Which downpipe should I get for the BMW B48 Engine? The BMW B48 is BMWs go to four-cylinder engine right now. Generally if you're upgrading your BMW B48 Downpipe, especially if you're from Europe or countries that have OPF filters installed from the factory, the first consideration you have to make is which fitment you have got in your vehicle. The B46 and B48 Downpipe upgrade is a hugely popular mod for those who are looking for bang for buck performance. In this guide, we will purely focus on the Exhaust system, mainly the downpipe. We are excited to guide you through the proces.

The downpipe is the exhaust part that directly connects to your turbo. The downpipe guides exhaust gases away from the engine and turbo. In most stock applications, the stock downpipe will also feature a Catalytic Converter. A downpipe is commonly regarded as one of the most cost effective ways to gain power together with a remap. It allows the turbo of the engine to be more effective and due to the reduced back pressure, you will also have less turbo lag. An aftermarket downpipe is commonly supplied in two options, Catless and with a High Flow Catalytic Converter. Aftermarket solutions are less restrictive than the stock downpipes. Installing a less restrictive Downpipe together with a remap (usually called a Stage 2 Remap due to the exhaust modifications), you can easily push high horsepower numbers while being relatively friendly to your wallet. A Stage 2 Remap for your BMW B48 is the best bang for buck tuning mod for those who aim for higher performance numbers.

In addition to changing the B48 Downpipe to a less restrictive version will also increase the exhaust sound levels. To most of us who chooses to go with a B48 Downpipe, this is also an added benefit. Generally, changing the B48 Downpipe while keeping the stock cat-back in place will not dramatically increase sound levels to an ear-deafening degree. Usually the B48 Downpipe modification remains silent until you increase the engine load. It will also be more noticeable during a cold start. If you choose to change the cat-back as well, we recommend to go with a Valvetronic system that is designed for Catless or High Flow Catted applications as these usually also filters out drone from a less restrictive B48 Downpipe and can be loud when you want to, but nearly as silent as OEM when you do not want the car to be as loud. They come with Flaps that can open and close with a push of a button to increase or decrease sound levels.

The BMW B46 and B48 Engines has been used in a lot of applications. For this guide, our downpipes will be applicable (but not limited) to the following cars, ranging from the UKL Front Wheel Drive platform to the flagship BMW 7 Series. We take good care to list the correct fitments, however we might miss one or two models here and there.

B48 applications with a Rear Wheel Drive and a Rear Wheel Drive based xDrive layout with the engine placed in a longitudinal direction.

• BMW 1-Serie F20 120i/125i
• BMW 1-Serie F21 120i/125i
• BMW 2-Serie F22 220i/230i
• BMW 2-Serie F23 220i/230i
• BMW 3-Serie F30 330e/330i/330iX
• BMW 3-Serie F31 330i/330iX
• BMW 3-Serie F34 GT 330i/330iX
• BMW 4-Serie F32 420i/420iX/430i/430iX
• BMW 4-Serie F33 420i/420iX/430i/430iX
• BMW 4-Serie F36 420i/420iX/430i/430iX
• BMW 7-Serie G11 730i/730Li/740e/740Le
• BMW 7-Serie G12 730i/730Li/740e/740Le

• BMW 3-Serie G20 320i/320iX/330e/330eX/330i/330iX
• BMW 3-Serie G21 320i/320iX/330e/330eX/330i/330iX
• BMW 5-Serie G30 520i/530e/530i/530iX
• BMW 5-Serie G31 520i/530i/530iX
• BMW 6-Serie GT G32 630i
• BMW X3 G01 20i/20iX/30iX
• BMW X4 G02 20iX/30iX

B48 applications with a Front Wheel Drive and Front Wheel Drive based xDrive layout with the engine placed in a Transverse direction. 

• Mini Cabrio F57 Cooper S (incl. JCW)
• Mini Clubman F54 Cooper S (incl. JCW / ALL4)
• Mini Cooper S F55 
• Mini Cooper S F56 (incl. JCW)
• Mini Countryman F60 Cooper S (incl. JCW / ALL4)
• BMW 1-Serie F40 M135i xDrive
• BMW 1-Serie F52 120i / 125i
• BMW 2-Serie F45 220i / 225i Active Tourer
• BMW 2-Serie F46 220i Gran Tourer
• BMW X1 F48 20i / 25i / 28i (incl. xDrive)
• BMW X1 F49 20i / 25i (incl. xDrive)
• BMW X2 F39 20i / 25i / 28i (incl. xDrive)
• BMW X2 F39 X2 M35i xDrive

US Spec models that meet the Super Low Emission Vehicle (SULEV) regulations. While this engine has also been used in Front Wheel drive layouts, we will focus on the Rear Wheel Drive based platform in this guide. The B46 UKL and B48 UKL have different downpipes.

• 2016 – 2020 F20 BMW 120i & 125i incl. xDrive
• 2016 – 2020 F22 BMW 220i & 230i  incl. xDrive
• 2016 – 2020 F30/F31 BMW 320i, 330e, 330i incl. xDrive
• 2016 – 2020 F32/F33/F36 BMW 420i, 430i incl. xDrive
• 2016 – 2020 F31/F32 BMW 730i & 740e  incl. xDrive
• 2016 – 2020 G30 BMW 530i incl. xDrive
• 2020+ G20 320i BMW incl. xDrive
• 2020+ G20 330i/330e BMW incl. xDrive

Ironically, the BMW B48 engine was first introduced in the MINI (the UKL platform) and not in a BMW. While now incredibly popular and capable of great performance numbers in all kinds of cars from BMW, it was the MINI F56 Cooper S that first got the new BMW four-cylinder engine. Due to the Front Wheel Drive layout with the engine in a Transverse layout, the B48 downpipe and B48 Engine for the UKL platform is different from the Rear Wheel Drive based platforms. 

At this time, BMW did not install OPF filters into their vehicles yet, so for the years 2014-2018 generation of vehicles, the United States and EU versions were similar in fitment. This is the BMW B48 Downpipe that features the Slip On connection to the cat-back exhaust. These B48 downpipes only fit vehicles without the OPF from the factory. In 2016 BMW introduced the B46 for the United States. The B46 and B48 require different downpipes. The B48 Downpipe Slip On only fits on vehicles without OPF. It was when the B46 was introduced and the OPF filters were mandatory in Europe and other parts of the world that the fitments started to change.

See our photo below for the B48 Downpipe Slip On Version, this outlet is the main difference between the B48 Non OPF and OPF.

In Europe, the OPF filters were introduced around 2018. BMW Also made a change to the fitment of the B48 Downpipes. The connection to the cat-back exhaust has been changed from the Slip On Type B48 Downpipe to the V-Clamp Version B48 Downpipe and BMW added OPF tubing to the B48 downpipe as well. Generally, the European BMW G-Series (220i, 230i, 320i, 330i, 420i, 440i etc.) will have the BMW OPF type B48 Downpipe, however, there are some late BMW F-Series B48 equipped vehicles that also have the OPF installed like the F30 330i 2018+. If you’re not sure, the best way to find out which B48 downpipe your car features is to actually check the connection to the cat-back exhaust under your car and check from above in the engine bay if you’re vehicle features OPF tubing on the B48 downpipe. 

If you're in doubt, it is always possible to contact us for help regarding the fitment. Easiest solution is to send us the photos of the connections of the downpipe. Approximate location of the Downpipe to Cat-back Connection (under the vehicle, around the passengers feet location) and the OPF tubing (in the engine bay, passenger side of the engine, on top of the downpipe).

The UKL Type B48 downpipes can also be roughly split into OPF and non OPF categories. They come with similar differences as the RWD based B48 downpipes for the 3 Series. They also have a Slip On Type or V-Clamp Type connection to the catback. OPF versions do have extra connections for the pressure sensors.

The US BMW B46 Downpipe uses a downpipe that looks like a combination of both the non OPF B48 Downpipe and the OPF B48 Downpipes. It basically features the V-Clamp, but does not have the OPF tubing on the downpipe. This means you will need a different downpipe for the B46 engines, specifically produced for the B46.

Once you’ve determined which B48 Downpipe you will need for your B48 engine, you will now have to make a choice between a Catless B48 Downpipe or High Flow Catalytic Converter B48 Downpipe. They come in a lot of different price ranges.

A Catalytic Converter decreases the emissions from your engine. A catalytic converter contains a ceramic honeycomb or metallic core structure and is placed parallel with the exhaust direction. Modern catalytic converters are designed to maximize the flow of the exhaust gasses while also maximizing the surface area of noble metals that trigger the chemical reaction converting harmful exhaust gasses to cleaner air.

For most customers, the largest factor in choosing between aftermarket Catless and Catted Downpipes is the difference in price and smell. We understand that the Check Engine Light will also be a consideration in this as 200 Cell B48 Downpipes will less likely throw a CEL, but 95% of the people who choose for a downpipe, also opt for a remap in the future. While a High Flow Catted Downpipe is usually cheaper than the OE downpipes, the price of a good High Flow Catted B48 Downpipe is still significantly more than the Catless version. In terms of power output, it is a misconception that a Catless B48 Downpipe automatically makes more power than the High Flow Catted Version. Modern catalytic converters are not as restrictive as they are used to be, especially the premium aftermarket solutions. 

When a customer chooses between a Catted or Catless B46 / B48 Downpipe, we advise our customers to take into consideration when running a Catless B46 / B48 Downpipe comes with the downside of smelly exhaust gasses. The lack of a Catalytic Converter means that no harmful gasses will be converted and that they will directly leave the tailpipes and enter the environment. You will be able to smell these harmful gasses if you run a Catless B46 / B48 Downpipe, which is not only harmful to the environment, but also to yourself and your passengers. You will also most likely fail your MOT and emission tests.

The positive is that the backpressures are significantly reduced, and it is possible to output higher power levels with less turbo-lag as it allows the turbo to spool faster. We recommend Catless B46 / B48 Downpipe for those who use their car offroad and are aiming for further tuning. Of course for those who like it, it usually is also a bit louder but also raspier than the catted version.

The High Flow Catted B46 / B48 Downpipe Versions reduces the smells of the exhaust gasses significantly, while also providing a huge improvement compared to the OE downpipes. Aftermarket downpipes usually come with 200 or 300 cell Catalytic Converters. Based on our inspections, the 200 Cell catalytic converters usually fulfil the requirements of the emission tests in most countries, but it is best to check if your local government. The 200 Cell is actually the best of both worlds for a daily driver because it most likely will not fail the emission testing, reduce a lot of the smell and also provide a huge improvement in terms of flow compared to the OE option. It also sounds about as loud as a Catless B46 / B48 Downpipe, but with a deeper note to the exhaust sound.

When you opt for a Catless Downpipe, it automatically means you will need a ECU tune, piggy-back tuner or Cat-deleter to prevent the CEL from appearing onto your dashboard.

With the Non-OPF BMW B48 Engines, you might be able to get away with just going for the High Flow Catted Downpipe which in most cases will prevent the CEL from appearing. However, since the B48 is a very sensitive engine, in some cases it will still throw a CEL.

When you opt for a Catless B46 / B48 Downpipe, it automatically means you will need a ECU tune, piggy-back tuner or Cat-deleter to prevent the CEL from appearing onto your dashboard.

Please take into consideration that at the time of writing (January 2023) the 2020+ BMW ECU have not been openly cracked for tuners to get into yet, which means the ECU have to be shipped physically to a tuner that is able to crack the ECU. Other solutions will be mentioned below.

With the OPF BMW B46/ B48 versions, a High Flow Catted B46 / B48 Downpipe is likely not enough to prevent the CEL due to a reduced back pressure in the exhaust when you're just changing the downpipe. While this brings performance benefits, the downside is that the ECU will measure a reduced back pressure and throw a CEL. 

Possible solutions for the OPF equipped vehicles with a 2020+ ECU are the LEIB OPF and CAT Deleter, which is essentially a small connector which tricks the ECU in thinking the OPF and CAT is still present. The LEIB solution is Plug & Play installation in about 60 minutes without cutting or soldering. It is not detectable for the BMW dealer and also reversible for those who want to remove it afterwards. We recommend this solution for those who want a more aggressive sound, but not necessarily want to tune the engine yet.

• LEIB OPF and CAT Deleter (no Performance Tune, only prevents CEL)

• Piggy-back ECU Tuner with OPF and CAT Deleter (Performance Tune Possible)

We have plenty of B46 / B48 Downpipe available in our store. See our recommendations for the Non-OPF Versions below:

Photo taken at DB Autotechniek - BMW / MINI Specialist - www.dbautotechniek.nl

DCE Parts offers a cost effective and high quality non-OPF version downpipe with great fitment.

See our recommendations for Downpipes for vehicles with the BMW B48 Downpipe with OPF below:

DCE Parts offers a very cost effective OPF version downpipe and in the market, our actual go-to solution due to the great fitment and great OPF solutions.

See our recommendations for Downpipes for vehicles with the BMW B46 Downpipe below:

DCE Parts offers a very cost effective OPF version downpipe and in the market, our actual go-to solution due to the great fitment and great OPF solutions.

Catless B46 / B48 downpipes are the least restrictive and offer the most performance benefit if tuned correctly with accommodating parts. The difference for street applications is not always hugely noticeable and for daily driven cars, we'd recommend 200 Cell High Flow Catted Downpipes in most cases due to the reduced smell and MOT and Emission requirements. Catless Downpipes are also technically against the law for street applications, so the 200 Cell HFC Downpipes offer a great balance between performance. 

For tuning, opting for a High Flow Catted Downpipe will allow you to push high horsepower numbers and your exhaust system will still be able to handle the increased air flow from the accommodating performance parts and tune. 

For the B48 vehicles without OPF, it is a straight-forward Downpipe swap that require a tune for those who go full Catless. Those with a High Flow Cat will in most cases be able to get away without a tune and not get a CEL. This varies from vehicle to vehicle though. For B48 vehicles with OPF installed, there are many ways to prevent the CEL, however, this always come with added costs, for example the LEIB OPF and CAT delete or a piggyback tune. For vehicles with a tuneable ECU (Pre-2020), you're able to flash the ECU for the CEL. 

Please note that any modifications to the engine, downpipe or ECU will void factory warranty unless stated differently.

Instagram - https://www.instagram.com/psrparts
Facebook - https://www.facebook.com/psrparts
Youtube - https://www.youtube.com/@psrparts

Feel free to contact us if you have any questions.

info@psr-parts.com