This is my first post, and it will be long, so bear with me. This is also my first time tuning a gen 4 platform. I really thought I would be able to figure this out on my own, but after working on this tune for 6 months I've realized that I'm not as smart as I thought I was. I decided that its finally time to ask for help. Please help!
The Car- 2009 CTS-V M6
Mods- BTR stage 2 cam (Intake- .615 lift, 227 duration, Exhaust- .593 lift, 242 duration, LSA- 122), Airaid intake, ZL1 lid, 2.38 pulley, FIC 1000 injectors, TSP longtubes, catless x pipe, DSX aux fuel pump kit, AEM CAN bus wideband, track attack heat exchanger
The Problems- The main issue I'm having is a very lean tip-in. When coasting or decelerating and then getting back on the throttle, it goes very lean for a second or two, then it either comes down to commanded or overshoots rich depending on how quickly I stab the throttle. If I'm really abrupt with the throttle, it is not uncommon to see the afr jump up to 17 then overshoot to 10 before it settles somewhere in the ballpark of the 11.4 I'm commanding in PE. (I know I should be talking in Lambda, but I just can't get used to it.) I only have this issue when running in VVE only or blended mode- not when running MAF only.
MAF mode- When I run the car of of MAF only, I don't have lean tip in problems, but I have other issues. If I really spend a lot of time logging MAF error and putting the corrections in my tune, I end up with this super nasty lean spike around 2500 rpm when everything else is in line. As a result, my MAF curve is a little on the rich side to mask this and make the car driveable- not the correct way to do things! The car drives somewhat okay like this, but I don't like it being rich (or my ltfts being through the roof in closed loop), and I don't feel like it runs nearly as smooth as it does in VVE mode.
VVE mode- In VVE mode the car seems to be much smoother and just feels better in general. Except for the horrible lean tip in. Once again, I have to keep this table on the rich side in order to help mask this issue, which pisses me off. It is also pig rich (9 afr) coming out of pe, but I feel like this is a result of the table being too rich everywhere. The car will also occasionally set a P0068- MAP/MAF Throttle Position Correlation code and go into Reduced Power Mode. This makes me wonder if I'm failing the MAF correctly.
Blended mode- The car drives best in this mode, but it is not good by any means- just okay and driveable. This is what I use when I actually need to use the car as a car. The fueling still looks really wacky if I watch the wideband while I'm driving, but if I ignore it and just get where I'm going it can seem okay. The main issues in this mode are the same- lean tip-in, unacceptable ltfts, rich overshoots going into pe, rich coming out of pe. I feel like I'm going to have to ultimately have a blended tune to ever be happy with this car. I'm a mechanic by trade and good driveability means a lot to me.
Tuning process- I've been tuning in open loop only. I do MAF and VVE separately, logging afr error with the wideband and doing the copy/paste multiply by % - half just like everybody else. I know there are more advanced ways to do this, and I'm open to suggestions. I'm aware of the rich after flash issue and I only log if my injector tip temp is under 110 degrees. The only filter I use is to filter out deceleration [50091.156]>2. I don't know if the filter helps or not, but I live in a very mountainous area and I have trouble getting really good steady state data. The elevation where I live is 4100 ft. and this is probably adding to my challenges, but I'm too ignorant to know why. Maybe baro updates? I haven't done any spark tuning at all- I feel like I need to get the fueling in line first, correct? Any changes in the spark table are from the idiot previous owner- I've tried to put it back to stock for the most part
What I've done to try to fix it- If you're an experienced tuner, It should be pretty clear to you by now that I have no idea what I'm doing. Fixing the lean tip-in is my main concentration at this point. The first thing I tried was adjusting my injection timing- this didn't fix the tip-in, but it did make the car less smelly and make it run better in general. Enrich desoot mode is disabled, catalyst overtemp protection is disabled. DFCO on or off doesn't make any impact on the tip-in. I have double checked my injector data, and I think it is right. I have tried raising the impact factor and the evaporation factor in the transient fuel table. I have tried stock prediction coefficients and zeroed prediction coefficients with no change. I'm completely out of ideas at this point.
If you made it this far, thank you for taking the time to read all of this. I would appreciate any input and constructive criticism- even if you want to tell me that I should just throw in the towel. I'm attaching a tune file and a log file- I have many more if they could be potentially useful.