If you’re looking to squeeze a few extra ponies out of your 335i, upgrading to some of the best downpipes for your N54 engine might be the best place to start.

Turbocharged engines like the one in your BMW offer plenty of new ways to make more power than the factory intended. After all, sometimes even the factory takes advantage of this offering one single engine with some minor changes and multiple levels of factory horsepower. When it comes time for you to modify your own car, one of the most important places to start is the downpipe. A new downpipe for your BMW N54 engine can unlock more power, improve turbo response, and add more volume to your exhaust. So here are some of the best N54 downpipes for your E92 or even your 1 Series.

AQXReight - E92 BMW 335iS Downpipes

The downpipes from AQXreight are made from 304 stainless steel, which should lead to a long life for the system. Like most of the others, they bypass the catalytic converter, something you may not want to do, but it also has a bung for the rear O2 sensor so at least you'll have somewhere to plug it in. Because BMW loves to use the same engine in many models, these N54 downpipes fit your E92 335i, but will also fit the 135i, various versions of the X6 and even Z4. The manufacturer says that up to 28 HP can be expected along with more torque, putting it on the list of best N54 downpipes. These 335i downpipes, though, are made from several bends cut and welded together, which may restrict flow when compared with some of the smoother models. A cast V-band flange for the outlet ensures a solid factory-like connection between the turbocharger and exhaust system and helps prevent leaks down the road.

Pros: 304 Stainless
Cons: Multiple pieces, some lower-cost options may have fitment troubles


Fabspeed Race Downpipes BMW 335i N54 08-10

These N54 downpipes from Fabspeed are meant for off-road and racing use. That doesn't mean that they're different, but that they don't have a catalytic converter inline. Instead, they have what look to be some very smooth bends despite being made from multiple pieces. Mandrel bends for smoothness and water jet cut flanges for a precise fitment are all part of what these downpipes offer. The 2.75” tubing from the turbo outlet to the end allows for more flow, less back pressure, and up to 32 horsepower over the factory offerings, should your engine be capable of the extra fueling. Fabspeed guarantees its components against manufacturing defects for life, even if you sell your car to someone else down the road. The downpipes for your BMW 335i come with installation hardware and everything you should need to get them in place and ready to go.

Pros: Lifetime warranty, full 2.75” diameter tube length
Cons: For competition use only


aFe Elite Twisted Steel Race Series Downpipes

aFe Power Race downpipes offer a 3” tube for maximum flow and a claimed 17 HP and 32 lb.-ft increase over the factory performance. These N54 downpipes are TIG welded with a brushed finish to give them a more appealing look under the hood of your vehicle, and 3/8” stainless steel flanges to help offer a leak-free and durable exhaust downpipes. For 135i and 335i models, all brackets and hardware are included to make these parts easy, or at least hassle-free, to install. All aFe exhaust systems are engineered and manufactured in California, for buyers looking to keep their spending closer to home. These downpipes for the N54 engine also have factory O2 sensor mounting locations, so your fuel management system will still work as it should.

Pros:3-inch diameter tubing, TIG welded
Cons: Not legal for street use


Racing Dynamics Race Downpipes with Smooth Bent Pipes

This is the only N54 downpipe on the list that uses one solid piece of tubing instead of being welded together from multiple pieces. Racing Dynamics has found a pipe bender that can make the entire 335i downpipe in one piece and that means smoother airflow and more performance potential for your engine. Every weld is a spot where airflow is disturbed, which is why this is a better design. The company claims typical power gains are 20-25 HP, though that will depend on what else you've done to your engine and the 3” tube allows plenty of headroom for more. Less heat trapped in the turbocharger means potentially longer life for that expensive part, while the lowered back pressure should let the turbos spool more quickly to get rid of turbo lag, making this one of the best N54 downpipes on the market today. To simplify installation, all gasket’s and bolts are included to fit your 135i, E92 335i, or even a 1M.

Pros: made from a single piece of tube
Cons: Doesn't offer a catalytic converter option


aFe Elite Twisted Steel Downpipe with Catalyst

This is the only that is 48-state legal, which alone might make it your best choice from our list of best downpipes for the N54. This aFe Elite downpipe comes equipped with a high-flow catalytic converter, meaning your tailpipe emissions are as clean as the day your BMW rolled out of the factory. This also means you don't need to worry about your 335i downpipe causing a constant check engine light. This pipe starts with 2.5” piping and widens to 3” after the cat to help increase exhaust velocity, which means more torque. Tig welded for long life and made from mandrel bent 304 stainless steel tubing for corrosion resistance, and to help prevent cracking. Noise will be slightly muffled compared with a catless pipe, but that is often a good thing, especially if you already have louder mufflers. Bungs for both O2 sensors keep everything electronic happy which means a smile on your face each time you go for a drive.

Pros: high-flow catalytic converter
Cons: Cat makes item more expensive


What is a Downpipe?
The downpipe is the name for the piece of the exhaust that goes from the turbocharger outlet to join the exhaust system under your car. It's a pipe that goes down, and that's where the name comes from. It's usually home to the first catalytic converter since the part is the first bit after the turbocharger and cats work best when there is the most heat available. While the engine side is normally bolted to the turbocharger, the exhaust side is attached to the under-car exhaust with a flexible pipe that allows the engine to move on its mounts. Using downpipes also allows a manufacturer to use the same exhaust system under the vehicle even if multiple engines are offered. All that's needed is the right downpipe.

What does a Downpipe Do?
OEM components, even on a BMW, are a balance of cost, emissions, power, fitment, ease of assembly, and countless other considerations. That leads to thinner diameter tubing, more restrictions, and an easy place to upgrade. The restrictions slow your turbocharger spooling, adding lag. The restrictions can get too high, meaning you hit a choke point and a horsepower limit. An aftermarket downpipe for your N54 allows for more flow and less restriction, allowing your other upgrades, and even the factory engine, to shine. More power, less lag. What's the downside? Most of these parts don't offer a catalytic converter, which means that they're not legal for road use. Even if your state doesn't have emissions testing. Perfect for your track car or get one with a cat for your daily driver.

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