Oxygen Sensors *lazy at idle* 02s EGT long tube headers closed loop
08-24-2006, 04:10 PM
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Oxygen Sensors *lazy at idle* 02s EGT long tube headers closed loop Hope my effort helps others here
Problem Symptoms
Poor Idle quality. Stalling. Rich fuel smell.
Cause of Problem
Factory O2 sensors become lazy at idle.
Result
Fuel correction goes full rich compensating for a false lean condition.
Symptoms
+25% LTFT long term fuel trims as well as +25% STFT short term fuel trims. Injector pulse width will be greater than needed to maintain 14.7 at idle.
Why
Factory Style Narrow Band Oxygen sensors must be heated to around 300 degrees Celsius (about 600 degrees F) before it will start to function, and operates best at around 1400 degrees Fahrenheit.
1. Shigeo Soejima and Shunzo Mase, SAE Paper No. 850378, 1985
Conditions Required to create problems
-Low Exhaust Gas Temperatures (light load on motor, stick, high spark adv., big cube motor with a little cam)
-Low exhaust system temperatures (long tube headers, no cats, free flowing exhaust, light weight exhaust materials retain very little heat)
-large overlap cam shafts (moves fresh air through the motor at overlap)
-exhaust outlet in close distance to the oxygen sensors (absolute fresh air pollution of exhaust sample)
-exhaust leaks (header flange, or air injection leak)
SAY NO to PAPER Pacesetter gaskets and always consider locking header bolts
Proposed Fixes
-reinstall Cats and cast manifolds ( ummmmm right...)
-Open loop tune (will ignore all O2 feedback, will absolutely resolve these 02 related idle fueling problems, and may create other problems if your OL tune is sub par, )
-Adjust Closed Loop Proportional Idle tables ( doesn't work! flat lineing lean o2's don’t average out even if the switch point was say 150mvs)
-Restrict the exhaust system volume at idle by 90% (works by raising EGTs and ESystemTemps, tested and proven!)
-Install Vette rear O2s (that supposedly have a better heater P/N 25317697)
-Lower Closed throttle Spark Adv. ( will raise EGT's and engine load, this may not be enough all on its own but will help. Proven! )
-Header wrap and coatings (will raise EGT's and engine load, this may not be enough all on its own but will help.)
Alternate Fix
To get a nice Closed Loop sweeping 02 reading an Innovate Wide band could be used to put out a simulated narrow band signal. Wide Band 02 gauges are a excelent purchase for a highly modifyed car and would provide for great street tuning and track performance tuning. Altough an expensive potential fix for such a simple problem a Wide Band 02 setup would have many benifts. The Innovate box has two analog outputs that could be used for this.
Anyone have any thoughts? ... Jimmy Blue?
08-24-2006, 05:28 PM
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Race-Prep 433ci LS-1 Stroker tunedbytad 11:05 AMish
At the time of this log capute the car was running great 7 minutes or so into a trip to lunch.
Good BLM's - Good STFTs - kinda Choppy o2's
5-6 Minutes later the same Race-Prep 433ci LS-1 Stroker tunedbytad 11:15
Arrived at destination and parked car. Idle pulse width goes from 3.4ms to 5 ms due to drop outs and lean bias 02 signals.
BLM's calculated high - STFT's calculated high - O2's are choppy and low
same car, same tune, same day, same drive cycle
To back up these findings I tested the EGTs / ESystemTemps findings on the lift. By cooling the 02's with a H20 spray bottle and massive amounts of forced air flow I could make the 02's drop outand flatline. By heating the o2's with a MAP gas torch, pluging the exhaust to raise EGT's, and lowing spark adv. to raise EGTs o2 retutn to sweeping. The forced EGTs definatly return closed loop idle back to a fuctioning system that can maintain 14.7:1 AFR.
At the time of this log capute the car was running great 7 minutes or so into a trip to lunch.
Good BLM's - Good STFTs - kinda Choppy o2's
5-6 Minutes later the same Race-Prep 433ci LS-1 Stroker tunedbytad 11:15
Arrived at destination and parked car. Idle pulse width goes from 3.4ms to 5 ms due to drop outs and lean bias 02 signals.
BLM's calculated high - STFT's calculated high - O2's are choppy and low
same car, same tune, same day, same drive cycle
To back up these findings I tested the EGTs / ESystemTemps findings on the lift. By cooling the 02's with a H20 spray bottle and massive amounts of forced air flow I could make the 02's drop outand flatline. By heating the o2's with a MAP gas torch, pluging the exhaust to raise EGT's, and lowing spark adv. to raise EGTs o2 retutn to sweeping. The forced EGTs definatly return closed loop idle back to a fuctioning system that can maintain 14.7:1 AFR.
08-24-2006, 05:57 PM
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Widebands have better heaters and control the element
temp. From the schematics I've looked at it seems the
stockers are running full time heat but it's just not good
enough if the exhaust gas is cooling them much.
Wonder about rigging something like a "boost-a-pump"
only backwards, where -low- TPS voltage jacks up the
heater power. This could be a simple fix, just hijack the
four high side heater wires. Have never heard of NB
sensors burning out heaters or going nonfunctional from
heat.
With bankwise fuel control you would need -two-
widebands for narrowband simulation. You could
probably make a much cheaper controller than the
"instrument grade" (supposedly) meters use, and
get a reasonable output. I've seen drawings of the
control and analog signal processing that look like
enough to go on. There is an upper limit to workable
heat and some folks have bumped into it, needed
heat -sinks- to keep them from flaking out at high
gas flows & temps. But probably set you back a few
tens of dollars in parts per bank plus your time to
get a decent controller. Controller also needs to light
'em up quick to get good service life, I gather; they
age badly when left in the stream and not hot. But
VW makes them work in consumer cars so must be
possible to maintain them right.
temp. From the schematics I've looked at it seems the
stockers are running full time heat but it's just not good
enough if the exhaust gas is cooling them much.
Wonder about rigging something like a "boost-a-pump"
only backwards, where -low- TPS voltage jacks up the
heater power. This could be a simple fix, just hijack the
four high side heater wires. Have never heard of NB
sensors burning out heaters or going nonfunctional from
heat.
With bankwise fuel control you would need -two-
widebands for narrowband simulation. You could
probably make a much cheaper controller than the
"instrument grade" (supposedly) meters use, and
get a reasonable output. I've seen drawings of the
control and analog signal processing that look like
enough to go on. There is an upper limit to workable
heat and some folks have bumped into it, needed
heat -sinks- to keep them from flaking out at high
gas flows & temps. But probably set you back a few
tens of dollars in parts per bank plus your time to
get a decent controller. Controller also needs to light
'em up quick to get good service life, I gather; they
age badly when left in the stream and not hot. But
VW makes them work in consumer cars so must be
possible to maintain them right.
08-24-2006, 09:37 PM
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Jimmy,
I did a bench test on 3 different LS1 compatable sensors this week.
Hooked them up to a 12volt source and hit them with the temp gun every couple of minutes.
Turns out at full temp in free 75deg f air sensors get between 350 and 450 deg f. on the outside of the case. If the pipe there mounted in is say 350 -250 like the car I have been currently testing that would definalty bring them down.
This up coming week I'll crank up the voltage to the max of my power supply (16 volts) and see what happens. If the temps go up, I might have a fix. To bad o2s are not like spark plugs, avaible with several different labled heat ranges.
I did a bench test on 3 different LS1 compatable sensors this week.
Hooked them up to a 12volt source and hit them with the temp gun every couple of minutes.
Turns out at full temp in free 75deg f air sensors get between 350 and 450 deg f. on the outside of the case. If the pipe there mounted in is say 350 -250 like the car I have been currently testing that would definalty bring them down.
This up coming week I'll crank up the voltage to the max of my power supply (16 volts) and see what happens. If the temps go up, I might have a fix. To bad o2s are not like spark plugs, avaible with several different labled heat ranges.
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08-25-2006, 10:24 AM
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Bosch 13111, telling them 2002 Corvette rear O2s
is good enough to get the right box but check the
box in case of counter clownery, should have a 2'
or so pigtail and a 2x2 pin square connector. But
this is only a "patch" which falls somewhere between
better and all better, on a clean running car. Chicken
and egg somewhat, but with a known single cylinder
problem I'd wait on installing since you can foul them
as quick as any other when you're coughing up goo.
is good enough to get the right box but check the
box in case of counter clownery, should have a 2'
or so pigtail and a 2x2 pin square connector. But
this is only a "patch" which falls somewhere between
better and all better, on a clean running car. Chicken
and egg somewhat, but with a known single cylinder
problem I'd wait on installing since you can foul them
as quick as any other when you're coughing up goo.
08-25-2006, 02:12 PM
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Must not be true, because you can put the WBO2 all
the way back at the tailpipe and have it work while
the NBO2 gets all wimped out with 2' of header.
A little bit of wrapping might not hurt, at least knock
down local thermal conduction as a heat sink path.
But I think I'd stop short of the first upstream weld
just to make sure I wasn't promoting extra rust or
allowing it to go too hot (too much wrap, not good).
I've thought about a little bit of fiberglass tape and
aluminum over that (being a cheap sort).
to
the way back at the tailpipe and have it work while
the NBO2 gets all wimped out with 2' of header.
A little bit of wrapping might not hurt, at least knock
down local thermal conduction as a heat sink path.
But I think I'd stop short of the first upstream weld
just to make sure I wasn't promoting extra rust or
allowing it to go too hot (too much wrap, not good).
I've thought about a little bit of fiberglass tape and
aluminum over that (being a cheap sort).
to
08-25-2006, 03:38 PM
#11
Great thread, we've all had these issues since 1999 really. Excellent summation in the first post (for future searches). Sadly I have nothing to add, just reinforcing that the 13111's are a semi fix. My Stainless Works headers have the bung closer to the engine than my FLP's did, so I don't have the +25 at idle issue but dang it smells sickening behind the car.
08-30-2006, 10:52 AM
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Customers car is back in the shop for a test of the fixes.
I am currently testing;
-an Oxygen senors with thermal wrap in free air to see if the tip gets hotter with out the back of the sensor losing heat.
-lowering idle spark adv. to elivate EGT
-wrapping the lower part of the header
-pricey vette rear 02 sensors PN 25317697
If thes fixes dont work then I will attempt to run the car in closed loop with my LM1 simulayting narrow band output. If the fixes workI will post pictures and part numbers.
TAD
I am currently testing;
-an Oxygen senors with thermal wrap in free air to see if the tip gets hotter with out the back of the sensor losing heat.
-lowering idle spark adv. to elivate EGT
-wrapping the lower part of the header
-pricey vette rear 02 sensors PN 25317697
If thes fixes dont work then I will attempt to run the car in closed loop with my LM1 simulayting narrow band output. If the fixes workI will post pictures and part numbers.
TAD
08-30-2006, 03:00 PM
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I just got off the phone with a Bosch tech about the
sensor options. No info about heater wattage is
available (even to them) because Bosch thinks it's
some big engineering secret.
One thing I found in digging, is that Bosch has a
"planar" sensor family they're all proud of for faster
light-off etc. I got the tech to dig me up a part
number. Bosch 15733 is a "universal" heated
planar type with a long pigtail and comes with a
universal connector kit, supposedly several bodies
and some pins to set up for the application.
Somebody ought to go buy a pair, install and
report (with cold-day idle O2 waveform logs).
sensor options. No info about heater wattage is
available (even to them) because Bosch thinks it's
some big engineering secret.
One thing I found in digging, is that Bosch has a
"planar" sensor family they're all proud of for faster
light-off etc. I got the tech to dig me up a part
number. Bosch 15733 is a "universal" heated
planar type with a long pigtail and comes with a
universal connector kit, supposedly several bodies
and some pins to set up for the application.
Somebody ought to go buy a pair, install and
report (with cold-day idle O2 waveform logs).
08-30-2006, 03:14 PM
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Here's more information. Quoted from their website "The planar sensor "lights off," or reaches operating temperature, in approximately 10 to 12 seconds". So obviousily it must have more wattage.
http://www.boschautoparts.com/Produc...nsors/PlanarO2
They list part # 15732 & 13444 for the 98 F-body.
http://www.boschautoparts.com/Produc...nsors/PlanarO2
They list part # 15732 & 13444 for the 98 F-body.
08-30-2006, 08:59 PM
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i think the best people to test this would be a shop with a shop car. i see a way to maybe go about this for each individual car. its a bit extreme though. what about installing a temp sensor in the exhuast and record the reading along with the mV the o2s are reading. do that for a cold and warm start. once you have an idea how consistant they are, you adjust for it in hpt or efi to make the o2s read differently. does that make sense? it may not be coming out right.
08-31-2006, 04:23 AM
#19
Originally Posted by jimmyblue
I just got off the phone with a Bosch tech about the
sensor options. No info about heater wattage is
available (even to them) because Bosch thinks it's
some big engineering secret.
One thing I found in digging, is that Bosch has a
"planar" sensor family they're all proud of for faster
light-off etc. I got the tech to dig me up a part
number. Bosch 15733 is a "universal" heated
planar type with a long pigtail and comes with a
universal connector kit, supposedly several bodies
and some pins to set up for the application.
Somebody ought to go buy a pair, install and
report (with cold-day idle O2 waveform logs).
sensor options. No info about heater wattage is
available (even to them) because Bosch thinks it's
some big engineering secret.
One thing I found in digging, is that Bosch has a
"planar" sensor family they're all proud of for faster
light-off etc. I got the tech to dig me up a part
number. Bosch 15733 is a "universal" heated
planar type with a long pigtail and comes with a
universal connector kit, supposedly several bodies
and some pins to set up for the application.
Somebody ought to go buy a pair, install and
report (with cold-day idle O2 waveform logs).
It wouldn't be that hard to figure out the "wattage" for an O2 sensor. Get a stable 12v bench power supply and use a amp meter to see how much current each O2 is pulling. Simple ohms law will tell you how many watts it really is. V*I=W