Hi there,

Each day I try to follow these posts in hope to better learn how to tune and use my HPTuner.

The question I have now:

After doing the Air Config in both park and in neutral and editing the new data, should you readjust your DBC throttle body to correct IAC Counts?

OR would that just throw off the numbers that you just got from the Config?

I read its best to do it two times in both park and drive.

Should you adjust IAC counts in between or leave the set screw alone?

I set my IAC's for 80 before doing this test.

 

This is how I idle all performance engines.

First, disconnect or disable the IAC. make sure the computer control is fully "closed". Some vehicles you cannot do this manually; you have to program the computer to lower the idle to force the IAC to close. For example set the idle in the computer to 200rpm or something really stupid low so the IAC will shut completely. THEN unplug it, so it can no longer adjust your idle speed.

Once you have that done, or did the best you could, your IAC is no longer in control of the engine idle speed. So now, with the engine fully WARMED UP, you set the idle manually using a screwdriver (or other device) at the IAC (some have adjustment on them) or at the throttle body (as you mentioned, also most cars have both) prefer to use the IAC for this. Set the idle to JUST BELOW the minimum rpm you EVER expect the engine to run at. For example, if you wanted a rock solid computer controlled idle on a stock cam at 850rpm, you want your manually adjusted setting to be 800rpm. If the engine has a huge camshaft, you might give it a little more air.

So essentially what you are doing is setting the minimum airflow of the engine through its hard parts (non moving parts while it sits at idle) by manually adjusting the airflow with no computer control. This way, the engine NEVER goes below that rpm. Oh it might dip down a little when you lift from the throttle- thats the whole reason we do this, to ensure it never goes far below that set point. If you depend on the IAC to do this, it will not work well, because the computer cannot predict (well, most cant) how low the rpm is going to drop when you lift, and this just gets more difficult for it to do as you add modifications like cam/head upgrades that will throw the computer off more and more.

So re-cap:
1. disable automatic idle control IAC motor somehow (unplug it)
2. With engine full warm, set the idle speed manually (at TB or IAC) to just below the minimum RPM of the engine you desire.
3. re-connect IAC and let the computer add the tiny bit of air to move the idle up to the desired point.

You want the IAC ADDING airflow to the engine by moving open, you NEVER want it to SUBTRACT air from the engine to lower the idle, that is how you wind up with a bouncing idle. The computer can "learn" it and control it somewhat smooth, sure, but that is still not as reliable as doing it this way, which guarantees the idle never drops too low.

 

Thx for the detailed post!
I'm am going to try that this evening!

 

Something I noticed when doing the Idle Config.

With the weather Toronto is having now the numbers in the histogram will start populating at 68F/ 20C wheather or not first start happens to be at 7am or 12 noon. That's fine.

However it populates different values from a cold start early am vs 12 noon when it can reach operating temp quicker, giving different values for each temp range it passes.

Why would it populate different values from one test to another?

If it passes a particular temp range early am or just hours after THE NEXT DAY it should give the same values for that temp range.

I understand it not reaching the colder temps now. I'll re-do the histogram in the winter to reach the colder temps but for the temp it passes both winter or summer it should populate the same values per temp range?

I'll get some 2.1 values doing the test for the first time early am vs 1.6 values at first start noon for the same temp range.

It requests more air in the am log vs noon at the same 68F/ 20C starting point.

 

So did a few histograms both in drive and in park. I matched the units both in the scanner and editor and killed the fans.

My first time I got idle trims of -21 and the second run double that.

I'm hearing this Idle Air Histogram brings you real close with the idle trims.

What am I doing wrong? It populates different numbers per heat range each day/ attempt.

Thx for any help

 

It's too much to repost, but check this thread out. It is very helpful for exactly the issue you are having

https://ls1tech.com/forums/pcm-diagn...AC+calibration

 

Don't do this. It is all wrong.

 

So the 200+ previous engines I've tuned all of which have rock solid idles and drive/start like stock, heavily modified high power daily drivers, are all wrong?


Well then, please do tell me a better way. I love when people come in just to say "its wrong" but then offer nothing else- as if they KNOW the right way, but do not wish to share it! I think the real truth is, you just don't know ****.

 

Do you know what RAF is? Desired RPM table? Throttle cracker? Adaptive idle? Overspeed/underspeed spark? You gave a long winded, generic answer that is completely wrong for LS applications. You can't just tune the idle by unplugging the IAC and adjusting the throttle stop. It just doesn't work that way.

Want good HP tuner idle tuning info for LS engines? Here: http://www.hptuners.com/forum/showth...de-(w-pictures)

 

Couldn't let this part go. See the info in my signature? It's my daily driver, runs 11s n/a, 10s on nitrous. I did 100% of the work myself including the tune. It idles wonderfully with a ok sized cam and 102 intake. I'd say I know some ****. I responded to your post to warn everyone else that it's wrong. The other post had the question covered correctly.

 

The problem is you arn't giving any useful information. All you are doing is complaining about what others are providing.

Instead of jerking off complaining about things and telling people that they are wrong, why not write some technical procedure or actually explain how to do something? None of your posts are useful, its just space-wasting garbage.

ALL engines have some minimum airflow expected and ALL engines need as much of that as they can get, without going over the minimum desired RPM controllable by the IAC or DBW. You cant let MORE air into the engine than necessary and then remove it with the IAC, the IAC system only ADDS air into the motor from 0% position to 100%. Doesn't matter what engine, or what ECU. If you think that the IAC needs to be in the 50% position all the time and that the minimum airflow should be lower than this... that your personal opinion and I disagree completely after having tried all of that and other various methods and found the one I posted to be the most effective, since it guarantees the engine cannot stall or stumble when the IAC decides to move too slowly or reacts poorly.

 

You should probably stick to import forums. How many LS or GM Gen 3,4,or 5 platforms have you tuned? Have you even looked at a GM calibration with HP Tuners or EFI Live?

 

It's obvious.

 

Both HPT and EFILive software are available for downloading for free/demo usage, meaning that you can very easily use them to view the tunes and logs that people post on here.

 

Sometimes the best help you can give someone is recognizing when someone else is giving bad advice and pointing it out. Also, it helps to know where already answered questions are and to link to them as I already did. You seem to think this isn't help, which is odd.

In closing, you absolutely want to allow the IAC to control both positive and negative airflow as the idle strategies provided by the factory computer need it. If you set the throttle blade so far open that your IAC is zero(no added airflow), the computer will not be able to correct for a high idle condition using airflow and your TPS will be out of the idle range. This screws up all sorts of things.

 

Read the two links provided. Don't touch the throttle set screw after doing the idle config or you have to do it again since airflow will be affected. Remember to do your TPS relearn. Also, sorry for all the mess in your thread.

 

1. Try reading my post. IAC position hot idle should be 5-12% and as steady. The less an IAC is having to move to maintain the engine idle, the more steady the idle will be (less ECU "chasing"). Large cam engines get more tolerance, a slower IAC rate of compensation, and I like to bring in air with the movement of the TPS (some ECU can do this such as AEM, can the HP tuner?) furthermore if the ECU has the ability to watch rate of change, you want to slap the IAC open when the rate of change is large and negative. This is because if you notice, even if we set the minimum engine rpm to some airflow value like 800rpm, and achieve a rock solid 800rpm idle, if you REV the engine briefly and let it fall it will usually shoot past 800rpm and into the 500 or 600's for an instant. The problem can be exascerbated by large injectors/plenums/manifolds and so forth, because VE and combustion quality may suffer at such low rpms with the momentum of the engine behind it. To combat this, the step I just mentioned is taken to set the rpm back down gently over a time period using the extra 80% of the IAC headroom you have, since the baseline value is 8-12% like I mentioned already, which also gives you a ton of headroom for cold start as well. Its @#*@# perfect and you need to lrn2read.

2. The tps sensor voltage is usually "found" when the computer starts, so that any changes to slight position are negated each time the user starts the vehicle. I couldn't see any tps manufactured by any company to maintain the exact same voltage every single day, through the wide range of operating conditions and battery life/alternator output etc... it isn't possible. Furthermore, I was never suggesting you move the tps anyways, I didn't even think of that (because it does not need be considered most of the time). There are at least 5 other ways to adjust idle speed, many IAC have their own steady flow channels that are adjusted by screwdrivers, and some people will drill holes in their throttle bodies if necessary. The throttle position should not become even the slightest thought when concerning idle speed/quality.

 

I am wayyyy to lazy. I know all about that stuff but without an engine to tune its pointless. I've never tuned an LS except in my sleep every god @#(*@ night and can't wait to get my hands on one. I know almost everything a computer is capable of from from multiple points of view so even without ever touching one I already know i can tune an engine using it in a couple hours and I am willing to bet that up if anybody wants to give me a try local, free. I've tuned plenty of V8 engines- just never an EFI live or HP tuners platform LSx, its always a custom job, MS, haltech, custom boss injectors procharged 355's etc

 

Go back to your import forum. GM IAC values are not in %.

 

there is a hole somewhere and it can open from 0-100%. I know you are referring to pulse width but that can be generated in many different forms with amplitude/frequency and phase and have varying effects to different types of control motors, but at the end of the day they all wind up doing the same thing: holding a hole somewhere open a certain amount, from 0-100%. It might cycle continuously between 8 and 9% as the pulse frequency adjusts to modify engine speed, but its just a hole open a certain percent of the total way.

Like where your humorous meets the radius/ulna, the special fossa there defines the range of motion of your forearm. It has its minimum and maximum limits, from 0-100%, even though we also send many forms of nerve frequency pulse width to a variety of different sensors like the golgi apparatus and spindle fiber structures which help modulate position exactly like many kinds of IAC motor does.