NefMoto

I just wanted to start a thread dedicated to boost tuning.   Here are the basic concepts of boost tuning with the stock ecu and n75 boost control solenoid.


the ME7.1 ecu doesn't really have a "boost" table. It does everything based on "specified load".

Requested boost = roughly 10*(spec load)+300mbar. (this pressure is in absolute pressure, which is relative boost[in charge piping]+atmospheric pressure at your elevation)
First, make sure the 100% pedal position requests enough load:
"Engine load desired" - specified load

Specified load/boost will never exceed these limits:
"Maximum specified load" - maximum specified load
"LDR altitude limitation (maximum pressure ratio)" - maximum requested pressure ratio


Specifically, on a full throttle pull, your boost profile will follow "maximum specified load".
K03s and K04s have some severe flow limitations, so unlike big turbos, you will want your boost to taper (not ramp up) to redline.



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to get a little more in depth, tony made a quick flowchart about how the ecu logic system works

ME7 ecu basically does it like this:

Desired Load -> Desired Cylinder Pressure -> Desired Boost Pressure
Desired Boost Pressure - Actual Boost Pressure -> Boost Deviation
Boost Deviation is used as an input by the Boost Controller to determine N75 duty cycle
which allows the wastegate to stay shut longer and boost to build higher.


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Personally for k03 turbos id say a spike of 16-18 PSI gradually tapering to 12.5 PSI by 6000 RPM is a nice boost profile
k04's and other turbos will be different.




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Now for stuff i dont know....

The only thing i cant find is the overboost limitations.  
What are the other maps that need to be changed to allow the car to hit its target boost over a stock level?


tony you mentioned it as "The ecu will throw many different codes if you raise the target load and change nothing else."

and do these have anything do with the limits and correction factors that are applied to the different values along the way?
are these perhaps the maps
Time for LDR overboost active (TLDOBAN)
Maximum load at E_ldo LDR (LDORXN)

if not, then what other maps need to be altered to allow boost to be raised?

Ok so i found what the limits are for turning up the boost.  It looks like you need to change Maximum airflow for load calculations flow SAE constant.

in stock form its set at approx 750 kg/hr which is around 210g/s.    Upper limit of flow on the stock k03 is around 1044kg/hr (290g/s) so setting the limit to 1080 kg/hr seems like enough buffer (300 g/s)

so input 1080 or so if you plan on maxing out your k03's at some point.

What is this map's name?

Correct me if I'm wrong, for an M-box it is MLMAX

KFMLDMX is the air mass limit for diagnosis. That is the only one you should have to raise.

Thank you!

I multiplied the whole table by 1.44, which is correction factor to go from 750 to 1080.  Any thing that ended up over 1080 I changed to 1080.  I'm just wondering if thy is enough to let me boost to 18 psi  on k03s and still be able to tell if my maf is going bad, or should I set the whole table to 1080?  It seems you would need to look in measuring blocks and make sure your maf was in spec every now and then if you set the whole table to 1080.

How did you find that w/o seeing this (http://s4wiki.com/wiki/Tuning)?

This is all quoted from the S4 wiki. That's a great place to start to get the basics on what requires to be changed when attempting to tune Motronic.