Long Lean Tips When Cruising! Transient Fuel? Bad O2? Injector Short Pulse Adder?

Seems like every time I try to tune a car I run into things I have never seen before. So I just installed a turbo on my 02 T/A. It's a stock LS1 that has already been dyno tuned previously for a TR224 cam. Ran great no problems, besides the turbo I added a set of Siemens 60# injectors. The car still runs and drives great (If it wasn't for the ugly scan I wouldn't think anything was wrong) but when I was logging the car when doing so testing the other day I noticed when driving around 30mpg constant speed that the car felt like I ran out of fuel for about 2 seconds and came right back. After looking at the scan I seen a big long lean tip in from the 02 sensor. After doing some reading I am scratching my head on where to start first because I am not sure if my 02s just became lazy all the sudden (But were fine before the turbo install) or if the Transient Fueling may need adjustment from what I have been reading, or my injector data is off. I have the Banish DVD with the data so I thought it would be a simple injector swap. But after looking at some other tunes with the same injectors I may have the wrong short pulse adder in but wanted to get another opinion quick on my issue first.

Attached is a scan of a 1/4mi run before the turbo and injectors. And a scan of the other day just testing with the turbo and new injectors. Also I included the tune that is currently in the car. I really only added fuel and removed some timing for testing. I usually try to get some kinks out before I take it to the dyno for tuning to make sure I don't waste his time if its something I need to replace or add.

Thanks in advance!

I would try lowering the fuel>Transient>Min Fuel Milligrams setting, maybe cut in half or even less. I'm thinking the fuel trims are fighting to get the injector pulse lower but the Min Fuel Milligrams setting wont let it go lower.

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Originally Posted by david_viny

I would try lowering the fuel>Transient>Min Fuel Milligrams setting, maybe cut in half or even less. I'm thinking the fuel trims are fighting to get the injector pulse lower but the Min Fuel Milligrams setting wont let it go lower.

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From what I have been reading this is the area to start from what the scan looks like but you would think with just changing injectors and not intake, heads, etc wouldn't effect the fuel delivery that much. I have seen these injectors run with a lower default pulse width between 1200rpm-2800rpm. I'll for sure try the Transient Min Fuel first.

The fuel>Transient>Min Fuel Milligrams setting as far as I know doesn't have anything directly to do with transient. I don't know why its not under the injector settings. From what I've read all it does is limit how small an injector pules can be. And large injectors may need a smaller pulse then the factory settings at idle and deceleration. And for whatever reason F-bodys have this setting set higher then many of the truck/corvette files I've seen.

This probably wont fix everything but at least that's one variable out of the way.

Quote:

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Originally Posted by david_viny

The fuel>Transient>Min Fuel Milligrams setting as far as I know doesn't have anything directly to do with transient. I don't know why its not under the injector settings. From what I've read all it does is limit how small an injector pules can be. And large injectors may need a smaller pulse then the factory settings at idle and deceleration. And for whatever reason F-bodys have this setting set higher then many of the truck/corvette files I've seen.

This probably wont fix everything but at least that's one variable out of the way.

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It actually did! A little update. I tweaked the short pulse adder a little from what I have seen done in other LS1's with these injectors and lowered the default injector pulse a touch in the 1200-2800 range and always enabled transient fuel qualifications plus lowered the Min to .032 instead of .041 for starters.

After doing this I went on a long drive and the O2s are transitioning very nicely now with a single rich or lean tip throughout the cruising range. Now with this changes I made, as soon as I left off the gas and or the engine idles it goes flat rich. But the fuel trims are telling me its normal and not pulling any fuel.

To see if the rich decel was caused by transient fuel settings I disabled it under 1% throttle. The first thing I noticed from doing this was between shifts the fuel trims spike to try and compensate a lean condition, with the transient enabled at 0% throttle the O2's still go lean but the trims do not ask for fuel.

At this point I am always going to have Transient fuel enabled with the settings I have right now but I need to pull fuel out of idle and decel conditions without having the computer think it is ok to be fat. I have not changed any commanded fueling so why the PCM think rich is ok?

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Anyone have any pointers on the rich idle/decel when not commanding rich?