Closed loop?
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
Closed loop is everything from idle to part throttle cruise. When you floor it, it enters into power enrichment which is an open loop operation. Closed loop the ECM reads the o2 and goes rich to lean (Called cross counts) and maintains 14.7 AFR. In power enrichment it runs right at 12:1 AFR.
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
My guess would be it is retarding timing not being hooked up and hurting performance. Although I'm not sure and maybe someone else knows how that circuit operates in greater detail.
Having the vehicle operate correctly is better for performance.
Having the vehicle operate correctly is better for performance.
Last edited by MrWillys; May 9, 2016 at 06:24 PM.
Race Director
Joined: Oct 2011
Posts: 16,079
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From: Dallas Texas
2025 C4 of the Year Finalist - Modified
Closed loop is everything from idle to part throttle cruise. When you floor it, it enters into power enrichment which is an open loop operation. Closed loop the ECM reads the o2 and goes rich to lean (Called cross counts) and maintains 14.7 AFR. In power enrichment it runs right at 12:1 AFR.
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Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
Race Director
Joined: Oct 2008
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From: Lansing MI
Supposedly within a few seconds after start up it will advance the timing until it senses knock then backs it off. That's the self test for the sensor. If it can't pick up a knock it assumes the sensor has failed and won't advance the timing properly again. Now all that being said to this very day I listen carefully for this to occur and I never hear it. So take it with a grain of salt, but that's what they tell you at the GM tech center in the fuel injection classes. So I agree with your thoughts on the timing.
Last edited by PatternDayTrader; May 9, 2016 at 08:33 PM.
Race Director
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From: Anaheim CA
Supposedly within a few seconds after start up it will advance the timing until it senses knock then backs it off. That's the self test for the sensor. If it can't pick up a knock it assumes the sensor has failed and won't advance the timing properly again. Now all that being said to this very day I listen carefully for this to occur and I never hear it. So take it with a grain of salt, but that's what they tell you at the GM tech center in the fuel injection classes. So I agree with your thoughts on the timing.
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
Here's where this ideal fails with me. We know that the O2 adjusts to 14.7 in normal operation using the narrow band o2 but when power enrichment is invoked the o2 is incapable of adjustment at such a rich mixture. Therefore, what is adjusting the fuel during power enrichment?
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
Here's where this ideal fails with me. We know that the O2 adjusts to 14.7 in normal operation using the narrow band o2 but when power enrichment is invoked the o2 is incapable of adjustment at such a rich mixture. Therefore, what is adjusting the fuel during power enrichment?
In Open Loop at WOT the timing/fuel is all controlled by TPS, MAF or MAP, Knock Sensor, IAT, CTS, Opti-Spark or Distributor Inputs depending on application.
Other words the ECM takes in ALL sensor data and following programming spits out fuel control and ignition timing.
Nothing adjusts the fuel during WOT per say. The ECM follows the inputs and looks at its programming to determine the outputs. Unlike closed loop which fine tunes the mixture with 02 feedback.
To the best of my knowledge even wideband 02 do not provide feedback during WOT. At least the ECM does not really watch them.
The 128 is just a default in the scan tool datastream during open loop operation. The 02's on C4's run 450mv during this time because the ECM provides a 450mv bias voltage to them.
The knock sensor (at least on LT1's) gets the same 450mv bias voltage.
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
Depends on the engine. Are we talking a MAF or MAP engine.
In Open Loop at WOT the timing/fuel is all controlled by TPS, MAF or MAP, Knock Sensor, IAT, CTS, Opti-Spark or Distributor Inputs depending on application.
Other words the ECM takes in ALL sensor data and following programming spits out fuel control and ignition timing.
Nothing adjusts the fuel during WOT per say. The ECM follows the inputs and looks at its programming to determine the outputs. Unlike closed loop which fine tunes the mixture with 02 feedback.
To the best of my knowledge even wideband 02 do not provide feedback during WOT. At least the ECM does not really watch them.
The 128 is just a default in the scan tool datastream during open loop operation. The 02's on C4's run 450mv during this time because the ECM provides a 450mv bias voltage to them.
The knock sensor (at least on LT1's) gets the same 450mv bias voltage.
In Open Loop at WOT the timing/fuel is all controlled by TPS, MAF or MAP, Knock Sensor, IAT, CTS, Opti-Spark or Distributor Inputs depending on application.
Other words the ECM takes in ALL sensor data and following programming spits out fuel control and ignition timing.
Nothing adjusts the fuel during WOT per say. The ECM follows the inputs and looks at its programming to determine the outputs. Unlike closed loop which fine tunes the mixture with 02 feedback.
To the best of my knowledge even wideband 02 do not provide feedback during WOT. At least the ECM does not really watch them.
The 128 is just a default in the scan tool datastream during open loop operation. The 02's on C4's run 450mv during this time because the ECM provides a 450mv bias voltage to them.
The knock sensor (at least on LT1's) gets the same 450mv bias voltage.
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
But the o2 is the heart of closed loop operation by reading the exhaust. No kidding.
If not accurate at the enriched mixture required for WOT operation then what is controlling blm operation? The inputs I mentioned and the programming, I did say that?
Your post reads if you can't dazzle them with brilliance baffle them with bullschitt. Just another reason I'm not posting around here much, I try to help people act like a bunch of kids....its not BS.
Show me in the coding blm operation for PE at 12.5 and I'll believe you. I don't have access to that or do I care. I'm not changing my fuel/ignition mapping on my car. Otherwise, PE is a simple % add to the open loop fuel map.
If not accurate at the enriched mixture required for WOT operation then what is controlling blm operation? The inputs I mentioned and the programming, I did say that?
Your post reads if you can't dazzle them with brilliance baffle them with bullschitt. Just another reason I'm not posting around here much, I try to help people act like a bunch of kids....its not BS.
Show me in the coding blm operation for PE at 12.5 and I'll believe you. I don't have access to that or do I care. I'm not changing my fuel/ignition mapping on my car. Otherwise, PE is a simple % add to the open loop fuel map.
My comments in RED.