BMW N55 F Chassis MHD – Flash Tunes Horsepower Gains

N55 F Chassis MHD Tunes

We’ll offer a quick background for MHD, flash tunes, and piggyback tunes. If you’re familiar with this please feel free to skip ahead. MHD offers off-the-shelf (OTS) tunes for the N55 F chassis. Flash tunes, such as MHD, essentially re-write the DME to target more aggressive boost. They also allow for control of fueling, load, ignition advance, etc. This is a huge advantage of flash tunes when compared to piggybacks.

The JB4 is the most notable example of an N55 piggyback tune. It acts as an advanced boost controller. However, it essentially tricks the DME. The DME thinks it’s running stock-like boost. We won’t go far into this, but a JB4 is limited by the factory DME parameters. It cannot actually re-write the factory tune. Enter flash tunes.

N55 F Series JB4 + MHD Back-End Flash (BEF)

We can’t help diverge for another quick discussion of flash vs piggyback tunes. You can actually stack a piggyback tune and flash tune together. It’s one of our favorite tuning set ups. Burger Motorsports’ JB4 is loaded with unique features that most flash tunes simply cannot offer. A few of those features include steering wheel controls, gauge hijacking, and on-the-fly map changes. Switch from a modest tune to kill-mode in seconds with the OE steering wheel buttons. The JB4 also allows for superior support and control of port and/or meth injection. Additionally, piggyback tunes often have better safety features.

Stacking the JB4 and MHD back-end flash comes with tons of benefits. The JB4 retains its features and is in full control of boost targets. However, the MHD back-end flash is in charge of ignition timing, fueling, load, etc. Flash tunes and piggyback tunes each have their benefits and downsides. Stacking the two allows for the best of both worlds, in our opinion.

Additional info on JB4 + N55 MHD F Chassis BEF

**You will need to purchase the JB4 and MHD software license to run a JB4 + MHD BEF tune. Once the MHD software is purchased the actual BEF maps are FREE.

N55 F Chassis MHD Maps (“Stages”)

Alright, now that we got some necessary information out of the way it’s time to move onto the fun parts. MHD offers three primary stages for the N55 F chassis engines. There is also a fourth stage dedicated to E20 fueling. Each stage has different supporting mod recommendations. Assuming all else equal, power and boost increase with each stage. The available stages include 1, 2, 2+, and E20. Within each stage there are numerous options based upon fueling (less the E20 tune which requires an ethanol blend). Throughout the rest of the post we’ll discuss the various stages, supporting mods, and expected horsepower gains. A few quick notes before:

1. We advise replacing spark plugs and ignition coils prior to tuning an N55. This is especially true if your spark plugs are 25,000+ miles old and/or your ignition coils are 40,000+ miles old. Modded F chassis N55’s are well suited to NGK 97506 1-step colder plugs. However, OEM plugs typically suffice on stock turbos and OTS tunes.

N55 NGK 97506 Plugs

OEM N55 Spark Plugs

OEM N55 Ignition Coils

2. All power figures are rough estimates. They also assume the N55 is running the recommended supporting mods – nothing more and nothing less. As such, additional mods that we don’t discuss (such as meth injection) may result in higher horsepower. Power can also vary significantly from car to car. This comes down to differences in dynos, correction factors, temperature, engine & turbo health, etc.

N55 F Chassis Stage 1 Horsepower & Mods

Mods Recommended: Intake

Stage 1 N55 tunes from MHD may be seen as too conservative for some. They’re basic, entry level tunes that do not require any additional engine mods. Although, we recommend opting for an upgraded open intake. Power gains from an intake on a modest tune may not be impressive. An open intake is still a good mod to have, in our opinion. If not for a potential minor horsepower boost we recommend the mod for the sounds alone.

91 Octane/95 RON: 310-320whp / 340-350wtq

93 Octane/98 RON: 320-330whp / 350-360wtq

95 Octane/102 RON: 325-335whp / 350-360wtq

Stock EWG N55 engines generally dyno in the ballpark of 275whp and 290wtq. Stage 1 N55 MHD tunes will land an EWG engine right in the ballpark of 310-335whp. These gains aren’t too bad for a very conservative tune. As evidenced, fueling plays an important role in horsepower gains. 91 octane is typically regarded as poor fueling. As such, expect lower results on 91 octane fuels. Better fuels will result in higher boost targets and will help the N55 pick up a bit more power.

N55 F Chassis Stage 2 Horsepower & Mods

Mods Recommended: Intake + FMIC

A downpipe is also a good mod that we’re excluding from the recommendations for stage 2 MHD F chassis tunes. We actually recommend a catless downpipe for any “stage”, but we’ll save it for stage 2+ next. There really aren’t any mods absolutely required to flash the stage 2 tunes. However, we’re now starting to push enough boost that IAT’s become a concern. Like a catless DP, an upgraded N55 FMIC is a great mod regardless of stages. An FMIC may not have promising power gains on glory runs. However, consistency and knock suppression (via colder intake air temps) are the primary benefits of N55 intercoolers.

91 Octane/95 RON: 340-350whp / 370-390wtq

93 Octane/98 RON: 350-360whp / 385-405wtq

95 Octane/102 RON: 360-375whp / 405-420wtq

N55 F chassis horsepower with MHD stage 2 tunes comes in around 340-375whp. As boost targets increase good fueling becomes more and more important. Again, IAT’s are also more important at higher boost. Either opt for an N55 FMIC upgrade up-front or keep an eye on IAT’s. If they’re consistently getting too hot then the tune will pull back timing and boost. In this case, you will not reap the full benefits of a stage 2 tune.

N55 F Chassis Stage 2+ Horsepower & Mods

Mods Recommended: Intake + FMIC + DP

Finally, we’re throwing in the downpipe as a recommended mod. A catless downpipe is going to provide the biggest gains, however a high-flow catted DP is still a viable option. Stage 2+ tunes are going to target the highest boost out of the maps mentioned so far. A downpipe will assist in reducing back-pressure and making the turbos job a bit easier. Power gains with the downpipe alone come in around 15-20whp (about 5-10whp less with a high-flow catted DP). Additionally, they will help reduce turbo spool. It may sound unnecessary since the N55 turbo is already pretty quick. However, you’ll definitely notice an improvement and feel a more aggressive jerk back into the seat. Awesome mod all around.

91 Octane/95 RON: 370-380whp / 390-410wtq

93 Octane/98 RON: 380-390whp / 400-420wtq

95 Octane/102 RON: 390-410whp / 420-440wtq

Expected power with stage 2+ tunes comes in at roughly 370-410whp. This is a pick up of roughly 30-40whp when compared to the base stage 2 MHD tune. However, a decent chunk of those gains comes from the assistance of a better flowing downpipe.

N55 F Chassis E20 Stage Horsepower & Mods

Mods Recommended: Various depending on stage (Intake + FMIC + DP)

We’re throwing in full-bolt ons for the recommended mods because we’re mostly focusing on the stage 2+ E20 fueling. The ethanol map actually offers stage 1, 2, and 2+. E85 has countless benefits as it burns cooler and requires additional fuel flow. More fuel sprayed into the cylinder reduces the chance of engine knock. As such, the N55 can safely target more boost and run more aggressive ignition timing. However, it’s tougher on the stock fueling system due to the required fuel flow.

Stage 1 E20 Map: 330-340whp / 360-370wtq

Stage 2 E20 Map: 365-380whp / 410-430wtq

Stage 2+ E20 Map: 400-420whp / 420-440wtq

The horsepower numbers assume you’re running the supporting mods for each stage (as mentioned in the various stages above). E85 is excellent fueling, however the N55 EWG unfortunately has very limited fuel flow capabilities. E20 simply isn’t enough to make a huge difference as compared to 95 octane. The results are still solid with power coming in up to 420whp on the stage 2+ tune.

N55 F Chassis MHD Summary

BMW’s move to EWG rather than PWG helped put a bit more life in the N55. It’s still not quite as capable as the older N54 engines, but it’s got a decent bit more breathing room when compared to N55 PWG examples. MHD flash tunes are an excellent option for anyone looking to get more power out of their F chassis N55. MHD offers several off-the-shelf tuning options designed for different supporting mods, power goals, and boost targets.

Stage 1 MHD tunes are pretty modest, and may not be enough for some. Stage 2 tunes receive a decent boost with power in the ballpark of 340-375whp. An addition of a catless downpipe for stage 2+ tunes adds quite a bit of a boost. Power comes in right around 400whp on good fueling. Finally, E20 maps offer some promising numbers but it’s not a huge gain over 95 octane. However, if you only have access to 91 octane then we highly recommend opting for an E20 map. Of course, assuming you also have access to E85.

What are your experiences with MHD on an EWG N55?