Closed Loop Mode

[JeepNmpg2]

Originally Posted by JeepNmpg2

Sure, when I get off work, I'll go and look.

Sorry guys, I didn't get a chance to as it was pouring rain and I don't have a garage or carport.

I'll try again this evening, but the weather is supposed to be the same.

[cfg83]

JeepNmpg2 -

Originally Posted by JeepNmpg2

Sorry guys, I didn't get a chance to as it was pouring rain and I don't have a garage or carport.

I'll try again this evening, but the weather is supposed to be the same.

No problem. Don't get all wet over it, .

CarloSW2

[cfg83]

jfitzpat -

Originally Posted by jfitzpat

...

A heated sensor is faster (and generally heated so that the vehicle can get closed loop for emissions purposes faster), but there are still some undesired delays. You can't pre-heat the sensor for startup, because unburnt fuel or condensation would shock cool the ceramic and crack it.

...

Yikes, that's egg-zactly what I am doing here :

http://ecomodder.com/forum/showthrea...2-a-10921.html

From what you just wrote, I should expect my heated 02 sensor to fail early.

I'm already committed, so I am going to keep using it as intented and see how long it lasts (aka a tootsie roll pop). Another sacrifice in the name of science!

CarloSW2

[mwebb]

...."You ALWAYs want to measure lambda pre-CAT.
The sensors don't really measure AFR, but equivalency ratio

(which is inverted to give lambda). Basically O2 is added or removed to the test chamber until stoich is reached. Since CAT is supposed to be removing hydrocarbons, the post cat sensors are there to see rather or not there is a proper shift from the real (pre-cat) equivelency ratio measurements.

When you get a 'cat efficiency' DTC it generally means that one of the sensors has gone bad, or the shift between pre and post CAT is below expected.
"....

The sensors don't really measure AFR, but equivalency ratio
the above statement is not really true
AFR sensors do measure AFR and
EQ ratio is a command NOT a measurement

in the real world
for actual cars driven on the road -
the ECM does not add or remove 02
the ECM changes the amount of fuel from a base value depending on inputs from various sensors
the amount of change is represented by fuel trim values
short term trim and long term trim on most cars
not all cars

when you get a cat efficiency DTC it almost always means bad cat
because
the cat test WILL NEVER RUN if there is a problem with the 02 or AFR sensors
the 02 or AFR sensor testing must be complete
and it must pass before cat testing will be enabled and
if a 02 or AFR sensor should set a DTC , cat testing will be disabled until the DTC has been cleared
and
then
the 02 or AFR sensor testing will have to run to completion and pass in order to enable cat testing

which would be the reason we save the last run mode 6 test for the cat
prior to clearing DTCs , so we have an idea if the cat will fail when testing is re enabled

if you have a cat efficiency DTC and no other DTC and
all mode 6 and mode 5 tests (if present) have passed
except the cat tests
the cat is bad -

a 2000 jeep has 02 sensors , plain jane bang bang sensors

[mwebb]

Originally Posted by cfg83

jfitzpat -



Yikes, that's egg-zactly what I am doing here :

http://ecomodder.com/forum/showthrea...2-a-10921.html

From what you just wrote, I should expect my heated 02 sensor to fail early.

I'm already committed, so I am going to keep using it as intented and see how long it lasts (aka a tootsie roll pop). Another sacrifice in the name of science!

CarloSW2

no it should not fail early
if anything it should last longer ,
remember the 02 heater does not get powered up until the engine is running.
it does not get preheated prior to start
so
the scenario described does not affect your system

assuming;
you selected a heated 02 sensor from a system that does not control or regulate 02 heater on time

[cfg83]

mwebb -

Originally Posted by mwebb

no it should not fail early
if anything it should last longer ,
remember the 02 heater does not get powered up until the engine is running.
it does not get preheated prior to start so the scenario described does not affect your system

assuming;
you selected a heated 02 sensor from a system that does not control or regulate 02 heater on time

Nope. I *implemented* it so that it's on when the key is turned to the on position. My goal was to pre-heat the 02 sensor before starting the car. I know it's heating up because I have a digital AFR gauge that I watch "go lean" as it heats up.

CarloSW2

[SomeOldBlindMan]

Interesting read... I've been pondering URDUSA.com's MAF Calibrator and AFR Calibrator for my 2TR Tacoma.. along with AFR Gauge.. not so much as to juice up the numbers for racing, but to tweak for economy as well. Anyone else doing the same?

[JeepNmpg2]

Ok, like the title says, there are two O2 sensors; one post exhaust manifold, one post catalytic converter and they each have four wires. I discovered this while under my Jeep changing the differential gear oil front and back for some royal purple synthetic 75-90 (got it half off it's normally ridiculous price of 18.99) and my transmission oil and filter (also went to synthetic, but not RP). Hopefully over my next few fuel logs there is some improvement. Can't be too much worse without any towing and running the vehicle for diagnistics for a little while

[cfg83]

JeepNmpg2 -

Originally Posted by JeepNmpg2

Ok, like the title says, there are two O2 sensors; one post exhaust manifold, one post catalytic converter and they each have four wires. I discovered this while under my Jeep changing the differential gear oil front and back for some royal purple synthetic 75-90 (got it half off it's normally ridiculous price of 18.99) and my transmission oil and filter (also went to synthetic, but not RP). Hopefully over my next few fuel logs there is some improvement. Can't be too much worse without any towing and running the vehicle for diagnistics for a little while

Cool. Four wires says (to me) that you have a heated sensor. I call that a superior setup. Unlike my home-made version, your ECU/PCM *knows* it's heated, hence the 30 second transition to closed-loop.

CarloSW2

[mwebb]

"Nope. I *implemented* it so that it's on when the key is turned to the on position. My goal was to pre-heat the 02 sensor before starting the car. I know it's heating up because I have a digital AFR gauge that I watch "go lean" as it heats up "....

ok
understand that with a heated 02 sensor or AFR ,
even in very cold ambient temperatures
(i have many many graphs which prove that on various makes and models )
most systems will get to closed loop in 1 to 2 minutes anyway so preheating the heater gains little ,
and if it were or is possible to wipe out the thimble because of temperature shock due to preheating .....

you could always reconfigure your modification such that it powers up when the key is in the RUN position .
and if you choose later to preheat , turn key to run for a minute prior to start .
having said that engineers position the 02 / AFR sensor to minimize the possibility of thermal shock and

and
you should not use an 02 sensor from a system with
an ECM CONTROLLED Heater on time , like for instance from a
2001 VW passat with ATQ engine or a BMW from the same era
because if one of those 02 heaters is run at 100% on , it will have a much shorter life than if it were installed in the correct type of system

a heated 02 sensor from say a 1997 chevy cavalier with a 2.2 IS designed to have the 02 heater powered up with the key in run and would be a better choice
for your particular application
imho
==========================
a digital AFR "gauge" connected to a system with heated 02 sensor
can show you only 1 thing
stoich or lambda or 14.7 to 1
OR unknown amount leaner than stoich
OR unknown amount richer than stoich
if it shows anything else it is showing blarney as 02 sensors CAN NOT measure any other condition

because 02 sensors only show stoich , if they are cycling , the system is at stoich , if the 02 sensors are not cycling , the system will set a DTC
if there is no DTC related to 02 sensors , the system is at stoich
so
on systems with 02 sensors ;
those "AFR Gauges" are as useless as mudflaps on a sledge hammer.
fact .