The great O2 sensor debate
#1
The great O2 sensor debate
Since I put the 5.0 in my truck I've been running without ANY 02 sensors.
I started thinking about it the other day, and figured it puts the truck in "limp mode" since it fails to see the circuit completed.
So I grabbed my 02 sensors, plugged them in, and zip-tied them to the frame.
Was this a good move?
Remember, I have a custom true-dual exhaust, no crossover, no H or Y pipe, and no catalytic converters. Just manifolds, pipes, and Flowmaster 40's.
I started thinking about it the other day, and figured it puts the truck in "limp mode" since it fails to see the circuit completed.
So I grabbed my 02 sensors, plugged them in, and zip-tied them to the frame.
Was this a good move?
Remember, I have a custom true-dual exhaust, no crossover, no H or Y pipe, and no catalytic converters. Just manifolds, pipes, and Flowmaster 40's.
#3
#5
With them unplugged, the ecu goes into "limp mode", correct?
I defiantly don't want to be running too rich. I'm gonna go pull the codes now and see what the computer tells me. That AutoXRay was the best investment ever!
#6
Which is why they are 4-wire O2 sensors with a separate heating circuit altogether.
With them unplugged, the ecu goes into "limp mode", correct?
I defiantly don't want to be running too rich. I'm gonna go pull the codes now and see what the computer tells me. That AutoXRay was the best investment ever!
With them unplugged, the ecu goes into "limp mode", correct?
I defiantly don't want to be running too rich. I'm gonna go pull the codes now and see what the computer tells me. That AutoXRay was the best investment ever!
#9
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there is open loop and closed loop. open loop is what they used on verry early FI systems, no O2 sensors. it adjusted the amount of fuel by engine temp, rpm, tps, iat, and iap. the more advanced closed loop is what used on all FI systems today along with all the other sensors it also has O2 sensors that tell the computer how the motor is running rich/leen to correct it self.
limp mode is just a basic fuel map that will allow the engine to run but it will have a lower max rpm and low performance.
limp mode is just a basic fuel map that will allow the engine to run but it will have a lower max rpm and low performance.
#10
there is open loop and closed loop. open loop is what they used on verry early FI systems, no O2 sensors. it adjusted the amount of fuel by engine temp, rpm, tps, iat, and iap. the more advanced closed loop is what used on all FI systems today along with all the other sensors it also has O2 sensors that tell the computer how the motor is running rich/leen to correct it self.
limp mode is just a basic fuel map that will allow the engine to run but it will have a lower max rpm and low performance.
limp mode is just a basic fuel map that will allow the engine to run but it will have a lower max rpm and low performance.
#11
Open loop:
The air/fuel ratio is taken from a PCM table that is based on load and RPM and corrected for other factors like barometric pressure, coolant temp, intake temp, etc. Open loop is commonly used at WOT or near WOT, during some decelerations and before the oxygen sensors come up to operating temperature. It is also used during the execution of certain OBDII monitors.
Closed loop:
The air/fuel ratio is controlled around stoichiometry by the PCM based on a feedback loop using input from the upstream oxygen sensor(s). Closed loop is typically employed during idle and part throttle operation after the oxygen sensors have warmed enough to make them effective. Closed loop operation can produce very high efficiency in a 3-way catalytic converter.
Limp mode:
This is the PCM's "last resort" attempt to keep the engine running and the vehicle moving. Most sensors are ignored and the PCM uses very crude spark and fuel delivery. Electronic automatic transmissions use only 2nd or 3rd of the forward gears and torque converter clutch operation is disabled. In limp mode, performance, driveability, fuel economy and emission control are severely compromised. Basically, the air/fuel portion of limp mode is open loop taken to its most primitive level.
The air/fuel ratio is taken from a PCM table that is based on load and RPM and corrected for other factors like barometric pressure, coolant temp, intake temp, etc. Open loop is commonly used at WOT or near WOT, during some decelerations and before the oxygen sensors come up to operating temperature. It is also used during the execution of certain OBDII monitors.
Closed loop:
The air/fuel ratio is controlled around stoichiometry by the PCM based on a feedback loop using input from the upstream oxygen sensor(s). Closed loop is typically employed during idle and part throttle operation after the oxygen sensors have warmed enough to make them effective. Closed loop operation can produce very high efficiency in a 3-way catalytic converter.
Limp mode:
This is the PCM's "last resort" attempt to keep the engine running and the vehicle moving. Most sensors are ignored and the PCM uses very crude spark and fuel delivery. Electronic automatic transmissions use only 2nd or 3rd of the forward gears and torque converter clutch operation is disabled. In limp mode, performance, driveability, fuel economy and emission control are severely compromised. Basically, the air/fuel portion of limp mode is open loop taken to its most primitive level.
#12
Since I put the 5.0 in my truck I've been running without ANY 02 sensors.
I started thinking about it the other day, and figured it puts the truck in "limp mode" since it fails to see the circuit completed.
So I grabbed my 02 sensors, plugged them in, and zip-tied them to the frame.
Was this a good move?
Remember, I have a custom true-dual exhaust, no crossover, no H or Y pipe, and no catalytic converters. Just manifolds, pipes, and Flowmaster 40's.
I started thinking about it the other day, and figured it puts the truck in "limp mode" since it fails to see the circuit completed.
So I grabbed my 02 sensors, plugged them in, and zip-tied them to the frame.
Was this a good move?
Remember, I have a custom true-dual exhaust, no crossover, no H or Y pipe, and no catalytic converters. Just manifolds, pipes, and Flowmaster 40's.
I'm sure that zip tying the sensors out in the air will not improve anything and it should actually cause the engine to run richer than ideal - at least for a while until the PCM hits the clip and reverts to open loop.
The best fuel control strategy should be to weld O2 bungs into the down pipes near the exhaust manifolds, install the upstream sensors and let the PCM use closed loop when appropriate.
#13
Without any oxygen sensor input, the PCM will go to the open fuel tables, light the CEL and store trouble codes in the PCM.
I'm sure that zip tying the sensors out in the air will not improve anything and it should actually cause the engine to run richer than ideal - at least for a while until the PCM hits the clip and reverts to open loop.
The best fuel control strategy should be to weld O2 bungs into the down pipes near the exhaust manifolds, install the upstream sensors and let the PCM use closed loop when appropriate.
I'm sure that zip tying the sensors out in the air will not improve anything and it should actually cause the engine to run richer than ideal - at least for a while until the PCM hits the clip and reverts to open loop.
The best fuel control strategy should be to weld O2 bungs into the down pipes near the exhaust manifolds, install the upstream sensors and let the PCM use closed loop when appropriate.
Now, do I understand correctly you're thinking I should install only 2 of the 4 total O2 sensors, those being the ones that usually are BEFORE the catalytic converter, and leave the two After-Cat sensors unplugged?
I'm starting to think investing in a decent catalyst system and installing O2 sensors would be the best route for fuel economy and performance.
#14
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Eh open loop is only for when you first start up your truck that allowes your o2's and other sensors to get to proper operating temps. Then your ecu turns to closed loop thuss relying on your o2's ect for engine timing ect. Sure your not thinking of old school mech injection? Also (correct me if im wrong) there is no such thing as "limp mode" only open/closed loop.
#15
Now, do I understand correctly you're thinking I should install only 2 of the 4 total O2 sensors, those being the ones that usually are BEFORE the catalytic converter, and leave the two After-Cat sensors unplugged?
I'm starting to think investing in a decent catalyst system and installing O2 sensors would be the best route for fuel economy and performance.
I'm starting to think investing in a decent catalyst system and installing O2 sensors would be the best route for fuel economy and performance.
I prefer to run with cats and O2's because they make such a huge difference in emissions without much impact on the performance of a mild street engine. The trick is to place the cats close enough to the engine to keep them hot enough to work at idle but far enough away that they are not damaged by heat at part throttle and WOT. I took the easy way out and used the stock front cats in the stock location and the rears in a near stock location.
Obviously, a Ranger V8 is not about fuel economy. I haven't bothered to measure FE in town but it's not great, partly because it's almost impossible to keep your foot out of it. At steady speeds on the highway, my 5.0 economy does not seem to be much lower than than the 4.0 was. I think that it's helped by the lower revs of the automatic's overdrive ratio.
#16
Limp mode:
This is the PCM's "last resort" attempt to keep the engine running and the vehicle moving. Most sensors are ignored and the PCM uses very crude spark and fuel delivery. Electronic automatic transmissions use only 2nd or 3rd of the forward gears and torque converter clutch operation is disabled. In limp mode, performance, driveability, fuel economy and emission control are severely compromised. Basically, the air/fuel portion of limp mode is open loop taken to its most primitive level.
This is the PCM's "last resort" attempt to keep the engine running and the vehicle moving. Most sensors are ignored and the PCM uses very crude spark and fuel delivery. Electronic automatic transmissions use only 2nd or 3rd of the forward gears and torque converter clutch operation is disabled. In limp mode, performance, driveability, fuel economy and emission control are severely compromised. Basically, the air/fuel portion of limp mode is open loop taken to its most primitive level.
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