Frequently Asked Questions

1. What makes Flowmaster mufflers different?
Flowmaster’s patented “chambered” design is what sets it apart from any other muffler. The theory behind the design is based on basic principles of physics. By splitting the exhaust stream (exhaust pulses & sound energy) and then recombining them in another chamber, the collision of energy cancels the sound waves, which creates a low pressure area in its place. This resulting low pressure area then helps scavenge/accelerate the following pulses into the muffler and out the tailpipe resulting in a more efficient and cleaner burn, which means more power.
2. How does Flowmaster compare to straight through mufflers?
Straight through mufflers are constructed using a perforated flow tube wrapped with either steel wool or fiberglass to simply absorb sound. This type of technology generally does the least in reducing sound, especially in the cab of the vehicle and cannot control drone. The packing materials can burn out fairly quickly resulting in a shortened life span and increasing sound levels both inside and outside the vehicle. The Flowmaster® designs use the sound energy to cancel itself out and not packing materials to burn out. Therefore will maintain its sound control over the life of the product. Also, Flowmaster has models that are designed to specifically reduce or remove the interior drone from most applications, if desired by the customer.
3. How do Flowmaster mufflers rate on a flowbench (CFM)?
Many muffler manufacturers advertise, test and rate the performance of their mufflers with the use of a flow bench. The problem with this methodology is that a flow bench produces a steady, low temperature stream of air and lacks the acoustical and thermal dynamics that are produced by an internal combustion engine. Flowmaster designs, tests, and proves its products under real world conditions in the dyno cell, at the track and on the road. After all, when was the last time you raced a flow bench?
4. What does a Flowmaster sound like?
The Flowmaster sound is unique to itself and is very different from that of glass packs or other packed style mufflers. The Flowmaster sound can best be described as a deep smooth sound and has proven to be the preferred and most recognized sound of most automotive enthusiasts. Flowmaster offers many different levels of sound from mild, to moderate, to aggressive. In general, the 60 series, 70 Series and Super 50 Series mufflers are milder with reduced interior sound. The 50 Series Delta Flows are moderate, and the 40 Series have a more aggressive tone.
5. What is the difference between a 40 series and a 50 series muffler?
The 50 series mufflers are incorporates an internal resonant chamber that helps reduce interior drone in the cab area of your vehicle, and provides a slightly milder exterior tone than the 40 series. The 40 series has a more aggressive tone and sound level. It does not have a built-in resonant chamber and will generally resonate or “drone” inside the vehicle, around 1800-2000 rpm, and again around 2400-2600 rpm. So if that’s your cruising rpm at highway speeds and don’t want any drone, you may want to consider a 50, 60 or 70 performance muffler.
6. How do I select the correct Flowmaster?
The sound of your exhaust is much like music; we all have different preferences so it’s important that the system be “tuned” to what you like. With the Flowmaster family of products we can help accomplish this by answering the questions below. This approach will allow you to choose the best product to suite your needs and expectations
1. What is the vehicle year, make, and model?
2. Which engine do you have or how much horsepower does it produce?
3. What is the vehicle used for? i.e.: daily driver, race, towing etc.
4. Preferred sound levels (interior and exterior?)
5. How are the space requirements?
6. Would you like a complete exhaust system or universal pipe kit if available? Single or dual outlet?
7. Will I lose power going from a 40 series to a 50 series, or to a 70 series?
No. Flowmaster engineers have designed each series of mufflers with maximum efficiency in mind. The differences between the various muffler series are in the varying sound levels produced both inside and outside your vehicle. This is why it is so important to take the time to carefully choose the right product that will suit your individual needs and sound preference.
8. What is “Delta Flow” technology?
This patented technology is an improvement over the original Flowmaster® design that provides improved scavenging and additional reduction of resonance inside the vehicle. This advancement was born out of Flowmaster’s extensive involvement in racing and its commitment to Research & Development. The Delta Flow design incorporates additional delta deflectors placed at precise angles, different spacing within .004-inch tolerance and in some series different sizes. The result is improved performance while maintaining a pleasant tone both inside and outside the vehicle, along with a reduction of interior resonance.
9. What is a Laminar Flow Technology Muffler?
Laminar Flow Technology mufflers are the latest generation in the Flowmaster family of performance products featuring innovative, patented technology. Flowmaster Laminar Flow Technology mufflers actually accelerate the exhaust flow as it passes through the tapered core and expands into the large volume outer core area in multiple layers. This all adds up to a design that delivers distinct torque and horsepower improvements over straight through designs, along with a deep mellow exhaust tone. See page 7 of the Flowmaster Catalog for more information.
10. What kind of performance gains can I expect when installing a Flowmaster system on my vehicle?
Performance gains will vary dependent upon your application. The more power the engine makes, the bigger the gains will be. Generally in full size vehicle applications, a 5-7% gain in power is fairly typical, while 1-2 mpg can be achieved. That is if you can keep your foot out of the gas to hear that Flowmaster sound.
11. How can I be sure that I’m buying a Flowmaster muffler?
The Flowmaster name is embossed in every muffler case that Flowmaster builds. If it doesn’t say Flowmaster on the case, it’s not a real Flowmaster muffler. Buyer beware; Flowmaster knock-offs may look similar, but may not perform or sound the same, and often have a high defect return rate.
12. What size exhaust tubing should I use for my street application?
Choosing the proper diameter of the tubing for your exhaust system is as important as selecting the right muffler. Your tubing diameter choice will affect the sound level and performance characteristics of the muffler, but keep in mind that bigger is not always better. Using tubing that is too large can actually hinder exhaust scavenging by slowing the velocity of exhaust pulses in the tubing resulting in a loss of torque. And torque is what moves the car. As a general rule, most stock to mildly modified V8 powered street applications will use 2.25” – 2.5” diameter tubing. There are many variables that need to be taken into consideration when choosing the correct tubing size for your application, such as: engine technology (flat head engines vs 60’s engines vs present day engines) cubic inch, catalytic convertors, head flow, vehicle weight, how the vehicle is driven and numerous others. Light to moderately modified street applications will generally use 2.5” and rarely some can use dual 3.00” tubing, again depending on the above named factors, sound desired etc. *We generally don’t encourage the use of dual 3” exhaust systems for just street use. Here are some guidelines for exhaust tubing size vs power that can be used for street applications: Street V8 applications – dual exhaust 2” tubing200 hp – 250 hp 2.25” tubing 250 hp – 375 hp 2.5” tubing 350 hp – 500 hp *3” tubing 500 hp – 600 hp
13. Do I need to install an “H” pipe in my dual exhaust system?
Flowmaster strongly recommends using a crossover tube, otherwise known as an “H” pipe or balance pipe on all true dual exhaust systems. The crossover pipe equalizes the exhaust pressure and allows the sounds waves to communicate between both banks of the engine. Not only does this usually improve torque in the low to mid rpm range, it also creates a deeper mellower tone both inside and outside of the vehicle and helps eliminate “back-rap” on deceleration.
14. Is an “X” pipe better than an “H” pipe?
Flowmaster has performed extensive testing and determined that the “H” and “X” pipes generally delivers no significant difference in performance, but does affect tone. The “X” pipe will change the sound to a higher pitched tone. Flowmaster Scavenger “X” pipes however do increase power and torque through use of their patented D-port technology and retains the deep Flowmaster muffler tone that is desired by most performance enthusiasts.
15. Will my late model vehicle run better if I replace the single inlet muffler with a true dual exhaust system?
Flowmaster does not recommend replacing factory single inlet exhaust systems with a “true dual” system on computer controlled vehicles. The computers in most late model vehicles may not be able to compensate with the fuel needed when increasing the exhaust flow, and may void your factory warranty and emission compliance. Flowmaster’s dual outlet kits will give you the look of a “true dual” system, while optimizing the vehicles performance.
16. Do I need to run tailpipes after the mufflers?
Yes, we recommend running a minimum of 12” tailpipe after the muffler and strongly recommend running the tailpipes out from under the car in street applications. This does two things; it directs the potentially harmful exhaust fumes away entering the drivers compartment, as well as helps minimize the sound transmitted into the cab area of the vehicle.
17. What is Flowmaster’s warranty?
All Flowmaster stainless steel products are covered by our lifetime warranty to the original purchaser. Flowmaster aluminized products have a 3-year limited warranty against defective materials and workmanship. This warranty excludes all race products regardless of material used. All warranty related returns must be processed through original retail outlet with original sales receipt.
18. What materials are used to build Flowmaster Mufflers?
All Flowmaster® chambered products are fully MIG welded and built from either 16-gauge aluminized steel or 409 stainless steel for durability and value. Select part numbers of the 40 and 50 series are offered in 409 stainless steel (check with the tech line for updates.) The internal construction of all Laminar flow mufflers is 409 stainless steel and the dBX® line of mufflers utilizes a 304 stainless steel outer casing that can be polished to a high luster. The Super HP2 mufflers are available in either 409 stainless steel or a polishable 304 stainless steel case.
19. Is stainless steel, a better material for manufacturing exhaust products than aluminized steel?
Not necessarily, it really depends on where you live geographically and the vehicle application. Through years of field testing under street and racing conditions, we’ve found in many applications, aluminized steel is just as durable as stainless steel at a slightly reduced cost. If you live where road salt can come in contact with your vehicle on a regular basis, a stainless steel muffler is the right choice. For most racing and high performance applications where daily driver chores are not common, aluminized mufflers are a great choice to consider.
20. Will installing a Flowmaster Cat-back exhaust system void my vehicle’s factory warranty?
There may be some modifications that have the potential to void a vehicle’s factory warranty, but modifying the exhaust system after the catalytic converter is not one of them. All Flowmaster® exhaust systems are designed vehicle specific and do not violate manufacturers factory warranty. If you’re having problems regarding this issue, please contact for more information regarding consumer’s rights on performance aftermarket parts.
21. Are Flowmaster Performance Cat-back exhaust systems and mufflers street legal?
Flowmaster has fifteen different styles of performance mufflers allowing customers the opportunity to choose a FLOWMASTER signature sound ranging from mild to moderate or aggressive to accommodate the customer’s local and state laws.

Please note: Using FLOWMASTER performance exhaust in conjunction with other performance modifications i.e. high flow air filters, air boxes, headers etc., can cause an increase in exhaust dB’s that could exceed allowable local limits. For additional information regarding exhaust laws please go to

If you have further questions, please call (707) 544-4761 or visit our website.
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