What Is Open Loop
01-05-2008, 01:55 AM
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What Is Open Loop WHAT IS MEANT WHEN SOMEONE SAYS IS THE CAR RUNNING ON OPEN LOOP? i DON'T KNOW WHAT THAT IS CAN SOEONE EXPLAIN THIS TO ME PLEASE. CAUSE I THINK THEY DID THIS TO MY CAR!
01-05-2008, 02:21 AM
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Our factory computers run in both Open Loop and Closed Loop:
1) When you first start the car, you're in open loop, and the PCM is NOT using oxygen sensor readings to adjust fueling. It's relying solely on the other sensors (MAF, MAP, rpm, etc.) to calculate how much fuel to inject into the engine, without knowing how good of a job its doing.
2) As I understand it, only after a timer has 'timed out' and the engine is above a certain temperature will the PCM then switch into closed loop mode. This is when it starts accepting oxygen sensor readings and adjusting the fuel trim accordingly.
If your car is running in open loop permanently, then your oxygen sensors are never used, and the PCM is not making corrections to the fuel trim. Not sure what year your vehicle is, but if you have datalogging software such as Datamaster, you can verify 'if' and 'when' the PCM is switching into closed loop mode.
1) When you first start the car, you're in open loop, and the PCM is NOT using oxygen sensor readings to adjust fueling. It's relying solely on the other sensors (MAF, MAP, rpm, etc.) to calculate how much fuel to inject into the engine, without knowing how good of a job its doing.
2) As I understand it, only after a timer has 'timed out' and the engine is above a certain temperature will the PCM then switch into closed loop mode. This is when it starts accepting oxygen sensor readings and adjusting the fuel trim accordingly.
If your car is running in open loop permanently, then your oxygen sensors are never used, and the PCM is not making corrections to the fuel trim. Not sure what year your vehicle is, but if you have datalogging software such as Datamaster, you can verify 'if' and 'when' the PCM is switching into closed loop mode.
01-05-2008, 12:50 PM
#4
Your answer is correct, but incomplete. You also run in Open Loop when you are at WOT after the engine warms up. That is why it is important to tune in both Closed Loop and in Open Loop modes. You use a wideband to tune the AFR in Open Loop mode, which is what you use a dyno for.
01-06-2008, 02:12 PM
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my car runs worse when it starts reading from the o2's... perhaps it's reversed? lol.. i think its because the o2 sensor wire is crimped together with a plastic connector (o2 sensor to harness, because harness end plug ripped off).. some ppl told me crimping the o2 wires can cause it to read wrong, so soldering it would solve this problem.. is that correct?
01-06-2008, 02:48 PM
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Your answer is correct, but incomplete. You also run in Open Loop when you are at WOT after the engine warms up. That is why it is important to tune in both Closed Loop and in Open Loop modes. You use a wideband to tune the AFR in Open Loop mode, which is what you use a dyno for.
Actually at WOT you use power enrichment (PE) mode. This is basically an effective open loop mode in the sense that it does not use the O2 sensors, but it is not the same mode as when the car is cold and it is controlled differently.
01-06-2008, 02:53 PM
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Your answer is correct, but incomplete. You also run in Open Loop when you are at WOT after the engine warms up. That is why it is important to tune in both Closed Loop and in Open Loop modes. You use a wideband to tune the AFR in Open Loop mode, which is what you use a dyno for.
There are two seperate tables for this. Open Loop, and PE tables. PE tables are used for WOT application.
Opps Edit.. Didn't see Ibird's reply.