How to Build a 500HP 40i B58 BMW for Less Than $1,500

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.

Mod List for 500HP

1. BMS B58 Performance Air Intake

BMS B58 IntakePin

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

Buy the BMS Intake here

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 🙂

2. BMS JB4 Piggyback Tuner

BMW B58 JB4 Flash TunerPin

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.

Price: $529

Horsepower/Torque Gains: 60-80whp / 40-60tq

Buy the B58 JB4 Here

3. Catless Downpipes - VRSF

VRSF B58 DownpipePin

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. For our European readers, we recommend the Masata Catless Downpipe which offers the same performance benefits as the VRSF option which is difficult to find overseas.

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.

Price: $299

Horsepower Gains: 25-30whp with the JB4 + faster turbo spool

4. Meth Injection

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.

Check out our B58 Upgraded Turbo Guide to learn how to build a 500whp B58.

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37 thoughts shared

  1. Comment author image

    Cliff Roberts

    says:

    Thanks for the info Zach, I see some changes on my 2018 440i immediately! Any thoughts on the down pipe and the dreaded factories after market extended warranty? I can’t get a straight answer out of my BMW dealer. Thanks again

  2. Zach– Thanks again for your knowledge and support. …I may just start with BMS intake– I like the sound it makes. Then may add the downpipe and possibly a tune later. 440 seems fast enough stock lol 🙂

  3. Hi! This is fantastic info. …Is it possible or okay to just install the intake and catted down pipe? Thanks for your time and service.

    1. Hi Chris,

      We appreciate the kind words! You can certainly just opt for a catted downpipe and intake. However, the power and torque gains will be pretty minimal without a proper tune. You might still pick up some power, but it’s really the tune that helps other mods gain power.

      Best Regards,
      Zach

    1. Hi Ammar,

      These mods absolutely work on the M340i xDrive. Just double check fitment on specific parts. For example, the downpipes are different and can be found from VRSF here.

      550 horsepower at the crank is likely obtainable, but that’s just about the max on the stock turbo assuming a 12-15% drivetrain loss. You can end up around 470-500whp with an aggressive tune and all of the proper supporting mods (tune, downpipe, intake, methanol injection, and ideally a small E85 mix). You may consider some cooling mods, too. If you want a very consistent and easily obtainable 550hp then you may want to consider a turbo upgrade.

      The M340i is an awesome car. Enjoy the modding and additional power. A few simple bolt-ons certainly turn the B58 into a whole different animal.

      Best Regards,
      BMW Tuning

  4. Great article guys!

    Lots of good info here for a new 340i owner.

    A small thing that stood out to me was the comment that, “Back pressure is actually good for naturally aspirated cars”.

    Back pressure is good for no cars. It is in fact scavenging that is good for NA cars (and to a lesser degree for supercharged cars).

    If you get the exhaust gas velocities correct, the pressure wave will help to remove more combustion gases from the cylinders for a desired RPM range. This results in an increased available volume within the combustion chamber at the start of the intake cycle. Less burnt fuel and more fresh fuel = more torque/power.

    Gas velocities are a function of pipe diameter which is why exhaust header design is crucial for NA engines. Too large a diameter results in slower gas velocities and shifts the ideal RPM range (for scavenging) beyond the physical capabilities of the engine.

    Exhaust back pressure is a function of gas velocity and pipe diameter. Keeping the exhaust diameter relatively small helps to maintain higher gas velocities but as a result the back pressure is higher. Hence the confusion why people think back pressure s actually good for naturally aspirated cars.

  5. Comment author image

    Anthony DellAnno Sr

    says:

    I am mechanically challenged but love the power. I have a 2020 340I x Drive and want to know if the install of the Pure 800 as advocated by Kies on you tube is a stand alone mod? What Whp will it deliver? Yhanks!

  6. I have a 2017 440i Xdrive convertible and would love to make these modifications to my ride. I’m mechanically challenged. Could you recommend an installer in Rhode Island?

    Phil

    1. Hi Phil,

      We’re not familiar with the Rhode Island area, so we can’t give any direction on that. However, installing a tune and intake are incredibly easy. The JB4 takes a little messing around, but it’s all straight-forward and easy. Otherwise, you can opt for Bootmod3 (BM3) which is also an excellent tune and it’s very easy to flash. Just charge the battery during the install to be extra safe. An intake install can take a little patience for those who are mechanically challenged, but it’s very do-able.

      Downpipes and intercooler/heat exchangers are where it gets a bit more complicated. However, we highly recommend starting with a tune alone or tune + intake. Downpipes are an incredible mod, but be cautious doing too much at once. You get used to the power and always want more. Spacing out the mods a little bit helps you buy some extra time.

      If you’re really not comfortable installing the tune or intake then it shouldn’t be hard to find a shop. I’d have faith in any trustworthy shop to get the job done, even if they don’t specialize in BMW. Look for a quality shop with fair rates. A tune and intake should be no more than 1 to 1.5 hours of labor. Downpipes and intercoolers will be at least a couple hours, but again I’d recommend saving those mods for a little down the road.

      Best Regards,
      Zach

  7. Comment author image

    Steven Kenniff

    says:

    I am going to share my experience with modding the B58.

    I have the BMS CAI, and it is nice and very well designed. Great product for the price. However, I think the stock Airbox is actually better, and you are better off just getting the BMS Silicon Intake Elbow for $69 and then your choice of a better drop-in filter for the stock Airbox.

    The VRSF Downpipe recommendation is spot on. Definitely get this. Easy to install on RWD models. I hear it’s trickier on AWD. On my RWD I was able to install it without using a Jack or lift. You do have to unbolt the exhaust hangers on the muffler to get it to slide on/off where it meets the midpipe.

    There are many options for tuning, of which the BMS JB4 is decent. The JB4 really only sees full potential when used with Backend flashes from an MHD flasher, and at that point it’s probably better to just skip the JB4 and go all in with the MHD Tune.

    Meth injection is alright but not completely necessary. If you want it definitely get the JB4 so you can use it as a controller and for the failsafes.

    Here would be my build suggestions:

    B58TU0 (475-525 rwhp)
    1. VRSF Catless Downpipe
    2. MHD Flasher and Super License (Stage 2+ E30)
    3. xHP Stage 3 Transmission license (Flashed Through MHD Dongle) (only if Automatic)
    4. Dorch Stage 1 HPFP
    5. BMS Silicone Intake Elbow

    B58TU1 (475-525 rwhp)
    1. VRSF Catless Downpipe
    2. MHD Flasher and Super License (Stage 2+ E30)
    3. xHP Stage 3 Transmission license (Flashed Through MHD Dongle) (only if Automatic)
    4. BMS Silicone Intake Elbow

  8. Does it matter if i get a jb4 tune i was looking into the MHD tuning kit but i dont wanna deviate from this mod list unless tunes are compatible with whatever parts.

    1. Hi Danny,

      You can go with either JB4, MHD, or bootmod3. Some of it just comes down to personal preference. Many prefer the standalone flash tuning options, but the JB4 has a lot to offer especially if you want to stack the JB4 with a back-end flash tune.

      Best Regards,
      Zach

  9. Hey guys, thanks for having this forum setup, tons of information. In like TJ and own a 18’ 440i xDrive 6MT. I was talking to my mechanic and state emissions would not be an issue for doing a careless downpipe. His only question was, would having this type of Dow pipe trigger a check engine light or anything noticeable that would require the error code to be addressed? Has anyone installed a catless Downpipe without any issues?

    Excited to do tune my car, was hoping the JB4 would remove the insanely low speed limiter…. leaning towards DINAN because of that reason but love what JB4 does…. decisions decisions.

    Still miss my e36 NA engine every single day, those were the days when a car gave you feedback… new ones are numb, but super thankful for the 440i 6MT and this forum to squeeze more power out of the B58

  10. Quick question. With a catless down pipe. Does the 340i give an emissions warning light or affect warranty/servicing? As I’m thinking of just the air pod and down pipe for now and love noise and bang for bucks.

  11. Hey,
    This is a great post.
    I am a happy owner of a built 2018 manual. I don’t have all the bells an whistles like some, but all I wanted was a manual who I can keep for year to come.
    I’m a big fan of Terry’s products at BMS as I used them for an older N55 I had.

    In your guys opinions, is this a decent setup for my manual 40i? It’s my everyday driver but I love getting on it when I’m in the car.

    Thanks for any feedback.

    1. Hi TJ,

      Awesome car equipped with the 6MT. I think the mods in this post would be a great compliment. A tune + intake is always a great starting point, in our opinion. The B58 can make some impressive power with a tune only and the power up-top is very flat. I’d say start with a tune or tune + intake and give it a few months. If you’re still wanting more power then a downpipe, meth injection, and/or small E85 mixes are a great next step. Let us know if you have any additional questions.

      Best Regards,
      Zach

  12. Hi I was wondering for the bms intake since it uses the factory piping is there anything that I can find that would upgrade the piping from factory to something more durable? Like how you can change the charge pipe from the regular plastic to aluminum. If I got the bms intake I would want to look into getting better piping as well.

  13. Comment author image

    Geoff Capes

    says:

    Hi, I have 2018 440iGP. I installed the MPPSK, Dinan Elite II and Dinan air intake. Would having the exhaust modified to accept the catless VRSF downpipe benefit WHP or would it confuse the programming of the MPPSK? If done, would lessen wear on the turbocharger (is there a need to be concerned having added the Dinan intake? Without have the dino test performed, any idea of where torque or HP sits? Thanks

    1. Hi Serj,

      These mods can be done to the 740i as it uses the same B58 engine. We believe the linked parts should fit, but just confirm the fitment of individual parts.

      Best Regards,
      BMWTuning

  14. Hey BMW Tuning,

    I was looking at getting a 2016-18 340i xdrive in a 6SPD but have found conflicting information online and was hoping you guys could help me.

    1.) Are these cars torque limited in gears 1-3? I am looking to do full bolt-ons and a decent tune with the car and I don’t wanna waste my time and money if its going to be cut out by the transmission itself.

    2.) Even though I really want a MT would I be better off with the AT if I’m looking to add the extra HP? I was hoping to be somewhere around 400whp.

    Any information would be great, and like I said I really do want the manual but I don’t wanna be totally let down either.

    Thanks,

    Tyler

    1. Hi Tyler,

      First off, good luck with the 340i search.

      1) The B58 is not torque limited in 1st through 3rd gear. Not to make things too confusing but there is a maximum torque value the transmission can see (torque limit). This doesn’t mean actual torque is limited. Tunes will essentially ensure torque is never cut by not allowing the ECU/TCU to see higher than the torque limit. So the B58 may actually be making more torque than the “limit”, but it doesn’t know that. There are additional solutions to raise these limits, such as XHP.
      I believe this is a far superior explanation than mine: https://www.facebook.com/xhpflashtool/posts/line-pressure-vs-engine-torqueand-what-this-has-to-do-with-the-durability-of-you/2103607396621945/

      2) In the long run, the manual transmission will likely hold up better with the additional power. An upgraded clutch may be required, though. The AT is still a stout transmission and should be more than fine under 500whp and 500wtq.

      Best Regards,

      BMW Tuning

      1. Really appreciate the expedited answer!

        I will definitely be looking for a 6 speed manual now that I know. You have really helped me out here,

        Cheers!

        Ty

  15. Title: How to Build a 500HP 40i B58 BMW for Less Than $1,500
    Ending: Right now the only way to make 500whp is with an upgraded stage 2 turbo system.

    Way to deliver.

    1. Hey Bill,

      There is a difference between 500hp and 500whp. A 500 horsepower B58 would make about 440whp assuming a pretty standard 12% drive-train loss. Long story short, a stock turbo B58 can make 500hp. However, it’s likely not going to make 500 wheel horsepower.

      Though, we should probably update that as I believe a few stock turbo B58’s have neared or just eclipsed the 500whp mark. Nonetheless, that is surely maxing out the stock turbo and we would still recommend an upgraded turbo for a legit 500whp.

      Regards,

      BMW Tuning

  16. How do the upgrades on this list pair with MPPSK package? I bought a 2016 340 with MPPSK package but not sure which upgrades are relevant to do or play well.

    Cheers!

    1. Hi Matt,

      All of these mods will work with the MPPK/MPPSK. The main difference is the exhaust on the MPPSK B58 so you may net a few extra horsepower when all is said and done. We don’t recommend upgraded exhausts just since they’re pricey for the performance gains. But in the case of the MPPSK B58 you’ve already got the exhaust (albeit not as beneficial as a fully catless exhaust). Otherwise, expect the mods to have similar benefits although power gains from the tune will be slightly less.

      To avoid confusion, overall power on a non-MPPSK and MPPSK car will end up about the same with mods. However, power gains will be slightly less on the MPPSK since it’s got a higher starting point in terms of horsepower. As an example, the MPPSK has 355hp while a non-MPPSK B58 has 335hp. Let’s say both end at 400hp with a tune only. They both end at the same power, but the MPPSK picks up less power gain from the tune. Maybe in reality the B58 MPPSK ends at 403hp due to its better exhaust.

      Best Regards,

      BMW Tuning

    1. Comment author image

      Roberto Clarindo

      says:

      Olá, eu sou do Brasil,
      Queria saber se, no BMW X3M40I no STAGE 2 B58 fica mais rápido doque o S58 X3Mcompetition?
      Outra pergunta, qual é o peso real desse carro X3M40I ?
      Obrigado! 🇧🇷

    1. Hi Ryan,

      Thank you for your comment. The same modifications can be done to the 340i xDrive just as with a RWD 340i. The main difference is that the 340i xDrive will make slightly less power to the wheels as compared to rear wheel drive.

      Mod away and enjoy!

      Best Regards,

      BMW Tuning Team

  17. Comment author image

    NewbBimmerGuy

    says:

    Guys, I LOVE the content, but I’d love to see an update that breaks out the differences between the B58 TU0 and the TU1 and whether this ups the max WHP limits without resorting to meth or other external fueling.

    From what I can gather there’s lots of updates from TU0 to TU1 including the cylinder head with a revised exhaust housing, move to a 1 piece chain drive, a small amount of weight savings, dual cooling circuits between the cylinder walls (hotter temps now) and heads cooling -existing programming and temps and most importantly a move to a max 350 BAR high pressure fuel system including new beefed up direct port fuel injectors. (My understanding is that it only runs 350 bar at WOT and at high RPM). The TU1 also includes the particulate filters.)

    I believe that the added fuel pressure, which BMW says was added to meet WLTP European emissions standards also provides more total fuel flow increasing the max WHP without having to resort to meth or port injection… no?

    It also sounds like the cylinder wall thickness may have been made thinner with TU1 and the crank had some lightening done to it and I’m curious whether this may potentially drop the max safe boost levels vs the TU0 or whether these components are so overbuilt already that that shouldn’t be a concern…