Today i was turning the boost up a bit and tuning it out with the datalogit. (15 psi) the afr's were rich, (around 10.5) but when i went back and looked at the log using a chart for rpm and afr, there were a couple lean spikes. One around 5500 rpm and then another around 7k for just a split second.

When looking at map watch the overall AVERAGE in those areas was still 10.5, but looking at the PEAK afr showed around 14 in one and 12 in another. My fuel pressure didnt seem to drop, although my fpr gauge has very short spacing so a few psi difference doesnt move the needle much. A pressure drop of 5psi or more would be noticeable though.The maps are nice and smooth and don't have strange peaks or valleys either.

So is this something to be concerned about? or is this something fairly normal when logging AFR's like this. I probably never would have noticed it had i not been studying the chart so closely. But i didnt want to tune further without first figuring out what it means, if anything. My wideband is an lc1. and the reaction time is on immediate. I have a 0 hold off under map watch. I can post my log if need be.

 

Okay an update. I discussed it a bit with Chuck Westbrook and Raymond Herchenroder, over on Chuck's yahoo tuning group. Decided the lean spikes are attributed to either a very slight misfire condition, which could be caused by the rich mixture, a corrupted log, or other discrepancy with the datalogit, laptop, or LC-1.

I don't think the spikes are a concern and will lean the maps out from the rich 10's to low 11's as soon as the weather dries up over here in TX. I may also slow the reaction time of my LC-1 from instant to 1/12 of a second to see if it helps smooth any spikes like this out.
Does anyone have any experience or feedback on the reaction times they use with the innovative wideband products?

 

I think 1/2 second will be OK for cruise but not for acceleration as you will not be in a cell long enough to get any readings.

 

Its 1/12 of a second, not half. Also has 1/6 and 1/3 is the slowest setting

 

I look for the difference between min and max reported afr in a cell to indicate misfire. But your reported max afr is so far beyond what I would consider misfire that it must have been very severe to get that high of a delta between min and max afr, or, it's something other than misfire. Did you feel a loss of power? Was there knock?

 

no i felt no power loss at all. No surging, just solid acceleration.

my knock sensor readings seem to never go above 1 or 2 in any situation, i don't think its working as it should and therefor don't rely on it for any valid information. My tune is on the conservative side, the air temps were low, boost was at 15 psi and mixture was 10- 10.5. Fuel pressure solid, duty cycles fine.

 

I'll see if i can dig up the log to post it.

 

Me going blind!

 

i tried the 1/12 sec setting but didnt like how slow the response was. When i would free rev it the afr's took awhile to go dead lean as the throttle was lifted. it basically just averaged them and they seemed to be put in the wrong cells. I put it back almost immediately. (maybe partially due to my resistance to change)

i went ahead and leaned the maps out to low 11's and the lean spikes went away. I also updated the firmware on my LC-1 from 1.00 to 1.10. So it was either a firmware glitch or missfire. My best guesses anyways.

 

Well ya, but why mention it now?