Topic: Standard O2 and MAF values?

[THe_Ghost]

I know most of you over here are on the Solstice forum too...Hoping maybe there are more "tuners" over here.  First I need to know what the range of both O2 sensors should be on a GXP.  And what the range is for the MAF sensor as well.  Next, since I'm ZZP dyno tuned, I'm wondering if anyone here might live in SE MI and be willing to data log my car and look at my tune????  Hoping to find someone.  If not, I guess I'll have to break down and buy HPTuners soon!! 

Situation:  My commanded AFR has always been a steady 14.7 or 29.4 (during DFCO).  Suddenly it's dropped to 13.58 and 27.58 and I can't figure out why.  I'm thinking it's an O2 sensor but no sure which one....and I only log with Torque.  Any help over here is appreciated!!!

[LatinVenom]

There was someone here at one time that was willing to lend the HP Tuner device, not sure about the credits. Maybe someone here knows who he was and is he still here on the forum.

[THe_Ghost]

   I see from some other posts here that Steelmesh lives by me....hmmm........  and I seen him at the Woodward cruise.

[Steelmesh]

I know most of you over here are on the Solstice forum too...Hoping maybe there are more "tuners" over here.  First I need to know what the range of both O2 sensors should be on a GXP.  And what the range is for the MAF sensor as well.  Next, since I'm ZZP dyno tuned, I'm wondering if anyone here might live in SE MI and be willing to data log my car and look at my tune????  Hoping to find someone.  If not, I guess I'll have to break down and buy HPTuners soon!! 

Situation:  My commanded AFR has always been a steady 14.7 or 29.4 (during DFCO).  Suddenly it's dropped to 13.58 and 27.58 and I can't figure out why.  I'm thinking it's an O2 sensor but no sure which one....and I only log with Torque.  Any help over here is appreciated!!!

Does it go into closed loop?

What are your long term fuel trims at? 

The computer will always control fueling to lambda 1.0 (lambda 1.0 = 14.7 for pure gas, 14.2 for E10, 9.8 for E85) unless you're under WOT conditions.

[THe_Ghost]

My LTFT are always betwen -8 and -4.  STFT bounces around.  I just need some direction as to what might have failed/be going bad.  My car has always run at 14.7 to 14.59 at idle.  Now it's down to 13.79 at idle.  It does go lower during WOT, but it's never gone below CAFR of 12.8 at WOT...now it's down to the 11's.  And my FCO has always been 29.4...now its 27.58 commanded AFR.  Furthermore, I'm getting missfires on 1,2, and 4 but not 3.  It doesn't happen all the time...  And they usually will clear themselves before the next one happens.  I've got a feeling the vibration that I have 1k rpm is from this issue because it gets really rich then.  And I'd like to solve it if I can!!  I just don't know why my commanded AFR has dropped so bad.  My car is still a rocket...still pulls hard up to 6k...still gets 22psi of boost....

[Steelmesh]

My LTFT are always betwen -8 and -4.  STFT bounces around.  I just need some direction as to what might have failed/be going bad.  My car has always run at 14.7 to 14.59 at idle.  Now it's down to 13.79 at idle.  It does go lower during WOT, but it's never gone below CAFR of 12.8 at WOT...now it's down to the 11's.  And my FCO has always been 29.4...now its 27.58 commanded AFR.  Furthermore, I'm getting missfires on 1,2, and 4 but not 3.  It doesn't happen all the time...  And they usually will clear themselves before the next one happens.  I've got a feeling the vibration that I have 1k rpm is from this issue because it gets really rich then.  And I'd like to solve it if I can!!  I just don't know why my commanded AFR has dropped so bad.  My car is still a rocket...still pulls hard up to 6k...still gets 22psi of boost....

Do you have feedback for the actual Commanded AFR?  During normal operating conditions it will be commanding stoich no matter what fuel you're running (E10 to E85).  Also note that the LTFT will be different for every load point including idle, make sure to double check the LTFT while experiencing the rich AFR, LTFT is not global to describe the whole calibration picture.  If the LTFT is closer to zero than (-)20 in all areas, then I would agree the 'Commanded AFR' is commanding it to be rich intentionally.

Looks like you said this is the GXP with the LNF, my understanding is this uses a WBO2 sensor, so it would indeed be capable of commanding a richer AFR while in closed loop (idle, cruise, low load).  Off the top of my head, what would cause the tune to want a rich mixture?  Maybe go through all of your temperatures during the rich condition to see if something is way off, like IAT shows 300F at idle.

For the misfire, I would at least pull your plugs (trust no one) and check your gap.  I have been running copper plugs with a 0.028 gap in my LE5, anything larger would cause misfiring/blowout under high load high rpm.  Is this when you are getting the misfiring, do you feel torque drops under WOT pulls?  However, excessively rich also causes misfires so it could be related to your fueling problem.

[THe_Ghost]

I do have a torque app log that I'm looking at.  My LTFT is steady at -8.79....never changes.  I put new plugs in it this spring...al are gapped properly.  It was steady at that number for my half hour drive in this morning.   Commanded AFR does does appear change, but it's hard to tell with torque if I'm lifting or its actually changing.  I'm pretty certain the misfires are being caused by it being too rich.  STFT do move around.  I will log some more with torque.  Anything specific I should try to log with torque? 

I did drive it to work today and thought I wasnt going to make it in this morning cause it had such a bad vibration.  Went out at lunch and that vibration was minimal now...  I'm getting really frustrated and I'm just about ready to get rid of it!!

That's the whole funny part of this...it still feels like power hasn't changed.  I do notice a bit more whooshing from the turbo...but probably because theres more fuel.

[THe_Ghost]

So I might be on to something???

Barometric pressure (from vehicle)(psi):  14.07
Commanded Equivalence Ratio(lambda):  1
Fuel Trim Bank 1 Long Term(%):  -8.59
Air Fuel Ratio(Commanded)(:1):  13.79
Air Fuel Ratio(Measured)(:1):  13.83
Ambient air temp(°F):  64.4

So...from what I posted, does it look like the barometer has failed?  It's calling 13.79...1.  The Commanded Equivalence Ratio stays at 1, but commandes an AFR of 13.79.  I have the log if anyone cares to look at it....

[Steelmesh]

14.07 psi is about an altitude of 1200 ft above sea level, Detroit is around 600 ft so there might be a little offset there.

Commanded Equivalence Ratio of lambda 1.0 is correct.

Gasoline at 14.7:1 AFR = lambda 1.0
E10 at 14.2:1 AFR = lambda 1.0
E85 at 9.8:1 AFR = lambda 1.0
Methanol at 6.5:1 AFR = lambda 1.0

Lambda 1.0 is the universal language of fueling, 1.0 = stoichiometric, the oxygen sensors do not care about fuel type.  This is why engine calibrators (tuners) use Lambda. 

Check this out, in particular the AFR for E15 gasoline (15% ethanol content fuel): http://ultra-gauge.com/customer_support/knowledgebase.php?article=29

[Sol Asylum]

That baro number will depend on atmospheric conditions as well as elevation.  Most barometers are in inches of mercury or mm for the metric places and can be converted to psi.  Standard atmospheric pressure at sea level is 29.92 inhg which is 14.7 psi.

[THe_Ghost]

That baro number will depend on atmospheric conditions as well as elevation.  Most barometers are in inches of mercury or mm for the metric places and can be converted to psi.  Standard atmospheric pressure at sea level is 29.92 inhg which is 14.7 psi.

Correct.  I appreciate the link and explanation.  I know enough about tuning to be dangerous.  So I know what stiochiometric is and what 14.7 is..and what AFR is.  All I'm trying to do is figure out why my car is commanding 13.79 when it used to command 14.7.  What sensors do I need to look at?  What do I need to do?  And nobody can seem to give me that straight answer...instead I get lectured on how to tune.  I asked which sensor provides the ambient barometric pressure...crickets.  I have merely asked and provided information hoping someone can say, "yeah, I think you're onto something" or "nope...can't be that".  Or give me some direction to look as to why a car, that the ECM has not been touched, can suddenly be commanding and AFR of 13.79 when it was, up until last year, commanding 14.7.   

[Sol Asylum]

It's possible your fuel has more ethanol in it then what you used to get.  That alone will cause the ratio to change and you may not have any sensor issues. 

Besides the ratio being lower are you having any issues with how the car runs?

[THe_Ghost]

Not really.  It still pulls hard.  Still gets rubber in the top end of 2nd.  But I've used 3 different filling stations...all have same effect.  My main concern is the vibration I have at 1k RPM.  That's what prompted the whole thing with logging again.  I found that my CAFR drops to 12.68 at about 1k.  Which is why I'm concerned...   Furthermore my car bogs and almost stalls when I push in the clutch...which means to me...super rich.  My car has ALWAYS been susceptible to not having true 93 octane because of my tune....  If I got 91, I knew it.  I took a road trip and the best I could find was 91 and I knew it....  My car burbles and backfires when I don't get true 93 when I let off the gas.  I just can't believe that they've changed the fuel.  We've always had ethanol in our gas in MI. 

[Steelmesh]

What mods are on your car? Tune?  What is the HP?  Milesage?

[THe_Ghost]

I have ic piping, Fujita CAI, Solo Street Race Exhaust and a ZZP dyno tune that was done at about 65kmiles.  Cat was replaced at about 58k when my WP went out.  They accidentally cut the cat.  Tune was done after that.  I have 82k on it now.    I have 283hp at the wheels, so about 330hp at the crank.  Full boost is about 23psi.  No CELs...none pending.  Had the HPFP 2 years ago and replaced it myself.  Car ran fine after...a little lean after that, but nothing to be concerned with at that time. I did also have part of my exhaust replaced last spring from the cat to the mesh portion.  This was done by an exhaust shop with Solo parts.

[Steelmesh]

With the E67 ECU (2.4 LE5, V8s), there is a table for Ethanol content vs. AFR.  My understanding is that if you don't have flex fuel capability then the ECU uses the knock sensors after gas station fill ups to estimate ethanol content. I don't have experience with the LNF engine controller to know if there are nuances with the fueling control. Ethanol content is for sure one factor that would request 1.0 lambda (EQ ratio) with acceptable LTFT while showing a lower than gas AFR; where 13.79:1 is right about E15 gasoline stoichiometric ratio, where E15 running 13.79:1 is the same thing as lambda 1.0 

Through deduction we can say the fuel is acting like E15, because the engine is running at 13.79:1 AFR while commanded EQ is 1.0 or lambda 1.0 and you're LTFT are within control parameters.  STFT will indeed bounce around, always targeting lambda 1.0.  STFT + LTFT = fueling offset to maintain lambda 1.0

With all your mods I question if there is something mechanical that has changed.  I would also suggest pulling the coils and plugs and checking condition and electrode gaps to diagnose the rough running / shaking condition.  Wouldn't hurt to do a compression check and boost leak test.

[THe_Ghost]

Honestly I have a feeling it has something to do with my very lazy downstream O2 sensor.  I can't tell how long its shows lean from torque but I know it's quite a while once the upstream is showing rich...  I need to find someone with hptuners that can do a log for me.  I have other people on other forums that can help me once I have that....

Plugs were just done less then 500 miles ago.  I've had the valve cover off...so the ignition coils are on tight because that was what I was thinking. 

[THe_Ghost]

With all your mods I question if there is something mechanical that has changed.

Yes...I'm sure something has changed...and I'm sure it's a bad sensor somewhere.  I just have to find it before it causes other issues. 

[THe_Ghost]

A little more information.  I finally went out and drove and logged with my primative torque app.  I put an old evap solenoid I had from when I had my HPFP issues.  It has really steadied out the downstream O2 sensor values, my STFT and my MAF readings.  It's not as erratic as it was.  But my commanded AFR is still really low at 13.79 and goes lower.  I saw one reading of 11.6!!  So I still need to find out what's causing that to be so low.  Getting an hptuners cable in the mail this next week to do some more logging, hopefully this will help find my issue.  

[Uranium-238]

But my commanded AFR is still really low at 13.79 and goes lower.  I saw one reading of 11.6!!  So I still need to find out what's causing that to be so low.  Getting an hptuners cable in the mail this next week to do some more logging, hopefully this will help find my issue. 

First off, is your WB O2 sensor calibrated?

If it is, what where the conditions when those reading occurred? Granted I've got an LS3 not an LNF, but those readings wouldn't be unusual in my Camaro is general driving conditions. Sure dead flat in cruise it's within a tenth or two of 14.7, but start actually using the throttle and it'll move from there.

[THe_Ghost]

The 2.0L has a wideband O2.  I've never touched it.  My battery was disconnected for 2 months this last winter for the first time ever.  But that wouldn't change a tune or calibration.  I had my car dyno tuned 4 years ago and never touched the tune.  Up to last year, my commanded afr was almost always 14.7.  My car would run great and would usually cruise at like 14.5 or 14.4 measured afr.  With this issue it's cruising 13.3 to 13.9.  It is continuously commanding 13.79.  Idle, cruising.  When I really get on it, it commands even less, I saw today 11.6, which my car has NEVER commanded before.  When I let off in gear and it enters FCO (or DFCO, depending on what you read) it is commanding 27.58, not 29.4 that it's been commanding since my tune was done.  So it's off on idle and FCO by the same amounts...so a sensor has to bad somewhere and hasn't set a CEL.  I've even read for pending codes...no pending codes either....  Unless I have a leak in my IC somewhere and it's just not bad enough to set a code....  But I would think that it would move back to a commanded 14.7 at idle if that was the case...and it doesn't budge.  13.79 for 90% of the time the engine is on.