HP Tuners Tutorials

[Gregski]

Idle Tuning - Chart vs Time: Group

I start by nuking all the default Charts and start with a clean canvas. Then I first add something called Group this is just a break or a section to keep all the squigly lines (aka Series) separated and not stepping all over each other

[Gregski]

Idle Tuning - Chart vs Time: Series

once we have the Group we populate it with something called Series. Series are just visual line representations of the Channels we added already on the left hand side

[Gregski]

Idle Tuning

here are the Properties of the three Series I have added

Engine Coolant Temp
Engine RPM
Idle Desired RPM

Unlike the channels which are frozen once you log, you can make changes to the Series after the fact, so don't sweat it if you missed a check box or chose the wrong color or something like that.

[Gregski]

Idle Timing

Time to take the kids for a haircut. But I leave you with this real Chart showing what my Idle Desired RPM is ie 550 and how my actual Engine RPM dances around it.

Why do you think that is?

Is this normal?

These questions are not rhetorical please chime in if you are following in real time.

[neal64ss]

Originally Posted by Gregski

Idle Timing

Time to take the kids for a haircut. But I leave you with this real Chart showing what my Idle Desired RPM is ie 550 and how my actual Engine RPM dances around it.

Why do you think that is?

Is this normal?

These questions are not rhetorical please chime in if you are following in real time.

Seems normal as the PCM is monitoring and adjusting fuel/spark/throttle position in real time to maintain required RPM.

BTW, I cant thank you enough for this thread. I have stumbled around for years without making any progress on my HP tuners (other than able to get stock engine to run stand alone). Suddenly with this thread I am starting to understand how it all works, and spending more time in the chevelle than I have in a long time.

[Gregski]

Originally Posted by neal64ss

Seems normal as the PCM is monitoring and adjusting fuel/spark/throttle position in real time to maintain required RPM.

Yep, you are spot on, let's take a deeper dive and explore how these system intertwine.

Originally Posted by neal64ss

BTW, I cant thank you enough for this thread. I have stumbled around for years without making any progress on my HP tuners (other than able to get stock engine to run stand alone). Suddenly with this thread I am starting to understand how it all works, and spending more time in the chevelle than I have in a long time.

Much appreciate the feedback.

[Gregski]

Idle Tuning

Before we answer those questions, I wanted to show you what the Chart vs Time looks like as we shift from Park to Reverse to Neutral to Drive and back to Park. I held each phase for one minute so that we can see them properly defined. It may be difficult to see the actual RPM numbers in the graph, so I will just tell you that the Idle Desired RPM green line shifts from 550 to 525 to 550 to 525 and back to 500 just as the Base table dictates. Pretty cool

[Gregski]

Idle Tuning - Idle Spark Advance

And as Neal pointed out this behavior is perfectly normal the PCM is monitoring and making these adjustments, you will not see your idle RPM be a flat line at the desired number say 550, it will oscillate above and below it (within reason, more on this soon).

This brings us to the second item of the Holy Trinity: Timing. Let's open up the VCM Editor and see how the PCM uses Timing advance to keep the RPMs in line. We find the Idle Spark Advance under:

Engine \ Spark \ Advance tab \ Idle Spark Advance section

[Gregski]

Idle Timing - Tables

Idle Timing is set by either of two tables depending what gear we are in

In Drive or In Park

So what we can gather from these tables, is that for example in Park (second table) in my case idling at 550 RPM my timing should be somewhere between (the 400 RPM column) 19° and (the 800 RPM column) 21° so obviously we can call that 20°. We are looking at the very top left hand corner of the table.

Note: These tables look very similar to the Base timing tables, ie High Octane and Low Octane ones, however note the column headings on the top, they go from 0 to only 4,800 (I guess that's high enough for idle, ha ha) but also note the break points, where is 600 RPM, where is 1,000 RPM? The point I am trying to make is that these tables do differ slightly, but it may be enough to trip you up if you try to reuse the Base timing Histograms we built earlier on, cause you get lazy or are not paying attention to detail.

[Gregski]

Idle Tuning - Timing Advance

Alright so back to the VCM Scaner we go to add some timing channels. First we add Timing Advance (the mother of all timing channels) this is the total of all timing advances and retards, it is as if we were holding a timing light to the crank pulley and reading the actual timing in real time.

[Gregski]

Idle Tuning - Base Advance

Now at this point just as with the RPMs we could write down what the In Drive and In Park tables say the timing should be, or we can once again work smarter not harder and use a special HP Tuners channel to do the work for us. We shall add such a channel next, it is called Base Advance

[Gregski]

Idle Tuning - Timing

I'm going to go log some more data for us to see what shows up in the two new timing channels we just added.

Just so you know you do not need to do it like this, you don't add the RPM channels and log data then add the timing channels and log more data, I am just doing this this gradually for demonstration purposes. This allows me to only show a few channels at a time so we don't get overwhelmed.

[Gregski]

Idle Tuning - Timing Advance

This time with the engine warmed up (somewhere's above 190° F) we have some timing numbers to look at. Here we see that the actual timing aka Timing Advance at this very precise point in time is 17° however it should be 20° according to the Base Advance that's 3° less than what it should be!

[Gregski]

Idle Tuning - Timing Advance

at a different point in time it's almost the opposite, now our actual timing Timing Advance is 24° where as the Base Timing (aka what it should be) is still at 20° that's 4° too much!

What is going on here, and why?

[Gregski]

Idle Tuning - Timing

let's take a quick look at the Timing Advance (white line) vs Base Timing using a Chart vs Time

ah yup, our timing (white line) is all over the place as compared to the green line of where it should be

[Gregski]

Idle Tuning

here are the Properties of the two series I used to make that comparison

FYI some of this stuff is me just going the extra mile to explain / demonstrate things, once you get the hang of it, you get to choose which weapons in HP Tuners you want to use to troubleshoot or tune, for now just muddle through it all please

[Gregski]

Idle Tuning - Idle Advance

let me share a very helpful channel that can help us make more sense of all this, it is called Idle Advance, and that name should really be Idle Advance Correction as it is not what the timing is at idle, but it is the difference between Timing Advance and Base Advance, ie the two channels we've been looking at so far, so it just does the math for us, win/win

[Gregski]

Idle Tuning - Idle Advance

alright so let's see that Idle Advance channel in action

note the numbers are a little bit off, but that's because I got rid of the decimal point and also there is a bit of a lag behind what the actual timing is and what HP Tuners reported, but it's close enough

again, the most important take away is that this Idle Advance parameter is the difference between the actual timing (Timing Advance) and what the timing should be (Base Advance) it is the PCM's attempt to make things right (how and why, coming up next)

[Gregski]

Idle Tuning - Idle Advance

something that i find useful and less cluttered is looking at this Idle Advance data by itself using a Chart vs Time like so

the scale is basically set to 10 and -10 degrees and I like for my timing to be within five, in this case the retard is fine it is well within 5° (bottom spikes) but the advance is too much (top spikes)

[Gregski]

Idle Tuning - Idle Adaptive Spark Controls

Ok, finally let's jump over to the VCM Editor and see what is causing this behavior. Lurking on the same tab as our In Drive and In Park idle timing tables are the Idle Adaptive Spark Controls

Engine \ Spark \ Advance tab \ Idle Adaptive Spark Controls section

more specifically the Overspeed and Underspeed tables

[Gregski]

Idle Tuning - Overspeed table

let's take a look at these tables one by one, starting with the Overspeed table first

at the top we have RPM, so for example when we go 50 revolutions over the desired RPM then according to this table the PCM will try to pull 5° of timing (hence the -5.0)

as you can see this table can pull us back from being as much as 300 RPM over budget (ha ha) by pulling 9° of timing, pretty cool, but I wouldn't set my timing willy nilly and depend on these "corrections" hope you follow

so I think of this table as Idle Retard Correction table, but you do you

[Gregski]

Idle Tuning - Underspeed table

now let's look at the fraternal twin, aka the Underspeed table

so the concept is basically reversed, but not directly proportional (in other words we don't add the same amount of degrees as we remove for being the same amount of RPMs off)

here if we are under by 50 revolutions we will actually add 10° of timing

again this table can reel us back from being 300 revs off by adding 14° so now that I think about it, we can add more timing than we pull (-10°) good to know I guess!

so I think of this table as Idle Advance Correction table, but you do you

[Gregski]

Idle Tuning - Overspeed & Underspeed tables

At this point I would not mess with these tables, I would just be happy knowing how and why my idle timing is changing, cause there's more to it...

we will cover Airflow next! and see how this Holy Trinity ties it all in together

[Gregski]

Idle Tuning - Airflow

So back to the VCM Scanner and it's time to add some more channels. We will be adding the following three channels:

Idle Desired Airflow
Idle Base PN Airflow
Idle Base Gear Airflow

the concept being the same as with the RPM and the Timing, the Idle Desired Airflow being what the engine needs to maintain our set RPM and the Idle Base timings are just reporting to what the hard coded values in Idle Airflow table are set to (we will look at that table next).

[Gregski]

Idle Tuning - Base Running Airflow

The Idle Airflow table can be found under

Engine \ Idle \ Airflow tab \ Base Running Airflow section

If we look at the bottom of the screen it reads: "This table is used to determine the base airflow (in g/sec) for the IAC/ETC control vs. Engine coolant temperature. This is used as a base setting (or startpoint) for the adaptive idle routines and also the base IAC position when the vehicle is moving."

Note the in grams per second part, I have actually changed mine to be in pounds per hour, it does not matter what units you tune in pounds or grams, as long as you are comparing apples to apples (just click the green g/s and it will toggle between the different units)