S55 Build Path
Background
We have 20 years experience with BMW engines including the S14 (E30 M3), S38 (E34 M5), M50/S50(E36), S54(E46), S65(E9x). We skipped the N54 and early N55 for reasons that you may already be aware of; safe to say it was not a great match for our work. When the S55 came out, BMW once again had our attention and our long history of tuning BMW Turbo engines was ready to be revisited.
Over the last 5 years we’ve tuned hundreds of cars and put together a comprehensive plan of attack for any S55 vehicle. We have extensive experience with mild OEM+ type builds, to drag and circuit cars. We have owned multiple S55 vehicles that have spend hundreds of days on our dyno and various circuits pursuing perfection.
Our nuanced approach is well reviewed and documented and our reputation speaks for itself so feel free to spend some time reading feedback on our work from others. Our goal is not to tune the most cars, but to do our best work, with the best tools, which the best clients and cars. That does not mean that we need a lot of modifications, or expensive modifications; just the right parts and calibration work.
Required Hardware
Completely stock is just fine; and in many cases better than the off-brand parts that tend to get purchased on the late-night death scroll adventure. Many clients ask about the crank hub and we are simply not technicians, so our advice here is limited. To get anything more than an opinion you’d need to find someone who’s done hundreds of diagnostics and recorded all of the data, as well as had runfile information on the car. I am not aware of anywhere that this is the case, so I think most of what you hear is conjecture. Anytime you hear, “never had a problem”, that can almost always be translated to, “I don’t have much experience”. Seasoned race car techs, race engineers, and diagnostic technicians rarely say such words and often utter some unintelligible dribble of frustration towards the last PITA vehicle they fought with that “never had a problem”.
In short, we had our crank hubs upgraded because it is a simple, clearcut way to prevent a catastrophic problem with your engine. As far as which is best, that’s for you to choose. If there is a shop we work with in your area, we can recommend a shop, and we’d suggest going with their recommendation.
Stock Hardware Calibrations
For cars that are completely stock, and or with bolt on modifications, tuning is quick and simple. The car is limited by a few things in stock form mechanically: The intercooling is not great, the octane of pump fuel, and the small turbochargers. Tuning along will wake the car up and add some power increases on pump fuel, along with better driveability, significantly more midrange torque, and a modest increase in top end power.
Any outfit offering to significantly increase high RPM power without changing some of the above parts is either not accomplishing their goals, or doing so at the expense and grave risk to your engine health.
Our stock hardware calibrations increase circuit performance significantly while maintaining safety features.
Stage 1 and Stage 2 Calibrations
Stage 1 and stage 2 hardware modifications as defined by this platform include bolt on breathing modifications such as intake, downpipe, midpipe, exhaust, charge pipe, and intercooler modifications. Turbochargers and fuel system remain stock.
Plan on modest gains from stock to stage 2 calibrations on pump fuel, and significant gains on Stage 2 + ethanol. Our calibrations are flex fuel only (meaning no fixed ethanol content). There is no reason to run fixed ethanol content calibrations when flex fuel is a matter of our ultimate kit or the BM3 ethanol content analyzer. This allows you to run any blend of pump fuel to full E85. We generally find that stock fuel system stock turbo cars will make peak power around E45 to E55. You are free to run full E85 and our calibration will automatically reduce power to stay within stock fuel system limits.
Any numbers outside of what we are showing below are either 1) dyno variance which is common or 2) running the car extremely lean which works for a short pull but will destroy the engine in a period of time.
Modifications:
Stock airboxes with drop in BMC filters
Downpipes, midpipe and exhaust of your choice
Charge pipes of your choice
Suggested for maximum effort:
Wagner TMIC
EU5 Injectors for safer fuel mixtures
The blue line is stock and the red line is stage 2 + ethanol. Typical power ranges from 550-600whp depending on the dyno and conditions.
Stage 3+ “The Sweet Spot”
When you’re looking for more power for your S55, the next step is simple and clear. We call it the sweet spot and you can read about this combination here.
We believe this is the best setup top to bottom for an S55 and covers almost every car.
Built by Garage Whiff Bitz and tuned by us, this has GWB Hybrid turbos, E50 with EU5 injectors, Dorch S55LK, and PR Stage 3 brushless LPFP.
Beyond the Sweet Spot
We can and have made way more power than the Sweet Spot setup above, but this definitely comes with compromise. There is no more stable, better driving setup for your S55 than the above, whether you want to cruise the back roads, drag race, or circuit race. That being said, for those who must push further, and are willing to accept the compromises and significant cost increase, we can deliver more.
Max effort DI only:
Maxx effort built motor with hybrid turbos, cams, and Nostrum Stage 3 injectors + Dorch S55LK HPFP + PR Stage 3 brushless LPFP. The hybrid style turbos do not generally live long at this power level, and these did not.
Built by Jimmy B with PS2+, EU5 injectors, Dorch S55 LK, upgraded LPFP this is a max effort direct injection only tune. This can and will bend factory rods, it is just a matter of “when”.
Built motor, G35-1050, Reflex 1050x Injectors, 4N OG Turbo Kit. Widebands pre-turbo, ecutek. This setup ran and runs reliably, consistently, and overall had decent delivery, driveability, and good power. Built by Brandon Tran at 4B Performance.
Maximum PSI Built S55 with G42 Turbo; very laggy but good power.
Maximum PSI built motor with PTE 7275 exhibits reasonable spool up and good power. Things at this power level are not stable or repeatable for racing on the S55.
Maximum PSI built S55 with G42-1200 and 4N Updated turbo kit. Good power but inconsistent fueling at this power level with currently available tools.
Things we will and will not tune
If you haven’t read our choose your own adventure blog, its worth a read. That will provide some background behind why we will, or will not tune a setup. Generally, it is not a matter of “we don’t know how” and more a matter of, “we know how this ends.
What we will tune:
S55: Stock/Stage1/Stage 2/Hybrid (stock style turbo upgrades) Can be done on BM3, MHD, or Ecutek. The Ecutek is more refined for specific needs, safety features, and or track cars. The BM3 work well for clients with less specific needs and we do countless S55 BM3 cars with good success. MHD + works well for DI only cars.
S55 With Reflex/PI: Ecutek only.
MHD + single turbo DI only but no PI (not integrated as of 2024-9-2)
No BM3 + PI as there is no integration
S55 Single turbo Ecutek or MHD. Widebands must be in manifold at time of fabrication which gives you the flexibility to choose the software platform that is the best at time of calibration.
What we will not tune:
BM3 with PI (The BM3 will not talk to the PI controller, this is a hard stop for us)
MHD with PI for S55 (while MHD offers integrated PI control with B58 and S58, they do not offer it for S55/N55 as of 2024-10-28. Please send MHD a mesage requesting this if you want this feature)
Kratos turbos: they do not live when pushed, and one turbo is always going faster than the other causing almost certain failure
Single Turbo Considerations
Without mentioning brands, our suggestion for a single turbo S55 is something in the 62-68mm turbo size with dual 45mm wastegates, widebands in the manifold pre-turbo, and good wastegate priority. Anything outside of this is likely something we will pass on; again not because we can’t do it, but because the results are rarely a happy client, which is always our goal.
If you put together a random combination of parts without consultation
If you assemble a combination of parts that doesn’t match our suggested program, we may not be a good fit for your project. On the flip side, if you’d like us to calibrate your vehicle, we’d really like to help you and if you please send us an email with your goals, we will guide your towards the best solutions. The S55 is a well sorted platform so we have a wide variety of experience to pull from.
Regardless of who you choose to calibrate your engine, we suggest you reach out to them with your goals, and follow their advice for both hardware and software.