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b5aar b5aar is offline
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Join Date: May 2010
Location: up and down the east coast
Posts: 131
Hey mark. Here goes I'm like a caveman with a hand grenade with this stuff. I know how to pull the pin but that's about it. Haha.

I believe k Lambda is in open loop until temperature switch (weber book pg 77?)send closed -open? signal to ecu to receive closed-loop control.also comes out of closed-loop with a throttle position sensor.....others commented from various threads.

Probst book also describes where closed-loop goes to open loop
Lambda sensor cool
engine cool
wide open throttle.

I know kinda vague language but paraphrasing

Hey..finallyfound the paragraph.

"because lambda sensor operation depends on high temperature the system operates open loop before the sensor warms up this can cause driveability problems and increased exhaust emissions do too imprecise mixture control. To correct this many cars have a lambda thermal switch located in the coolant or on the cylinder head of air cooled Porsches to give the control unit an additional input and ensure proper fuel metering during engine warm up. When the engine is cold the thermal switch is closed the control unit send a fixed slightly rich duty cycle signal of 60 percent to the lambda control valve. When the thermal switch warm enough to open the control unit sense of fixed middle signal 50 percent duty cycle when the lambda sensor reaches operating temperature so it signals are valid the control unit switches to close the loop operation. Remember in closed loop the duty cycle signals are constantly changing cycling back and forth between about 45 percent and 55 percent so that the air fuel ratio is maintained near the way to metric lambda equals 1.
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Old 02-23-2014, 06:23 PM
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