Life with a daily wideband - different AFRs???
 

Well I've had my LM-1 wideband permanently installed in my car for about 4 months now. However, I'm scared to do anymore tuning because my AFR's seem to be varying quite drastically. I glance at the AFR display constantly, and I've noticed a fairly significant difference in AFRs under seemingly identical situations Anyone else noticed this? I'm getting almost a full point difference at cruise in the same cells. Not sure if there's something going on with the engine (bad injector, iffy compression, etc), the changing weather (though I'm not talking about the difference in a 30 degree day and a 70 degree one), or it might be our freaking gas forumlations changing without anyone telling us. Anyway, it's sure making tuning difficult at best...... :(

I have been running my LM-1 for about 2000 miles non stop now. I used to just plug it in and monitor it for a bit and the remove it. But I have not noticed the A/Fs varying in cells.

I'll keep an eye on that.

One thing you could try is a re cal in free air and see if you see 20.1:1 ratio (I think that is the number for free air, it should say in the book somewhere).

Also I don't think the life of the O2 sensor is that great so that could be a factor too.

Does a real rich runnig car possibly contribute to the shorten life of the O2?

Just some thoughts.
Thanks

Yep, I checked the free air and it's still reading exactly 20.9 which is what it's supposed to. I have a feeling it's the stupid oxygenated gas causing the problems. There was a thread on the LM1 site that said it could easily cause readings to vary by 0.5. Just frustrates the hell out of me cuz I don't know how you tune when you don't have any way of knowing what kind of gas you're putting in........

And it would suck to have to place another one in just to get and average or to check the first one. uhmm.

Sorry if you know all this stuff but here's a stab at it ...

If you are only seeing variances at cruise I would not worry too much. The AFR as you have seen can vary all over the place depending on slight changes in load and how well each cell is tuned. This is especially true if you have not tuned ALL the cells to perfection. Example, if you do rough tuning in a few cruise cells, the surrounding cells may be way off and as the rpm and mani pressure change the pfc may start averaging the fuel from those adjacent cells that may not have been precision tuned. Also can take a look at the fuel for each cell and adjust for progressive increases in fuel from lo to hi n column and p row (works in boost areas too). The first time I looked at the total fuel in the base map after a recalc I was shocked to see all the holes in what I thought was a well tuned map (tuned by me of course). Takes a hell of a lot of time to get this sorted to perfection.

I would just lean out the cruise areas with the commander till it runs rough and then add a little back to smooth it out. If I found a rich cruise area while monitoring the wideband that would be the next spot to lean out. I found I coul lean out entire p rows by alot (>10%) without affecting smoothness or transition, this sped up cruise tuning. Once you get it really lean you may need to bump up acel maps to prevent lean tip-in condition.

If you are seeing that big of a swing at full throttle then it's time to take a long look at everything from air temp correction factors. I never got it very repeatable but within a +/- 0.1 to 0.2 afr or so. Tough to get it spot on with the slow stock air intake sensor anywhere under the hood IMO.

Great response, twokrx7, thanks! Yeah, it's cruise that I'm noticing the difference in, mainly. That and also idle. My idle can vary by exactly 2 full points. Sometimes it sits at 12:1, sometimes it ventures to 14:1. Same vacuum, same rpm. Haven't figured that one out yet... Cruise is just a seat of the pants hunch. I drive the same route everyday, so when cruising at the same speed, and not going up/downhill, I expect it to read about the same thing. Fortunately WOT is fine...though it's still pig rich since I can't afford any mistakes right now... :)

As I've been leaning out cruise, I'm definitely getting tip-in problems. Problem is, I can't seem to get rid of it despite drastic changes to accel values. My biggest problem is shifting. It seems to be using the same cells as I sometimes cruise in, so if I get them lean, it stumbles badly when shifting. Again, the accel numbers don't seem to help me. Do you change the decay values at all? I've yet to understand whether a larger value there causes a longer squirt or a shorter one...

Thanks again!

PM me with your email addy and I can send some info via email