BMW really did it this time. The N54 shattered expectations in the tuning world, but suffered early reliability issues. BMW took a step back with the N55, focusing on improving reliability. Enter the BMW S55. The engine that took some of the great aspects from each engine, but took it 7000 levels higher. BMW’s S55 is proving to be reliable, powerful, and an instant legend in its young career. We’ll just say it now – this is NOT the modern 2jz. The S55 is better from top to bottom in every possible way. It’s that good. Actually, it’s so good these simple bolt-ons will push the S55 to 600whp and beyond.
BMW S55 Mods
As stated, the S55 achieves 600+whp with a few simple bolt-ons mods. The 600+whp mods include:
- Catless Downpipes
- Upgraded Top Mount Intercooler
Not to diverge too much, but the results really are incredible with these simple mods. They can all be had for around $2,000 and take the S55 to an entirely new level. In this post, we will examine the above bolt-on mods and the expected horsepower gains with each.
1) BMW S55 Tune
The first mod that comes to mind is a tune. A simple tune, such as the JB4, is able to push the S55 to 500+whp. This is already mind blowing power for a small 3.0L engine straight out of the factory. However, a tune only S55 is barely scratching the surface of its true potential. Let’s take a look at some common tuning options on the road to 600+whp.
BMW S55 JB4 Piggyback
Burger Motorsports (BMS) JB4 tune is a popular option for modern turbo BMW’s. We run the JB4 on all of our N54’s and it has earned our highest praises. The JB4 is a simple plug and play tune loaded with unique features. It allows boost limits in lower gears, on the fly map changes in seconds, gauge hijacking, and E85 support just to name a few. BMS’ JB4 also comes with free data-logging ability (with cable or wireless option). As an added benefit, BMS offers excellent support and development.
Additionally, the JB4 allows for the use of back-end flash (BEF) tunes. BMS provides their own flash maps for free along with MHD flash maps. The best part? Their back-end flash maps are completely unlocked. This means you can tweak the tune to your liking. You also have the option to flash BEF maps.
JB4 Cost: $599. Optional $35 data-logging cable or $140 wireless connection
JB4 HP Gains (Tune Only): ~80whp on pump gas / ~120whp on E85
Buy Here: BMW S55 JB4 Piggyback Tune
The below video shows an F80 M3 running a stock turbo record pass with a JB4 and custom back-end flash from BMS. As you can see, the results speak for themselves.
BMW S55 MHD Flash Tune
*Split into two sections for JB4 + MHD BEF & MHD Standalone Flash
S55 JB4 + MHD BEF
Our recommended option for the S55 M3/M4/M2C. You will need to purchase the MHD flash license for $249. Once purchased, the MHD back-end flash maps are free. It includes three BEF options:
- Race – pump gas & up to 40% E85
- E85 – 40-60% E85
- E85_IGN 60-100% E85
Not only do the JB4 + MHD offer these maps, but the JB4 also retains its on the fly map changes. For example, you can switch from Map 2 (22psi peak boost) to Map 7 (28psi peak boost) in seconds. This is an awesome feature for those who want a “modest” daily driver tune with the ability to instantly turn things to kill mode. Additionally, the JB4 retains all of its other advanced features.
S55 JB4 + MHD Cost: $599 (JB4) + $249 (MHD license)
S55 JB4 + MHD HP Gains: 120-200whp depending upon fueling and supporting mods
*Quoted HP is higher as these BEF tunes are best suited to full bolt-on (FBO) S55 engines.
S55 MHD Standalone Flash Tune
If the JB4 or JB4 + MHD BEF are not appealing to you, a standalone MHD or BM3 flash tune is a great option. Similar to the BEF tunes through MHD, you must purchase the MHD license for $249. However, unlike with the JB4 BEF maps, you must purchase MHD flash maps individually. Data-logging capabilities must also be purchased. There are 4 map packs ($99 each) that have different tuning options within, depending on fuel.
- Stage 1 – up to 530whp (Tune or Tune + Intake only)
- E30+ – up to 600whp (Different tuning options for different mods)
- Stage 2 – up to 560whp (Tune + Intake + DP’s recommended)
- Stage 2+ – up to 575whp (FBO recommended)
You may also opt for custom flash maps. These can unlock additional MHD features such as exhaust burble, limit power per gear, top speed limiter removal, etc. Of course, custom flash tunes come with additional costs.
S55 MHD Cost: $249 license + $99 per map pack + $99 data-logging
S55 MHD HP Gains: See above
2) BMW S55 BMS Elite Performance Intake
The factory intake on the BMW S55 is fairly efficient as is. However, at higher than stock boost, the factory intake becomes restrictive. BMS noted power gains of 10+whp at 25+psi. At lower boost, the performance intake is slightly less beneficial from a power perspective.
But…the sound! The open intake produces dramatic improvements to sound. Installation is easy, they look great, and turbo/induction noises are awesome. While some power gains may be had, we recommend these intakes for the sound alone. We also have a complete guide on S55 intake upgrades.
S55 Performance Intake Cost: $199
S55 Performance Intake HP Gains: ~10whp at higher boost levels
Buy Here: BMW S55 BMS Elite Performance Intake
Alternate Option: BMW S55 Phoenix Racing Performance Intake
3) BMW S55 VRSF Catless Downpipes
Catless downpipes (DPs) are probably our favorite mod following a tune. They offer a great combination of power, sound, and feel. The butt-dyno definitely approves. Catalytic converters in the stock downpipes are restrictive and do not allow turbos to reach their full potential. No exhaust is actually the best exhaust on a turbo engine. However, that likely isn’t realistic for most of us.
The next best option is catless DPs. Removing the restrictive cats allows the S55 turbos to spool and build boost much faster. What is the result? Instant torque that pins you into the seat. Dyno proven and butt-dyno approved. Catless downpipes result in impressive peak power gains of roughly 20-25whp.
Additionally, catless DPs provide awesome sound improvements without becoming annoying or overly intrusive. Cold-starts will be a bit louder and WOT pulls result in an aggressive, deeper note. Although, catless downpipes are hardly noticeable while cruising on the highway or driving around town. The one downside – emissions testing. Don’t miss the full guide on BMW S55 downpipe upgrades.
S55 VRSF Catless DPs Cost: $500
S55 VRSF Catless DPs HP Gains: 20-25whp
Buy Here: BMW S55 VRSF Catless Downpipes
For International readers, we recommend the Masata S55 Downpipes.
4) BMW S55 VRSF Top Mount Intercooler
The S55 received a top mounted air to liquid intercooler, as opposed to the air to air FMIC on previous turbo BMW engines. Part of the goal with a top mount intercooler is to reduce the length of the intake tract. Shorter intake tracts assist in reducing turbo lag. However, the stock S55 air to liquid intercooler has its shortcomings.
It does a good job at keeping IAT’s down for short pulls. Although, once you do several multi-gear pulls, IAT’s begin increasing rapidly.This is due in part to the flaw of air to liquid intercoolers. Water/coolant takes a lot longer to cool down as compared to an air to air intercooler. Fortunately, there are some great aftermarket air to liquid intercooler options.
VRSF’s intercooler offers a high density, dual pass bar & plate core and has 62% higher capacity. It should be noted – an upgraded intercooler doesn’t necessarily add much horsepower for glory runs. However, they do help the S55 run consistently during long pulls, extended aggressive driving, etc. For more on the TMIC, check out our S55 Intercooler & Heat Exchanger guide.
S55 VRSF Intercooler Cost: $550
S55 VRSF Intercooler HP Gains: 0-15+whp (may not add power on short single gear pulls, but helps mitigate heat soak and power loss)
Buy Here: BMW S55 VRSF Top Mount Intercooler
5) BMW S55 E85 Mixtures
E85 provides significant performance benefits for performance engines, like the BMW S55. If you have access to E85, we highly recommend mixing at least 20-30% E85 with proper tuning. Not only does E85 burn cooler, but it also reduces the change of knock/pre-detonation.
The stock S55 fueling is able to keep up with 100% E85 up to roughly 600whp. Though, it is important to pay attention to AFR’s. You must also have the appropriate tune to keep up with the demanding fuel flow. A JB4 alone can handle up to 30% E85. The various JB4 MHD BEF maps allow for 0-100% E85. MHD flash maps have varying options for E85, as well.
Horsepower gains from E85 greatly depend upon tuning and specific E85 mixtures. A FBO S55 tuned for 100% E85 will see generally see horsepower gains of 30-50whp. Whereas, a tune only S55 on 25% E85 may only see power gains of 10whp. Although, horsepower gains are only a small portion of the benefits offered by E85. Most importantly, E85 reduces change of knock and pre-detonation.
S55 E85 Cost: Usually about the same price as 85/87 octane (downside is reduced fuel efficiency)
S55 E85 HP Gains: 10-50+whp (greatly depends upon tune, supporting mods, and specific E85 mix)
BMW S55 Supporting Mods for 600+WHP
Depending on how aggressively you want to push your BMW S55, the above mods will result in 550-600+whp. Not too shabby for a few basic bolt-ons and fueling. However, you’re now pushing the S55 to 100-200whp over its stock configuration. A few supporting mods and maintenance items to consider prior to modding the S55 include:
1) S55 VRSF Charge Pipe Upgrade
As with every turbo BMW motor, the stock charge pipes on the S55 are made from thin plastic. Higher boost puts additional stress on the charge pipe and may cause it to crack or snap. Upgrading the charge pipe is optional, but may be a good idea to do up-front. We’ve seen plenty of failures on all turbo BMW engines. Although, all of our N54’s are running more than double stock boost without issues on the OEM charge pipes.
S55 Charge Pipe Cost: $300 (hot side pipes) and/or $140 (cold side)
2) S55 Crank Hub Fix
There is plenty of information on the S55 crank hub issues. The N55 and S55 actually use the same crank hub design and parts. Issues with the N55 are beginning to surface as more people are pushing the N55 upwards of 600+whp. However, this problem first became “common” on the S55 due to the ease of making 550-600+whp.
3) S55 1-Step Colder Spark Plugs
Tuned and modded BMW S55 engines will burn through spark plugs quickly. In addition to burning through plugs, it may be a good idea to upgrade to 1-step colder spark plugs. A colder spark plug transfers more heat away from the tip of the spark plugs. This helps prevent misfires and potential pre-detonation events.
We recommend the NGK 97506 plugs below. These are two-steps colder to the N54 and one-step colder to the S55. They are also the OEM plugs for the N20 engine. The N20, N54, and S55 crowds alike all have great experiences with these plugs.
**Note – they must be individually gapped to .022 or .023″
Buy Here: BMW S55 1-Step Colder Spark Plugs
BMW S55 600+WHP Summary
BMW’s S55 engine has already proven itself as one of the best modern 6-cylinder turbo engines. A few simple bolt-ons and E85 can rocket the S55 into 600+whp territory. It is highly impressive the stock fueling, stock turbos, and almost all other stock components can handle this power. However, the S55 is not without flaws. Higher horsepower and boost may uncover charge pipe or crank hub issues. Additionally, colder spark plugs (and frequent replacements) may be required to keep the engine running well.
Nonetheless, these are minor “issues” for 550-600+whp engines. We still struggle to wrap our heads around what the S55 is accomplishing. Rather than writing another 1000 words of high praises for the S55, we’ll leave it at this. It is one hell of an engine. Mod away and have fun.
Not sold on the S55? Check out our 500hp B58 for under $1,500 post