Idle Tuning How-To & Guide (w/pictures)

im adding a copy of the tune thats in the car and also the configuration. I added an idle log, the configuration and my tune let me know what you think I need to tweek. The airfuel ratio looks pretty good it starts out a little rich right at start up arround 12.1 or so but comes up quick to mid 14s to low 15s
Thanks,

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Originally Posted by Frost

Someone put a lot of time into this with the intent to help others, so don't take this wrong way, but there are some sweeping assumptions in there for sure.

Many of them are related to airflow tables. It mentions the throttle follower, throttle cracker, and adaptive idle's operation being absolute. They are in THE particular OS and revision that was written about above, but it ends there. It looks like a truck at a glance. F-bodies and Vettes will not operate the same. In some OS's, the throttle cracker (IAC cars, not most vettes) will act like a rolling idle, adding airflow whenever the enable threshold speed is passed (vehicle is moving). In many of the later OS's (including the popular '156' 01M6-02M6/A4 OS), the throttle cracker (TC from here) works when the clutch is out (car is moving, in gear, or had been put in neutral and clutch is out) but not IN. That makes it pretty useless when it's disabled at clutch in. Most all Vette's fall into this group as well. The information posted above also mentions zero'ing the throttle cracker for the purpose of return to adaptive idle [while moving]. Most car OS's do not return to adaptive idle until the car is stopped, so what is there in the TC may be irrelevant.

What it SHOULD tell you is to use the idle cfg and go out and SEE what your particular car/OS does in these situations. See WHEN adaptive idle comes and goes firstly. Do this by watching the STIT's. When they stop, so does adaptive idle. If you have an automatic car, the TC is almost certainly active when the car is moving. Just a tip, if you have cam surge, make sure you don't have the spot with buck on the TC loaded up with airlfow. If you have an M6 car, it's important to know for sure when the table is used. Go log, and watch the TC values to see what they add. Try clutching in and see if the TC zero's or continues.... while you are at it, glance back at adaptive idle just for grins through both clutch in and clutch out as well, so that you know for sure when it's operational and when it's not. While going through your log, pay attention to the throttle follower (TF from here). Many times, return to idle issues on IAC cars are caused by a TF that hangs on too long. With the car sitting still, rev and release. Watch the follower decay as the revs fall back to idle. If the follower decays too late, the idle RPMs may fall below the idle set point before adaptive idle can begin working. If the follower decays too soon, adaptive idle will begin to early, and the STIT will be pulled artificially negative. The programming does not consider the fact that 1600 RPMs at zero throttle could be different in a return to idle scenario vs. just an unusual high idle. To counter what it perceives as a high idle, it can pull the STIT too far negative, and the car will dip below idle set point or worse; stall. The point with explaining this is that the TF, TC, and adaptive idle operate differently between different years and OS's, and the only way to know for sure what you have is to do a little logging and see.

There are more things that are in similar fashion, it's just all I have time for at the moment.

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Hit the nail on the head... I find it most time consuming figuring out what the OS that's in a particular vehicle does as opposed to tuning the tables. Once you know when/what/if/then on a particular OS then the tuning falls into place.

The Idle programming is very complex and takes alot of tinkering and hours to truly figure out.

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Originally Posted by LSxpwrdZ

The Idle programming is very complex and takes alot of tinkering and hours to truly figure out.

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now that's the truth! :cheers:

I believe I have read somewhere that some disable the Closed Loop proportional. Wondering if I should mess with this or not?

Great info..This is my first post .. I'm subscribing :)

This is a very good source of information.
I wanted this information saved as HTML for offline use, but the pictures were too large to fit the screen and the text didn't fit either so I needed to scroll over and over.

This PDF file I made is this exact same information but with a little formatting and cropped/resized pictures to fit the screen for easy reading.

Thanks for sharing this information.

Here is the file if anyone wants to have it for offline use.

Change .hpt to .pdf file extension

Thanks for the conversion...looks good. I can echo Frosts' strategy to idle/return to idle tuning. I have spent hundreds of hours logging various parameters and seeing how the react/effect idle quality. Large cams make the situation even more challenging. Very frustrating at times as you think you get it figured out and make changes and then...no effect, or worse :-(. The secret is don't give up on it. My biggest find several years ago was RussK Idle .cfg approach, the rolling/clutch in TC/TF operation in my vette and end of injection timing.

The Gen III PCM/OS's require much more "attention" than the Gen IV's. Keep up the efforts and don't get frustrated. Your end result when right is a great feeling.

Ed M

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Originally Posted by mowton

RussK Idle .cfg approach, the rolling/clutch in TC/TF operation in my vette and end of injection timing.

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Ed

What are you doing for rolling/clutch in TC/TF adjustments and logging?
Thanks
Sarge

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Originally Posted by SargeZ06

Ed

What are you doing for rolling/clutch in TC/TF adjustments and logging?
Thanks
Sarge

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Sarge,

I wish I could say I have the Holy Grail of idle tuning, but it seems it is different for every setup. The following is how I go about it and in no means is the only way. The ultimate goal, at the 50,000 ft level is to get all the critical parameters like LTIT/STIT, VE/MAF, RAF and Timing (both idle and main) as close to zero as possible so as you depress the clutch the engine returns to idle conditions without the aide of Adaptive idle (timing/air control) or TF/TC. Depressing the clutch to my mind is the same as a quick transition to idle....only moving. There is no zero throttle load/decel coastdown effects you would see in an Automatic setup where the TF/TC would come into play. To me it is the same as trying to establish idle without Adaptive Idle Control while rolling. HPTuners has even provided several tables in the Beta Version which allows you to set the rolling idle air, rpm and TC/TF elements. I jave played with them a bit, but consider them to be a crutch and am determined (or stubburn) to do it the old fashion way.

So whether you use the base parameters or the Beta versions, the ultimate goal is to get the air and timing correct so you have the best chance return to a stop smoothly and then let adaptive idle take over. This of course is my theory and any semblance to reality is purely coincidental ;)


Some key elements include:

If car has non-stock Throttle Body, set the Scalar (DBW) or IAC Effective area tables (DBC) accordingly. You will have to set the RAF to bring in the LTIT/STIT. The goal is to get the LTIT as close to zero as possible. I try to get the best idle condition without over/underspeed correction. Set the idle timing to give you the maximum vacumn (lower MAP kPa) and then back off 4-6 degrees. Run RussK idle .cfg to set RAF; may need to do it several times.

Set the idle and main timing tables to the same values from 1200 rpm and down and say .12 to .04 g/cyl. Idle timing should not be set to MBT so you can have a bit of plus/minus from the under/overspeed correction (see above). Base timing (used in the coastdown) should be set to MBT to provide the best stability as you are transitioning to a stop/idle condition. Smooth the main table into the idle area. Set timing in 400 rpm column a bit higher to increase torque to fight through an RPM sag.

Tune the VE/MAF as close as possible to zero error (open loop) in the idle area's by working backwards from say 1200 rpm.

Tweak RAF at any problem area's just short of "cruise control" levels. No science here...trial and error.

Well that is my limited thoughts on tuning the idle/return to idle on Gen III manual vehicles. Look forward to any other opinions/strategies especially on large cam vehicles. My quest for perfection has really never be reached, but does come out very good.

Ed M

Seams reasonable enough to me. ^^^

I'm going to borrow the tip of VE tuning around idle areas by raising idle with the scanner to 1200, and back it down to as low as possible. This way you're not trying to dial in those 800-1200 cells by driving around, probably only hitting them a handful of times to get your average. With mowton's tip, you can use the scanner to raise the idle and dial in the VE from 600-1200 easily. Once the fueling is within spec, move on to spark tuning in the same fasion. I like it!

Usually if I can get the idle down to a stable 600rpms on big cam'd cars and trucks, I know I've done my job as a tuner and can rest calmly. Afterwards I'll ask the owner of the vehicle (or go by personal preference) what he or she wants the idle set at (sometimes talking them down from their desired 1500rpm idle speed) and then I'll raise the idle a bit from the 600rpm I tuned the engine to, just to make the exhaust note sweeter. :D

New to GM & great Info. Working with a C5 Z06 w TSP 233/239 Cam .595/.603 112LSA. The Tune the car came with seems to run and idle rich and LTFTs still adding fuel. I'll give this a try.

from witch table can i adjust idle AFR

thanks

Good thread

I have a potentially dumb question about an aftermarket throttle body and the tune modifications.
If I have a cable driven aftermarket (Fast 90mm) throttle body and intake, what tables do I need to adjust to make sure that everything is calculated correctly?

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Originally Posted by abdulroof-alkhoja

from witch table can i adjust idle AFR

thanks

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MAF and VE

Ed M

Thanks for the time and information in this post.
I’m curious as to why you lower the O2 sensor switching points in the big overlap cam section to lean the idle when you already have the car in OLSD up to 1,200 RPMs? It would seem that to O2s are out of the picture below 1,200 RPMs. Wouldn’t that cause the properly tuned car to go lean at part throttle cruising speeds above just 1200 RPMs?

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Originally Posted by 99LS1SS

If I have a cable driven aftermarket (Fast 90mm) throttle body and intake, what tables do I need to adjust to make sure that everything is calculated correctly?

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What is the correct way to adjust idle for a 90mm tb?

Also interested in the post by Sunny.

??

This thread was outstanding for us struggling with rich idle.
My issue was 12.3 AFR @ idle, found that the idle grams were about 4 high across the scale. I did the cfg scan from cold, copy and pasted to the idle air chart and brought it to 15.2. Then lowered to the final of about 7.1 grams to get my 14.6.

Thanks again for helping / posting up this!!!

My first post here on HP tuners. In the process of idle tuning my 04 GTO. I have followed this step by step as a guide but have a question. I dont this step- add 4º of idle timing 1200 RPM and under and 0.08 – 0.28 g/cyl inclusive (HPT > Engine > Spark Control > Spark Advance > Idle Spark Advance (in Park).
Later it says to Make sure that your Idle Spark Advance table (both “In Drive” and “In Park”) match your High and Low Octane Table for all columns up to 1200 RPM (HPT > Engine > Spark Control > Spark Advance > Idle Spark Advance (in Park, in Gear), Hi and Lo Octane). Blend the timing numbers into the 1600 RPM+ columns so there are no huge numerical transitions.

Am I just copying and pasting from the Idle Spark Advance (in Park) table to the other three. Then smoothing all colums and rows from 1600 rpm. Im probably overthinking this but i want to make sure I did it right.

Thanks