Since there's not much tuning love or data for the N63TU, I thought I'd share my tuning (and learning) journey backed by logging and performance data. Hopefully there are useful bits in here both for those new to tuning and for the die-hard gearheads.
The car is a '14 550xi and all the runs for the data shown below are at 4600 ft elevation, with temperature noted where relevant (mostly around 80 degF, with equivalent density altitudes around 7600 ft). At this elevation, ambient pressure is about 2psi less than sea level, which would result in a 15% loss of power for a naturally aspirated engine. Turbos mostly make up the difference, though they have to work harder of course.
Data was logged using the Torque app on Android, with standard OBD data from a Bluetooth OBD adapter and other data (WGDC, intercooler air temperature) from a pair of custom piggy-back logging/tuning devices (details later). Performance information is from a Dragy GPS device and app, along with some verification 1/4 mile runs at the local drag strip. I try to explain things in detail through this journey along with lots of data, which may be tedious to those experienced in tuning, but hopefully it is helpful to others. All this data is over a 3+ year span, starting with roughly 10k miles on the odometer and currently at 70k. Despite all the known issues with previous generation N63 engine, my car and it's N63TU have been bulletproof (I estimate it's made over 200 1/4 mile runs from a dig with no issues at all, knock on wood...).
Let's get to some data - here's fully stock (with the exception of a pair of piggy-back logging devices and BootMod3 stock flash with speed limiter removed):
These are back-to-back 1/2 mile runs on the same stretch of private road in opposite directions to provide extra data and 0-60 mph and 1/4 mile statistics. The horizontal axis is time in seconds, and the time gap between the runs (typically 2-3 minutes) has been removed. The pressure data in this plot is units of absolute pressure, psia (relative to a perfect vacuum), as read from the intake manifold and intercooler pressure sensors. The following plot shows relative pressure (units of psi), aka gauge pressure, aka boost, computed as the difference between the absolute pressure sensor readings and the ambient pressure reading from a pressure sensor located inside each engine control unit (DME – “digital motor electronics”).
Stock at this elevation the car runs 13-15 psi of boost. At sea level, I would expect the car to run about 11-13 psi of boost, since the DME essentially tries to make the same power regardless of ambient pressure (up to a point, of course). I’m not an expert on the algorithms in the DMEs, but based on what I've read and my experience, this engine is somewhat unique in that the DMEs control engine output primarily through feedback from the mass airflow (MAF) sensors, not the intake pressure (TMAP) sensors like many other engines. In theory this seems more straightforward than using intake pressure, since the engine is a pump and the power output should be nearly a linear relationship with airflow through it. I'd imagine there are real-world constraints such as sensor accuracy, reliability, and transient response that make this type of control less than ideal, since BMW apparently went back to TMAP based control in the N63TU2. All the more reason there is no love for the N63TU...
Here are the performance numbers for these runs (83 degF, 7700 ft DA per airdensityonline.com):
Since stock wasn't fun for long, the next step was to add water-methanol injection (WMI). This could have been a later upgrade, but I wanted to take safety measures up front since I was eventually going to increase boost and pump gas is only 91 octane where I live and summer high temps are often 100+ degF. I ended up going with Snow Performance for the pump, controller, and nozzles, tapping into the MAF signal from the passenger side bank (bank #1) as input to the controller. Each bank uses a #4 (225 ml/min) nozzle at the outlet of the intercooler. Here are a few pics:
I built this tank before BMS starting making drop-in F-series WMI tanks - that would have saved me a bunch of time... Anyway, to insure the tank never runs dry, I tapped a level sensor (through an inverting relay) into the windshield washer fluid tank sensor wiring so I get an in-dash warning whenever washer fluid or WMI is low (typically WMI…). WMI by itself didn’t really add any power at stock boost levels, but it did significantly reduce intake temps and slightly improve timing:
If you compare this data to the pure stock data, you can see the intake temperatures rise only 5-10 degF over the full 1/2 mile runs compared to 25-30 degF without WMI. This chart also shows the difference between the temperatures reported by the intake manifold pressure/temperature sensors and the temperatures reported by the intercooler pressure/temperature sensors. The intercooler sensors are essentially pre-WMI due to the WMI nozzle locations so it provides a useful measurement of the WMI cooling effect. Note that the intercooler sensor temperature signals are not wired from the factory. I had to wire them, condition the signals, and transmit them to my phone for logging – more on that later.
Here are the performance numbers for these runs (82 degF, 7650 ft DA):
Next up was a mild increase in boost. I went with BMS JB+ piggy-back tuners primarily because of Terry Burger and his team's excellent customer support. The JB+ tuners modify the MAF signal to "trick" the DME into increasing airflow and therefore power output. Here’s a pic with them installed (one for each bank):
In this pic you can see an extra wire coming out of the bank 1 (left side in this pic) tuner. That is the MAF signal tap I added to feed the WMI controller in the trunk.
After some hot summer days, I realized this wasn’t the best installation location – the plastic cases were starting to warp due to the heat from the engine exhaust and turbos (which gets quite high above the center of the engine for an hour or two after running on a hot day…). Moving them away from the center of the engine solved that problem:
Here's data with these adjustable tuners set to the 12 o'clock position:
Compared to stock, the easy-to-install tuners added a noticeable bump in power, increasing boost by about 2 psi at the 12 o'clock setting:
Here are the performance numbers for these runs (78 degF, 7588 ft DA):
Since the JB+ tuners are adjustable, the next step was to turn them up:
Here’s data with them adjusted to the max setting:
Well, this data looks basically identical to the runs with them set to 12 o’clock. Performance numbers show the same thing (77 degF, 7573 ft DA):
What’s going on? Was the adjustment actually doing anything? Well, here are plots of MAF signals directly from the sensors and after modification by the JB+ tuners for the two settings:
These plot shows the JB+ tuners were working and the max setting was in fact adjusting the MAF signal quite a bit more than at the 12 o’clock setting. So what’s going on? Looking at turbo wastegate duty cycle (WGDC), which controls turbo boost, it is higher at the 12 o’clock setting than stock, but not any higher at the max setting:
Well, we’ve hit the DME’s programmed WGDC limit. This limit is hit sooner at 4600 ft elevation than at sea level since the air is less dense and the WGDC is higher to start with to achieve the same power levels (mass airflow) as at sea level, which explains why other people with the JB+ tuners do see a bump in performance when going to the JB+’s max setting.
To get around this limit and output more power, either the DME needs to be flashed or the WGDC control signals altered. At the time, nobody had flashed the DMEs yet and BMS was still developing the JB4 for the N63TU to tie into the wastegate control signals for increasing WGDC. BMS eventually produced a beta JB4 but support is limited and it runs with the check engine light (CEL) on since it requires disconnection of the MAF sensors, forcing the DME to switch to a secondary control method using intake pressure for control. I’d imagine they could have redesigned the JB4 for MAF based control, but that would presumably be a large investment of development and test time with limited payback given the relatively small market (especially since BMW apparently went back to pressure based control for the N63TU2). In addition, the location of the pneumatic wastegate control connectors requires at least partial removal of the bank 1 intercooler for access, which is not super easy. That means the market for a piggy-back solution would be further limited since, I believe, a large portion of the piggy-back tuner market is for cars under warranty where the tuner can be easily removed.
Anyway, I decided to build my own piggy-back device, largely since I enjoy that type of thing. The electronics are based around a Microchip PIC32 microcontroller for the digital side and various active and passive components for the analog side. I threw in a Bluetooth module to communicate wirelessly with an app on my phone. After a few (hundred...) hours of designing, programming, and testing the electronics, it was finally able to process and manipulate MAF, pressure, temperature, and WGDC signals and transmit data to my phone.
To install the devices, I decided to tap into those signals at the DME connectors since they are all readily available there. After finding appropriate crimp connectors online and making a little extraction tool it was not too difficult to pull wires from the connector and insert new tap wires. This required no cutting of wires and resulted in a fairly clean install. It also allows me to remove the device for testing in a purely stock mode. Here’s a pic of one connector on bank 1:
And with both connectors and the electronic device installed (bank 2):
With this pair of devices (one for each bank) I can log data and control the various signals. Logging includes intercooler temperature data, which is not wired from the factory. WMI pump duty cycle is also logged and is helpful to see operation of WMI, but I eventually plan to install a flow sensor which should be more useful. These electronic devices have a Bluetooth interface that connects to my phone, allowing data to be viewed and logged at 5 Hz. I originally planned to increase that to 10 Hz, but after working with the 5 Hz data, I think it’s probably not necessary. I have a custom app that forwards the data to the Torque app for combined logging with normal OBD data (and is shown on Torque’s nice graphical displays). All the data in the previous charts labelled with the “AB” prefix is from these devices.
Along the way of developing these devices, proTUNING Freaks (BootMod3, aka BM3) figured out how to flash the DMEs through the OBD port. This rendered most of the tuning and logging capabilities of my devices unnecessary. I initially flashed the DMEs just to remove the speed limiter (for ½ mile testing and runs at a local AirStrip Attack event), but since I found their web interface so easy to use, full of features, and professionally done, I subsequently flashed the DMEs with their off-the-shelf 93 octane stage 1 flash. This flash runs smoother than the pure piggy-back alteration of signals and I’ve been very satisfied with it. I now use my devices to tweak the signals for each bank (including quickly changing settings on the fly) and for logging. With the flash tune and my devices, I’m able to max out performance with the stock turbos:
I’ve run a little bit higher boost than shown in this chart, but performance numbers starts to drop – this seems to be the sweet spot. Here's a better look at boost pressures:
Since the air temperatures coming out of the intercoolers are cut off on the combined data chart, here’s the full temperature data:
The intercoolers are obviously completely unable to keep the intake charge cool over a half-mile run at these boost levels, but at least the WMI is limiting the temperature rise to about 20 degF (and reducing the charge air temperature by a good 50 degF!).
Here are the performance numbers for these runs (82 degF, 7750 ft DA):
Since the stock turbos are now maxed out (and I haven’t blown the motor yet…) next up are some Pure Stage 2 turbos. I’m planning that upgrade within the next year or so – I’ll post the results here.
The car is a '14 550xi and all the runs for the data shown below are at 4600 ft elevation, with temperature noted where relevant (mostly around 80 degF, with equivalent density altitudes around 7600 ft). At this elevation, ambient pressure is about 2psi less than sea level, which would result in a 15% loss of power for a naturally aspirated engine. Turbos mostly make up the difference, though they have to work harder of course.
Data was logged using the Torque app on Android, with standard OBD data from a Bluetooth OBD adapter and other data (WGDC, intercooler air temperature) from a pair of custom piggy-back logging/tuning devices (details later). Performance information is from a Dragy GPS device and app, along with some verification 1/4 mile runs at the local drag strip. I try to explain things in detail through this journey along with lots of data, which may be tedious to those experienced in tuning, but hopefully it is helpful to others. All this data is over a 3+ year span, starting with roughly 10k miles on the odometer and currently at 70k. Despite all the known issues with previous generation N63 engine, my car and it's N63TU have been bulletproof (I estimate it's made over 200 1/4 mile runs from a dig with no issues at all, knock on wood...).
Let's get to some data - here's fully stock (with the exception of a pair of piggy-back logging devices and BootMod3 stock flash with speed limiter removed):
These are back-to-back 1/2 mile runs on the same stretch of private road in opposite directions to provide extra data and 0-60 mph and 1/4 mile statistics. The horizontal axis is time in seconds, and the time gap between the runs (typically 2-3 minutes) has been removed. The pressure data in this plot is units of absolute pressure, psia (relative to a perfect vacuum), as read from the intake manifold and intercooler pressure sensors. The following plot shows relative pressure (units of psi), aka gauge pressure, aka boost, computed as the difference between the absolute pressure sensor readings and the ambient pressure reading from a pressure sensor located inside each engine control unit (DME – “digital motor electronics”).
Stock at this elevation the car runs 13-15 psi of boost. At sea level, I would expect the car to run about 11-13 psi of boost, since the DME essentially tries to make the same power regardless of ambient pressure (up to a point, of course). I’m not an expert on the algorithms in the DMEs, but based on what I've read and my experience, this engine is somewhat unique in that the DMEs control engine output primarily through feedback from the mass airflow (MAF) sensors, not the intake pressure (TMAP) sensors like many other engines. In theory this seems more straightforward than using intake pressure, since the engine is a pump and the power output should be nearly a linear relationship with airflow through it. I'd imagine there are real-world constraints such as sensor accuracy, reliability, and transient response that make this type of control less than ideal, since BMW apparently went back to TMAP based control in the N63TU2. All the more reason there is no love for the N63TU...
Here are the performance numbers for these runs (83 degF, 7700 ft DA per airdensityonline.com):
- 0-60mph: 4.56, 4.59 sec
- 1/4 mile: 12.76 sec @ 108.4 mph, [email protected]
- 1/2 mile: 133.6, 132.9 mph
Since stock wasn't fun for long, the next step was to add water-methanol injection (WMI). This could have been a later upgrade, but I wanted to take safety measures up front since I was eventually going to increase boost and pump gas is only 91 octane where I live and summer high temps are often 100+ degF. I ended up going with Snow Performance for the pump, controller, and nozzles, tapping into the MAF signal from the passenger side bank (bank #1) as input to the controller. Each bank uses a #4 (225 ml/min) nozzle at the outlet of the intercooler. Here are a few pics:
I built this tank before BMS starting making drop-in F-series WMI tanks - that would have saved me a bunch of time... Anyway, to insure the tank never runs dry, I tapped a level sensor (through an inverting relay) into the windshield washer fluid tank sensor wiring so I get an in-dash warning whenever washer fluid or WMI is low (typically WMI…). WMI by itself didn’t really add any power at stock boost levels, but it did significantly reduce intake temps and slightly improve timing:
If you compare this data to the pure stock data, you can see the intake temperatures rise only 5-10 degF over the full 1/2 mile runs compared to 25-30 degF without WMI. This chart also shows the difference between the temperatures reported by the intake manifold pressure/temperature sensors and the temperatures reported by the intercooler pressure/temperature sensors. The intercooler sensors are essentially pre-WMI due to the WMI nozzle locations so it provides a useful measurement of the WMI cooling effect. Note that the intercooler sensor temperature signals are not wired from the factory. I had to wire them, condition the signals, and transmit them to my phone for logging – more on that later.
Here are the performance numbers for these runs (82 degF, 7650 ft DA):
- 0-60mph: 4.58, 4.54 sec
- 1/4 mile: [email protected], [email protected]
- 1/2 mile: 134.7, 134.1 mph
Next up was a mild increase in boost. I went with BMS JB+ piggy-back tuners primarily because of Terry Burger and his team's excellent customer support. The JB+ tuners modify the MAF signal to "trick" the DME into increasing airflow and therefore power output. Here’s a pic with them installed (one for each bank):
In this pic you can see an extra wire coming out of the bank 1 (left side in this pic) tuner. That is the MAF signal tap I added to feed the WMI controller in the trunk.
After some hot summer days, I realized this wasn’t the best installation location – the plastic cases were starting to warp due to the heat from the engine exhaust and turbos (which gets quite high above the center of the engine for an hour or two after running on a hot day…). Moving them away from the center of the engine solved that problem:
Here's data with these adjustable tuners set to the 12 o'clock position:
Compared to stock, the easy-to-install tuners added a noticeable bump in power, increasing boost by about 2 psi at the 12 o'clock setting:
Here are the performance numbers for these runs (78 degF, 7588 ft DA):
- 0-60mph: 4.16, 4.25 sec
- 1/4 mile: [email protected], [email protected]
- 1/2 mile: 138.9, 136.0 mph
Since the JB+ tuners are adjustable, the next step was to turn them up:
Here’s data with them adjusted to the max setting:
Well, this data looks basically identical to the runs with them set to 12 o’clock. Performance numbers show the same thing (77 degF, 7573 ft DA):
- 0-60mph: 4.25, 4.21 sec
- 1/4 mile: [email protected], [email protected]
- 1/2 mile: 138.9, 137.0 mph
What’s going on? Was the adjustment actually doing anything? Well, here are plots of MAF signals directly from the sensors and after modification by the JB+ tuners for the two settings:
These plot shows the JB+ tuners were working and the max setting was in fact adjusting the MAF signal quite a bit more than at the 12 o’clock setting. So what’s going on? Looking at turbo wastegate duty cycle (WGDC), which controls turbo boost, it is higher at the 12 o’clock setting than stock, but not any higher at the max setting:
Well, we’ve hit the DME’s programmed WGDC limit. This limit is hit sooner at 4600 ft elevation than at sea level since the air is less dense and the WGDC is higher to start with to achieve the same power levels (mass airflow) as at sea level, which explains why other people with the JB+ tuners do see a bump in performance when going to the JB+’s max setting.
To get around this limit and output more power, either the DME needs to be flashed or the WGDC control signals altered. At the time, nobody had flashed the DMEs yet and BMS was still developing the JB4 for the N63TU to tie into the wastegate control signals for increasing WGDC. BMS eventually produced a beta JB4 but support is limited and it runs with the check engine light (CEL) on since it requires disconnection of the MAF sensors, forcing the DME to switch to a secondary control method using intake pressure for control. I’d imagine they could have redesigned the JB4 for MAF based control, but that would presumably be a large investment of development and test time with limited payback given the relatively small market (especially since BMW apparently went back to pressure based control for the N63TU2). In addition, the location of the pneumatic wastegate control connectors requires at least partial removal of the bank 1 intercooler for access, which is not super easy. That means the market for a piggy-back solution would be further limited since, I believe, a large portion of the piggy-back tuner market is for cars under warranty where the tuner can be easily removed.
Anyway, I decided to build my own piggy-back device, largely since I enjoy that type of thing. The electronics are based around a Microchip PIC32 microcontroller for the digital side and various active and passive components for the analog side. I threw in a Bluetooth module to communicate wirelessly with an app on my phone. After a few (hundred...) hours of designing, programming, and testing the electronics, it was finally able to process and manipulate MAF, pressure, temperature, and WGDC signals and transmit data to my phone.
To install the devices, I decided to tap into those signals at the DME connectors since they are all readily available there. After finding appropriate crimp connectors online and making a little extraction tool it was not too difficult to pull wires from the connector and insert new tap wires. This required no cutting of wires and resulted in a fairly clean install. It also allows me to remove the device for testing in a purely stock mode. Here’s a pic of one connector on bank 1:
And with both connectors and the electronic device installed (bank 2):
With this pair of devices (one for each bank) I can log data and control the various signals. Logging includes intercooler temperature data, which is not wired from the factory. WMI pump duty cycle is also logged and is helpful to see operation of WMI, but I eventually plan to install a flow sensor which should be more useful. These electronic devices have a Bluetooth interface that connects to my phone, allowing data to be viewed and logged at 5 Hz. I originally planned to increase that to 10 Hz, but after working with the 5 Hz data, I think it’s probably not necessary. I have a custom app that forwards the data to the Torque app for combined logging with normal OBD data (and is shown on Torque’s nice graphical displays). All the data in the previous charts labelled with the “AB” prefix is from these devices.
Along the way of developing these devices, proTUNING Freaks (BootMod3, aka BM3) figured out how to flash the DMEs through the OBD port. This rendered most of the tuning and logging capabilities of my devices unnecessary. I initially flashed the DMEs just to remove the speed limiter (for ½ mile testing and runs at a local AirStrip Attack event), but since I found their web interface so easy to use, full of features, and professionally done, I subsequently flashed the DMEs with their off-the-shelf 93 octane stage 1 flash. This flash runs smoother than the pure piggy-back alteration of signals and I’ve been very satisfied with it. I now use my devices to tweak the signals for each bank (including quickly changing settings on the fly) and for logging. With the flash tune and my devices, I’m able to max out performance with the stock turbos:
I’ve run a little bit higher boost than shown in this chart, but performance numbers starts to drop – this seems to be the sweet spot. Here's a better look at boost pressures:
Since the air temperatures coming out of the intercoolers are cut off on the combined data chart, here’s the full temperature data:
The intercoolers are obviously completely unable to keep the intake charge cool over a half-mile run at these boost levels, but at least the WMI is limiting the temperature rise to about 20 degF (and reducing the charge air temperature by a good 50 degF!).
Here are the performance numbers for these runs (82 degF, 7750 ft DA):
- 0-60mph: 3.87, 3.88 sec
- 1/4 mile: [email protected], [email protected]
- 1/2 mile: 144.0, 143.3 mph
Since the stock turbos are now maxed out (and I haven’t blown the motor yet…) next up are some Pure Stage 2 turbos. I’m planning that upgrade within the next year or so – I’ll post the results here.
. I'll be installing those at the end of the month.
