A. Only the 14 inch Flowmaster (part #53545-10) and the Schoenfeld (part # 14272735-78) mufflers will be permitted unless otherwise notified in writing prior to any event and subject to rule 15.3-B. The specified mufflers must remain unaltered from the manufacturer.
B. Several tracks have a locally enforced decibel rule, which preempt any particular muffler rule. In those instances the rules may be enforced by local government agencies. Track restriction decibel rules preempt utilizing the required mufflers in sub-section 15.3.A.
C. Titanium, carbon fiber and/or any other type of exotic material mufflers will not be permitted.
D. All mufflers must be securely mounted. Mufflers that are mounted with pop rivets and/or sheet metal screws will not be permitted.
E. Any muffler changes after the car has been through inspection will not be permitted. Mufflers used in qualifying must be used through the entire racing program. The only changes that will be permitted will be at the discretion of the World of Outlaws NOS Energy Drink Sprint Cars Series Director. Physical damage from a crash and/or other incident will permit a change, but then the car must be inspected again.
F. The mufflers must remain attached to the headers at all times. All muffler and header components must remain intact and operating. If the muffler becomes disconnected from the header and/or failures to operate it could result in disqualification from that race. If the muffler and/or header is damaged from and/or altered from track debris, a crash and/or a physical defect and/or no muffler components were lost and/or missing the penalty will be at the discretion of the World of Outlaws NOS Energy Drink Sprint Cars Series Officials.
G. Any muffler and/or header that has been altered in an attempt to gain a competitive advantage will not be permitted into competition and could result in disqualification.
H. All muffler rules and/or decibel (DBA) constraints are subject to state and local regulations as well as monitoring. World of Outlaws Series Sprint Car Officials will aid in enforcing the rules and regulations of those agencies.
I. When qualifying, any car determined to be in excess of the Decibel limit(s) set by either the track and/or any local agency, will receive only one (1) lap of qualifying at the end of time trials and the highest qualifying position the car may achieve is 50% plus one (1) of the field (50%+1).  If the car pulls off and no time is recorded, the car will be permitted one (1) lap at the end of time trials. If during that attempt the car remains louder than the limit it will result in an automatic disqualification.

2022 World of Outlaws NOS Energy Drink Sprint Car Series Muffler Rules

Track Location Muffler Rule
Volusia Speedway Park Barberville, FL Mufflers Not Required
Magnolia Motor Speedway Columbus, MS Mufflers Not Required
Revolution Park Monroe, LA Mufflers Not Required
Cotton Bowl Speedway Paige, TX Mufflers Not Required
Thunderbowl Raceway Tulare, CA Required: DBA Rule (Schoenfeld 14272735-78 is legal)
Merced Speedway Merced, CA Required: DBA Rule (Schoenfeld 14272735-78 is legal)
Ocean Speedway Watsonville, CA Required: DBA (Must use Flowmaster 53545-10)
Bakersfield Speedway Bakersfield, CA Required: DBA Rule (Schoenfeld 14272735-78 is legal)
Perris Auto Speedway Perris, CA Required: DBA Rule (Schoenfeld 14272735-78 is legal)
Vado Speedway Park Vado, NM Required: WoO Muffler Rule
Lawton Speedway Lawton, OK Required: WoO Muffler Rule
Devil’s Bowl Speedway Mesquite, TX Required: WoO Muffler Rule
US 36 Raceway Osborn, MO Mufflers Not Required
Lake Ozark Speedway Eldon, MO Mufflers Not Required
Federated Auto Parts Raceway at I-55 Pevely, MO Mufflers Not Required
Tri-City Speedway Pontoon Beach, IL Mufflers Not Required
Tri-State Speedway Haubstadt, IN Mufflers Not Required
Bristol Motor Speedway Bristol, TN Mufflers Not Required
Eldora Speedway Rossburg, OH Mufflers Not Required
Lincoln Speedway Abbottstown, PA Mufflers Not Required
Williams Grove Speedway Mechanicsburg, PA Mufflers Not Required
Bridgeport Speedway Swedesboro, NJ Mufflers Not Required
Attica Raceway Park Attica, OH Required: Must use Schoenfeld 14272735-78
Sharon Speedway Hartford, OH Mufflers Not Required
Atomic Speedway Chillicothe, OH Mufflers Not Required
Lawrenceburg Speedway Lawrenceburg, IN Required: WoO Muffler Rule
River Cities Speedway Grand Forks, ND Mufflers Not Required
Huset’s Speedway Brandon, SD Mufflers Not Required
Knoxville Raceway Knoxville, IA Required: Must use Schoenfeld 14272735-78
Beaver Dam Raceway Beaver Dam, WI Mufflers Not Required
Huset’s Speedway Brandon, SD Mufflers Not Required
Cedar Lake Speedway New Richmond, WI Mufflers Not Required
34 Raceway West Burlington, IA Mufflers Not Required
Wilmot Raceway Wilmot, WI Mufflers Not Required
Attica Raceway Park Attica, OH Required: Must use Schoenfeld 14272735-78
Eldora Speedway Rossburg, OH Mufflers Not Required
Port Royal Speedway Port Royal, PA Required: Must use Schoenfeld 14272735-78
Williams Grove Speedway Mechanicsburg, PA Mufflers Not Required
Weedsport Speedway Weedsport, NY Mufflers Not Required
Federated Auto Parts Raceway at I-55 Pevely, MO Mufflers Not Required
Knoxville Raceway Knoxville, IA Required: Must use Schoenfeld 14272735-78
Jackson Motorplex Jackson, MN Mufflers Not Required
River Cities Speedway Grand Forks, ND Mufflers Not Required
Red River Valley Speedway West Fargo, ND Mufflers Not Required
Skagit Speedway Alger, WA Required: DBA Rule (Schoenfeld 14272735-78 is legal)
Grays Harbor Raceway Elma, WA Required: DBA Rule (Schoenfeld 14272735-78 is legal)
Silver Dollar Speedway Chico, CA Required: DBA Rule (Schoenfeld 14272735-78 is NOT legal)
Keller Auto Speedway Hanford, CA Required: DBA Rule (Schoenfeld 14272735-78 is legal)
Placerville Speedway Placerville, CA Required: Must use Flowmaster 53545-10 or Spin Tech 1545
Eldora Speedway Rossburg, OH Mufflers Not Required
Sharon Speedway Hartford, OH Mufflers Not Required
Williams Grove Speedway Mechanicsburg, PA Mufflers Not Required
Port Royal Speedway Port Royal, PA Required: Must use Schoenfeld 14272735-78
I-80 Speedway Greenwood, NE Mufflers Not Required
Lakeside Speedway Kansas City, KS Mufflers Not Required
The Dirt Track at Charlotte Concord, NC Mufflers Not Required