Another Rich Decel Thread..Need Help

[WeathermanShawn]

2002 Camaro Z-28 H/C as noted in signature. Stock 2002 injectors. Car is mechanically sound.

I have had difficulty accomplishing OLSD as my primary tuning option. Many hills and elevation changes in my area. I end up sampling multiple and widely varying g*K/kPa values at the same RPM. I have noticed the BARO value doesn't change accordingly while driving, and without holding pressure constant I am sampling data at RPM/MAP cells that becomes unreliable.

But my question is on the widely familiar Rich Decel problem many of us have. Whether I run CLSD, CLMAF, or 'regular' CLSDMAF (stock closed-loop), if I let off the throttle at any RPM, my AFR reads 12.9-13.2 for at least 9-10 seconds. Why does it do this?

I have lowered VE in the 15-20 MAP to almost zero g/kPa values, and it has no effect. I have even logged FTC cell 21 and it always indicates it is pulling 7-9% fuel, but my wideband reads rich. Is this just a reality with injectors, even stock? Is it just a reality of having a bigger cam?

The wideband is calibrated, I have no vacuum or exhaust leaks. Ultimately I realize I can just utilize DFCO and my problem is solved. But, it makes lower MAP tuning difficult, and I am just very curious why.

Anybody have any constructive opinions or comments to enlighten me?

[alwaysinboost]

bump for you, I'm having the same issue...

[jetblast]

go to the minimum pulse tables and decrease them by 5 to 10%.

[WeathermanShawn]

I'll give that a shot and let you know how it works out.

[hquick]

I've noticed the injector voltage offset table makes a big difference, B3701.

[WeathermanShawn]

Thanks hquick:

Yea, it is definitely odd to be so rich on decel with stock injectors. Perhaps I never noticed, because I previously used DFCO 100% of the time. It is only in doing the more advanced tuning (DFCO disabled) that I noticed it. My narrowband O2's are less than a year old, but maybe they are are switching too slow and contributing to the issue.

Just recently began logging GM.Volts. While my voltage looks good, I have seen a number of threads addressing B3701, especially with larger injectors.

Any new insight into adjusting this table, or should I read through some of the search posts?

[5.7ute]

I dont really see the point in changing the B3701 until this is known to be the cause. With stock injectors & the stock values it should be accurate.
There is the possibility that the transient fuelling tables may be adding fuel in this scenario. Or that the small pulse adders, min pulsewidth etc are active. I have a thread on here somewhere on calculating actual IBPW that may help pinpoint the problem you are having. Once you have the calc.pid made for your tune, and change the cal link txt to reference this pid things should become more evident.

[WeathermanShawn]

For those interested and especially running closed-loop...

Appeared to be a function of B4309 Throttle Cracker in Gear Table. In order to address some 'bucking' I had previously 'zeroed' out B4309. So what was happening upon throttle let-off was the MAP was following rapidly..much faster than the RPM's were falling. So it always took about 8-15+ seconds before wideband AFR's came back to 14.63.

On a hunch, put B4309 back to stock. It worked in that there was no further rich decel. Can't say I like the snail pace RPM's fall, but perhaps the previous setup was too fast for the STFT's to adjust to. Had no idea 'zeroing' out TC would do that, but guess it makes sense. Hope to find a happy medium.

[redhardsupra]

Shawn do you have logs for the 'before and after'? i'd love to see it on a graph

[WeathermanShawn]

Yes, I do. Got a before and after run this morning.

I'll attach and send them out later this evening, when I get off work.