BMW Datalogging Guide
Intro to Datalogging
Whether a stock daily driver or a dedicated track car, keeping track of how your car is running is vital to making sure your car will last without needing expensive repairs. While monitoring gauges on your car can let you know what is happening with a few parameters at a given moment, it won't be able to give you a full scope of how the car is running. In order to gain perspective over a wider range of time and parameters we run a datalog.
Here's a helpful reference on how to datalog.
How To: Datalog
What is a Datalog?
A Datalog is where the Accessport or another system records a user-specified set of sensor data and/or information which the vehicle's computer is using to run the engine. This can include things from simple data like coolant temperature, to how often the computer wants the fuel injector to be open during a given engine cycle.
Why Can't I Datalog Everything?
While each generation of ECU has different limitations there is generally a limit to the number of parameters you can select. In most cases this is because the ECU needs to process the requests for data and output that information to whatever device is requesting it. As a result the more monitors you request, the more work the computer has to do in order to keep up. On some vehicles as you approach the limit you won't see any differences until it simply can't log more items. However on other platforms you will see the approach to the limit show itself as a slow down in the logging rate, so if you are logging a bunch of different items make sure to keep an eye on the amount of time in between each sample to keep things in perspective.
Things Every Good Datalog Needs
A map with no reference points is never going to help you get from one place to another. There are a few parameters that do wonders for helping to put other monitors into context, as well as showing your environment and driving style. A good starting point when datalogging is to ensure your logging the default monitors as that will give you all of the core data needed. To ensure your logging the default monitors please click on Gauges, than Setup, than Configure Datalogging, Setup once more, and finally click on Reset to Defaults. If your protuner asks you for any additional monitors those can also be quickly added under the Configure Datalogging setup menu when needed.
Accelerator Pedal Position - (Accel Ped. Pos.) (drive by wire cars only)
Measures the amount the accelerator pedal is pressed down by the driver. Does not always equate to the same amount of throttle blade position and can give us additional information similar to what throttle position offers.
- Actual Load - (Load)
- Engine load after all compensations. The amount of power being given based on what the computer sees going on with the engine.
Barometric Pressure (Baro Pressure - (PSI, kPA, kPA)
A Measure of Barometric Pressure which is the air pressure at your location caused by multiple factors like temperature and elevation. Different pressures have an impact on air density which in turn will impact the amount of fuel necessary as well as peak boost and the way in which the turbo spools. At lower pressures (higher elevation) the turbocharger will have to work harder to achieve the same boost pressures.
RPM - (RPM)
Engine Revolutions per minute. This let's us see what speed the engine is moving at. Additionally conditions of acceleration, deceleration and maintaining a steady speed will all cause variations in the fueling and ignition timing
Throttle Position (TPS Act.)
How far open the throttle is open changes airflow to the engine and when combined with the RPM helps to give an indication of the amount of load the vehicle is under.
Quick Reference Guide - All BMW Platforms
N54 - Twin turbos one for each set of 3 cylinders. Inline 3.0L 6 cylinder.
High precision direct fuel injection, single hole tips. All aluminum alloy block with cast cylinder liners. Uses Vanos which is a variable intake and exhaust valve timing system. Cyclonic air/oil separator.
N55 - Single dual scroll turbo. Inline 3.0L 6 cylinder.
High precision direct fuel injection, multi-hole tips. All aluminum alloy block with cast cylinder liners. Uses Vanos which is a variable intake and exhaust valve timing system. Cylinder and head cover have integrated blow-by passages to recirculate exhaust gasses directly back into the intake ports.
V3 Guidance
What to look for
In general, when we look at BMW datalogs, we first look at individual cylinder timing correction under full throttle. Timing correction under part throttle would be very normal. Under load though, you want to see minimal corrections in the cylinders, but small corrections in 1-3 would be normal. Consistent corrections in 3+ cylinders or corrections that re-increment would indicate the mapping is too aggressive for the mechanical condition of the car.
Common Mechanical Ailments:
- Bad spark plugs/coilpacks
- Carbon build up on intake valves
- Bad tank of fuel or low octane fuel
Custom Tunes
With a custom tune, keep in mind that since they're made to specifications other than what we use, normal values may vary. For troubleshooting on a custom map reach out to the Protuner responsible for your tune and they should be able to help you out!
Engine Swaps
With thousands of cars around the world utilizing these engines, oftentimes swapping a used motor into your car can be a cost-effective alternative to rebuilding a tired or broken engine. However there are many important things to keep in mind when doing this as not all engines are created equal. Oftentimes foreign engines can come from the exact same model but have completely different hook-ups, sensors, or manifolds attached to the engine itself. Harder to detect are the engines that have different cam specs or a different compression ratio (a common occurrence between United States (USDM) and Japanese market (JDM) vehicles). This means that while getting it to fit can be a simple matter of just swapping a few parts over, getting it to run healthily and correctly is a different matter. Due to the fact that none of the engine's sensors will detect any of these changes, or the potential for a difference in sensor to cause skewed values, you will need to get a custom tune when swapping your engine out for anything other than the exact same engine your car had initially with stock specifications.
Built Engines
In the quest for ever more speed and power, eventually you come to the point of ordering up a built engine block, or even having one custom built to your specifications. This is an incredibly exciting day, as you'll no longer be held back by the limitations of the stock bottom end and can explore the upper limits of what your car (and in some cases you) are capable of. Similar to swapping for another stock engine, you'll need to get a custom tune in order to keep your engine running safe and in optimal condition. An added reason for this is that when using aftermarket parts that are forged or billet, there are differences in how much expansion the materials will undergo when they start to absorb the heat of the engine running. As a result when attempting to run a stock tune with a built engine, you'll probably see a lot of knock numbers from piston noise. It's important to tune the car appropriately for that so that these false knock readings don't mask the ones which are real, just like brakes can help you avoid an accident and keep your car safe, a tune can help avoid detonation or running lean, and keep your new engine safe.
Links and Related Videos
How To: Update Accessport Firmware - Can provide assistance with getting your Accessport running the most up-to-date firmware.
How To: Change Datalog Monitors - Shows you how to adjust your datalog monitors so that you are viewing what you'd like to look at.
Map Notes for BMW N54 - All N54 equipped models OTS map notes. Helps you to determine what map you should be flashed to for the octane rating and parts equipped on your vehicle.
Map Notes for BMW N54 - N54, E30 and 100 octane separate maps.
Map Notes for BMW N55 - Certain N55 2011 MY equipped models OTS map notes. Helps you to determine what map you should be flashed to for the octane rating and parts equipped on your vehicle.
Side note with OTS map octane verbiage:
Drive is to be used when lower quality 91AKI octane fuel is being used such as fuel found in Canada, Arizona, California, or Nevada.
Sport is for all other states that have higher quality 91AKI fuel.
Aggressive is only for states that have high quality 93AKI fuel.
You can always run equal to or greater than octane rating on a given map and never the other way around. Example, your flashed to a "Stage 1 Drive" map which is designed for low quality 91 fuel. You recently found high quality 93 octane fuel and decided to pump that, this is perfectly safe to run.
512100 - A list of all data monitors used by the various BMW platforms.
Knowledge Base - For additional support.
Customer Support
Have additional questions? Please don't hesitate to contact our Customer Support Team!
Email: support@cobbtuning.com
Phone support available 9am to 6pm Monday-Thursday. 9am to 4pm Friday (CST)
866.922.3059