Open and Closed loop?
05-09-2005, 07:43 PM
#1
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Open and Closed loop?
How do you exactly explain what these terms are? im just curious cause i see these terms used alot throughout different threads.
I kno somewhat what they are, but anyone who could further explain what they mean would be cool!
I kno somewhat what they are, but anyone who could further explain what they mean would be cool!
05-09-2005, 07:47 PM
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Re: Open and Closed loop?
Basically, open loop means the car isn't learning. It is running off a set of predetermined values until certain conditions are met which cause it to switch to closed loop.
In closed loop, the car looks at all the data and constantly adjusts to hit its target. Mainly a/f.
In closed loop, the car looks at all the data and constantly adjusts to hit its target. Mainly a/f.
05-09-2005, 08:32 PM
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Re: Open and Closed loop?
Originally Posted by slimdawson
Basically, open loop means the car isn't learning. It is running off a set of predetermined values until certain conditions are met which cause it to switch to closed loop.
In closed loop, the car looks at all the data and constantly adjusts to hit its target. Mainly a/f.
In closed loop, the car looks at all the data and constantly adjusts to hit its target. Mainly a/f.
05-09-2005, 08:38 PM
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Re: Open and Closed loop?
Originally Posted by bow94z
o ok, so open loop starts at startup, and doesnt switch to closed loop until 140degrees correct?
05-10-2005, 09:06 AM
#6
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Re: Open and Closed loop?
Required for closed loop:
-O2 sensors heated up and active
-Coolant temp meets minimum (variable, between 120-140degF)
-timer from "start" times out (ususally about 2 minutes).
The only real difference between open loop and closed loop is the use of the O2 sensors for feedback. In open loop, the PCM ignores the O2 sensors, because they may not be warm enough to provide meaningful data. In closed loop, the O2 sensors become part of the "loop".... the PCM looks at the data from the O2 sensors, and uses it to set the short term fuel corrections (INT's). If the short term corrections are repeatedly on the "add" side or the "cut" side, the PCM adjusts the long term fuel corrections and saves them (BLM's) as a permanent part of the fuel calculation.
When you go to wide open throttle (WOT) the PCM will again ignore the O2 sensor readings, and may use the saved long term corrections (depends on whether it was adding or cutting fuel) to calculate the fuel required. It also sets a new, richer "target" A/F ratio. This is called power enrichment (PE) mode. In "closed loop" the PCM is always trying to maintain a 14.7:1 A/F ratio.
You might want to look over the "Air/Fuel Management" section of my online scanner guide.
http://members.aol.com/InjuneerZZ/ScanMast.htm
-O2 sensors heated up and active
-Coolant temp meets minimum (variable, between 120-140degF)
-timer from "start" times out (ususally about 2 minutes).
The only real difference between open loop and closed loop is the use of the O2 sensors for feedback. In open loop, the PCM ignores the O2 sensors, because they may not be warm enough to provide meaningful data. In closed loop, the O2 sensors become part of the "loop".... the PCM looks at the data from the O2 sensors, and uses it to set the short term fuel corrections (INT's). If the short term corrections are repeatedly on the "add" side or the "cut" side, the PCM adjusts the long term fuel corrections and saves them (BLM's) as a permanent part of the fuel calculation.
When you go to wide open throttle (WOT) the PCM will again ignore the O2 sensor readings, and may use the saved long term corrections (depends on whether it was adding or cutting fuel) to calculate the fuel required. It also sets a new, richer "target" A/F ratio. This is called power enrichment (PE) mode. In "closed loop" the PCM is always trying to maintain a 14.7:1 A/F ratio.
You might want to look over the "Air/Fuel Management" section of my online scanner guide.
http://members.aol.com/InjuneerZZ/ScanMast.htm
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