Rich during coast down

[edge04]

2006 corvette ls2 with ls3 heads and intake, cam, headers, no cats, CAI.

Been dialing in A/F using WB.I currently filter out anything where the TPS is less than 20%, it idles right about 18%. Anyway, I go rich when I let off the throttle, either shifting or coasting in to a stop. It finds idle great and holds it however it is rich

Is this corrected in airflow final minimum? That table is currently close to stock. Thanks

here is the tune

Edgar Ramon 2006Vette_COS_VE.hpt

[MikeOD]

Can you post up a log? Are you ever seeing DFCO turn on?

[edge04]

I can post a log tonight but a light blue may have just lit.

Does DFCO only work with the fuel trims on? I ask because I tune with them off and WB only? If not then I am not noticing it coming on.

also wondering if its in idle spark coast down. in the areas where I am noticing it it is close to stock

[10_SS]

you may need to lower your injector min pulse width? This is the case for bigger injectors usually, but you changed the cam, so maybe? you would see max lean on WB and 02's if dfcu was coming on, then WB error histogram showing need for positive fuel in that area since it's sensing lean...

[gmtech16450yz]

I'd work on getting that 18% throttle angle at idle lower before going much further. You really want that percentage below 10%. You're using 1/5 of your throttle just to idle, that's too much. The most likely reason for that would be low ignition timing, that is assuming the throttle body and plate itself is clean. What is your ignition timing at idle? Also look at what your adaptive idle ignition timing is running at, is it adding or taking away a bunch of timing?

The reason I would get the throttle percentage correct at idle is so that all the rest of the ECM tables work properly. When the TPS is at 20% at idle, in many of the tables the ECM isn't going to know if it's actually idling or not, or if the throttle is "closed" or not.

[edge04]

Ignition timing at idle is 24. Are you referring to the idle adaptive spark control tables? If so the overspeed ones are pulling timing.

My dfco is working and at higher speeds I don't experience the rich coast down.

forgot to mention that my TB was ported by yours truly. Starting to think and read that that's not a good idea and could be the cause of my tuning issues.

I'd work on getting that 18% throttle angle at idle lower before going much further. You really want that percentage below 10%. You're using 1/5 of your throttle just to idle, that's too much. The most likely reason for that would be low ignition timing, that is assuming the throttle body and plate itself is clean. What is your ignition timing at idle? Also look at what your adaptive idle ignition timing is running at, is it adding or taking away a bunch of timing?

The reason I would get the throttle percentage correct at idle is so that all the rest of the ECM tables work properly. When the TPS is at 20% at idle, in many of the tables the ECM isn't going to know if it's actually idling or not, or if the throttle is "closed" or not.

[gmtech16450yz]

Ignition timing at idle is 24. Are you referring to the idle adaptive spark control tables? If so the overspeed ones are pulling timing.

My dfco is working and at higher speeds I don't experience the rich coast down.

forgot to mention that my TB was ported by yours truly. Starting to think and read that that's not a good idea and could be the cause of my tuning issues.

So is the running idle timing 24 while the throttle is at 18-20 or is 24 what you have the idle timing set to in the tune? How much timing is the adaptive spark pulling? That in itself would be telling you that there's too much airflow.

On the DFCO, it will also work better when you get the throttle closing further. Having the throttle close further on decel will increase the manifold vacuum and it will be more likely to go into DFCO, even with stock settings.

On the ported throttle body, that usually makes the running throttle position too low, not too high. If anything you might need to tweak the ETC Area Scalar to speed up or slow down the throttle movement. Other than that, the ported throttle body most likely is ok and not the cause of your issue.

[edge04]

I will try and post a log tonight. I am still dialing my A/F within my VE table.

I was able to start fixing the problem by removing fuel from the idle base air flow table. I did notice that timing drops down to 16 when coasting to idle then hovers around 23 and my TPC hovers between 17 and 18. Guessing that because idle is fluctuating down 50 rpms or so.

I also notice when I do a normal take off from a dead stop I go lean right away and need to give it a bit more throttle. Guessing because the TB is open to 17-18?

[edge04]

BTW, here are my cam specs for what its worth

ADV DUR INT 279 EXH 297 DUR @ .050 INT 227 EXH 243 LOBE 114

[edge04]

I read the entire 5_Liter thread on idle and started to apply some of that. Like mentioned my idle is smooth, no surging and no dipping BUT it is rich so I'm still dialing that in. It does still go rich when first letting of the throttle and at stop idle my TPC is still 17%. Will mess with it a bit more (still also dialing in the VE) and then post a log.