Tuning the ms45.1 for the ESS twin screw supercharger kits
Not sure where to post this here, but I posted this on e46f and know we're all MS45.1 guys here so you might find this helpful too.
SOLVED IT
Perfect cold starts
Smooth power delivery straight to red line
Smooth throttle action on and off throttle
OEM-level drivability (just with more torque obviously)
Correct fueling
All the things the ESS tune should've had, but didn't, and couldn't.
I’ve learned a lot during this long journey and I’ve posted most of the basics including scaling for larger injectors up in the wiki on ms4x.net. https://www.ms4x.net/index.php?title=Siemens_MS45
More specific to positive displacement supercharger kits you need to make a few more corrections, which I think you should make for centrifugal kits too but it seems you can probably get away without it?
Anyway, the solution is with the intake manifold model and the torque reference tables.
There is a pressure quotient that will trigger full wide open throttle at about .950 (default) of the maximum airflow according to the intake manifold model. The intake manifold model must be increased to account for the higher airflow so that wide open throttle doesn’t happen way too soon (and suddenly) along the pedal travel.
Next the torque reference tables need to be rescaled for higher levels of mg/stk engine load as a result of the higher airflow. If these tables are left untouched then throttle will be limited based on the maximum mg/stk values in these tables (e.g. only 750mg/stk in stock form, or only 3/4 of what the twin screw will produce) as a “safety” function of the electronic throttle control, and you will never reach wide open throttle.
When adjusting these two sets of tables I would suggest only scaling the values above 2500 rpm or 100mg/stk or ~75nm of torque, because remember at low load and low rpm the bypass valve is open and under those conditions the engine management should be identical to stock.
Don’t forget to update c_maf_max_diag and ip_maf_1_diag__n__tps_av to appropriate values to prevent false alarm DTCs.
Also it should go without saying but be sure to dial back the ignition timing a bit, need to be safe here. I’m running at about 15-16 degrees of timing (21 is stock IIRC…) under full load and I’m just barely seeing the DME pull some timing every once in a while. If you run a larger pulley you can probably get a degree or more of timing back. I’d be real curious to see an experiment on the dyno: what makes more power, a small pulley with less timing or a larger pulley with more timing? I digress…
There are a few other tweaks I’ve made in my tune for pedal sensitivity, cold start fueling, raised idle to 850, disabled lower o2 sensors and sap delete, etc and I’ve added most of that to the wiki. Out of 2500 parameters in the ms45.1 I only modified about 40 total.
My tune was developed by me based on my car:
2003 ZHP Manual transmission
Current BMW MS45.1 base firmware (7561520)
ESS TS2 kit using slightly smaller 79mm (stock ts2 is 83/85mm)
Bosch 42lb green giant injectors (stock ts2 is red 30lb)
E46 M3 fuel pump (stock ts2 uses stock fuel pump)
Catless headers
SAP delete
Disclaimer: I’m not a tuner, I’m just a stubborn guy with high standards when it comes to my car and what ESS gave me was junk. I’ve done my best to figure out how to tune the car “the right way”, no hacks, patch jobs, or tricks. Use this information at your own risk, or work with an experienced tuner.
Frank Smith has a copy of my tune and can handle your custom tuning needs, and I’ll be posting my tune publicly on bimmerlabs.com shortly.
Huge thanks to Frank Smith and Hassmachine for their support and tools, without them I wouldn't have figured it out.
AJ @ ESS can kiss my butt. :p :p
