Lean at start up then rich at Idle

[pwilson22000]

I'm tuning a friends vehicle in which we installed the COS 03 with 2 bar map. Currently the vehicle is set up to run MAFless. The vehicle is a 2003 Silverado SS with twin T04V-Trims. Currently the truck has 60 lb delphi injectors with approximately 45 psi of fuel pressure at idle. With the fuel status per PID SAE.FUEL SYS, set to OL and B4108 set to disable at start up the AFR reads 20:1 then slowly I can see the STFT come on and it goes rich to 13.6:1. From what I have read the PW should be based of the VE and Commanded AFR table if OL is acheived. So with this thought I made a 20% increase to VE table to to lean out the rich idle after the initial start up. This had no effect on the AFR. I'm thinking that somehow I'm not fully in OL. Any help or advice would be appreciated.

[joecar]

TTT for you.

[Tordne]

Ok...

What WBO2 are you using, and are you satisfied that it is calibrated and configured in EFILive correctly?

If it is super lean on startup check the after start enrichment tables B3632 and the ones below (they basically relate to decay rate etc). This will add fuel on startup and slowly decay out to what is set in your B3605 or B3647 table.

On the rich idle I have some recent insite to this I just installed SVO 42's into a stock internals motor (I had my reasons )

To bore you with a bit of background on my situation: I scaled the injectors and basically the VE table is EXACTLY the same as it was in my tune pre new injector install, so that is brilliant!!! My idle is also fine cause of the injectors are not as big as yours. On decel I was seeing (am still seeing) really rich ~12 AFRs.

Now what I found may help you. I injector pulse width is really important! Pulse width is determined from the Default/Minimum table + the offset table. There is a very fine balance between the pulse width being enough to allow the injector to open and flow fuel, or not be able to open at all.

So.. you could try lowering the pulse width in the B4003 & B4004 table, check the offset table. You may also find that because of the size of the injector the minimum flow is too much for idle. I found tat i reduced my ve by 50% to test and it made NO difference

Anyway, I hope that helps and makes some sense

Cheers,

[Tordne]

Oh.. Forgot t mention that if you see STFT coing on you are not in full OL. If you are using Custom OS V3 and have the B3647 table and are commanding 14.63:1 (EQ Ratio 1.0) then you will be in what is called Semi-Open Loop and O2 feedback is used.

Generally what you do is set the points (except where you want enrichment - obviously) to something like 14.7:1, then it will be in full Open Loop

Also check B3801 is Disabled, B4205 is set to max values.

Cheers,