatal crashes of
Rusty Wallace tested a car at Talladega Superspeedway 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).[7] 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."[7]
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.
The competitive quality of restrictor plate racing
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 increase in positional passing; at
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 1988 Daytona 500, 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 Bobby Allison, Darrell Waltrip, Neil Bonnett, and Buddy Baker.
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 drive his way around me."
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 Michigan International Speedway broke 35 official lead changes in both of its 1971 races.
References
- ^ Formula SAE Rules 2019 v1.0
- ^ IMSA/ALMS Competitor Bulletin #10-01: Technical Specifications, 2010 Archived 2010-12-05 at the Wayback Machine
- ^ Aumann, Mark. "NASCAR takes 'really big step' with fuel injection". NASCAR. Retrieved 30 January 2012.
- ^ Demmons, Doug (October 23, 2011). "NASCAR's change to fuel injection won't mean the end of restrictor plates". The Birmingham News. Retrieved February 16, 2013.
- ^ "Monster Energy Series to forgo restrictor plates at Daytona, 'Dega | NASCAR.com".
- ^ "Top 10 NASCAR Crashes That Changed Racing (With Videos!)", Popular Mechanics (retrieved 10 Aug 2010)
- ^ a b NASCAR.com – Rusty Wallace hits 228 mph in Talladega trial – June 10, 2004