juice12ufo

I am trying to tune my idle. I am a newb at tuning by the way. Anyways, I added 2 g/sec across the board for idle because it keeps wanting to die on me after cruising. So I did that and then went for a drive logging STIT and LTIT. Well, I got -.26 #/hr or whatever which ends up being -2 g/sec. So, do I need to take 2 g/sec off now, but it idled like **** like that.

Also, isn't the base idle airflow supposed to be by gear like 1-6? Mine looks like an auto table... gear and P/N. I am an M6, it seems totally messed up to me.

foff667

iTrader: (2)

LS1's all use the same basic pcm so they are going to have the same tables, just modified slightly to fit the need...m6's & auto's have the same base airflow table.

Idle isnt always cut & dry as to what needs to be done...there are probably 1/2 dozen of common ways to do it...some people log only stit & apply that correction, some people log stit & ltit then add the two together & apply that correction, some people log desired airflow & just apply what you get to the table...not as a correction, just a replacement to the whole table. Also remember idle doesnt completly rely on idle airflow, there are other factors like idle rpm, spark & fueling that come into play Not to mention things like cam size plays a huge roll in how you go about tuning idle.

ChrisS@sdpc

Make sure you have your units correct. 1 lb/hr = .125 g/s

It sounds like you have the general idea. There are many, many threads here and on HPTuners site regarding idle airflow. You will probably want to check (alter) your Cracker & Follower settings as well.

Like foff indicated, idle is also greatly affected by fueling and timing. Have you modified your VE and used RTT to test different timing values and/or different AFR's?

jimmyblue

iTrader: (11)

I think you're best off to start with more logging,
do a cold idle startup logging the Dynamic Airflow
as well as your temps, desired airflows & trims etc.
and see what the car is really using and then put
the base running airflow to values that are close to
observed. If the idle is doing the yo-yo this may
take some judgement but if you err to the high side
the PCM will have to work to bring it down, not
hustle to keep it from crashing.

juice12ufo

Great post! That alone opened my mind up to the concept. What I am going to do is log the cold start to warm tonight. Is the desired airflow that I log the values I want to populate my RAF table with? Should I add a bit to that as well? Also, what should I set my timing at for idle. From what I have read it seems I need to scale my idle spark advance about 20 degrees positive across the board. Is this correct? ALso I have zeroed out my throttle cracker table. Anything else I should do beyond that?

SSpdDmon

iTrader: (10)

My 232/238 cam idles just fine with 25* of timing. Get your base running airflow close with the idle trims. But, don't sweat the small numbers. If you get it to be within -1~0 grams/second, call it quits because it won't always be the same. That's why the idle trims are there....to adjust for the day-to-day variances. One of the biggest keys that I found and posted on here about earlier was regarding the delay timers that affect the IAC and it's learning habits. If you can find them in HPT, they should have a 1.3 or 1.8 second setting from the factory. If you up them to 4~5 seconds, it really helps cut down on the yo-yo effect. In EFILive, they're called "Airflow Learning Control Delay" and "Airflow Direct Speed Control Delay."

They hurt the idle because.....ok....you have a base running airflow (desired idle airflow) that the car is told, "This is what you need airflow wise in order to sustain idle." The idle trims then tweak that number as conditions and temps change. Ideally, the closer they stay to zero, the better. Now, when you get on the gas (say you rev the motor up to 4,000rpms) and then lift your foot, it's going to take more than 1.3 seconds for the motor to drop down to the desired idle of say 900rpms. After the first 1.3 seconds since you lifted your right foot, the PCM sees the revs higher than 900 (say you're still in the 1800~2200rpm range). So, it lets the idle trims take airflow out of that base running airflow number it was tweaking. By the time you reach 900rpm, the 6.1grams/second that was needed to idle is now down to 5 grams/second and the revs keep dropping. Then, the other supporting factors have to chime in and bring it back up to 900. So they're compensating and the idle trims are realizing, "Hey, we took out too much...put some more back in." The process repeats itself until the idle finally finds 900rpm....only to start all over the next time you rev the motor or find a similar situation while driving.

juice12ufo

Okay, I think I found them... They're called Startup P Delay, Startup I Delay, and Startup D Delay. I changed them from 1.3 to 4

SSpdDmon

iTrader: (10)

They should be under the idle learning sections. I don't think they're related to startup. Also, be careful as one of the timers controls spark control delay. You don't want to change that number. Just the ones affecting the IAC's learning and direct idle control abilities.

juice12ufo

I think I have them right. It isn't startup of the car, it is startup of that process. It is described like that as you hover over the button.