modenaf1

iTrader: (3)

Forgive me if this sounds like an absolutely retarded question but I haven't been able to find anything through the search on this specific question.


I bought a wideband setup a while ago and need to do a tune on my car, unfortunately I don't have a testpipe yet and I have plans to remove the stock y with the pre-cats for equal length OBX headers/y in the future.

For now I have both pre-cats and my cat which will surely throw off the tune.


The car has 3 02 sensor locations, one behind the cat, and the two front ones for each bank before the pre-cats.


Since the ECU is in open loop at wide open throttle and doesn't use the front o2 sensors in open loop anyway, there shouldn't be any problems with temporarily disconnecting a front o2 sensor and putting the wideband up there just to do my tune is there?

maxgtr2000

iTrader: (29)

Some widebands have a simulated narrowband output so technically you could still allow the ecu to see the narrowband signal and still read the wideband reading but you really don't want it to be running off one bank since they can read differently. You could just wait and do it right by having a bung welded in after you get your y pipe.

modenaf1

iTrader: (3)

Ok cool, sounds like I'll just have to wait. In the mean time, if I just get a testpipe to remove my main cat, will that work or do the pre-cats in the y-pipe still come into play even after the car has warmed up?

The Wizard

iTrader: (43)

Getting a Test pipe will work for sure.

modenaf1

iTrader: (3)

Ok, well I got a testpipe and my O2 sensor is hooked up behind the testpipe. I calibrated the o2 sensor and it is a brand new wideband o2 sensor. Keep in mind, my car is untuned and theoretically should be running much more rich than factory settings because it is untouched but is running DEK injectors at the stock fuel pressure. Both tables of data started at WOT in 2nd gear at 2000rpm and ended at WOT in 2nd gear at 6500RPM.

RUN 1
19.74
20.17
18.55
12.7
14.24
13.59
16.53
15.94
17.16
20.62
34.28
18.93
19.32
20.62
19.32
18.93
18.55
18.93
15.1
18.18
18.18
17.49
17.49
17.49
17.49
17.16
15.94
15.37
15.37
14.7
14.53
14.7
14.24
13.84
13.23
13.84
13.23
13.35
13.84
13.35
12.8
12.91
12.91
12.6
13.01
13.35
13.47
13.01
13.84
12.91
13.23
13.97
13.71
14.24
13.97
13.23
14.1
12.91
13.35
12.8
12.8
12.91
12.91
13.47
13.84
13.23
12.6
13.47
12.7





RUN 2
20.17
18.18
11.8
15.1
14.68
16.23
17.83
17.16
20.17
21.59
20.62
19.74
18.18
19.32
18.18
19.74
18.93
20.62
20.17
17.16
14.68
17.83
18.55
19.32
17.16
15.37
15.65
15.65
16.84
15.94
15.94
15.37
15.1
14.68
14.38
14.53
13.23
14.1
13.97
13.97
12.91
14.24
13.23
12.91
13.59
12.8
12.7
12.41
13.35
12.51
12.32
12.8
12.41
13.59
13.23
13.23
13.35
13.12
12.91
13.84
13.84
13.84
13.35
13.47
14.38
13.97
13.01
13.71
14.38
13.97
13.84
13.59
13.59
14.1
12.6
12.7
13.01
13.23
13.59
12.51
12.7
12.6
13.59
12.51
12.51
12.14
13.59
15.94
18.18
19.32
17.83
17.49
15.94
15.1
15.94
15.37
15.94
16.84
18.55





Any ideas on why these AFR's are so lean and jump around so much? When I drive around part throttle and less than 3000rpm, my AFR is usually around 19-21 according to my wideband. Any ideas on whats up with this?

MoncefA33

iTrader: (6)

The wideband shouldn't be behind the test pipe. It should be right before the test pipe.

modenaf1

iTrader: (3)

Ok, I'll try and get a bung put in farther up, but do you think a foot or two in placement really matters that much? I mean since there is no main cat, its the same exact exhaust gas behind the testpipe, only difference being that maybe it is a few degrees cooler?

Still though, these readings are REALLY off. Would it even be possible for the car to be running this lean without MAJOR problems? Partial throttle should be 14.7 right? Maybe mine is running a bit richer because of the DEK injectors, not a whopping 6 points leaner.

The Wizard

iTrader: (43)

That doesn't make any sense. A test pipe is just a pipe, so putting the O2 sensor before or after the test pipe will yield the same results. I believe the OP wanted to go behind the the test pipe so he can pull his utmost dowstream factory O2, plug in his wideband, and tune.

OP, what brand wideband did yo go with?

modenaf1

iTrader: (3)

And yes, that is correct, I went behind the testpipe so I could just run the wideband cable out the factory hole underneath the drivers seat and plug into the existing O2 bung.


I went with one of those DIY kits, the JAW 1.03. I actually purchased it off someone who used it to dyno tune his Evo. When I bought it, I saw it working perfectly in his car, so I am pretty sure it isn't the wideband. But then again, it has sat in my garage for a while.

http://14point7.com/Widebands/JAW_1_03/JAW_1_03.htm





I just went back and poured over the data though, apparently as I floor it and do my pull, the temperature reading shows that the wideband sensor starts to cool off. I guess the ideal heatrange is something between 14 and 18 on the o2 sensor, the lower the number the hotter the sensor (dont ask me why), as I go wot and the RPM's climb over 3K the o2 sensor starts to cool off to around 22.


Normally I would think this is my problem, but I read that the O2 sensor will start to read more rich as it cools off, meaning my car is really running even leaner than the results posted? That can't be right.


This weekend I will get detailed pictures up of my sparkplugs and datalog my short and long term fuel trims as well as ignition timing advance. I refuse to believe the car is running this lean.

The Wizard

iTrader: (43)

I'm still at a loss to explain your weird data.

Unfortunately, I'm not familiar with DIY widebands, specifically the JAW 1.03

As you let off the gas, you should be going lean.

modenaf1

iTrader: (3)

Yup, when I let off the gas it goes up into the 30's. I'll have to fiddle with it some, maybe I'll try doing another free-air calibration on the sensor.

EsQueue

iTrader: (2)

My car pretty much stays at approximately 11.4 at wot. Only thing is that I removed the front precats with a WS y-pipe. I have the WB welded in right after the flex pipe section.

modenaf1

iTrader: (3)

Thanks to Kaz from the Colorado Nissan Owners Club for running some of this data through Excel and graphing it. Here are the graphs:


I found a very minor exhaust leak in my flex section and one of my flanges, perhaps this is the cause of the sensor reading lean. I'm still a bit worried about all the spikes though.