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Are you thinking about flashing your N55 powered BMW to a Stage 1 tune? If you're curious about what to expect, we're here with some insights. We took a 2011 135i which has the N55 engine and DCT and put it through the paces after flashing the MHD N55 Stage 1 OTS tune. In this blog post, we will cover everything from power output and installation experience to 0-60mph, 1/4 mile times, and 60-130mph testing.
STAGE 1 DYNO TESTING
The 135i is using 100% OEM hardware, with an MHD N55 Stage 1 OTS tune. The dyno used is a Mustang dyno, which is known to be somewhat of a heartbreaker, typically reading 5-10% lower than a Dynojet. Our N55 powered 135i was able to put down a best of 328whp and 360wtq.
With torque peaking at about 3,250rpm, and power peaking at about 5,450rpm and tapering down to 290whp at redline. Although we would ideally like to see the peak power holding more towards redline, it will not be possible without a turbo upgrade. The best we can aim for is to raise the entire power band with more aggressive tuning, but the power tapering from 5,500 RPM to redline remains a characteristic of the turbo's efficiency curve.
The MHD interface was relatively straightforward to use. Essentially, it involves downloading an app and connecting an OBD cable/adapter. We used the bluetooth/wifi adapter to connect the car to the app wirelessly. However, we encountered some bugs in the app that required multiple restarts, and on several occasions, it wouldn't flash the vehicle at all. In the future we'll opt for the wired OBD connection to circumvent these issues.
STAGE 1 PERFORMANCE TESTING
The driving feel after the tune was fantastic. Throttle response was notably sharper, and the increase in power and torque was undeniable. Below are the best results we were able to achieve on the Stage 1 Tuning:
0-60mph: The 0-60mph time of 5.6 seconds does not reflect the Stage 1 power levels due to traction issue. With proper tires it is very reasonable to expect to shave almost 1 full second off this time.
1/4 Mile: As with the 0-60mph time, the 1/4 mile time of 13.6 seconds is not reflective of the Stage 1 power levels, and with a proper tire setup we could see approximately 1 second faster. The trap speed of 107mph is on point for an N55 with Stage 1 tuning.
60-130mph: A time of 15.5 seconds for the 60-130mph isn't great, but we'll see how much we can improve it with future tuning and upgrades.
LAUNCH CONTROL IN THE 135i
Surprisingly, the 2011 135i does have a built in launch control feature. To activate it, you have to put the car in SPORT mode by pressing the button below the shifter, enable DTC by pressing it once and tipping the shifter over into S mode. This will get the launch sequence to initiate when you press the brake and gas pedal at the same time. The engine will spin up to 4k RPM and hold it until you let off the brake, at which point it will engage the clutch, and you're off. Any other method than this, and the official launch control will not initiate. That means if you want traction control completely off, or if you want to put the car in manual shifting mode, you will lose launch control. But BMW must know what they're doing because every other way we attempted resulted in worse times across the board.
Traction was and issue on launch, as we were using Bridgestone A/S tires, which while it makes a good year round tire, it is definitely not optimal for a RWD car making over 360ft/lb of torque. That said, we are going to be focusing primarily on the 60-130mph times and 1/4 mile trap speeds to determine progress, but 0-60mph and 1/4 mile times were recorded as well for referencing.
HOW DOES THIS COMPARE TO AN N54?
In short, the N54 will produce more power on the stock turbos than the N55 with the same upgrades, there's no doubt about that. Our FBO N54 335xi put down just a tick above 400AWHP on the Mustang dyno. We expect our 135i RWD track car to make around 360WHP with the same modifications. The N54 and N55 both have the same taper in power from 5,500rpm to redline. The main advantages of the N55 over the N54 are not performance related, they are in the category of maintenance and repairs. The N54's in general are more complex (think 2 turbos instead of 1) and have more frequent and expensive repairs (think $1,500 injectors vs $500 injectors). This is why we went with an N55 specifically for our track car, since straight line performance isn't the objective on road courses. However, if you are building a car for straight line performance, there are few cars better than an N54 for the price point.
STAGE 2+ FBO
There is no power upgrade that has a better cost to power value than a tune, but a Stage 1 tune will only take you so far, and we want to go further than that. MHD does a great job with their OTS tune files and we're excited to test out the higher levels once we get the correct supporting modifications installed to run these files. The next steps for this 135i is to prepare it for a FBO Stage 2+ tune. We'll be installing our 7" FMIC with Intercooler Piping, Intake, Downpipe, and Charge Pipe.
The dyno results and performance testing of the Stage 1 N55 135i have left us eager and ready for more. Stay tuned for those results coming soon!
At ARM, we're passionate about pushing the limits and unlocking the full potential of your BMW. If you'd like us to help you with your build, let us know, and we'll be thrilled to assist you.