Equipping the proper size of exhaust pipe on your car is important, as an incorrectly sized pipe may lead to backpressure and increased engine heat, which are things that reduce torque and horsepower. The key to knowing whether you have the proper diameter of exhaust pipe equipped on your car is the size and power of your engine. Choose the correct size of exhaust pipe by reviewing your car's engine specifications.
Review the size of your engine by consulting your automobile's owner's manual.
Review the horsepower of your engine by consulting your automobile's owner's manual. If you do not have your owner's manual, take your car to a professional mechanic and ask that they determine the specifications of your engine.
Determine the correct diameter of exhaust pipe you should use on your car by consulting a general guide for pipe sizing. As a rule of thumb, an engine with 150 to 200 cubic inches of displacement (CID) that produces 100 to 150 horsepower (HP) should be paired with a 2 to 2 1/4-inch diameter pipe if you are using a single exhaust system or a 2-inch pipe if you are using a dual exhaust system. An engine with 200 to 250 CID that produces 100 to 200 HP should be paired with a 2 1/4 to 2 1/2-inch pipe with a single exhaust system or a 2 to 2 1/4-inch pipe with a dual exhaust system. An engine with 250 to 300 CID that produces 150 to 250 HP should be paired with a 2 1/2 to 3-inch pipe with a single exhaust system or a 2 to 2 1/2-inch pipe with a dual exhaust system. An engine with 300 to 350 CID that produces 200 to 350 HP should be paired with a 2 1/2 to 3-inch pipe with a single exhaust system or a 2 1/4 to 2 1/2- inch pipe with a dual exhaust system. An engine with 350 to 400 CID that produces 250 to 550 HP should be paired with a 3 to 4-inch pipe with a single exhaust system or a 2 1/2 to 3-inch pipe with a dual exhaust system
