What is the actual difference from 10.5 a/f to 11.5 a/f? Is it enough to even notice in daily driving? Assume a full turboback with mbc.

Also, I tuned my a/f to 11.2 the other day and today it was registering in the low 10's. In some cases, I bottomed out at 10. Why is there such a large fluctuation? The temperature during the tune was 45 and today's temp was high 50's so I don't think that the temp was the cause.

Thanks for the help!

 

absolutley...
when you tuned to 11.2, was it in 4th or 3rd. its a good idea to get that afr in 4th gear. in 3rd, it will read about 0.5 points leaner, which is ok.

 

The fluctuation is in all of the gears, more noticeable in the higher gears.

How much power difference do you think 10.5 to 11.2 is?

 

Are you seeing wide fluctuations in the same load cells or just in the same gear? Are these WOT runs or partial throttle?

 

I see pretty large fluctuation too. I'm still trying to finger out why. Highway runs in 3rd and 4th gear.

I'm thinking perhaps my closed loop trims affecting my open loop map.

 

Why is that "ok"?
If you're at the same load and same timing but your AFR is .5 leaner...I wouldn't think it'd be ok.

 

Please clarify -- are you seeing large fluctautions during WOT ? How do the AFRs compare to the respective load cells? You should not be seeing a fluctuation unless you are going from open to closed or are bouncing around in load and have not smoothed the AFR curve.

 

WOT 4th gear pulls. I tuned it to 11.5 consistent about 3 weeks ago.
I've been finding during my datalogs to and from work that my AF ratio varies as far down as 10.2 consistently.

These are highway pulls and I'm not bouncing in and out of closed loop.
My fuel map isn't Jagged, though it could be smoother, however I don't believe that to be an issue either.

 

Did you check your boost? Are you boosting the same, check for leaks to see if that is a reason for your loss in power.

 

If I had a boost leak, I wouldn't hit the same load cells.

 

search for old threads regarding inconsistant afr readings. i got the same readings when i was tunning using zeitronix.
also, its good to tune for 4th gear on the streets and 3rd gear on the dyno.

 

Ok...but why is it safe to run leaner on the same tune in a different gear under similar loads?

 

Sophie, You are correct. I didn't realize you were hitting the same load cells. Just an FYI I tune using 3rd gear on the street.

 

I'm actually curious of this too, since when I dyno'd my A/F was at 10:1 up to ~5500rpms, when it went to 11.5:1. This was read at the tailpipe also... would there be a big difference in the A/F reading there as opposed to a wideband placed in the downpipe? Sorry for the thread jack, but pretty much the same question (that hasn't been answered completely).