I have noticed over the years that when I start my car, it runs very lean compared to commanded for a short while. Then it seems to fall into a BEN of ~0.98-1.00. I command 14.65 AFR in my idle cells. I have tuned the start such that I get a perfect start with minimal rpm flare. It starts very quickly, hot or cold w/o touching the gas pedal.

Now, for some reason it starts and runs in the 16-17 AFR range for like 2-3 minutes after I start it, if I just let it idle to warm up. Once its warm up, my AFRs are perfect. It doesn't have to do with the IAT, as I'm on COS3 and I've tuned the A0014 table pretty extensively and it seems to do a pretty good job.

Does this point to a deficiency in the IAT/ECT temperature blending for my engine? I do not have the coolant lines routed through my throttle body like normal, and my intake system differs significantly from stock (its a dual ramhorn looking 3.5" intake system going to two seperate cone filters behind big openings in the bumper cover.

Seems like its not a problem with the commanded AFR, but the actual resultant AFR. What tables/curves/settings effect acutal AFR, but not commanded after startup?

Anyone care to point me into the right direction?

 

If it starts up and idles fine then a 15-16 AFR is fine, even at cruise this is ok since there is no load on the engine. Usually you need a richer mixture at startup but if your starts ok then leave it. A lot of people worry about cruising with ARR's in the 15 and 16's, this makes for better fuel economy but of course you do not want this at wot...

 

Its not an issue of where its idling at as far as AFR, its an issue that the actual is so far off of the command only during warmup. Once its up to temp, the actual and command are within 1%.

 

is that a real lean or a fake lean?

 

Not sure to be honest. I have a large cam, so I'm not sure that at idle my WB02 is accurate, however it should be precise. Since it reads normal once the engine is warm I'm thinking its actually lean during warmup. I've even let the senor warmup fully to make sure its not a sensor warmup effect or something like that.

 

is this something that comes and goes or does it happen every time?

 

Every time.