Gen4 idle tuning guide

[MikeOD]

For what it's worth, if you're in open loop, I've found you need to set all open loop fueling to a 1.0 eq ratio also, otherwise after a flash/restart it'll be a little fat for a couple minutes, and it will effect the minimum airflow...I also have the injector tip temp offset disabled, and I still find i need about 3.5 minutes to let things settle in to find the true minimum airflow at idle RPM.

By keeping proportional enabled the car (mines a stick shift) is better at doing things like driving itself up a sloped driveway without stalling too. Just food for thought.

Either way, thank you for posting this. I've struggled with finding the best way to make my car idle properly for a long time...this is the nicest it's been since it was stock.

[Phillipm]

Okay this seems simple, but I need help creating the Idle RPM Error report.. Can someone point me in the right direction or post the process to get that going in my charts. Thanks!

[Phillipm]

One other question I had is when I "blip" the throttle to get the timing where it needs to be the rpms will begin to run away, idle will raise all the way to 3,000 rpms and I have to shut it off. Am I doing something wrong or is this normal?

My truck actually idles great when warm on the Day 2 file. I'm just trying to fix when it cold starts it seemed like it had too much air and was pulling a bunch of timing to bring the idle down, making it run awful until fully up to temp.

[Area47]

One other question I had is when I "blip" the throttle to get the timing where it needs to be the rpms will begin to run away, idle will raise all the way to 3,000 rpms and I have to shut it off. Am I doing something wrong or is this normal?

My truck actually idles great when warm on the Day 2 file. I'm just trying to fix when it cold starts it seemed like it had too much air and was pulling a bunch of timing to bring the idle down, making it run awful until fully up to temp.

if it's pulling timing to pull it back down. the air flow is too high.

[Phillipm]

if it's pulling timing to pull it back down. the air flow is too high.

So if it's only doing it while cold/warming up and not at operating temps I should be pulling from the Airflow vs ECT Mult tab in the temps where I'm having trouble correct?

[Area47]

So if it's only doing it while cold/warming up and not at operating temps I should be pulling from the Airflow vs ECT Mult tab in the temps where I'm having trouble correct?

Sometimes on cold starts the engine does run negative timing for cat warm up. are you still running cats?

[Phillipm]

Sometimes on cold starts the engine does run negative timing for cat warm up. are you still running cats?

I do have cats. However this thing shakes around and really idles like poop until it's warm. It's a stock LY6 with headers swapped into a 78 Chevy Blazer. Here is a scan from stone cold to operating temp. I really appreciate the help.

[Area47]

stock cam? any other mods?

[Phillipm]

Yup. Stock cam. Just headers and a cold air intake. I already did the MAF tune but haven't done the VVE yet.

[Area47]

you should need to touch anything idle wise on stock parts aside from the air intake and headers.

[Brian P]

Just wanted to drop a quick note that my idle smoothed out quite a bit after INCREASING the integral idle error- it's set onto 40 right now, but I may drop it back a little and retest. It's still not quite where I want it to be, but getting better. It might be due to my cam having a 112 LSA, as it's much choppier at idle than I originally expected.

[russ472]

This needs to be a sticky

[mowton]

There is a lot of great info in this thread as well as several different ways to skin the cat. Top level review....

The secret as far as I see is to get the max TB settings close to where they need to be based on you your new airflow/startup requirements. I have since determined that these adjustments aren't as critical and stock values normally will do. If you cam is radical, you may need to increase a bit to give more air at cold startup scenarios. Think of this as the TB setscrew in the DBC setups....

Secondly, remove the Prop and Integ tables (set to zero) and get the idle timing in line using the final airflow minimum settings at temp and in the idle rpm area. Watch the timing to set the min airflow. Make airflow adjustments until the logged timing and the idle base timing are equal.

Make sure you have sufficient headroom in the High Octane spark table at the idle rpm/load areas to support adaptive idle timing increases...don't make them the same! This will limit your idle timing and not allow the adaptive under/over-speed timing functions to do their job.

Monitor timing and TPS % and reinstall the stock Integ and Prop tables. Interpolate from the 0 to -512 and 0 to +512 rpm cells. Start by removing like 25% of these values and with a moderate cam, increase the RPM setting by say 50% to give the cam natural lope a bit more room to "roam". Setting the Prop/Integral values is done to stabilize the airflow adjustment so do this with the Over/Under-speed adaptive spark tables zero'd out first. Get to a stable idle with minimum timing/TPS% changes. Once you have the best idle without adaptive timing oversight, add it back for further improvement. The secret to this table is too much is worse than not enough. With higher overlap cams, you do not want to "strangle" the natural lope of the cam or you will force instability and hunting.

Once you have gotten to this point, all that is left to do is fill in the Final minimum Airflow table.work up from the idle values and recreate the slope you see in the stock setup. The airflow should slowly decrease as you go down in RPM.

Happy Idle tuning...:-)

Ed M

[Higgs Boson]

Personally, I get a great, strong idle on GenIV cars with no dipping or surging by loosening up the idle corrections to something closer to the natural lope of the engine, maybe shift the 0 spark correction up to 100 RPM of error and raise the airflow corrections up to like 100 and 75 (depending on the cam of course).

I run a breath (like 50 RPMs worth) more Base Airflow than the cam needs and I do run the same timing value at idle in Main and Idle tables (in fact I make the whole tables the exact same). This way it never dips below desired and the only correction needed is Idle Adapt pulling spark, I set it up to where it only pulls 0-6 degrees of spark to maintain idle.

This means you never have a weak idle and there is no chance for surging from underspeed overcorrection, which I used to always try to have 0 correction in both directions.

I changed my thought process when I saw all the newer ECMs torque management pulling spark for idle at all times, as much as 10 degrees.

[GHuggins]

Do you have an example to post of this Higg's - perhaps a tune with just these adjustments made for a demonstration

Sounds like your tuning a lot more idle torque into it and forcing the motor to pull timing to go back to desired - yes? In other words holding the throttle more open and relying on timing to be pulled...

[mowton]

I run a breath (like 50 RPMs worth) more Base Airflow than the cam needs and I do run the same timing value at idle in Main and Idle tables (in fact I make the whole tables the exact same). This way it never dips below desired and the only correction needed is Idle Adapt pulling spark, I set it up to where it only pulls 0-6 degrees of spark to maintain idle.

Higgs, I have seen that the Gen IV PCM's will limit the base idle timing to the values in the High Octane table and as the idle timing really shouldn't be set to MBT because we want to have torque reserve to handle quick changes in load. Seems by doing this you will never be able to get that extra torque needed to ride through trans P/D shifts or hard stops with a tight converter etc.

I too have altered my approach and totally agree 100%...let the cam lope roam where it wants with both air and timing settings :-)

Ed M

[Higgs Boson]

Higgs, I have seen that the Gen IV PCM's will limit the base idle timing to the values in the High Octane table and as the idle timing really shouldn't be set to MBT because we want to have torque reserve to handle quick changes in load. Seems by doing this you will never be able to get that extra torque needed to ride through trans P/D shifts or hard stops with a tight converter etc.

I too have altered my approach and totally agree 100%...let the cam lope roam where it wants with both air and timing settings :-)

Ed M

I should add, I was thinking of manual trans tunes with this strategy. Autos do require some differences for sure.

[Higgs Boson]

Do you have an example to post of this Higg's - perhaps a tune with just these adjustments made for a demonstration

Sounds like your tuning a lot more idle torque into it and forcing the motor to pull timing to go back to desired - yes? In other words holding the throttle more open and relying on timing to be pulled...

I wouldn't say a lot more. Basically, you let the cam do it's thing regarding it's lope and then allow correction after that, which you know that already.

Find the right Base Airflow for the cam at about 50 RPM higher than desired and let the Spark Adapt pull about 5 degrees out to hit desired RPM. Of course the numbers will vary depending on the combo.

I'll post the latest tune I am doing this with next weekend if you remind me.

BTW, with the Spark Adapt pulling out spark you are no longer technically at MBT I wouldn't think. Actually I don't think I have tuned an auto GenIV in a long time. You can set Base Airflow different in Park vs Drive/Gears so if I get an auto to mess with I will try it out.

[No fear]

I read through your idle thread and I'm just wanting some guidance on my situation, I am very new to HP Tuners and I get a little overwhelmed trying to follow some of this stuff. I have a 2009 Sierra Denali with the 6.2L (L92) motor. I did a Texas Speed camshaft package with some long tubes and a CAI. They sent me the tune I currently have with my purchase. The issue I am having after the install is that the truck is really hard starting if you shut the truck off and immediately try to fire it back up. It struggles to start for a second, takes way longer then it should to fire up, sometimes even helps to give it a little throttle. The truck starts like stock on an initial cold start up, no issues at all with a cold start. Its just the hot re-starts right after you shut her down. (EI: Like shutting your truck off at a drive through window, then firing back up) Any way if you could give this newbie some guidance it would be much appreciated. This Link has my tune and a log file on this thread on post #3.

Thanks
http://www.hptuners.com/forum/showth...rt-up-guidance

[Higgs Boson]

Try adding to your Startup Airflow table