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Old 09-28-2007, 04:00 PM   #1
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Default open vs close loop

well im still playing whit my aeroforce scan gauge to find my KR between 2000 and 4500 so everything beside that look normal in close loop

02=905 to 920
pwi =18 to 19
maf freq = 8972
timing at WOT ==26

but on open loop 60 degrees outside the timing WOT goes to 30 degrees and wow pull much harder and the sound is differend is this normal for a L36
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Old 09-28-2007, 04:13 PM   #2
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I don't quite understand...are you saying that the data you tabulated is closed loop data?
Because whenever you are in WOT, you are in open loop.

Otherwise, your data looks pretty normal to me; factory-set overly rich WOT O2'*, MAF just under 9000, and timing of 26 degrees (more aggressive factory program than the 21-22 degrees of my LeSabre)
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Old 09-28-2007, 04:47 PM   #3
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well the data that when the engine hot at 180 degrees that what i call close loop


but whit the engine cold and the IAT at 60 degrees (what i think is open loop ) i see up to 30 degrees of timing and i can feel it pull much better
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Old 09-28-2007, 05:09 PM   #4
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(someone please tell me if I'm too off topic)
What is the difference between open loop and closed loop and what does it mean? I think I remember PeterG telling me something about it, but I forgot
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Old 09-28-2007, 06:10 PM   #5
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open loop is when you first start the car and it is warming up. It is added fuel and what not

closed loop is after the car has warmed up. Fueling and what not relate back to the learned memory in the pcm


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Old 09-28-2007, 06:11 PM   #6
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And Don this is the exact same thing i am going through. But with me i am seeing 15 degrees of KR in closed and 0 timing.

In open loop 0 KR and full (19 degrees) of timing.


Hence the reason my next investment is in a custom pcm.
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Old 09-28-2007, 08:41 PM   #7
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Quote:
Originally Posted by TJ'sblackbonne
open loop is when you first start the car and it is warming up. It is added fuel and what not

closed loop is after the car has warmed up. Fueling and what not relate back to the learned memory in the pcm
When you go WOT you go into open loop too.
Watch your ST fuel trims at WOT they will lock at 128 or 0%.
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Old 09-28-2007, 11:16 PM   #8
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Quote:
When you go WOT you go into open loop too
so why do i get more timing when the engine is cold 26 vs 30 and do i feel it pulling much more also i have no KR when the engine is cold
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Old 09-29-2007, 01:07 AM   #9
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Snipped from http://engine.firebirdv6.com/

3800 PCM Operation

STARTING MODE
When the ignition is turned ON the PCM energizes the fuel pump relay for two seconds, allowing the fuel pump to build up pressure. The PCM then checks the Engine Coolant temperature (ECT) sensor and the Throttle Position (TP) sensor. During cranking, the PCM checks the crankshaft position signal in order to determine the proper air/fuel ratio for starting. The PCM controls the amount of fuel delivered in the STARTING Mode by changing how long the fuel injectors are energized. This is done by pulsing the fuel injectors for very short times.

RUN MODE
The RUN Mode has two CONDITIONS called Open Loop and Closed Loop. When the engine is first started and engine speed is above 725 RPM, the system is in Open Loop operation. In Open Loop the PCM ignores the signal from the Heated Oxygen Sensor (HO2S), and calculates the air/fuel ratio based on inputs from the TP, ECT, MAF sensors. The system remains in Open Loop until the following conditions are met:

1. The HO2S has a varying voltage output showing that it is hot enough to operate properly (this depends on temperature).
2. The ECT has reached a specific temperature (reported to be 170 degrees).
3. A specific amount of time has passed since starting the engine.

When these conditions are met, the system enters Closed Loop. In Closed Loop the PCM changes fuel injector on-time based on the signal from the HO2S. This allows the air/fuel ratio to stay very close to 14.7:1.

ACCELERATION MODE
The PCM provides extra fuel when it detects a rapid increase in throttle position and airflow.


I also wanted to add....you are also in Open Loop when you get into Power Enrichment (PE) mode (typically when you got WOT.)

Esentially...closed loop uses O2 sensor to adjust fuel delivery and maintain a 14.7 AFR. Open loop uses other sensors and fueling tables to adjust fuel delivery. Typically on the boosted car it'* between 11.7 - 12.4 AFR.
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Old 09-29-2007, 01:11 AM   #10
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Quote:
so why do i get more timing when the engine is cold 26 vs 30 and do i feel it pulling much more also i have no KR when the engine is cold
The PCM has settings that adjust timing based on coolant temp and air intake temp. Typically KR is not monitored until the coolant temp gets to ~160-170*. This also why it'* not advisable to run a 160* t-stat. If you never get above 160*, the PCM will stay in open loop and throw a code.

I typically keep out of WOT until it gets up to operating temp.

Just my 2 cents.
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