BMW B58 MHD Tuning Guide – Info & HP Gains
Zach is a BMW enthusiast with a passion for performance. With over 10 years of experience modifying and performing DIY work on BMWs, he’s developed a deep understanding of virtually every BMW engine. He’s also the proud owner of a 600whp N54 with upgraded twin turbos and an E30 325i drift car and has a particular affinity for the S58 engine. Zach is highly knowledgeable about all things BMW, but his expertise in tuning and performance mods sets him apart. His experience as an enthusiast, combined with his technical knowledge, makes him an essential resource for anyone looking to improve the performance of their BMW.
Following our general MHD post, we will now go more in-depth on B58 MHD tunes and expected power gains. Scroll down a bit if you’re only interested in the power gains. Otherwise, let’s quickly discuss some basic MHD B58 tuning concepts.
About B58 MHD Flash Tunes
MHD offers OTS (off the shelf) flash tunes for the B58 engine. OTS tunes from MHD are extensively tested and highly proven in the BMW tuning world. Additionally, B58 MHD tunes are easy to install and affordable. A quick breakdown of MHD costs for B58:
- Flasher Module – $249 (required)
- Map Packs – $99 each (two available, only one required)
- Monitor Module – $99 (optional, but highly recommended unless stacking with JB4)
All in, you’re looking at $546 for the flasher module, both stage 1 and 2 map packs, and the flasher module. We recommend starting with only 1 map pack and getting the 2nd later on, if needed. However, we strongly advise spending the $99 on the monitor module. This allows data-logging capabilities so you can monitor your engines operation. Once tuned, it’s never a bad idea to data-log frequently to keep an eye on engine performance. The JB4 offers free data-logging features, so disregard the MHD option if you’re looking to stack a JB4 and MHD back-end flash. More on this in the next couple paragraphs.
B58 Flash vs Piggyback Tunes
B58 flash tunes, such as MHD, re-write the factory DME programming. Essentially, flash tunes gain complete control of all engine tuning parameters. This includes boost, fueling, timing, and load – just to name a few. Ultimately, the goal of a B58 flash tune is to increase turbo boost pressure. The flash tune is then also programmed to account for the additional fuel flow required, any necessary timing adjustments, etc. To summarize, flash tunes allow for excellent precision and tuning capabilities.
Piggyback tunes for the B58, such as JB4’s, take a different approach. These tunes basically function as advanced boost controllers. They do NOT rewrite the DME. A JB4 essentially sets the boost target and lets the factory DME tune make the necessary adjustments. However, the DME never sees the true boost target the JB4 is setting. Some people knock piggyback tunes since they “trick” the DME. Though, we love the JB4. It’s easy to install, comes loaded with features, and is a great overall tune. Piggyback tunes function as advanced boost controllers, but they are limited by the factory DME tune.
B58 JB4 + MHD Back-End Flash
For ultimate B58 tuning, we recommend stacking the JB4 and an MHD back-end flash tune. The B58 JB4 comes with, in our opinion, superior features and better boost control. It also allows for on-the-fly map changes in just seconds. No need to completely re-flash the DME. However, the JB4 is limited by factory tuning variables. Enter the B58 MHD back-end flash. The flash tune re-writes the factory DME allowing for precise, aggressive tuning. With this route, you will not need the MHD monitor module or any map packs. Simply purchase the JB4 and MHD flasher module and the actual flash maps are free.
Beware though. Stacking these tunes can be pretty aggressive on stock turbo B58’s. With proper supporting mods, a JB4 and MHD back-end flash have the ability to nearly max the stock turbo. The back-end flash maps can run up to 50% E85. Again, beware. This tune combination is plenty aggressive to max the B58 fueling with too much E85.
Learn more about the JB4 + MHD stack here
B58 MHD Stages & Maps
As discussed briefly above, MHD offers two stages for the B58 engine. Within each stage there are multiple maps for different fueling. We’ll discuss the two stages and different fuel maps throughout the remainder of the post. This will include estimated power on each stage and fuel.
*We highly recommend replacing B58 spark plugs prior to flashing MHD tunes, especially if the spark plugs are 25,000+ miles old. Ignition coils may also be a good idea for those with 50,000+ miles.
**Horsepower figures are estimates. They also assume you are running all recommended mods. Additional mods that we do not mention may result in extra power, such as meth injection. Furthermore, power may vary from car to car even with the exact same mods. Some differences come down to dynos, temperature, altitude, engine health, etc. Even when all things are equal some natural variance is normal.
B58 MHD Stage 1 HP Gains & Mods
Mods Recommended: Intake
First off, performance intake power gains are questionable. The B58 factory airbox is pretty efficient as is. Intakes really only add power if the stock intake is struggling to keep up with air flow demand. Stage 1 MHD tunes likely are not aggressive enough for this to be an issue. Nonetheless, if not for the small potential power gains, we recommend an open intake for the sound alone.
With that said, MHD stage 1 tunes are the least aggressive MHD offering for the B58. No mods are absolutely required. Simply flash the DME and go.
MHD Stage 1 HP
91 octane/95 RON: 360-370whp
93 octane/98 RON: 370-380whp
95 octane/102 RON: 380-390whp
Expect hp figures in the 360-400whp ballpark on stage 1 MHD tunes with an upgraded intake. As suggested, power increases with fuel quality. 91 octane is poor fueling and only recommended if you do not have access to better fuel. If E85 is available, we highly recommend mixing 20-30%. Power approaching 400whp on a pretty conservative tune is impressive to say the least.
B58 MHD Stage 2 HP Gains & Mods
Mods Recommended: Catless DP + Intake
Stage 2 B58 tunes provide a respectable bump above stage 1 performance. It is highly recommended to install a catless downpipe or high flow catted downpipe prior to stage 2 MHD tunes. A catless downpipe will provide a nice bump in power by itself. Additionally, catless downpipes reduce turbo lag and help the B58 hold more boost up top. The butt-dyno will definitely approve of this mod thanks to the lightning quick spool.
MHD Stage 2 HP
91 octane/95 RON: 380-390whp
93 octane/98 RON: 390-400whp
95 octane/102 RON: 400-410whp
B58 MHD stage 2 figures come in around 380-430whp. Nothing to snarl at for a few basic bolt-ons and a flash tune. Again, we advise running an E85 mix if available. You may even consider running meth injection to pick up a bit of extra power.
B58 JB4 + MHD BEF HP Gains & Mods
Mods Recommended: Catless DP + Intake + WMI
We’re throwing meth injection into the list of recommended mods here. You can absolutely run this setup with no other mods. Also, regardless of mods, we believe this is a great setup for anyone. However, the goal here is to showcase the capabilities for those looking to push the B58 stock turbo limits.
B58 JB4 + MHD HP
91 octane/95 RON: 400-430whp
93 octane/98 RON: 410-440whp
95 octane/102 RON: 420-450whp
E85 map w/ E40 mix: 450-480+whp
These are pretty aggressive power assumptions here. We also provided a rather large range since power will be highly dependent upon many factors. There are several different back-end flash maps. Additionally, you can then select a map on the JB4. Basically, there are is a wide variety of options to choose from to dial in the tune and boost to your goals. Meth injection will assist in reducing overall fuel demand. However, on E40 fueling be sure you’re data-logging and keeping an eye on fuel flow. Ensure you’re not leaning out.
BMS (JB4) pushed a B58, with only E40 fuel and an intake, to 460whp on 19 pounds of boost. They were running AFR’s as lean as they felt comfortable. This highlights the fact that fueling becomes a concern at this kind of power. Again, meth should help. Nonetheless, this is incredible power for stock turbo B58’s. We’re impressed the B58 has accomplished so much already. Look no further than the JB4 and MHD combo to push things towards the limit.
B58 MHD Flash Tunes Summary
The B58 has already proven to be one heck of an impressive performance engine. Conservative stage 1 MHD tunes are able to push the B58 into the 400whp ballpark with some E85 to help. Stage 2 tunes take things up a notch with expected power in the 380-430whp range. These are both excellent tuning options for the B58 and you cannot go wrong.
However, we ultimately recommend stacking a JB4 with an MHD back-end flash. We truly believe this is the best tuning solution on the market. Things can get aggressive quickly, though. You can, of course, stack this tunes and opt for a conservative tune. The JB4 also offers on-the-fly map changes so you can switch from a conservative daily driver tune to kill mode in seconds. Push things too far on this setup and you may quickly find the stock turbo and stock fueling limitations.
I wonder where the WHP values come from? They appear unrealistic and inconsistent with what MHD specify themselves (which is assumed to be already exaggerated).
Example – MHD Stage 1 – up to 390WHP with 102 RON. With 15% losses, this would give nearly 460HP at the crank !?? And that’s Stage 1…. In my humble opinion completely unrealistic. MHD specify up to 420 PS with 102 RON (which is most likely already quite optimistic). This would be max 360 WHP… optimistically!
As we state, the horsepower numbers are estimates. For an AWD automatic 15% drive-train loss might be realistic. RWD manuals are probably closer to 10% and RWD autos about 12%. It’s also based on DynoJet numbers since that’s the popular dyno of choice across the BMW community. They read a fair bit more generous than Mustang dynos.
Anyways, the B58 dynos about 320-330whp bone stock on 91/93 octane (at least those are roughly the baseline numbers we went by). Some dyno more some dyno less. By your logic of 15% drive-train losses that’s about 395hp at the crank. Regardless, power numbers are always tough to say because of differences in dynos, correction factors, etc. Dynos are tools for baseline numbers, tuning, adjustments etc to determine how the car responds to different mods, tunes, etc.
BMW doesn’t necessarily under-rate their engines but rather uses ratings obtainable in less than desirable conditions. So run the car in average conditions and it will make more power than they quote. MHD numbers are also somewhat of a middle ground. If you take their numbers are whp then it’s likely over-rated whereas it’s underrated if you assume crank hp. They don’t necessarily clarify. If you look at N54 numbers the E85 maps say up to 440hp (maps up to E60 fuel). A FBO N54 on E60 fueling can fairly easily eclipse 400whp. Once again, using your 15% assumed loss that’s 470hp at the crank, but MHD states 440hp. Are they quoting aggressive wheel horsepower numbers, conservative crank hp numbers, crank hp numbers with a minimal 10% drive-train losses, or something else?
You can never factor in drive train losses, just cant do it! 10-15% is a stab in the dark and depending on car, drivetrain etc it could be far far higher. There are lots of things to take into account and a dyno only measures static losses not dynamic so that is literally a number for you to take away and keep you happy. It will never be accurate as it cant measure the car for dynamic losses under load on on coast!
This website explains it rather than me re-writing it if you are interested!
You’re correct in that drivetrain losses are nothing but a shot in the dark. It’s a large part of the reason we try to keep things uniform in primarily quoting WHP numbers based on a dynojet with STD correction. Dynojets read fairly high in general and STD correction reads higher than SAE. However, dynojet STD correction is the most commonly used method in the BMW world which is why we estimate power based on that.
You’d have to actually use an engine dyno for realistic crank numbers. You could then go to a chassis dyno and compare the numbers to see the difference. However, even then there is no uniform way since dynos read different. Drivetrain losses would appear lower on a dynojet with STD correction compared to a Mustang dyno. That said, even chassis dynos and WHP numbers aren’t the best estimate of how a car will perform on the road. Dynos are mostly meant for tuning and getting baseline numbers and measuring gains or losses from certain adjustments, mods, etc.
Sorry if I missed this, but how well are the manual transmission-equipped cars handling stage 1 and 2 power levels? Any weak/failure points that owners are advised to upgrade in tandem with the tunes? Thanks for this resource
Ive spoken many renown tuners and they say that 440, ie stage two MHD you don’t need to remove the cat. In fact there’s lots of tuners out there like Litchfield that run 440 with the car set as OEM.
MHD say they “recommend” a cat less or high flow DP. To me that’s a get out answer and doesn’t really answer the question, Will it run stage two with an OEM cat?
You can run stage 2 with the factory downpipe. The reason it’s recommended is because it reduces back-pressure which relieves stress from the turbo and engine.
Will A91 Supra owners with the current locked ECU be able to use the MHD BEF along side the JB4+?
I noticed that on your B58 BM3 tuning guide you suggest HPFP for stage 2+ whereas for MHD + JB4 you suggest WMI instead. Can you please explain the reasons? Seems like BM3 may achieve more power.
What would a HPFP do on a MHD with intake, catless DP and HPFP (no JB4)? What if JB4 is added to it?