Open Loop O2 question

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Feb 12, 2006 | 02:52 PM

steve40th

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From: South Carolina

St. Jude Donor '03 & '05

Open Loop O2 question

I am getting ready to install Heated O2 sensors, and just for general knowledge I need to know one thing.
Can the mapping table for fuel and spark etc, (correct terminology) be changed for open loop, or is this set in stone on a speed density 93?

Feb 12, 2006 | 03:18 PM

Ramanstud

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From: Cincinnati Oh

my understanding is that the fuel/spark maps ARE what's used in open loop by default.

Only when the O2 heats up (and when certain parameters relating to this in the ECM are met) is it then used to adjust fuel for efficiency.

Feb 12, 2006 | 05:09 PM

steve40th

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St. Jude Donor '03 & '05

Quote:

Originally Posted by Ramanstud

Okay, i am under the impression that when the car is cold and has not met parameters to go into closed loop, it uses predetermined mapping(non tuner mapping?). SO, I am thinking that the reason people go to heated is to get it to the tuning that the tuner has done, by going into closed loop, so it doesnt stay in the factory tuning, and thats why some pre heated O2 cars run real rich with long tubes, because they dont heat up the sensors and get into closed loop.

Feb 12, 2006 | 05:39 PM

Alvin

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From: Charlotte NC

St. Jude Donor '05

Quote:

Originally Posted by steve40th

No thats not the case.. the problem though is that open loop has enrichments that aren't needed on a warm engine..

For instance.. a warmed closed loop operation might target 14.7 while a open loop in the same senerio could call for a 13.8.

Feb 12, 2006 | 05:56 PM

steve40th

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St. Jude Donor '03 & '05

Quote:

Originally Posted by Alvin

Thanks Alvin, I am trying to understand how this hole thing works. A friends doing a 383 with long tubes, 1993, and I need to explain to him why he needs to go to Heated O2's. His will be very similiar to mine, as far as the motor goes.
So, basically my motor, as well as others who have modified engines or long tubes, arent needing the enrichments. And when it gets hot enough, the O2's, the motor leans out to the tuners specs, or what the car needs.
So, can you tune the open loop mode?

Feb 12, 2006 | 07:59 PM

Morley

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From: GA

Quote:

Originally Posted by steve40th

A friends doing a 383 with long tubes, 1993, and I need to explain to him why he needs to go to Heated O2's.

The main reason people go to heated O2 sensors is to keep the ECM in closed loop while the engine is running and up to operating temp. With long tube headers the sensor is usually located further down the exhaust than the stock location and the exhaust gasses are cooler down there and may not keep the sensor hot enough to operate. Another reason to use heated sensors is to get the O2 up to its operating temp faster, allowing the ECM to enter closed loop as soon as the coolant reaches the temp for closed loop operation.

Feb 12, 2006 | 10:10 PM

Alvin

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From: Charlotte NC

St. Jude Donor '05

Yep, thats hit it right on the head.

Steve, Open loop can be controlled very easily. Closed loop AFR is a bit harder to control but it is possible. What I mean by that is you can throw a crappy tune in a car and it will still try to hit its desired AFR's.. Doesn't mean it can or can do it effectively and quickly but its got a hard target AFR that the O2's look for.