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      10-22-2012, 11:33 AM   #1
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Question OL/CL Fueling Clarification...

Tried searching/googling but got some conflicting information. So at WOT, are our cars in closed loop or open loop fueling? I thought it was CL fueling and is in OL while warming up, etc. My understanding of closed loop fueling is that it relies on the oxygen sensors to provide feedback to adjust air/fuel mixtures since our cars do not have MAF sensors. Is this true? OL fueling relies on settings in the DME, right?

Thanks.
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      10-22-2012, 12:38 PM   #2
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closed loop.
The OL in procede is just upping fuel pressure.
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      10-22-2012, 12:56 PM   #3
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Quote:
Originally Posted by enrita View Post
closed loop.
The OL in procede is just upping fuel pressure.
Thanks enrita. Is my understanding of how CL fueling works correct vis a vis oxygen sensor input?
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      10-22-2012, 01:21 PM   #4
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correct. closed loop bases AFR and such of sensors and open loop is a preset "map" to run on until the car heats up and also to boost fuel pressure as said before
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      10-22-2012, 01:28 PM   #5
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ECU is always doing both. OL fueling is preset fuel values that depend on rpm, load, boost. This provides the base amount of fuel. You want this value to be as close as possible to the amount of fuel needed for a given situation.

Closed loop fuel (Short term fuel trims -STFT) is always working as well. This provides the fine tuning of the fueling and is based off the car's O2 sensors. It has an authority range of +34% to -34% (not exactly sure what value the percent is based on). This will fill in any gaps that the OL fueling may be off. It can enlean or richen the fuel mixture up or down to its authority range. It does this based on measured O2 values in comparison to AFR setpoints.

Lets say for example at a certain WOT situation (rpm, load, boost) the preset OL fuel value is X and the AFR preset value is 12.5. When the car provides X fuel (OL value), the measured AFR is 13. This is lean compared to the preset 12.5. Closed loop fueling sees this difference, then adds fuel up to its 34% to bring the AFR down to 12.5. This runs continuously and is very fast reacting.
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      10-22-2012, 03:27 PM   #6
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Quote:
Originally Posted by BostonBeemah View Post
correct. closed loop bases AFR and such of sensors and open loop is a preset "map" to run on until the car heats up and also to boost fuel pressure as said before
Quote:
Originally Posted by GeorgiaTech335coupe View Post
ECU is always doing both. OL fueling is preset fuel values that depend on rpm, load, boost. This provides the base amount of fuel. You want this value to be as close as possible to the amount of fuel needed for a given situation.

Closed loop fuel (Short term fuel trims -STFT) is always working as well. This provides the fine tuning of the fueling and is based off the car's O2 sensors. It has an authority range of +34% to -34% (not exactly sure what value the percent is based on). This will fill in any gaps that the OL fueling may be off. It can enlean or richen the fuel mixture up or down to its authority range. It does this based on measured O2 values in comparison to AFR setpoints.

Lets say for example at a certain WOT situation (rpm, load, boost) the preset OL fuel value is X and the AFR preset value is 12.5. When the car provides X fuel (OL value), the measured AFR is 13. This is lean compared to the preset 12.5. Closed loop fueling sees this difference, then adds fuel up to its 34% to bring the AFR down to 12.5. This runs continuously and is very fast reacting.
thank you guys for the clarification!
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