Help Troubleshooting FAST O2

[turbo_bu]

Just got back from the track today tuning on a friends TTA. I put the FAST system on his car about 2 months ago and finally got a chance to take it to the track. Right away, the car was running very rich and I had to adjust the VE's to get it to stop popping under load. With that cured, he tried to make a couple of passes, but it was still too rich. A little more VE tuning and it finally made some clean passes. Looking at the data logs, the Actual AF would go to 9.19 everytime the car was at WOT. This occurred for 5 straight runs. I kept leaning it out a little at a time, but the AF was stuck at 9.19. Looking at the plugs and feeling the car told me that the settings were about right. I had another friend with a very similar car drive it one last time to feel the tranny (it is just starting to slip a little) and lo and behold, the Actual AF starts to read correctly (believable numbers like 11.9 to 12.4)

SO ..... was the O2 sensor just "fouled" and needed those 5 or 6 full pass runs to "clean" it out ???? We were using 110 octane race gas for all of the track testing.

The car still runs OK and the O2's seem to be reading correctly. I am just confused why it was reading pig rich then finally cleared out. Note: between my last run and my friends last run, there were no changes made to any of the map settings.

 

[bobc455]

When I use nitrous, for some reason my O2 reads very, very rich (9.19). However the tune is just about right, so I disable the O2 correction when using nitrous (don't want the engine to go lean!).

I haven't heard of an O2 sensor having to get "cleaned off" or anything like that. Is there a dyno around where you could double-check the O2 sensor under WOT?

I hate to just start leaning stuff out when you think everything is working correctly, just for the sake of the computer. I would trust the plug readings more than the O2 sensor, until you find out what's happening.

Does the A/F ratio look reasonable under other conditions (idling, driving, etc.)?

-Bob Cunningham

 

[turbo_bu]

Don't have access to the car right now. I know that when sitting in the staging lanes, the O2's were reading pretty rich, 10.5 to 11.0 This might be true, but I have not had time to work with the car on idling / driving issues. I know that when I started, it was very rich, but I think that is starting to get cured

I agree not to tune by a questionable sensor .... go with plugs and other indicators first

No, no dyno time in the near future either. I do have the O2 off of my FAST system ... but I have heard that each O2 has a slightly different calibration file that comes with it ????? Is this true ... if so, how much difference could it make ?????

 

[HighPSI]

You can't swap O2 sensors from one box to the next. I have never heard of an O2 sensor needing to be "cleaned". I know the heater in it is a bad mo-fo.
Is the Air Temp Sensor working correctly? If so, where is it located?

 

[turbo_bu]

Yes, the air temp sensor is working just fine. Unfortunately, it is still in the stock location on this car ..... right behind the air cleaner. I am hoping to get him to move it to the up pipe soon so we can have a true intake temperature.

 

[Reginald West]

I had this problem a few weeks back. We had a new motor in the car and had it dialed in. On the last run on the dyno the A/F went from 11.5 to 9.5 and we could not get it to change. The 02 was highlighted red in the control panel so we thought the 02 was bad.I shipped the unit to FAST they checked the 02 and the computer but they could not find anything wrong with the unit. I guess I will put it back on the car and try the Dyno one more time. We were getting 767 to the wheels with 21 lbs of boost before it went south. Anybody got any ideals what could cause this?


REG

 

[DOHC Vobra]

You guys *might* be seeing problems caused by the heater in the o2 sensor. While there may be nothing wrong with the actual sensor, if the exhaust gas gets too hot (beyond the point that the o2 heater is controlling the o2 temp), the o2 readings will be incorrect.

The temp. of the o2 must be controlled very precisely by the FAST in order to measure oxygen content in the exhaust, at the point it no longer has control of the temperature, it will no longer produce accurate results.

If this is a turbo car, how close is the o2 sensor to the turbo? If it's too close, moving it downstream a little bit may help the problem, where the EGT's go down significantly.

Justin

 

[turbo_bu]

The O2 on the TTA is before the turbo. This is the stock location which I think is similar for all the turbo Buicks too.

Should it be after the turbo? How hot is too hot? How hot is the heater is trying to maintain?

 

[DOHC Vobra]

Everything that I've seen about Wide Band sensors says to mount it in the downpipe, since pre-turbo exhaust temps can get VERY hot.

I've got mine mounted about 12-14 inches away from the turbo in the downpipe.

Jusitn

 

[turbo_bu]

Just finished looking at Pro Stock John's thread about O2 problems and there is more good info in there.

http://www.turbobuick.com/forums/showthread.php?s=&threadid=100368

Craig / Lance .... can you help by giving some specs of where we should put the O2's ????

Before turbo? after turbo? try to keep it less than 1800 degrees F?????

 

[TurboTerry87gn]

wide band o2

Wide-Band Oxygen Sensors

The third and most recent zirconia dioxide oxygen sensor is the ‘wide band’ ‘lean burn’ type (or Air Fuel Sensor) and available at NTK only in five-wire. The heater resistance ranges from 12 to 15 ohms. The output signal is considered discrete voltage levels between 0 and 5 volts to offer exact air/fuel mixtures. Bosch announced the development of this ‘wide-band’ heated oxygen sensor in November 2001. NTK has developed a “wide-band’ originally for Honda under the number “H1L1”. Today, the five-wire ‘wide-band’ is available under special order from NTK with the part number LZA03-E1. This newest design expands upon the original ‘planar’ design and adds the ability to actually measure the air/fuel ratio directly for the first time. Instead of switching back and forth like all previous sensor designs, the new ‘wide-band’ oxygen sensor produces a (voltage) signal that is directly proportional to the air/fuel ratio. To accomplish this, the wide-band sensor’s construction uses a dual sensing element that combines the Nernst effect cell (yttrium stabilized zirconia) ((http://www.nernst.de)) in the ‘planar’ design with an additional oxygen pump layer and diffusion gap on the same strip of ceramic. The result is a sensor element that can precisely measure air/fuel ratios from a very rich condition (10:1 air/fuel ratio) to extremely lean (considered straight air). This allows the future engine computer to use an entirely different operating strategy to control the air/fuel ratio. Instead of switching the air/fuel ratio back and forth from rich to lean (as in previous oxygen sensor designs) to create and average balanced stoichiometric mixture, it can simply add or subtract fuel as needed to maintain a desirable steady ratio of 14.7:1. Recapping: Under current OBD-II designs, the ECM detects the change and strength of current flow and emits a voltage signal relatively proportional to exhaust oxygen content. Therefore, an ‘exact’ air/fuel mixture can be determined with the current OBD-II exhaust gas oxygen sensor instead of a ‘high’ or ‘low’ mixture above the stoich 14.7:1 air/fuel mixture. This range can start at 10.0:1 upwards to 18.0:1 air/fuel mixture ratio. To accomplish this more accurate measurement, the “wide band” air/fuel ratio sensor operates at about 1200 degrees Fahrenheit instead of the previously mentioned operation temperature of about 600 degrees Fahrenheit for the standard sensors. The heater circuit also has been enhanced.

*This circuit is pulse-width modulated to maintain a consistent operating temperature of 1292 to 1472 degrees Fahrenheit.

The sensor now takes about 20 seconds to reach operating temperature.

Information compiled and written by:

Ralph Harris
NGK Spark Plugs (USA), Inc.
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