Open loop in the 5s-fe

[turboyota]

Ok. Does anyone have any websites/info on the operation of the ecu in closed and open loop for the 5s-fe (I have a 3rd gen camry)? Specifically where is the transition of to open loop from closed loop? Sensors used to determine transition point? What sensors are disregarded? Etc.

I've been reading and it was quoted several times that the ECU disregards the MAP sensor in open loop...??? That seams rather autistic to me . . .

[DarkMastyr]

Disregarding sensors is, by definition, what open loop does. The idea is that when a system in general is in open loop mode, it runs without any type of feedback control. Thus there is no use for any sensor readings.

[turboyota]

So you're telling me that as I get on the gas and there is a change in vacuum (airflow) engine coolant temp, air intake temp through traveling though the atmosphere (which is not consistant), etc. that the ecu know how much fuel to dump into the engine to hit the target air/fuel ratio on the rpm map??????

How does the ecu know how much air is coming into the engine in open loop? My car seams to be running good at 10 feet above sealevel here on the Delmarva peninsula. Calculating the change in air intake for denver, colorado (map/barometric pressure sensor, intake temp differences), the engine would be running super rich (7.5:1 afr) and have little to know power to even "pull a sick whore off a pee pot".

Wouldn't it be feezable to assume that the ecu simply disregards the o2 sensor when going into openloop. All the cars I've ever tuned (w/ efi) have been the same.

EDIT:

P.S. There are countless posts of guys getting gains from tuning their 5s-fe w/ SAFC this alters the map sensor readings in open loop (i guess beginning somewhere near WOT at above 2500-3000 rpms). If altering the map sensor at wot increases horsepower/torque amounts, then the ecu MUST be using this sensor to extrapolate proper air/fuel mixtures which when adjusted can in fact yield an increase in horsepower/torque output.

[OEMonkey]

Originally Posted by DarkMastyr

Disregarding sensors is, by definition, what open loop does. The idea is that when a system in general is in open loop mode, it runs without any type of feedback control. Thus there is no use for any sensor readings.

No use for any sensor readings is news to me.

MAP sensor signal is never disregarded. O2s signal is the only sensor ignored during open loop. Vehicle's in open loop when the engine coolant(ECT sensor signal) is cold. Under this condition, the O2s is too cold to produce a satisfactory signal and the ECU program controls a/f ratio without the O2s( or HO2s) input. As the engine and O2s reach operating temps., the ECU starts using O2s feedback(closed loop) to control a/f ratio. Certain conditions such as WOT(TPS signal, another unignored sensor) will automatically throw it back to open loop(no O2s feedback.)

[turboyota]

Originally Posted by OEMonkey

No use for any sensor readings is news to me.

MAP sensor signal is never disregarded. O2s signal is the only sensor ignored during open loop. Vehicle's in open loop when the engine coolant(ECT sensor signal) is cold. Under this condition, the O2s is too cold to produce a satisfactory signal and the ECU program controls a/f ratio without the O2s( or HO2s) input. As the engine and O2s reach operating temps., the ECU starts using O2s feedback(closed loop) to control a/f ratio. Certain conditions such as WOT(TPS signal, another unignored sensor) will automatically throw it back to open loop(no O2s feedback.)

Ok this is what I was thinking... what approximate throttle position precentage does this transition occur? Approximately, what map voltage, or vacuum reading, or boost reading (if map also can "throw it back to open loop") does this happen?

[JetspeedCamry]

Heres one technical definitioon of Open Loop:

Definition: A mode of operation in a computerized engine management system that occurs after a cold start. During open loop, the computer provides a fixed air/fuel ratio that is richer than normal to improve cold derivability until the engine warms up. See also Closed Loop.

http://autorepair.about.com/library/.../bldef-590.htm

[turboyota]

Originally Posted by JetspeedCamry

Heres one technical definitioon of Open Loop:

Definition: A mode of operation in a computerized engine management system that occurs after a cold start. During open loop, the computer provides a fixed air/fuel ratio that is richer than normal to improve cold derivability until the engine warms up. See also Closed Loop.

http://autorepair.about.com/library/.../bldef-590.htm

HAHA! yea. I know generally what open loop is. I was wondering what the 5s-fe ecu defines open loop as being? I've been tuning engines for a while; just not the 5s...

thanx though. Never thought to look there.

[JetspeedCamry]

I don't think the 5S has the capacity to define its own definition of Open Loop. I would say that its basic principle is the same, that it relies on a locked, stock map to control the motor in circumstances where the sensor hardware is not operating fully yet, i.e. Cold Start etc.

[scdtrd]

For what it is worth, I believe open loop happens when the TPS is 80% open, reguardless of the RPM or speed.

SCDTRD