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Old 10-06-2011, 12:35 PM   #305
the suicidal eggroll
Scooby Guru
Member#: 51961
Join Date: Jan 2004
Chapter/Region: RMIC
Location: Broomfield, CO
2005 STi
2012 WRX


The problem is you'll find a million different opinions of how one should go about tuning boost, just like any other part of the system. I prefer to tune my MAF by disabling the closed loop fueling system and directly observing the AFR error while logging, then applying that % error to whatever MAF cell is active at the time. Other people never disable closed loop, and instead USE the closed loop system to tell them what their error is at any given time (the closed loop system is adding 10% fuel to hit stoich, so I need to add 10% to my MAF at that spot), etc. Both approaches are valid and have their advantages and disadvantages.

My approach stems from my [limited] experience with designing closed loop control systems. Trying to tune the system while the entire thing is active can be a HORRIBLE pain in the butt, and will often leave you chasing your own tail, trying to correct issues at one time using values that were derived a second and a half earlier, etc. You can really only do that IF the system is at steady-state, which the boost control system never will be unless you're tuning on a dyno that has the ability to hold RPM constant while you sit there at WOT. For that reason, I always prefer to turn off the closed loop corrections, get it working properly in open loop first, then add the feedback system back in just to keep the system on target in the future. That's not the only way to do things though.
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