BMW M3/M4 Exhaust – Let’s Discuss the Different Components

Downpipes:

Stock downpipes have catalytic converters. In order to increase sound and power, you can replace stock DP with aftermarket catless or high flow catted downpipes. One thing to keep in mind is that aftermarket downpipes will not pass emission and will throw a CEL (even catted ones). You can hide the code by using a piggyback like the Burger Tuning JB4 stage 2 or a flash tune.

Catless downpipes are louder than catted, offer more air flow and power. Only downside is fuel smell outside the car if it has been on idle for some time. Good news is that the M3/M4 comes with secondary cats so fuel smell is barely noticeable. Even though it is not a popular option, some choose to go with high flow catted to completely eliminate the smell.

Stock downpipes come with a flex fuel section that expands and help when the pipes get really hot. Catless downpipes do not have this problem, but some aftermarket companies choose to keep the flex section for added reliability.

Another option that helps with heat is ceramic coating. If you track your car often, it is recommended that you choose this option for best results. Different ceramic coatings are offered with Swain coating being the best.

Midpipes:

One problem with the stock exhaust is raspiness; M3/M4 is not one of the best sounding sports cars. Fortunately this problem can be fixed when replacing the stock midpipes with a single one. Another benefit of the single mid pipe is the extra power that Dynos are showing.

If you are not bothered by exhaust rasp and are looking for a more aggressive sound, most companies offer the dual midpipes for a louder more aggressive tone. Some think the dual midpipes are too loud, fortunately some companies offer a resonated option that will give you a more aggressive tone than a single midpipe but still be quieter than non-resonated dual pipes.

Rear Section:

Replacing the rear section will change the tone of your exhaust the most. Lots of options are available and they are all different. Active Autowerke offers a 3 muffler setup for the cleanest possible sound, paired with a single midpipe this exhaust will eliminate rasp completely. One downside to this exhaust is that it will not be as aggressive as other exhausts on the market.

If you are looking for a deep and aggressive sound, options like REMUS and Fabspeed are available to you. These exhausts will not be loud during casual driving but once you go wide open throttle, they will shine.

GThaus offers the Meisterschaft GT2 exhaust, this option is one of the most aggressive on the market. This kind of exhaust is for users looking for an eye catcher system.

Another factor to consider is weight. Although most aftermarket exhausts are lighter than stock, some companies take it a step further. Burger Tuning achieves this result by offering an all-aluminum exhaust. If you do not mind paying extra money for a lighter exhaust, you can get a titanium system like GTHaus Meisterschaft, Akrapovic or the M-performance exhaust.

Exhaust Valves:

Stock exhaust comes with valves; it will control the sound level of your BMW M3 / M4 exhaust. Stock valves cannot be controlled by user (unless you purchase an exhaust flap module like the one BMS offers). Some aftermarket companies use the stock valves on their system; others give the user the ability to control these valves.

Tips:

Last but not least are the exhaust tips, stock tips are tiny and do not give the M3/M4 the aggressive look it deserves. All aftermarket exhausts are offered with upgraded tips and the different options are endless. Some companies also offer upgraded tips for the stock exhaust in case user decides to keep the rear section and just upgrade the look of the tips.