Tuning your BMW B58 140i, 240i, 340i, 440i, 540i, Z4 for 500HP
The B58 is the successor to the N54 and N55 engines, both of which were highly tune-able and able to make lots of horsepower with only a handful of supporting mods. The N54 takes the cake in regards to horsepower capabilities, but it had many engine problems as a result. The N55 platform was made more restrictive from a tuning perspective in order to improve engine reliability, which worked well.
The B58 is still in its early stages of being tuned, but it appears to stack up somewhere in between the N54 and the N55. With that being said, as the engine is still very new there are currently a few limitations that are holding the engine back until the aftermarket companies and tuning shops can break past them. The two main limitations are the DME/ECU and fueling. Regardless of these limitations, the B58 is capable of making 500hp, with 450 or so to the wheels with only a handful of supporting mods.
Pre-Tuning Must Do’s: Spark Plugs and Ignition Coils
The B58 has pretty good ignition from the factory, but unless your plugs and coils are less than 20,000 miles old, we recommend replacing them. To create more horsepower, the car needs to pump more gas into the engine to create the additional combustion. Old spark plugs get worn down and become less effective, resulting in extra gas being left in the combustion chamber which can then pre-detonate and cause misfires.
If you are simply running a JB4 tune and other bolt-on mods then we suggest replacing the spark plugs with OEM plugs. If you are planning on upgrading your turbos, then we recommend using the 1-step colder option. Always stick to the OEM ignition coils.
- OEM B58 Spark Plugs: for all tuned and FBO cars running stock turbos
- 1-Step Colder Spark Plugs: for all B58’s with upgraded turbos, note these are the same 1-step colder plugs used by the N55
- OEM B58 Ignition Coils: use these coils regardless of the spark plug you are using
Mod List for 500HP
An upgraded intake allows your car to bring more air into the engine which creates more horsepower, faster turbo spool, and an awesome sound. The extra air flow is crucial for creating more pressure inside the engine and also maximizing horsepower gains from additional mods. We consider this a necessity if you are going to use a tuner such as the JB4 on your B58. The sound made by the intake makes it worth it by itself.
There are a handful of manufacturers out there and all intake systems are more or less the same. We recommend BMS because they are one of the best in the tuning game.
Read our full-guide on B58 intakes here: BMW B58 Upgraded Performance Intake Guide
Price: $179 + Shipping
Horsepower/Torque Gains: 10-20whp / 15-20tq
Note: we do receive a small % of the sale when you buy it through Amazon, which helps pay for the cost of keeping this website up and helps compensate us for the hours and hours we spend on each post we write. The shipping on Amazon is actually cheaper than buying on BMS’ website so don’t be afraid to help us out 🙂
Burger Motorsports JB4 tuner is the most popular tuner used on both the N54 and N55 platforms, which is why we recommend it for the B58 platform. This is a piggyback tuner, verses a flash tuner. The flash tuner requires the ECU to be overwritten and it wasn’t until late 2018 that tuning companies were able to crack into the DME and ECU. With that being said, all the flash tuner options are relatively new to the market and not fully proven.
As additional tuning options open up for the B58, we will update this post. However, even on the N54 platform which has a handful of piggyback tuners, flash tuners, etc. we still recommend the JB4, so I don’t anticipate our recommendation will change here regardless of new options.
Horsepower/Torque Gains: 60-80whp / 40-60tq
With an intake and tune, your B58 will be bringing significantly more air into the engine. Which means, now we need to be able to get all of that air out. If the air can’t leave as fast as it comes in, back pressure is created. Back pressure is actually good for naturally aspirated cars, but it is terrible for turbocharged cars. The factory downpipe has a catalytic converter on it, which for emissions purposes, is very restrictive. By replacing the restrictive OEM downpipes with catless downpipes, we eliminate all of the back pressure and create more horsepower and boost.
I would note a few things here. First, just replacing your downpipes will not make your car crazy loud. It will make a slightly deeper tone, but its not very noticeable from the front of the car and definitely not noticeable inside of it. Your wife won’t even know you did anything to it! Secondly, we only recommend a full exhaust system if you really care about the sound of the car. A full exhaust system will run you more than this list of mods and will get you probably 5 additional horsepower. Full systems aren’t worth it unless you want the loud noise.
VRSF is the best balance of price and performance. Zach and I run the VRSF downpipes on our N54’s and they are great.
Read our full guide on B58 downpipes here: BMW B58 Upgraded Downpipe Guide
We strongly recommend catless, but high-flow catted is still better than stock if you are concerned about emissions testing.
Horsepower Gains: 25-30whp with the JB4 + faster turbo spool
Meth injection is the key to making 500hp at the crank and 450whp. Meth injection, referred to as WMI (water/meth injection), sprays a mixture of water and methanol into the intake air just prior to it entering the combustion chamber. The spray reduces the air temperature and also boosts the octane of the gas entering the combustion chamber. Overall result is more combustion aka more power. On the N54 and N55, a chargepipe with a meth bung would be needed, but the chargepipe on the B58 is a pain to remove, so BMS built and adapter which mounts up to the throttle body.
A big limitation of the B58 is fueling. The only way to get around this limitation is through the addition of meth injection. With the above mods, but no meth, you will probably push approx. 400-415whp on 93 octane pump gas. Meth will get you to the 450whp mark.
Price: Depends but approx. $500
We recommend running the BMS kit which you can find all about here: B58 BMS Meth Injection Kit
Also, read this thread from the owner of BMS: https://www.n54tech.com/forums/showthread.php?t=37053
What about Intercooler (FMIC) Upgrades?
If you were reading through our N54 or N55 mod list, you would find an upgraded intercooler on the list. Intercoolers cool the air prior to it entering the engine, which increases the oxygen content of the air ultimately resulting in more combustion and power. The stock B58 intercooler is definitely good, and better than the N55 and N54 ones, but until we see B58’s breaking past the 600whp mark, we won’t be sure if upgraded intercoolers will be needed.
There are virtually no options on the market since the stock intercooler is air to water cooled and integrated into the intake manifold. Manufacturing a new intercooler would require a new intake manifold which would be very expensive both to develop and for the end consumer. It’s safe to say that there won’t be any FMIC mods coming out quite yet.
Read our guide on B58 heat exchanger upgrades: BMW B58 Intercooler & Heat Exchanger Upgrade Guide
How do I make 500 Wheel Horsepower?
Right now the only way to make 500whp is with an upgraded stage 2 turbo system.