Idle (Transition) Tuning

[jfpilla]

The following assumes a reasonable tune has been done to the car. Here is a quick outline of my preferred method.
-Put back all stock airflow and timing values.
-Input the stock IFR values for stock injectors, or calculate new values aftermarket injectors.
-Put in A/F multiplier values(PE RPM), calculated to your preference. (ex.14.7/12.8 = 1.15 mult.)
-Work on VE's with the MAF zeroed. Bring the MAF back on line and adjust it for ltrims.
-Then do Idle Transition Tuning.

Idle transition tuning:
-Start with Ltrims reasonably negative and your Standing Idle is set where you are happy with it at all temps.
-If your VE's are off by 20% or more they need to be set. Auto tune works great and is suggested to get closer than 20%.

-Return all airflow tables to stock, except idle and idle airflow(RAF). This is so the car will idle. If you can return all the airflow tables to stock, go ahead.
-Log, IATc, ECTc, SAE MAFgms/s, GM IACDES_Bgms/s, DYNAIR.
Since you are in open loop when you first start the car, watch for your trims to show(closed loop) and your idle to settle to where it's set and start the tuning log.
Log while parked, from the coldest engine temperature to fully warmed.
Log for at least five minutes after warm up to get better averages and since this is the temperarture where problems are noticed.
-If it's an a4, log in gear with the A/C on. You may want to repeat this process in neutral later or just check to see if your RPM's stay up when driving and you put the car in neutral.
-If it's an M6 log in neutral.
-Input the logged MAF values into the Desired Airflow (raf) table, by temperature.
You want to get logged desiac and maf values close.
-For 90 mm TB for F-bodies move the Effective Area table values 6 places towards the higher values and leave the IAP values stock.
-For C5's and 90mm TB adjust the ETC B4349.
Adjusting TB area will help get Desiac and MAF gms closer.

When you have completed this process, MAF g/s, Desiac_B, MAF freq and DAF should be close in values. If DYNAIR and MAFgms are not close the MAF is likely not set right.
-Finally, timing will help idle and flare at start up, you should also check to see if the Airflow P/N is too high, by putting the car in neutral while coasting.
If you have EFI Pro you
can use BIDI Controls to test(SOP)timing changes, otherwise program
timing changes a little at a time. Make the changes in Base Spark in
Gear and Base Spark in Park/Neutral.
-Check, ltrims, AFR and adjust.
-When you change IFR's, MAF #'s, timing and airflow table values, the
trims are affected.
You will likely need to do some SOP tuning of DAF and spark. DAF may not line up with MAFgms. There are other Airflow tables like Throttle follower airflow that contribute. If you have used the MAF to get trims negative it will not match IACDESg/s by that %. BIDI is great for adjusting low rpm/cylair(spark) to get rid of that last little bit of surge.

This process will help eliminate, stalling, surging, false idle learn and unlearn, colds, headaches, etc.

There are some situations that make perfection a little harder.(Maybe impossible). Don't have knowledge past a G5X3.
-Really big cam. ex. Mine is a 230/595/112 in an a4 and tuning is easy.
-Long tubes that place the 02 sensors far back, which allow them to cool fast and take longer to heat up.
-Cold air intake, which causes rapid IAT changes.
-Any throttle body with a ridge that's been worked.*
-Descreened MAF/ not properly calibrated.
-Low rear gears(3.73 and lower) and a stock or almost stock stall converter.
-The tuners ability.



Don't look for perfection in the numbers, they do bounce around. If after you do this it idles and transitions well, be happy.


The following is from Nick Williams.

Process is the same for the F-body. You just have to make sure the IAC motor is within range to give the motor the air it wants. With a big cam car the IAC uses up alot of its range or all of it just to get enough air thru for idle on a cold start. Two ways to fix this. You can drill the hole in the blade out bigger or you can adjust the closed position set screw to open the blade more. Adjusting the screw will require a reset on the TPS to get it to read 0% at idle. The stock camaro that I have idles around 65 steps when hot. Use that as a target to determine how big of an adjustment to make. Once you have the IAC motor within range, then start trying to get the DESIAC gms/sec to match close to the MAF gms/sec.