Tuning Guide BMW B48
The B48 is one of BMW’s newer modular engines, that are fitted in a host of entry level models in their lineup including the 230i, 330i, 430i, and 530i. You will find this 4 cylinder turbo to be responsive and fuel efficient. Though once you get used to the power, the B48 may feel a bit flat and could use performance and tuning upgrades. To unleash easy horsepower gains, we will be going over 5 modding options in this guide that are available for your BMW or Mini with the B48 engine. Given the BMW B48 is a relatively new engine, you may consider the fact that you could be voiding your warranty with certain B48 performance mods.
B48 Flash & Piggyback Tunes
Tunes are one of the easiest modifications to unleash an additional 30-50hp and similar torque on the B48 engine. There are two common tunes you will come across: flash and piggyback tunes. Though both types tunes increase power there are some major differences between how they go about it. A flash tune essentially re-writes the factory ECU whereas a piggyback tune controls boost and allows the factory ECU to make the necessary adjustments.
In other words, a piggyback tune uses stock timing, load, fuel tables, etc; it simply tricks the ECU into thinking boost is too low. For example, assuming stock B48 boost target is 10psi, the piggyback tune would trick the ECU into thinking it is only running at say 5psi. The ECU would then increase boost another 5psi to reach its 10psi target when in reality the B48 is now actually making 15psi. Various sensors then make the necessary adjustments to compensate for the additional load, AFR, fueling, etc. required for the increase in boost.
*Since piggyback tunes “trick” the ECU they are hard or impossible for dealerships to recognize. As long as you uninstall the tune, there should not be any evidence your B48 was ever tuned.
Flash tunes re-write the parameters on the ECU and as such they are more adjustable and precise as compared to piggyback tunes. They use their own timing, load, and fueling tables, just to name a few. However, flash tunes typically do not feature advanced safety functions as found on piggybacks such as the JB4.
*Since flash tunes re-write the ECU dealership can identify that the B48 is or has been tuned/modified in the past.
JB4 Piggyback Tune B48
JB4’s are one of the most common tunes in the BMW turbo era – and for good reason. The JB4 is an excellent piggyback tune with advanced safety features, simple data-logging, and tons of product support. You can’t go wrong with the simple plug and play installation, on the fly map changes in seconds, and impressive power gains. Additionally, the steering wheel controls and gauge hijacking are unique, convenient features that compliment an already excellent product for the B48 engine.
JB4 B48 HP Gains: 30-40whp
JB4 B48 TQ Gains: 30-40wtq
*All tune horsepower and torque numbers assume the car is otherwise stock running 91/93 octane pump gas
Dinan Piggyback Tunes B48
Dinan offers two piggyback tunes for the B48: a simple boost controller (Sport Performance Tuner), and a more advanced piggyback (Elite V2). The sport performance tuner is a solid budget option that simply controls and raises boost. It is about as basic as a piggyback tune can get, and does not come with the same features or flexibility as compared to the JB4.
Dinan’s Elite V2 for the BMW B48 has a large price increase compared with the sport performance tuner but offers more advanced control. The Elite V2 actually adjusts more parameters than simply boost. Dinan claims this delivers the smoothest performance. Take it as you will – we don’t fully buy into that claim. Nonetheless, it offers additional power over the Dinan boost controller.
Dinan Sport Performance Tuner HP Gains: 20-25whp
Dinan Sport Performance Tuner TQ Gains: 25-30wtq
Elite V2 HP Gains: 30-35whp
Elite V2 TQ Gains: 30-40wtq
Bootmod 3 (bm3) Flash Tune B48
The bootmod 3 from Pro Tuning Freaks, commonly referred to as bm3, is one of the most common flash tuning options on the newer modular B series BMW engines. The bm3 flash tunes come with some excellent features including an app, multiple flash tuning options, and simple data-logging. Custom maps also have the ability to remove top speed limiters and adjust exhaust flaps, to name a few features.
BM3 B48 HP Gains: 30-40whp
BM3 B48 TQ Gains: 30-40wtq
A catless downpipe for the B48 is likely the second best bolt-on modification, only behind a tune. While a catless downpipe provides impressive power gains the real benefit is in turbo spool. The restrictive OEM downpipe with a catalytic converter results in increased back pressure. A quick physics/engineering point – the drop in pressure from pre-turbo to post-turbo plays a significant role in building boost. Therefore, the best exhaust on a turbo car is no exhaust at all. Unrealistic for daily driving for most of us. However, a catless downpipe is the next best option to improve turbo spool.
Dyno tested and proven to make significant power gains. Most importantly, the butt-dyno will definitely approve. You will immediately notice a surge in low-end torque that hits almost instantly.
B48 Catless Downpipe Sound
Some people are concerned about making their B48 too loud with the installation of a catless downpipe. While it will make the car louder it is nothing absurd. Cold-start will make a bit more noise and WOT pulls will sound slightly louder and deeper. However, accelerate “normal” or cruise at highway speed and the B48 sounds nearly stock. Therefore, in our opinion, it is really the best of both worlds. Great sounds when you want them at WOT, and stock sounds cruising around town.
B48 Catless Downpipe HP Gains: 10-15whp
B48 Catless Downpipe TQ Gains: 15-20wtq
Upgraded Air Intake (“Cold Air Intake”) B48
B48 cold air intakes are an excellent mod not only for the power gains, but also for the intoxicating sound. Unlike some older turbo BMW’s, such as the N54, the stock B48 air intake is not quite as restrictive. An upgraded air intake will likely increase power and torque slightly. However, they do make for noisier turbo spool and more dramatic induction sounds.
The dinan intake pictured above is beautiful. However, we recommend opting for an open intake for the sound. If you like the sound of turbos and induction you will not regret buying an open intake.
B48 Intake HP Gains: ~5whp
B48 Intake TQ Gains: ~5wtq
With the right tune, we recommend running a 20-30% E85 mixture on the B48 engine, if available. Really, we recommend E85 on any tuned, turbo BMW engine. E85 is like a god-send in the tuning and performance world. We won’t waste time delving into all of the specifics, but E85 is incredible. It burns cooler and is higher octane as compared to pump gas. This leads to significant benefits such as reducing the chance of knocks and pre-detonation events. As such, higher boost and more aggressive timing can be run on E85. In layman’s terms – power, power, and more horsepower.
The JB4 can handle roughly 20-30% E85 mixtures. Certain flash tunes can handle similar E85 mixtures, and possibly more with the right supporting mods. More E85 equals more power.
B48 E85 Gains: 10-30+whp
B48 E85 Gains: 10-30+ wtq
*20% E85 mixtures will be on the lower end while 100% E85 will be on the higher end of power gains. Exact power gains also highly dependent upon tune.
Charge Pipe B48
Although a charge pipe will not increase power it is a highly recommended supporting mod for the BMW B48. Like many of the other turbo BMW engines, the B48 chargepipe is susceptible to bursting or cracking even on stock boost. Upgrade the chargepipe sooner than later and avoid being left stranded on the road side.
At the time of writing, the B48 is still a relatively new tuning platform. Not many are out of factory warranty so few people are really pushing the limits of the B48 platform. However, the above mods can be had for roughly $1,500 or less in total. The B48 is already proven as underrated from the factory making 220+whp and 240+wtq stock. Tune only cars are able to push over 260 wheel horsepower and 290 wheel torque. Throw a few bolt-ons and some E85 in the mix and you’ve got an engine capable of pushing upwards of 300whp.
300whp may not seem overly impressive in today’s world of big horsepower cars. Though, the B48 is a newer platform that has a long way to go in the aftermarket world. We suspect the B48 will be an affordable, high-performance engine once the full potential is tapped. With instant low-end torque and a broad power band it is hard to go wrong with modding your B48.
Check out our guide for the N55 here. What have you done to your engine so far?