LNF Idle w/AC On

[Process]

Hey everyone. Hoping someone can steer me in the right direction with getting my idle at a good place.

I've managed to get my Idle almost perfect (in terms of feel, timing, throttle position, etc) with the AC off, however whenever I turn the AC on, the timing fluctuates heavily and the idle surges.

I'm running no MAF (it still did this before removing the MAF), that being the only real change to the vehicle that affects airflow. I've tuned the car accordingly otherwise. Everything else is good, such as timing, no knock, fuel trims, etc.

Where do I start to try and get a good idle both with and without AC?
I've tried changing my DALs around but it never seems to have an effect on the idle with the AC on. I've made 1% changes in both directions up until the car will barely idle and it doesn't affect the surging.
Any suggestions?
I'll post a log when I get a chance as well.

[TCSS07]

how are you running the lnf without a maf? I thought those were a maf only ecm given there isnt any other fueling charts like ve/vve. But make sure your fueling is spot on at idle and you will have to play around with the spark settings for vvt, regular and optimum spark along with your torque model for optimum torque and torque to load to make it be any better if at all since that ecm is based or torque. you'll probably have to make a few histograms logging them against certain things like rpm,spark,load and everything to see what cells you fall in when the compressor is on and adjust those cells to how you need. remember it is a 4cy. the idle isnt going to be perfect with ac on. my lsj was horrible when it was factory and now modded get real lol. you can also add more idle rpm for the compressor. I usually set it to 50-100 rpm higher for ac idle vs non ac idle

[Process]

So when you unplug the MAF, it defaults to the OEM VE tables. Although we can't access them, if you unplug MAF you just need to tune your fuelling via MAF base (VE calculations take from this table) and injector constant using EQ Error. Regardless, trims/lambda at Idle are fine even with the AC on.
What should I adjust in my spark tables? Idle area Im at 10% opt torque, 0 on opt spark, ~42 degrees normal timing commanded, and like I said above my DALs don't fix anything so I'm ruling that out. Also have my base idle set to 900, and my AC on idle set to 1150 and it doesn't help. I've tried raising it to 1500 just to see if it would do anything at all and it doesn't affect the idle quality or speed with the AC on.

[TCSS07]

I dont know. I think maf would be easier because you will probably end up going off the load axis but also maybe not. Your ecm has the ability to change the axis numbers so as long as you increase the resolution you should be ok if you do that but if you dont then fueling will just use the last cell which can be iffy. Also your probably not going to get a iat1 temp reading. It will probably read -40 which wont be good for fueling calculations either. How bad does it surge? Enough to where you cant drive the car or just a annoyance. logs and tune? ac idle will usually be ok at 50-100 rpm above normal non ac idle. im guessing you will have to mess with the actually spark advance and mbt to get it dialed in as mbt isnt really spark per say as it is torque calculations

[cobaltssoverbooster]

So when you unplug the MAF, it defaults to the OEM VE tables. Although we can't access them, if you unplug MAF you just need to tune your fuelling via MAF base (VE calculations take from this table) and injector constant using EQ Error. Regardless, trims/lambda at Idle are fine even with the AC on.
What should I adjust in my spark tables? Idle area Im at 10% opt torque, 0 on opt spark, ~42 degrees normal timing commanded, and like I said above my DALs don't fix anything so I'm ruling that out. Also have my base idle set to 900, and my AC on idle set to 1150 and it doesn't help. I've tried raising it to 1500 just to see if it would do anything at all and it doesn't affect the idle quality or speed with the AC on.

last i checked that wasnt true... unplugging the maf makes the ecu default to a certain cell based on a signal voltage of 0 which would be on the maf curve and then the 3d correction table came into play as your main tuning table. This is how it worked for us in 2010 and last i checked no one else besides me has taken the time to attempt to find the missing tables in this ecu.
Now is your opportunity to find them since HPT released the user defined upgrade. Find the missing links

[cobaltssoverbooster]

correction-- a poster that i know from about 8 years ago would have the knowledge to look into it like i did but i havent seen john post in the 4 cylinder section in a very long time.

[Process]

The car surges only around 200 rpms above or below my normal with AC on. Just annoying and loud really. Also doesn't the LNF take its IAT calculations for fueling from the IAT2 (Tmap)? I've had absolutely no issue with fuelling with this method (only doing it because I have a VTA blowoff and MAF relocation made the car run like shit even with an experienced LNF tuner helping me) , but like I said even with or without maf it does the same thing. Ill try some minor changes to my main spark table to see if anything improves.

Also what it this about user defined upgrade? I can possibly find the tables to properly tune for speed density? How???

[cobaltssoverbooster]

i forgot but its not to hard to figure out if the maf iat has priority. tune the maf in and then pull the iat maf wire and see how far off it gets.

as for user define parameters i hope you know computer code language very well because you will need it. specifically HEX.
1) log into your hpt account
2) go to your registered device
3) in the device description is a link where you can 'purchase' user defined parameters. (below is an example...i have my serial and access code blocked out)

Capture.JPG

from here you will need to know how to use the new features. basically this allows you to upgrade a single ecu to accept custom made parameters (tables or single scalars) based on utilizing and modifying known or unused locations within the ecu.
it works something like this thread from the v6 section:
https://forum.hptuners.com/showthrea...uners-Database

[TCSS07]

im pretty sure gm uses the maf for iat1 unless it has a stand alone sensor. iat2 temp is from the map sensor or tmap unless thats a standalone sensor as well. if it doesnt mess with your fueling to much then i guess forget about it and if how your doing works then just keep at it. i just know my trims change depending on what the iat1 sensor reads at 34F to 90F. im running the lnf 3 bar map sensor in my lsj and reads iat2 correctly. i havent dabbled in the custom pids to comment on that. i have seen it and thought about it but im not too familiar with it so maybe one day.

[cobaltssoverbooster]

keep in mind tiny tuner is more specific to the gtp gang...v6 gm3000 series engines.