Some AutoXray scan results (pic test)

[Paul Workman]

I'm Not making a point, except to illustrate one of the "real time" files I captured with my scanner, newly upgraded to work with my "new" Z. (The data was imported into an Excel file for futher manipulation at some point.)

But, for the curious, it is easy to see how much dynamic info is possible to collect on a second by second basis and much more too (several options). Bottom line...It makes shorting pins on the ALDL connector seem VERY crude. This scanner has helped me on several occations pinpoint problems in just a few minutes. (Even though this was as much of a test of the upgraded software for the EZ Link 1000, this test data raises some questions I may have questions on. e.g. O2 Cross Counts...What is that, and what does it mean when the left/right sides not ballanced???)



FWIW,

P.

[bradslt5]

the cross counts are when it goes from low to high dont quote me but i believe the number is 400-450 . from what i have been told the cross counts help you to tell if the o2 sensors are getting lazy . when the cross counts get slow the o2 sensors need replacing.. you might ck to see if the cross counts on the side thats 117 is slower than the other side you might consider replacing that o2 sensor . what model auto xray do you have i wonder if my 4000 can download to my lapptop

[Paul Workman]

Originally Posted by bradslt5

the cross counts are when it goes from low to high dont quote me but i believe the number is 400-450 . from what i have been told the cross counts help you to tell if the o2 sensors are getting lazy . when the cross counts get slow the o2 sensors need replacing.. you might ck to see if the cross counts on the side thats 117 is slower than the other side you might consider replacing that o2 sensor . what model auto xray do you have i wonder if my 4000 can download to my lapptop

Cross counts...Good to know, and thanks. Looks like I might have a "lazy" O2, huh? (I guess that makes our (yours and my) points: The scanner beats the hell out of a paperclip and standing on your head, huh? )

My scanner was being discontinued when I bought it 5 years ago, tho they still support it (which makes me a happy camper!) Mine is the EZ Link 1000, and the EZ-PC 500 USB software (USB cable provided) does import scanner data to my computer (obviously). I'm not familiar with the your particular unit, however, but I would think it would be possible.

If you have a laptop, it might be worth looking into some of the s/w available that would allow you to link your computer directly to the Vette's computer. I would have gone that route, except I didn't have a laptop at the time I bought the Link scanner. That said, tho the scanner is passive (it won't modify air/fuel tables, for example), it has paid for itself many times over...in lack of frustrtion if nothing else!

P.

[WB9MCW]

good post nice info from that tool.

[XfireZ51]

Cross counts deal with the AFR swinging between lean and rich. The AFR actually oscillates and that is done because of the catalytic converter. If you look at the calibrations in our cars you'll see that the rich voltage is actually lower than the lean voltage. This is done to force the oscillation in AFR. If it oscillates too quickly you'll sense a surge in the motor. Looks like the Right O2 sensor is a bit lazy. BTW, you have quite a bit of canister purge going on there.

[Paul Workman]

Originally Posted by XfireZ51

BTW, you have quite a bit of canister purge going on there.

Now that you mention it, it does seem to be so. However, a later (near WOT) base run started out at that 99.4% initially, and then dropped to zero followed by a few fluctuations below 10% before remaining at zero (after the WOT period). Hmmmm... sez me. A sticking valve perhaps? (How could that be after sitting almost 10 years???)

This is from Wikipedia re O2 sensor design and operation - an interesting read.

P.

Operation of the probe


[edit] Zirconia sensor

The zirconium dioxide, or zirconia, lambda sensor is based on a solid-state electrochemical fuel cell called the Nernst cell. Its two electrodes provide an output voltage corresponding to the quantity of oxygen in the exhaust relative to that in the atmosphere. An output voltage of 0.2 V (200 mV) DC represents a lean mixture. That is one where the amount of oxygen entering the cylinder is sufficient to fully oxidize the carbon monoxide (CO), produced in burning the air and fuel, into carbon dioxide (CO2). A reading of 0.8 V (800 mV) DC represents a rich mixture, one which is high in unburned fuel and low in remaining oxygen. The ideal point is 0.45 V (450 mV) DC; this is where the quantities of air and fuel are in the optimum ratio, called the stoichiometric point, and the exhaust output will mainly consist of fully oxidized CO2.
The voltage produced by the sensor is so nonlinear with respect to oxygen concentration that it is impractical for the electronic control unit (ECU) to measure intermediate values - it merely registers "lean" or "rich", and adjusts the fuel/air mixture to keep the output of the sensor alternating equally between these two values.
This type of sensor is called 'narrow band', referring to the narrow range of fuel/air ratios to which the sensor responds. The main disadvantage of narrow band sensors is their slow response: the control unit determines the exhaust gas composition by averaging the high and low swings in the sensor's output, and this process creates an inevitable delay (this statement may be misleading - see discussion).

[edit] Wideband zirconia sensor

A variation on the zirconia sensor, called the 'wideband' sensor, was introduced by Robert Bosch in 1994 but is (as of 2006) used in only a few vehicles. It is based on a planar zirconia element, but also incorporates an electrochemical gas pump. An electronic circuit containing a feedback loop controls the gas pump current to keep the output of the electrochemical cell constant, so that the pump current directly indicates the oxygen content of the exhaust gas. This sensor eliminates the averaging delay inherent in narrow band sensors, allowing the control unit to adjust the fuel delivery and ignition timing of the engine much more rapidly. In the automotive industry this sensor is also called a UEGO (for Universal Exhaust Gas Oxygen) sensor. UEGO sensors are also commonly used in aftermarket dyno tuning and high performance driver A/F display equipment. Wideband zirconia sensor is used for Stratified Fuel Injection systems and for the first time can be used for diesel engines as essential ECU's feedback sensor for oxygen content in exhaust gas in the next EURO and ULEV emission stages.

[edit] Titania sensor

A less common type of narrow band lambda sensor has a ceramic element made of titanium dioxide (titania). This type does not generate its own voltage, but changes its electrical resistance in response to the oxygen concentration. Its value varies from about 20 kilohm for a lean mixture to about one kilohm for a rich mixture. The control unit feeds the sensor with a low-current five volt supply and measures the resulting voltage across the sensor. Like the zirconia sensor, this type is so nonlinear that in practice it is used simply as a binary "rich or lean" indicator. Titania sensors are more expensive than zirconia sensors, but they also respond faster. In automotive applications the Titania sensor, unlike the zirconia sensor does not require a reference sample of atmospheric air to operate properly. This makes the sensor assembly easier body easier to design against water contamination. While most automotive sensors are submersible, zirconia-based sensors require a very small supply of reference air from the atmosphere. In theory, the sensor wire harness and connector are sealed. Air that leaches through the wire harness to the sensor is assumed to come from an open point in the harness - usually the ECU which is housed in an enclosed space like the trunk or vehicle interior.

[XfireZ51]

Paul,

CCP at WOT would be a problem IMO. Difficult to control fueling when the CCP comes in and enrichens the mixture or dilutes it by introducing air. I would expect CCP to take place at startup and idle. I have a few scans of my car and I'll take a look to see what mine is doing.

[bradslt5]

please enlighten me to the effects of the canister purge?this is new to me i have learned some stuff and am a dodo on other stuff . could this be bypassed ?

[Aurora40]

Originally Posted by XfireZ51

Paul,

CCP at WOT would be a problem IMO. Difficult to control fueling when the CCP comes in and enrichens the mixture or dilutes it by introducing air. I would expect CCP to take place at startup and idle. I have a few scans of my car and I'll take a look to see what mine is doing.

I'm pretty sure the manual describes when it happens, and I thought it was after the car was warm and at sort of a cruising rpm? I suspect if it purged at 0% throttle/idle, it would cause some lack of smoothness. But I dunno... I do recall reading about it though, so it's in there somewhere.

FWIW, I have an AutoXray EZ-Scan 6000. Mostly I find a laptop more useful for datalogging things like knock retard on a run, but the hand-held tool is useful for troubleshooting and is way more convenient to take with you. Plus it works on just about every car.

[tpepmeie]

Looking at a BMCB calibration (93-95), purge can be active if...

Coolant > 65C
MPH > 10
TPS > 3.5
BLM > 100

Then, once purge is active, the duty cycle of the solenoid is increased/decreased as the Integrator moves outside set boundaries (100-118). There are many other parameters involved, but this is the jist of it.

Todd