Tell me why my commanded AFR does not match my WB reading! I'm running closed loop with locked fuel trims. Once its warmed up and commanded goes to 14.73, WB is dead on, and the rest of my VE table is pretty much spot on. First started, if the commanded AFR is 13.x the WB might read 15 or so. Like I said it comes in line when it hits closed loop, probably more so when it is fully warmed up. Is there something else I need to look at or tweak?

Thanks,
Ben

 

So, your INT works, and BLM is locked at 128, right?

When commanded 14.7, what does your INT do? That IS fuel trim (short term).

If your VE table is spot on, then INT would stay right near 128 all the time in closed loop. I'm guessing that you're seeing 14.7 commanded and 14.7 actual, and assuming that means VE is spot on... But, if INT is having to work to get 14.7 actual, then VE is not spot on.

Your 90-100kPa table has too little VE, probably...

 

No no, locked BLM AND INT. If I unlocked both, I'd have 128 BLMs and very close to 128 INT. So I'm leaving both locked right now and tuning with my WB and scannerpro histograms, no PE.

When the car is warmed to the 'normal' temp, IOW what it was tuned at ( approx. 190 degrees coolant temp, 75-85 degrees air temp), the commanded meets the actual. It's only when the car is started after sitting a bit (I don't know, maybe even a half hour) when it's in actual open loop, commanding AFR other than 14.7 that it will be different. If I change say my open loop % change vs coolant temp by + 10%, that will bring it more in line of what it should be. Commanded might then be something like 11.x and actual might be 13.x, but after it runs for a minute the difference gets smaller and smaller and by the time it hits closed loop (although really open since locked trims) the commanded and actual is exactly in line at 14.7.

I was thinking of maybe some sort of air temp/coolant temp factor table but I don't seem to be able to make anything of whats available in the 8D xdf. There's the MAT vs Airflow table but I don't see how that could cause what I'm seeing.

Edit, forgot to mention, I'm not even looking at high load situation (you say add some in 90-100kpa area), this is just starting up and idling the car.

 

Sounds more like a heat soak issue.
You may want to tune you MAT tables. Some people just live with it.
Is you MAT sensor in the intake?

If you move your % change vs coolant temp settings, you CAFR will move to follow that change.

 

Well, I can always make a greater change in open loop factor vs coolant temp, and that will bring it more inline, but the commanded will not be actual until its warmed up. Commanded is always congruent with actual at all operating points (rpm/load) when its at temp, so maybe I can just live with this and overcompensate in open loop.

The MAT sensor is just zip tied close to the intake filter right now, I haven't gotten to building an actual intake tract (CAI) for it yet.

 

I see what you're saying now. It's normal. The extra fuel is going through mostly unburnt. That's why it needs enrichment in the first place. The coolant enrichment needs more than just what you want it to actually burn at. If you set the commanded to 14.7 from a cold engine, it'd get about 18:1 of burned charge.

It might also be your AIR pump, if you're using one still.

 

Ok so to recap everything, it is normal to, when first started with a cold engine, to have maybe a commanded AFR of 13.0 when in open loop and the actual wideband reading would be like 15.0 at the same instant (maybe not that exaggerated but at least quite a bit leaner).

 

Dont mean to go off subject, but what and how do you lock//unlock blm, int. ???--- Im pretty new and leaning here.