As part of the BMW F series development EcuTek has developed an example ROM for the 435i. The testing has revealed the best methods to achieve reasonable gains without large risks. The end result of our testing was the creation of a series of Example ROMs that would give the tuner the basic modifications to the ROM that increase horsepower and remove the limits. This 435i ROM file (BMW 435i Stage 0 Example v01 000020DC-029-160-003-enc.bin) should be used as a guide to tune from and any "self tunes" should be based on this ROM.
When running our development cars on the dyno we simply strapped them down then pressed and held the traction control button allowing the car to run unhindered on the dyno. X drive cars may need to be run on a linked dyno.
Results & Map Changes
The example ROM gained 100lbs.ft torque and roughly 80hp at the flywheel (385hp 441lbs.ft) over the stock calibration (305hp 389lbs.ft). It uses a combination of increase torque, load and pressure ratio limits on top of changed fuel and ignition targets to achieve the increase.
The list of maps changes is relatively low to achieve such a gain, below is a ROM compare of a stock and tuned ROM.
Fuel Target Bank 1, 2 & SuperKnock
The high RPM and high engine load regions of these maps have been leaned out by about 3% or 0.5AFR points.
Ignition Base Timing - Warm - Path 1
Added 1 degree at high load and RPM regions.
Leakage Detection - Min Limit & Upper Limit
These maps prevent boost related DTC's occurring putting the car in limp modes
Load Limit - Knock Correction & Knock Correction (in SuperKnock)
This limits the load based on the amount over overall correction applied to the base ignition timing target. The X-axis of the map is not just the amount of knock correction it also includes pre-ignition calculations charge temperature corrections and other addition / subtractions to the timing function.
Max Load Factor
This will limit the maximum VE considered when calculating the load limit based on turbo limits, typically can remain unaltered if turbo limits are raised, but can be maxed to remove turbo based load limits.
This map sets a limit on the calculated maximum power of the engine, in Kilowatts.
Ratio difference to bypass ratio check
Cat diagnosis factor that set the amount of lambda difference allowed between inlet and outlet of the catalyst.
The rev limits for Factory testing, Knock Control, Overshoot, Overshoot AT, Overshoot AT w/o upshift, Overshoot, (lowered) - Overshoot - AT, (lowered) - Overshoot - AT w/o upshift we increased by 200RPM. This is only applicable to AT and DKG models to avoid the limit being hit with additional power and faster rate of change of RPM.
Torque Max - AT, DKG & MT
The starting point drivers torque request, corrections don't reduce engine load, they change the torque request. Engine load is regulated based on the final torque request after all the corrections to the drivers torque request.
Torque Max Multiplier - Inlet Temp
Multiplier for the torque max map based on manifold inlet (charge) temperature. It starts to reduce the torque limit when the charge temperature gets to high from repeated power runs. With a stock intercooler this will not take long to reach
Torque Max per Gear - Mode 1 & 2
The maximum allowed flywheel calculated torque, the torque is limited to this value if this is exceeded. These further limit the 2D torque max maps from above.
Torque Reduction Factor - Engine Speed
Factor on the low speed correction and possibly max power map based on RPM.
Turbo Pressure Ratio Limit
This is a turbo pressure limit, the output is limiting the allow pressure ration (between atmospheric and absolute boost pressure)
Volumetric Efficiency Limit for Calculation
Max. volumetric efficiency that can be achieved under full load. Used to cap the cylinder fill input to the torque from the "Torque Actual" maps for calculating torque, so may need to be raised to allow higher load and torque values.