Need Help with fueling - idle into cruise

[StopGap]

Hi Guys:

This is my FIRST and ONLY tune. I took this project on to learn; once I get through this one tune I'll have made it! Car - 09 Vette, stock except for an A&A Si-Trim (small blower) kit. I am ready to tackle my first tune issue. It's the low end up to about 2500 rpm, so nothing really to do with boost.

I've had the issue since shortly after kit install. First thing I did was ensure everything was good mechanically. There are no vacuum leaks. I am pulling 17" vac at 650 idle on a warm engine and at 2500' altitude. Fuel pressure at idle is 62lbs via gauge off the fuel rail.

My fuel trims (LTFTs) from idle up to about 2500 rpm are off the map correcting for lean. If I am cruising around town, stop/go driving, nothing above 3K rpm, LTFTs drift higher and higher until I hit MIL 171/174. So, I need some help/advice, where to begin getting more fuel in this range; or. a method to get LTFTs back toward zeros. Once I start running aggressively above 3K rpm, LTFTs start correcting and go back down to +12% and into single digits above 4K. These too are still too high, but I am trying to focus one place at a time.

I was out today, running stop/go and started a short 2 min DL from a stoplight (idle) through 4th gear. I've attached my tune as well. Thanks for your help guys.

[StopGap]

So, I'm experimenting on my own. Trying to get LTFTs back in control at idle and cruise. One simple step I am considering taking is high octane table. Although I haven't pulled the trigger and saved the tune yet, I am experimenting with smoothing the 3d. When I did that, it pulled 1* of timing from the low cylinder mass/low rpm part of the table. I am thinking about saving that change and flashing it in to see if it helps?

Also as an alternative, I tried highlighting the entire high octane table from 0 to 3500 rpm and the complete range of cyl mass and subtracting 1*

Anyone with advice, am I on the right track? I'm pretty sure I am safe....I just want to stay safe until I get the effects of these changes.

[StopGap]

Well, playing with the high octane table was fun...didn't accomplish what I thought it would. But, it was interesting and my first experiment making a change to something and getting back. Getting more confident with the editor and wasting a little gas in the meantime.

I still need to get fuel to the lower range - idle to cruise. Any advice is appreciated. I'm poking around fuel tab now....along with reading a lot.

[NJ_Phil]

You just can't put a blower on the car without doing some VE tuning. Even with the BOV open, airflow is higher and the motor doesn't know about this increase in airflow..
Speaking of BOV, make sure it's bypassing at idle and is connected to the vacuum side of the throttle body.

You're running about 20% lean so why don't you experiment by multiplying your entire VE table by 10% to see the effects on the trim. Good way to get your feet wet. You probably have an E38 with VVE so you will have to run the Virtual VE editor, increase it 10%, then "save" the equations that will generate that VE table, then write the tune.

Just save your stock tune first.

[GHuggins]

Contrary to what a lot of people will think - fueling is controlled off of the air model - you'll need to tune your MAF and VE tables to get the fueling dialed in to where it needs to be... Now with that being said there are other things that also control fueling, but the air model is where you will make the majority of your corrections

Also the higher the numbers = the more air it thinks is going into the motor so it'll add more fuel...

[schpenxel]

The biggest problem right now is you're running a MAF only tune but aren't logging MAF frequency, so you have no way of knowing what area of the MAF table to adjust... normally you would look at the log and say at 4,950hz MAF frequency you see that fuel trims are +15%. So, increase the 4,950hz cell of the MAF table 15% (this is just an example I made up.. can't do this without knowing MAF Frequency). Of course you'd want to set up a graph to figure this out for you vs trying to go cell by cell and figure it out by hand

Same thing once you're in PE.. say at 9,000hz your AFR (or EQ ratio) error is +5%. So, increase the 9000hz cell of the MAF table by 5% to correct for this.

The previous posts are totally right that there is no true 100% "MAF only" on these cars, though if you want a down and dirty tune you can just change the MAF table and get away with it more or less. It's not ideal, but I do know this is how the shop you bought the kit and got the base tune from does it every day

As a rough start to keep it from being so lean I would just increase the entire MAF table by 15%

[StopGap]

OK, so I'm taking in this advice, thanks! Put timing back to to the target FI tune. Now I'm going to experiment with the MAF freq table in airflow. I took advice above and another post from Carson who was advising someone in a similar situation. I am increasing the MAF table by 12% across the board. I'll flash and DL some more. All of this is helping me come to learn the impacts of these various tune parameters.

I've created a solid system of always being able to return to the safe FI tune or any variation of it I've created so far. I am also ONLY focusing right now on idle and cruise fueling/timing, etc. I haven't entered PE or WOT, other than a couple of blips when I first installed weeks ago. Won't go there until I am satisfied with the low end, although I've probably read as much about fine tuning PE and WOT than I have idle as it seems to be everyone's focus.

I already know that my FI tune is set to trigger PE from throttle command, and I've read that some change that to trigger from MAP Kpa. I'll want to do that eventually given my driving habits. I'm not a dragstrip guy. I am seldom launching at 100% commanded throttle, instead I more roll into WOT which is causing PE to come on too late. But...I am way too early right now working on the big end of the tune.

Thanks, keep any info coming, I'm taking it all in.

EDIT - Carson, you apparently posted while I was typing. I am going with the MAP (12%) increase, and will DL just to see the results. I am confident now I can back out of anything and return to where I was or any step along the way. This, in my mind, is still roughing in. I'll keep fine tuning as I learn more. Difficult to eat the elephant all in one big bite!

[justhereforinfo]

Just curious about your injectors and fuel pressure regultor setup. Is it all stock? If not, even before you start touching maf and ve, you'd need the get your injector data correct. Just a thought, havent seen it mentioned yet.

[schpenxel]

The base tune he used for injector data and some other stuff was setup for the same injectors he's using

[StopGap]

Just curious about your injectors and fuel pressure regultor setup. Is it all stock? If not, even before you start touching maf and ve, you'd need the get your injector data correct. Just a thought, havent seen it mentioned yet.

Yeah, thanks, I have been a little vague, but this is a story a few weeks old. I have 80lb injectors and the injector data is correct. This is a small A&A kit SI-Trim on a stock LS3, and I am using a known good startup tune that has me roughed in. Now I am working on getting from rough to fine on my own as an opportunity to learn. Dealt with a little anomaly, in that LTFTs started going south 25% lean and throwing 171/174s. I needed to get that back dialed down so I can concentrate on the finer tuning points.

[StopGap]

So, good news. Just loaded the tune with the +12% Maf Freq adjustment across the table and LTFTs are now 0 to -2% throughout idle and cruise up to about 2500/3000. Now, if it stays there I can relax a little and get the finer tuning down. Still need to drive more DLs and get LTFTs settled in.

Thanks guys.

[StopGap]

I wanted to open another topic, any opinions. Even though I am staying out of the PE/boosted range and focusing on getting the low RPM end tightened up now, I picked up some info on older threads about different ways to trigger PE. I cannot get back to who said what as I've copied over 50 pages of posts in a long string as part of the research/reading I am doing.

In the few blips where I crossed over into higher RPMs and boost I have DLs that show I am not entering PE until about 50% commanded throttle. I read this excerpt:
"You need to lower your PE Throttle/Pedal table down to 10. I see you have it at 20. As goofy as it sounds...a setting of 10 in this table makes the PE trigger at right around exactly 43% throttle and not 10%. I've got the logs to prove this. Some goofy glitch in the software where the numer in the setting definitely does not equal reality. You can even look in your own logs and see exactly what throttle % the PE is triggering (assuming you are logging throttle % PID). "

I am going to make this change even though I am not really concentrating on PE at the moment. Mentioned this earlier that my driving style is not 100% throttle launches. Instead I find myself consistently rolling into boost. So, as I am theorizing, I could end up well into boost and still in CL.

Any thoughts?

EDIT: Should have mentioned 50% throttle command and 4926 RPM before entering PE. Wasn't boosted yet, but right at about 0 going into boost.