Improving BMW B48 & B46 Performance – Step-By-Step Engine Tuning Guide

When you think of BMW, there’s a high chance you imagine a sporty coupé powered by a very smooth and powerful inline-six. After all, this engine type became somewhat of a trademark for the Bavarians.

However, if your bimmer is powered by a smaller turbocharged inline-four, like the BMW B48 engine, you aren’t stuck with its factory performance. Obviously, there isn’t really a way to physically enlarge it by adding two extra cylinders to it, but there sure is a way to improve its operating characteristics and to add more excitement to your driving experience – we are talking about BMW B48 tuning. 

Want to learn more? Read on to find out!

BMW B48 Engine Specs & History

Let’s start by explaining what the deal is with the B48. Designed quite recently and produced from 2014, it’s the middle member of the modular engine family launched by the Bavarians around 2013. That started with a turbocharged straight-three B38 that was first installed in a futuristic-looking BMW i8 hybrid. 

Three, Four or Six? Modular BMW Engine Family Has Them All!

If you follow our blog, you may have already read our article where we explored the subject of B58 engine tuning and briefly described its design and history – the B58 is a straight-six and is the third, largest sibling of the bunch. For our newest readers, here’s a brief recap of what the modularity of those engines means. 

The modular BMW engine family consists of three-, four-, and six-cylinder configurations that can be fueled either by gasoline or diesel. They all have the same displacement of 0.5L per cylinder and they use many similar parts such as piston rods or crankcases. Interestingly, there is some part commonality not only among the gas-thirsty variants, but also between both fuel types. According to the information available online, 60% of parts are shared among either gasoline or diesel engines and there is up to 40% overlap in components between the two. This allows BMW to significantly lower their production costs.

Here’s the entire engine lineup in all its glory:

• Three-cylinders – B38 (gasoline), B37 (diesel)
• Four-cylinders – B48/46 (gasoline), B47 (diesel)
• Six-cylinders – B58 (gasoline), B57 (diesel)

BMW B48 Engine Specs

Now when it comes to the B48 engine itself, there are a few things that are worth noting about it. Like every member of the modular B series family, it uses a closed-deck aluminum block, forged piston rods, and a forged crankshaft, which are supposed to offer even greater durability than its predecessor, the N20. 

It’s also packed with many modern technologies meant to increase its efficiency, such as a twin-scroll turbocharger to deliver more torque at lower RPM as well as solutions aimed at lowering fuel consumption and emissions. Like, for example, direct fuel injection, variable valve lift (Valvetronic) and timing (Double VANOS).

All of that results in a powerhouse that can put out 154-255 HP and 250-400 Nm of torque in its regular form or even 302 HP and 450 Nm in an upgraded, sporty version designed for the newest BMW 35i M models and some of the John Cooper Works variants of MINIs. Interestingly, the B48 engine debuted in the F56 generation of MINI Cooper in 2014.

Stronger Crankshaft and Revised Pistons – A B48 for the Track

The changes in the performance-oriented B48 include a stronger crankshaft and revised pistons with a different compression ratio of 9.5:1, compared to 11.0:1 of the standard versions. Thanks to those modifications, the engine can easily take much more boost from a bigger turbo that was also fitted to it in the factory as one of the upgrades over the standard version. 

The stronger B48 was installed in:

• M135i xDrive (F40), 2019–present 
• M235i xDrive Gran Coupé (F44), 2019–present 
• X2 M35i xDrive (F39), 2019–present 
• MINI Clubman JCW (F54), 2019–present 
• MINI Countryman JCW (F60), 2019–present 
• MINI John Cooper Works GP (F56), 2020–present 

However, you don’t really need any physical upgrades to improve the performance of your BMW’s B48… But we’ll talk about that in a moment. Before we dive deeper into the subject of B48 tuning, let’s take a closer look at the BMW N20, which is the engine it replaces, as there are some interesting similarities and differences between the two. 

B48 vs. N20 – Like Father, Like Son?

The N20 was produced from 2013 to 2017 as a replacement for the naturally aspirated inline-sixes codenamed N52 and N53. Its power and torque output varies depending on the application (154-241 HP, 240-350 Nm). Just like the newer design, the BMW N20 utilizes the same kind of a turbocharger (twin-scroll) as well as a similar cylinder head construction (with both Valvetronic and Double VANOS). The fuel is also injected directly to the combustion chamber and the redline of the two is exactly the same (7000 RPM). 

What sets them apart then? Besides a slightly lower compression ratio of 10.3:1, the engine block of the N20 is of an open-deck type, while its internals are cast, not forged – those characteristics are key for engine’s durability, meaning that they directly affect its tuning potential. In case of the BMW N20 vs. B48 tuning debate, everything suggests that the younger of the pair is better equipped for additional power gains. 

That is not to say the N20 is not tunable or weak: there are many cars with this engine pushing impressive horsepower and torque numbers, all thanks to some smart ECU programming changes. What we mean is that the B48 is an improvement over an already solid tuning platform. 

B48 vs. B46 – Same or Different?

You might be surprised, but the answer is: both. From the end-user standpoint, the engines designated B48 and B46 are basically the same – they generate the same power and torque, and they behave identical when you press down on the gas pedal or even when you cruise around without any haste. What made them deserving of the separate nameplates is the fact that the B46 is designed to comply with much stricter emission norms.

There isn't much information available regarding the B48 vs. B46 differences, but it’s safe to assume the changes between the variants. Those include things like air intake, sensors or catalytic converters, as well as a different tune to take full advantage of those factory modifications. This makes it possible for the B46 engine to meet the requirements of SULEV (Super Ultra Low Emissions Vehicle) classification given by the American Environmental Protection Agency. 

The bottom line is that the B46 version is meant for the US market and complies with the local emission standards, while the B48 is installed in cars sold elsewhere. A situation just like with the previous BMW inline-four, which also had two regulation-specific versions: the N20 and the SULEV-compliant N26 offered in the United States.

Which BMWs Have a B48/B46 Engine?

We know, it’s a lot of variety for just one engine. We’ve prepared something to make it easier for you to keep track of which models are powered by which engine. Take a look below!

As you can see, the B48 engine is installed in a really wide range of cars. If you aren’t sure which engine powers your car, decode your VIN and we’ll send you the full vehicle specification list. You probably also noticed that this flexible powerhouse comes with a number of different power outputs right out of the factory. Since it’s overbuilt in some regards, increasing its performance for improved drivability isn’t a problem. Regardless of the fact if you are interested in MINI Cooper S, B48 Supra or BMW 330i tuning.

BMW B48 Reliability

Obviously, it’s still a relatively new design, so it’s too soon to gauge the BMW B48 reliability in a more long-term context. However, it’s already safe to say that things are looking good, because no major issues were detected as of yet.

As mentioned earlier, the most important components of this engine are very solid and should be able to withstand tremendously high mileages. The elements such as a closed-deck block or forged internals are also what’s usually used in performance applications, so the B48 seems to have a great tuning potential for some power gains, not to mention the fact that the tuning itself can also improve reliability – but we will talk about it more in a bit.

One thing to note though is that the list of BMW B48 engine problems definitely includes carbon build-up on the intake valves, but this is a problem of all direct injection gasoline engines.  

BMW B48 Engine Chip Tuning – Awaken Performance

Now, let’s finally get to the meat of the matter and the reason you got here in the first place: how to squeeze the most out of your B48. It doesn’t really matter how you came to the conclusion that you need to improve the way your car behaves – it could have been this one time it felt sluggish when overtaking a slow-moving truck or when you were trying to merge on the highway, but couldn’t do it swiftly enough. 

The “why” doesn’t matter, because what matters is the fact that you just want to feel the excitement behind the steering wheel of your vehicle. And to get that, you’ll need a fully-customized B48 tune…

What Will Change?

Perfecting the performance of your B48-powered bimmer with us will mean changing a couple of aspects, that is: 

• Performance – our precise tweaking of certain engine parameters provides you with approximately 25% more power and torque, more flexibility, and a much smoother power delivery for a total confidence in acceleration, overtaking, merging, or safely crossing dangerous intersections.
• Fuel consumption – as opposed to the universal OEM map, thanks to the new tune your ECU will make sure that the injectors spray just the right amount of fuel every time, which will result in around 10% improvement in gas mileage under normal driving conditions, e.g., your everyday commute.
• Durability – chances are your factory-tuned BMW is running a bit hotter than it could, to increase wear of vital components and make frequent dealership visits necessary; our tunes are designed to lower the engine operating temperature, taking a few years off your car by increasing the longevity of its heart.

In short: you can make your car exciting to drive, less gas-thirsty, and more reliable. If you ask us, it’s kind of like buying a new car at just a tiny fraction of the cost.

What Does the Chip Tuning Process Look Like?

Our ECU tuning service called Awaken Performance is fully remote, so that you can benefit from the knowledge of an experienced BMW tuner without having to visit a specialized workshop. What’s more, you don’t even have to leave your home, the tuning itself takes two hours at most, and you don’t need any technical expertise. Our technicians do everything for you.

We’ll go over how it works on the basis of a realistic example: let’s say you have a 330i that you love driving, but at the same time you feel something is no longer there in terms of how it performs. 

When you decide Awaken Performance is the way to go for your BMW 330i tuning, all you need to do is book the tuning session. After that we will send you detailed instructions on how to prepare yourself and your car for the process. 

The list of things you’ll need is very short and the necessary equipment can be ordered from us:

• An ENET cable.
• A Windows laptop. 
• Software to facilitate the connection between you and our technician (don’t worry, we explain how to install and use it).
• Knowing where to plug in the cable.

How about the tuning process itself? Our technician will do a couple of things:

1. They will start by scanning the data from the ECU of your car.
2. Having analyzed the information extracted from your vehicle, they will introduce appropriate changes in the ECU software and save them.

To ensure everything’s running smoothly, final logging will be required. Our tuners will do a check-up and adjust the ECU map if necessary.

The whole process isn’t very complicated, but this simplicity can be misleading. Engine tuning has to take many variables into account. Incorrect parameter changes will lead to engine components wearing off much faster, not to mention the fact that they could even cause a major mechanical failure. 

Awaken Performance is meant to take care of the difficult stuff so that you don’t have to learn about engine tuning or worry that you’ll make some fatal mistakes – our professional tuners have years of experience working with BMWs and know what they are doing. For you, the process is simple and effortless.

Is BMW B48 Tuning Safe?

Since it’s such a durably constructed engine, tuning the B48 should be safe if any software adjustments are made by an experienced tuner and if the car is well-maintained (e.g., the oil changes are performed regularly). 

Moreover, our tunes are designed not only with additional power in mind: we want you to enjoy your car for as long as possible, so we program the ECU within the factory limits. This is also the reason why we ask for your car’s VIN before the tuning session – it’s how we are able to verify if and what we can do for you safely. 

However, there are some considerations to be made before you decide to tune your bimmer. Firstly, if you have already modded your vehicle in the past (either by installing some aftermarket parts or getting an ECU tune somewhere else), be sure to let us know – it will give us a proper overview of how your engine operates. Secondly, you should be aware that chip tuning will void your engine’s warranty (but not the warranty for the entire car).

It’s also worth noting that vehicles after chip tuning require proper care. Don’t worry, it doesn’t mean more hassle for you! We mean things like regular maintenance, timely filter and spark plug changes, as well as using the best available fuel grades (91–94 octane in the US and 98–100 octane in Europe).

Can You Untune a Car?

Just like you can install and uninstall various apps on your PC, it’s possible to revert any changes introduced with an ECU tune – after all, the whole operation relies on changing the programming of your car. 

What makes the Awaken Performance service unique is the fact that we will help you not only improve the performance of your vehicle, but also restore the factory settings if you decide to do so. Contact us at [email protected] for more info on a satisfaction guarantee.

Awaken Performance vs. Other Engine Tuning Options

Simply put, there are two ways you can take when trying to improve the performance of your car. There is a plug and play option called a piggyback tune (sometimes also called a box tune), which is basically a device you hook up to your car’s ECU and sensors to trick the engine into producing more power. Generally speaking, it’s not the best tuning method: granted, it’s easy to see some effects, but the reliability leaves much to be desired. 

The other option, partly described above, is to introduce changes into the ECU programming and to alter the engine mapping. Where Awaken Performance differs from the other chip tuning services is in how we approach the entire process: we don’t push your engine further than its factory limits to ensure maximum reliability, and we make it as simple as possible for you to improve how your car behaves, since it all happens remotely.

ECU Tuning vs. Piggyback Tunes vs. Awaken Performance

Want to learn more about the available engine performance increase options? Check out our article where we explored the subject of ECU tuning vs. piggyback tunes.

Other B48 Performance Upgrades

Although still considered relatively new from a design standpoint, there is already a substantial performance parts aftermarket for the B48. A reasonable ECU tune is the first step you can take to increase the power of your car without straining the internal engine components. If you still find yourself wanting to push it afterwards, upgrading certain parts will be necessary. What upgrades are worth considering?

• Cold air intake – this simple improvement makes it possible for the engine to “breathe” cooler air in a less restrictive manner. More air, more fuel, more power. 
• B48 turbo upgrade – slapping on a bigger turbocharger in your car will provide more boost, but any modifications in this regard should be used in conjunction with BMW B48 intercooler upgrades, to further enhance the stock cooling capacity of the engine. 
• BMW B48 downpipe upgrades – the stock tubing that connects the turbocharger to the exhaust system also could be improved with an aftermarket part, which would result in a lowered back pressure for a better turbo spool.

Of course, all component replacements should be followed by a customized ECU tune to get the most of them – modifying a car effectively isn’t like playing with LEGOs. 

Is BMW B48 Tuning Worth It?

The question is simple, but the answer really isn’t, because it depends on so many factors, some of them being very subjective. B48 tuning is worth at least considering: when performed by someone experienced, it has the potential to bring back the thrill of driving you felt right after purchasing your car, lower the fuel consumption, and greatly increase the longevity of your bimmer’s heart. 

Remember though that ECU tuning will void your manufacturer’s warranty, despite the fact that it’s reversible. The question you should be asking yourself then should be “is B48 tuning worth it for me?”