HP Tuners Tutorials

[Gregski]

Timing

What I would do is first I would select all the cells in the histogram.

Then I would copy all of them, like so.

[Gregski]

Timing

Then go to the VCM Editor and pull up the High Octane table.

Next right click anywhere in it and select Paste Special - Subtract.

[Gregski]

Timing

This will remove the right amount of timing advance in the precise cells where the knocking is occurring. Or you can change the values manually.

Either way, eye ball the results and make sure there are no huge jumps, 2 to 4 degree differences between cells are acceptable, anything more than that and I would interpolate, meaning adjust the neighboring cells a little so the changes are more gradual

For example, if we changed what ever number to 16 below

9 - 11 - 16 - 21 - 23

I would make the end result look something like this

9 - 12 - 16 - 20 - 23

to make the transitions be more gradual

Keep in mind we are pasting values that are averages so there is some gentleness already built in to what we are doing, however it still may take some time to get this dialed in.

TOP TIP: Before making any timing adjustments, top off your fuel tank with some fresh high octane 91+ as it does make a difference, and retest ie repeat the test drive and collect another set of data, the knocking may have subsided on it's own.

[Gregski]

and that's that for Timing, we will cover Idle Tuning next

[Gregski]

Idle Tuning

Idle tuning can be the most challenging, let's see if it has to be that way. We will begin with a few assumptions:

1. Your engine starts, so this is not about getting it to fire up after a cam swap.

2. We will allow the engine to fully warm up to operating temperature prior to tuning idle, so we pick up after the warm up phase.

3. AC is off or has been deleted and is not of any consequence

As we dive in deeper you will see that this reduces our complexity from 4 conditions to only two, where we idle either:

1. In Park
2. In Gear

[Gregski]

Idle Tuning

So to tune the idle phase of your engines operation we will focus on the Holy Trinity:

1. RPM
2. Timing
4. Airflow

As always we start off with a clean canvas in the VCM Scaner, and begin by adding the channels we will need.

[Gregski]

Idle Tuning

Hopefully by this time I don't need to convince you why we always start with the Engine Coolant Temp channel regardless of what we are doing.

This channel is just something we have accepted we will always need to guide us with the meat and potatoes of what ever our mission is.

[Gregski]

Idle Tuning - RPM

We start tuning idle by expecting or dictating at what Engine RPM (Revolutions Per Minute) our engine will sit there in our garage or driveway and purr like a kitten. So what should that be? A wise old timer once told me, "let her idle at the lowest RPM she will stay running at." that advice has stayed with me for over 20 years, cause otherwise you are just sending dollar bills out your tailpipe sort of speak. Now there's more to it then that, she needs to stay running at all conditions so in Drive aka in gear as well as in Park/Neutral. So just cause we can get our engines to idle at 450 RPM in Park doesn't mean they will like that when we are stopped at a red light in gear.

So let's add our first channel for idle tuning, Engine RPM and see where she idles at.

A nice analog Tach is highly recommended for idle tuning, anyone who calls themselves a Hot Rodder ought to have a tachometer installed in their rig.

Please Note: we also assume your build is complete, in other words the Air Filter housing is on, the air intake is on, you have complete exhaust system bolted up, etc.

[Gregski]

Idle Tuning

Now things have gotten a bit more advanced, since that old man's advice. GM engineers have already predetermined at what Engine RPM our LS engines ought to idle at, so lets take a peak at those settings in the VCM Editor.

Engine \ Idle \ RPM tab \ Base Setpoint section \ Base table

[Gregski]

Idle Tuning - Base table

In the Base table we see the four conditions our engine can be operating at while idling. We agreed to only focus on the two without the AC to make things a bit easier.

1. In Gear AC off
2. in Gear AC on
3. P/N AC off
4. P/N AC on

Once warmed up we should be in the green zone so our RPM should be 550 in Park and 525 in Gear.

Note: My numbers are based on a 2001 GMC Sierra 4.8L 4L60e 2WD, your numbers may vary.

[Gregski]

Idle Tuning - Idle Desired RPM

Now we could commit those numbers to memory, or write them on a post it note, or take a pic of that table with our iPhones, but we don't need to. You see HP Tuners makes our lives so much easier, by providing us with a channel called Idle Desired RPM.

The nice thing about this parameter / channel is that the value will change in real time based on whether we are in Park or in Gear so it will always show us what the PCM expects the idle RPM to be dynamically, very cool.

So let's add it to our Channels.

[Gregski]

Idle Tuning - Engine RPM vs Idle Desired RPM

So now our Channels look like this:

Engine Coolant Temp


Engine RPM
Idle Desired RPM

and that is the first part of the Holy Trinity, that's all we need to discuss the engine RPM aspect of the idle tuning process

[Gregski]

Idle Tuning

So let's go out there and get some data in this NorCal early March treacherous weather (pronounced: sprinkling)

[Gregski]

Idle Tuning

Having logged over 20 minutes of data lets take a look at the numbers.

We have learned that my in Park Idle Desired RPM should be 550, so why is it 700 in the screen shot below?

[Gregski]

Idle Tuning

lets troubleshoot / explain what is going on here together

we start by looking at our ever important Engine Coolant Temp channel and it clearly only reads 90° F this has got to be a red flag, seems kinda low for a fully warmed up engine

[Gregski]

Idle Tuning

lets go back and consult our idle Base table to see what should be happening at 90° F

and sure enough, the Desired Idle RPM is 700 at 90° F in Park, the engine hasn't fully warmed up yet, I just jumped the gun, this happens to more people than you know

now I wasn't trying to trick you, or be a smart alleck, you must fully warm up your engine for it to settle in the specs it needs to settle in at

[Gregski]

Idle Tuning - Engine RPM vs Idle Desired RPM

It may have taken me 20 minutes for my truck to fully warm up to about 194° F where she likes to settle in, and that's ok, it would have happened faster if I was to drive her around the block, but I wanted just to log some pure data in Park

So here's what the numbers look like in Park when the engine is warmed up:

Engine RPM = 552
Idle Desried RPM = 550

pretty darn perfect

[Gregski]

Idle Tuning - Engine RPM vs Idle Desired RPM

now watch what happens when I shift her into Gear

Engine RPM = 525
Idle Desried RPM = 525

the Idle Desired RPM changed from 550 to 525 and the actual Engine RPM followed, as it should per the Base table, see how that works

[Gregski]

Idle Tuning - Chart vs Time

In order to further our RPM discussion it is time to get acquainted with a new feature of HP Tuners called Chart vs Time.

[Gregski]

Idle Tuning - Chart vs Time Layout

We add a Chart to our Layout in a similar fashion we have been adding the Histograms from the main Menu above

Layout \ Add to Layout \ Chart vs time

[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.