Subaru WRX Forums banner

1 - 5 of 5 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
does the ECU "learn"

2 weeks after installing SPT catback; car seemed weaker at first and I was a bit disappointed, but now feels like it is accelerating much stronger and smoother. I have read that the ECU "learns" to adjust to changes (like a more free flowing exhaust). Is this true? How does it do that?
 

·
Registered
Joined
·
220 Posts
Re: does the ECU "learn"

The ECU has many learning tables that it populates realtime - what you may or may not be noticing is dynamic advance being maxed at 1.0 (which is good) and you are taking advantage of full timing advance. You may have been at a DAM of 1.0 all along though. Also, it could be the butt-dyno telling you your mod is working - placebo effect plays a part!

Did you reset your ECU after the install (unplug negative battery terminal)? This would explain a sluggish first 50ish miles even if you stayed stock.

It wont however reprogram its primary tables to take advantage of mods. So it won't LEARN your mods, it will only +/- primary tables based on the learning table parameters - sorry if that sounds confusing!!
 

·
Registered
Joined
·
220 Posts
Re: does the ECU "learn"

Your tune will always seek the predetermined AF ratio of 14.7 for cruise and full temp idle through closed loop control, and will revert to an open loop AF under WOT conditions. WOT is what you need to be most concerned with for any mods to the intake system because the fuel is NOT monitored and adjusted for during WOT - its simply injected according to load value and that's that.

However for closed loop - If your new intake is allowing more air through for the same g/s reading, then your ECU will see a lean condition at the O2 sensor and will use the short term fuel trims STFT to compensate - adding more fuel for the particular event that it experiences the lean condition. This STFT will be stored into the long term fuel trim LTFT such that the ECU has effectively learned the specifics of your intake flow.

The problem is that aftermarket intakes are usually MUCH TOO DIFFERENT in flow charateristics compared to the stock system, and the ECU cannot effectively trim just a few % here and there to compensate.
 
1 - 5 of 5 Posts
Top