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Running Lean?

4K views 39 replies 11 participants last post by  JZW 
#1 ·
Ok so my friend has an identical ng900 to mine. Its a 1998 Saab 900se and it has a GS Intake and 2.5 inch Catback exhaust and a Viggen intercooler. He wanted to try my Nordic stage 4 tune in his car so i let him, but when we started driving around it boosted fine 22psi and ran good but it sputtered a lit bit at low rpms in like 3rd gear at 55mph like struggling to build boost and making a popping noise??? Then eventually after 65mph it would seem like its pulling like a bat out of hell. I looked at his A/f Gauge and it goes to lean at WOT??? Can someone tell me why?

Then to compare we tried my automotion ECU and it ran good. 20 PSI at WOT it went to rich on the Gauge. No sputtering or nothing. So I know nothing is wrong with his car. No check engine lights or anything some input please?
 
#6 ·
while it isn't required might that be the reason it is lean though...? stage 2 to stage 4 is a huge jump. Plus as they are done by different tuners they may be programmed to run differently. in your car do they do the same thing? or have you tried them in something different..
 
#11 ·
so...your putting a tune for a td04 in a car with no td04 and no 3 inch dp and your wondering why the A/F may or may not be off, since you really have no idea since your using what is basically a toy and has no bearing on what the mixture actually is?

this thread is full of fail...we need a facepalm smiley on here these days.
 
#13 ·
good one

your still gauging this off a toy gauge that has pretty lights. its just showing you the voltage output of the o2, which is converted downstream by the ecu.

you have no idea if its actually lean or rich.

you also keep running ecu's on inappropriately/inadequately equipped setups...what did you expect to happen?
 
#16 ·
Yea, find out what it actually is reading before you make any assumptions.

The narrow band really is useless, I have seen them go inverted under extreme conditions and read rich when lean and visa-versa, I would not trust them in any way what-so-ever, its just a light show.

Check it with wide-band and see what ya got!

John
 
#25 · (Edited)
If your narrowband is not reading correctly you should do some troubleshooting, hook a meter to it and check to see that it's working in line with the graph above.

Under normal conditions with everything working correctly you shouldn't be seeing any inverted signals or anything like that. Despite what JZW posts, I sure don't see any inverted sections on any charasteristic output curves for any O2 sensors. Maybe if you've saturated/contaminated/improperly loaded or otherwise blinded the sensor your reading won't be correct temporarily, it may recover, but watch what it's doing, you may have a maintenace item to address. If the sensor is inverting itself that's a strong indication of a problem. For instance, what are your exhaust gas temperatures? If you're way out of normal operating range for the sensor how do you know what the gauge should be reading? If your EGT's are that hot, then you have another issue. What does your fueling actually look like? Are you waay rich and blinding the sensor? Does it in fact fully recover? For example, lets say you're running a pig rich JZW tune that fouls the sensor with soot and unburnt byproducts and seals off the sensor junction, how much oxygen will the sensor read then? Or maybe the raw fuel that's washing down your cylinder walls is making it's way out the turbo and igniting right on top of the sensor, what does the sensor read then?

The ECU needs a functioning sensor to trim fuel correctly, so don't just shrug your shoulders and think "oh well, JZW saw a bad sensor reading one time, and a noted tuner that JZW knows also saw a bad sensor reading one time, and JZW read about a bad sensor reading one time, so that means it's okay".

Check to make sure it's reading correctly and fix it if it's not. The first step is to decide if you believe that the sensor system is operating correctly? You can get an idea of the answer to that question by watching the raw voltage readings while cruising around under low load conditions.
 
#26 ·
If your narrowband is not reading correctly you should do some troubleshooting, hook a meter to it and check to see that it's working in line with the graph above.

Under normal conditions with everything working correctly you shouldn't be seeing any inverted signals or anything like that. Despite what JZW posts, I sure don't see any inverted sections on any charasteristic output curves for any O2 sensors. Maybe if you've saturated/contaminated/improperly loaded or otherwise blinded the sensor your reading won't be correct temporarily, it may recover, but watch what it's doing, you may have a maintenace item to address. If the sensor is inverting itself that's a strong indication of a problem. For instance, what are your exhaust gas temperatures? If you're way out of normal operating range for the sensor how do you know what the gauge should be reading? If your EGT's are that hot, then you have another issue. What does your fueling actually look like? Are you waay rich and blinding the sensor? Does it in fact fully recover?

The ECU needs a functioning sensor to trim fuel correctly, so don't just shrug your shoulders and think "oh well, JZW saw a bad sensor reading one time, and a noted tuner that JZW knows also saw a bad sensor reading one time, and JZW read about a bad sensor reading one time, so that means it's okay".

Check to make sure it's reading correctly and fix it if it's not. The first step is to decide if you believe that the sensor system is operating correctly? You can get an idea of the answer to that question by watching the raw voltage readings while cruising around under low load conditions.
Although i agree with what you wrote above, i would imagine that the sensor was replaced by the wideband. Maybe not, maybe he is still using the narrowband for the signal to the ecu and the wide band for tuning purposes. Although i would say 13.1 was just a touch high for afr's(would rather see them around 12.5 or so) at WOT seeing that he his in fact not runnign too lean i don't see a concern here.

Its possible that the narrow band gauge its self was a fluke. Like everyone else has said before they can't really be trusted and they just are not practical for getting solid afrs. As far as going inverted as voltage readings from the o2 sensor doing a 180 never seen that before and i dont see how it could. Most bad o2 sensors that i see are either from contamination or broken wires. Also wrong o2 sensors being installed.
 
#36 ·
I was just writing about the problems that the original poster seems to be having.

Telling someone who suspects that their car is having fueling issues, 'oh don't worry about that, sometimes narrow band O2 signals go inverted don't trust that' doesn't help too much.

For the control loop to function correctly it needs a functional O2 sensor for feedback. And yes John, I know you can turn the sensors off and run open loop, the problem with that is then your control isn't nearly as good as it could be, and other adaptions that might happen aren't ever corrected back, and you won't pass emissions.
 
#40 ·
I did not say don't worry about it, I said don't put too much credit in the narrow band light show and get it checked on a wide-band.

Completely different from what you are suggesting. Many people have seen narrow band set-ups not read accurately, this is nothing new. Just because the narrow band gage is not working well, does not mean the ecu is not working well and the wide-band will tell the true story.

John
 
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