Lean Air fuel spike on the 2 - 3 shift

[Roc87]

Today was the first time I have gotten to mess around with the powerlogger and it happend to be opening day of the track. Each run right when the trans shifts from 2nd to 3rd, the wideband is showing a lean spike, goes from around 10.4 to 13.0 and back to 10.7, doesnt last long and there isn't any knock that happens. The O2 milivolts don't seem to move Any ideas why it would spike? Wasn't able to improve my ET's over last years best, but was able to get 118.3 mph, et 11.63

As a side note, the power logger is years ahead of direct scan, it's great having the wideband on SM, and it was really simple to install since I had a direct scan years ago.

 

[norbs]

Be interesting to see the log. Your going to get spikes on the shift, I see it on most logs, how long do they last? Is the maf dropping on the shifts?

 

[Roc87]

MAF seems to drop a little more on the 1 to 2 shift than the 2 to 3? Ok, here's my last run of the day, it hooked great for about 5 feet off the line, then spun a little.

 

[norbs]

I see the spike also, but the maf is maxed out, I would not be too concerned about it. Your stock o2 sensor is pretty flat.You need to do a log of driving the car around normally and see the X counts, they should be well over 100, yours are 30, but its hard to tell on wot runs as it rich.

 

[Roc87]

Thanks for checking it out Norbs The stock o2 is a heated one and cross counts are pretty fast during normal driving.

 

[norbs]

I do not like the heated sensors, The stock ones work best. They seem to respond faster and last longer , as strange as it sounds, just my opinion. What are your x counts usually driving around normally?

 

[Roc87]

Before I put in the heated sensor, I'd get a check engine light for the O2 every few months, not even running leaded gas. Tried all the brands suggested. May give the stockers another chance if they've improved any in the past few years, got nothing to lose

 

[norbs]

When your pulling these sensors out how do they look? totally black?

 

[Roc87]

I honestly don't remember 100%, but I don't think they looked all that bad. It was when I was running an extender chip, msd 50#'s, & a pt51, probably been 6 or 7 years ago.

 

[Eric Stage I]

I see these spikes fairly frequently with widebands on a shift, especially if there is a large, fast RPM drop (which you had). I think there is a rapid change in exhaust flow which can throw the reading off temporarily (just my opinion). This may have to do with the temperature control of the heater in the sensor.
On the O2 x-counts, it is a counter that counts from 0 to 255 then starts over again, so it could be anywhere. When cruising in closed loop, I would expect it to rise around 10-20 numbers per second. In open loop or WOT, it won't change much at all.

 

[norbs]

Eric, what is your preference on narrow band 02 sensors, heated or non heated?

 

[Eric Stage I]

I don't really have a preference on the narrowband, as long as keeps the A/F averaging 14.7 in closed loop.

The heated can be beneficial on some cars where the O2 sensor cools down at idle, causing the BLM to rise (falsely). I use open loop idle so I don't run into that problem.