I have an Enthalpy tuned nissan ECU on my S14 SR20.

What are the conditions for the ECU to enter closed loop mode?

 

The feature is like a choke on a car with a carb so when its open its running rich till the car warms up then the system will go into a closed loop condition and lean out

 

No, it isn't. You're referring to coolant temperature correction:

Fuel Correction

Even when warm, the ECU only operates in closed loop in cruise. During periods of positive boost pressure, the ECU goes open loop.

Here's a list of conditions that will keep the Haltech unit out of closed loop:

• The startup time described in Post Start Delay setting has not yet elapsed since startup
• The throttle or MAP thresholds selected in the O2 Control settings are exceeded
• The engine is operating outside of the Lower RPM and Upper RPM
• Transient Throttle Enrichment is active
• Engine is not above the operating temp threshold as defined in O2 Control settings
• Deceleration Fuel cut is performing cut or enrichment operations

What I want to know is what sensor(s) drives the ECU into/out of open loop, and what the cutoffs are.

 

I'm pretty sure the ECU is programmed for engine under vacuum and under 4000rpms. The other parameters are above 60*C, not in limp-mode, and under 68mph. Under those conditions, it calculates a long term and short term fuel correction % based on O2 sensor switching high/low. Basically whatever is in the KA-DE FSM under closed-loop.

 

This is the closest I can find:



Am I not seeing the right page?

The <68mph is a bummer. I want closed loop control when I'm cruising at 75!

 

How does it know this on a MAF setup?

 

The same way it calculates load (TP). Take the mafs voltage, linearize it, divide by RPM. That, plus some scalars, are basically the load value. RSE can correlate that load (TP) to manifold pressure, plus or minus the effects of VE. Then RSE turns the O2 correction on in the areas under 0psi manifold pressure (gauge).

 

a-ha, so it's a best guess based on VE. pretty cool.

 

The later US ECUs have VE tables to remove the assumption, but then you have to know what your VE is at all the points on the map. The old way is easier. Adding cams will improve VE and shift everything a little bit, but that goes into the tune. The VE also changes as the VE (and TP) goes shitty as the cams lose efficiency up top, which is in the tune as well.

 

Good to know. Is there anywhere I can read up on this stuff? You seem to be the only source, and I don't want to keep bugging you.