The purchase of a ‘Tune It Yourself’ ECU comes with support only for hardware. At the time of purchase a minimally modified base tune will be emailed to you, as well as flashed to the ECU prior to shipment. This base tune is a factory 607 or 608 ‘rev5’ tune, only modified if the ECU is to be run in an 850 or if additional options are purchased, such as VVT control, wideband lambda control, COP or burbles/crackles.
The ‘rev5’ tune comes with additional, non factory code which helps aide in tuning. These code additions were collectively created years ago, as part of a collaborative open source tuning project. The three main additions are data logging, CEL (check engine light) toggle in response to knock and map switching.
The data logging routine was created with maximum output speed in mind. This routine outputs 45 parameters at a speed of 4 to 20 samples a second, depending on engine RPM.
The CEL toggle in response to knock routine will toggle the CEL when the sum of ignition retard due to knock is greater than 15º. The ECU will preemptively attempt to prevent pre-ignition/knock from occurring by pulling 2.25º of timing from a cylinder in which knock was detected. It will do this in a narrow RPM and load range where the knock was detected. This ignition retard will be applied any time the ECU detects the engine is operating within this load and RPM range. This routine will look at the total amount of ignition retard due to knock, and while it is greater than the specified threshold it will toggle the CEL.
Map switching allows the switching of fuel, ignition, boost and injector main scalar maps between 4 available map sets on the fly. Map switching is accomplished by depressing the throttle pedal with the engine off and key in POSII.
The program which can most easily be used to modify the parameters on the ECU for tuning is TunerPro. A data definition and acquisition logging file can be found at M44.wikia.com.
While it is possible to tune M4.4 oneself, the learning curve is much greater than tuning using a standalone engine management system. M4.4 was created by Bosch, to be tuned by a team of OEM engineers. There are literally 1000’s of programmable parameters, and the relationship between parameters isn’t well documented. While access to the primary maps and scalars is simple, there are many other variables that must be modified when tuning any setup more modified than slightly stock. Some of these parameters are not in the public domain, and thus aren’t available for modification. Some examples of these parameters are cold start enrichment, radiator fan speed setpoints and wall wetting characteristics (necessary for large injector calibration).
Why Purchase a Full Tune?
The purchase of a full tune (tune-builder) comes with all the necessary support, logging and retuning to fully tune your car. The greatest benefit provided from purchasing a full tune is diagnostic troubleshooting. Believe it or not, the majority of time spent tuning a car is actually spent on troubleshooting mechanical issues. Hardware deficiencies are frequently encountered during the tuning of 25 year old cars. Out of the 550+ cars we have tuned, less than 10 have been ready to fully tune from the start.
The base tune used for all customers is based on the ‘rev5’ code, but has been improved significantly.
The CEL toggle in response to knock routine has been improved, such that the CEL will actively flash in response to real knock. A problem with the ‘rev5’ CEL toggle code is that most of the time when the CEL toggles, the engine isn’t actually knocking. The ‘rev5’ CEL toggle routine only alerts you when the ECU is retarding timing, due to previously detected knock, it doesn’t necessarily indicate that knock is currently occurring. This can be annoying as you won’t know when the engine is actually knocking vs when the ECU is just retarding ignition timing. For full tunes, the CEL routine has been re-written so that the CEL will actively flash when 2 or more actual knock events are detected within 3 seconds. Furthermore, a flashing CEL is much more noticeable than a toggling CEL.
The datalogging routine in the ‘rev5’ code interferes with standard OBDII functionality. With a ‘rev5’ tune you cannot read OBDII codes with the engine off, unless you connect your laptop and send a logging disable command. This will disable logging until the ECU is reset. With a full tune, OBDII functionality functions just like stock.
For all full tunes, a significant amount of ‘bloat’ code has been removed. This ‘bloat’ code is related to emissions compliance and other unnecessary functions. The removal of this code frees up resources and increases M4.4’s processing power.