Re: HP Tuners Tutorials - Timing
 

Timing

GM sets timing in the Gen 3 engines in two places relying on four different tables.

1. Idle Spark Advance section (In Drive table or In Park table)

2. Base section (High Octane table and or Low Octane table)

All four of these tables live under Engine \ Spark \ Advance in your VCM Editor

We will start out by talking about the Base ignition timing ie the main timing.

Re: HP Tuners Tutorials - Timing
 

Timing

First the High Octane & Low Octane table names to me are a bit of a misnomer, I look at them as Aggressive Timing table and Moderate Timing table. The PCM does not sense octane levels in our fuel, it uses something called the Knock Learn Factor to determine which timing table to depend on or a combination of the two. We will cover Knock Learn Factor later on.

GM considers 93 Octane to be High Octane. Well I live in Northern California and I can't seem to find 93 Octane at the pump, so what table am I using?

The PCM wants to run off of the High Octane table however it is capable of averaging out between the two tables when it senses knock so your timing may not precisely match the High Octane table nor the Low Octane table at any given time, and that's ok. Also if you put in cheap gas you may find yourself running off of the Low Octane table exclusively and even then may still have some knock.

We will address all that, but first we take a peak at these two tables. Please note the differences at the higher load (larger Cylinder Airmass numbers) and RPM levels aka bottom right hand corners of the tables, ha ha.

Re: HP Tuners Tutorials - Timing
 

Timing

Let's take a closer look at one of these tables (it don't matter which one at this point in time)

The X axis ie the title on top Engine Speed (rpm) is self explanatory. However please look at the Y axis label on the left hand side Cylinder Airmass (g).

Unlike other manufacturers who use RPM vs Load (aka Vacuum / Manifold Absolute Pressure) for their timing tables, GM uses Cylinder Airmass (g). It is important for us to acknowledge this for various reasons.

1. The stock Histograms / graphs that come out of the box from HP Tuners are useless for us in terms of tuning or troubleshooting. They will all need to be modified / corrected to reference this Cylinder Airmass parameter instead of Manifold Absolute Pressure.

2. Cylinder Airmass is a calculation that takes the MAF input as well as the VE Table input into account. This is why we calibrate the MAF and the VE Table first. If the MAF / VE Table are off, than the wrong timing will be applied to your engine as it is based on this very important Cylinder Airmass (g) computation, and you will be left chasing your tail.

And yes just as with the VE Table the timing tables can also be viewed as a three dimensional graph.

Re: HP Tuners Tutorials - Timing
 

Timing

Example: Let's assume at 2,200 RPM the PCM calculates the Cylinder Airmass as 0.44 grams, according to this table that calls for 29* of timing advance. However the MAF and or the VE Table were not calibrated and are off, so the actual Cylinder Airmass should be 0.48 grams, now the correct timing should be 26* degrees. That's three degrees off, it could mean the difference between a smooth running engine or engine knock occurring. In higher RPM ranges under higher load, such a discrepancy can easily rob you of some power, and this was only a difference of one cell, imaging being two or three cells off.

Re: HP Tuners Tutorials - Timing
 

Timing

At this point let's jump to the VCM Scanner and setup a Histogram / graph to show us what exactly our egnine's timing looks like.

We only need three Channels to get started:

1. Timing Advance (this will give us the meat and potatoes aka the values in the cells)

2. Engine RPM (this will be our X axis ie the Title on the top of the graph just like in the High (or Low) Octane table)

3. Cylinder Airmass (this will be our Y axis label, again just like that of the Hight Octane (or Low Octane) table)

Re: HP Tuners Tutorials - Timing
 

Timing

Next we build our Histogram aka graph to match the High and Low Octane timing tables

Re: HP Tuners Tutorials - Timing
 

Timing

Lets take a close look at the Properties of our Timing Advance graph

Label: call it what ever you like, such as: Timing Advance

Parameter: although we select Timing Advance this silly program changes the name to Spark Advance on this screen

Decimals: I start with 0 you can get more granular later

Filtering
Function: this is important but it's a bit more of an advance feature which we will touch on later (you could use it to exclude things above your idle RPM say anything above 550 or Throttle Position greater than .5)

High Value: 50 cause that's the highest thing in my High Octane table (though this can be exceeded)

Low Value: -15

Column Axis
Parameter: Engine Speed aka Engine RPM

Values: copy the Column Axis labels from the High RPM table in the VCM Editor

Row Axis
Parameter: Cylinder Airmass

Values: copy the Row Axis labels from the High RPM table in the VCM Editor

Re: HP Tuners Tutorials - Timing
 

Timing

So after you have your Channels and your Graph all setup, you can go for a test drive and record/log some data. You do not need to write/Flash anything from the VCM Editor to do this.

Here is a look at some of my numbers.

I highlighted a cell at 1400 RPM and 0.28 grams with a value of 26 degrees advance to show you that it does not match either of my High Octane or Low Octane Tables. You may find yourself in a similar situation. So what gives?

So far this is what I wanted you to discover.

1. Where your timing settings come from (High and Low Octane tables), aka what they should be.

2. And what they actually are, aka the new Histogram / graph we just populated with data.

So we may not have all the answers but we at least now realize that there may be a discrepancy.

Re: HP Tuners Tutorials - Timing
 

Timing

To answer our question of why our actual Timing Advance does not match our Base timing, we must explore what we call Modifiers, ie there are additional tables that alter the Base table values, based on some condition.

Let's meet these dirty rascals:

Lurking on the same tab as our Base tables under Engine \ Spark \ Advance tab Base Corrections section we start with:

• Fuel aka AFR
• IAT
• ECT
• EGR
• Catalyst Heating

all eager to mess with our Base timing, ha ha

Re: HP Tuners Tutorials - Timing
 

Timing

Those of you who followed along from the beginning, you most likely turned off the EGR (Part IV) and the Catalyst Heating (Part VIII) as instructed in the Housekeeping section. Now we began to see why that may have been a good idea, especially on an engine swap where those components have been deleted.

Let's add some more Channels to monitor these Base Corrections to see if any are actually kicking in and altering our Base timing.

We will leave the Cranking Advance and Idle Advance for later when we tackle Idle tuning.

Note: In addition to these five Base Corrections, Torque Management is the biggest power thief when not tuned properly. This is also worthy of it's own Section / discussion.

Re: HP Tuners Tutorials - Timing
 

Timing

After you have added more timing Channels you can go for another test drive and record/log some more data. You do not need to write/Flash anything from the VCM Editor to do this.

You also don't need to pre build the additional Histograms / graphs at this time, as long as you are capturing the additional Channels, you can make the graphs later.

Re: HP Tuners Tutorials - Timing
 

Timing

After your second test drive, you can replay the log on the computer in the comfort of your own home, and just look at the values next to these additional five channels to see if any of them are making any changes to our base timing:

• Fuel / AFR
• IAT
• ECT
• EGR
• Catalyst Heating

And or you can clone the Timing Advance graph for each one of these to Geek out even more. It is a bit more work but it will show you exactly precisely where the timing is being altered.

Let's clone/copy one graph together. Let's make a graph for ECT Advance (which again in the graph wizard HP Tuners calls Coolant Advance)

All we have to do is change the following:

Label: Coolant Advance

Parameter: Coolant Advance

View: over on the right hand side we can choose how to show our data the default being Average but if you want to scare yourself a bit especially when it comes to engine knock change that pull down to Max, ha ha

and we are done and ready to see the results on our newly cloned graph

Re: HP Tuners Tutorials - Timing
 

Timing

Alright so I went out and drove around for about 8 minutes and got us some sample data. Using our basic timing channels here we can see that indeed the PCM is pulling out a tiny bit of timing based on the Engine Coolant Temp ECT as per the Collant Advance channel.

Now what's the point of this exercise? It is simply to make us aware of the things that the PCM may be influenced by to alter our base timing. It is not for us to go out and 0 out all these tables, leave them alone. The PCM is doing what it is designed to do, essentially protect the engine, from overheating for example.

This is different than zeroing out tables for the EGR and the CATs because those components no longer exist. If you are seeing numbers for your EGR Advance below, yet you have deleted it, you may want to revisit Section IV under Housekeeping.

Re: HP Tuners Tutorials - Timing
 

Timing - Knock Parameters / Channels

No discussion of timing would be complete without the subject of knock, (engine knock also commonly known as pinging) or more specifically Knock Retard.

Engine knock is caused by the piston still coming up in the cylinder and the spark igniting too soon forcing it down before the piston had the chance to reach top dead center and began its decent downwords.

Have you ever pushed a friend or a sibling on a swing and and stood too close and had the swing slam into you, well you experienced something very similar to engine knock, had you stood further back the swing would have reached the end of the pendulum (equivalent of TDC for a piston) and began to swing back on it's own, just as the piston would start falling back down in the cylinder, then if you gave the swing a push it would be as if the piston had proper timing set to ignite the flame somewhere after TDC to push the piston down just like you pushing the swing much easier.

Knock Retard is the PCMs way of protecting itself from literally blowing up the engine. So lets add the three Channels related to Knock:

• Knock Retard
• Burst Knock Retard
• Knock Learn Factor

Re: HP Tuners Tutorials - Timing
 

Timing - Knock Retard Histogram Properties

Now that we have our Channels we can build our graph to help us monitor Knock Retard. Same as before we can clone one of the existing sister timing graphs. Then we can tweak a few things:

Label: Knock Retard

Parameter: Knock Retard (which again the HP Tuner guys rename to Spark Retard)

Shading
High Value: 15 should get us started, we can adjust this later
Color: we want this to stand out so lets make it Red

Re: HP Tuners Tutorials - Timing
 

Timing - Knock Retard Histogram

And at this point we can go for a short 5 to 10 minute test drive around the block, these short test drives are essential to ensure our Channels work, our Graphs read data, etc. We don't want to set out to work on a Monday morning to log our first set of data only to find out some parameter did not come through because of a silly error.

Here is my sample data from my first test drive around the block. Nothing special, no knock, but we at least confirmed all the Channels and parameters are working.

Re: HP Tuners Tutorials
 

Greg, I wanted to say thank you for this write up. I have been dabbling with HP tuners for several years but what you have here brings it all together. Very well written and helpful.
My recent jump is into the gen 5 stuff, that has proven to be tricky and haven't gotten too far along.
I am only tuning my own stuff and helped a couple friends get theirs going so it is just a hobby in my hobby so to say.
Again thanks
Dave

Re: HP Tuners Tutorials
 

You're very welcome I really appreciate you taking the time to provide this feedback, as I knew my mum isn't the only one reading this thread, ha ha. Funny thing is that after a while I start referring to my own thread for reference, ha ha.

You are a brave man, I can't imagine the extra complexity in the Gen 5 stuff, I am quite happy beating the Gen 3s into submission still, great little engines.

Re: HP Tuners Tutorials - Timing
 

Timing - Knock Retard Histogram

and here is a sample of a log with some knock, truth be told this was supposed to be my longer drive, aka 20 or 30 minutes, but the log stopped recording, (hey just being honest with you all, it happens) let's just say that HP Mini netbook is no longer with us, ha ha!

anyway this is a good screen shot to share two observations regarding engine knock:

1. some engine knock is acceptable, after all if you log your factory tune for the first time you will see some knock, so the GM engineers are cool with that. I would think less than 1 degree retard is ok, that is for daily driving occuring here and there, if it's always in the same cell then by all means do something about it

2. False knock, without proper audio equipment to truly verify if our know is actual engine knock we really have no way of knowing. Again for stock engines and normal driving the stock knock sensors will do and we can rely on them, however if you were to heavily modify your engine or transmission you may experience false knock. This is yet another reason why minimal knock ie less than 1 degree can be tolerated.

Re: HP Tuners Tutorials
 

Timing - Retard / Knock Sensors

We will come back to the VCM Scanner and review more timing graphs in a bit, but at this time let's jump over to the VCM Editor and talk about the knock settings.

We find knock settings under two tabs:

Engine \ Spark \ Retard
Engine \ Spark \ Knock Sensors

Under the Ratard tab we find knock limits in the form of Knock Retard Amount and Maximum Knock Retard vs RPM (PE) or vs. MAP (Non-PE) It is important for us to acknowledge these but keep in mind just because the PCM can pull you in say 20 degrees to prevent engine knock that doesn't mean we can just set our Base timing willy-nilly and depend on the knock retard feature to make it right. Under this tab we also see Recovery Rate. When we get to performance tuning this may be a setting we revisit as it tells the PCM how long to hold the retard timing before returning it to normal, staying retarded for too long can rob you of some horse power.

Think of the Knock Sensors tab settings as the internals of the VCR (you 40 plus something year olds, lol) say you want to be an actor or a director, yes you need to know how to operate a VCR (pronounced YouTube of the 80s) but that doesn't mean you need to know how to build one, or know exactly how it works, other than we put the VHS tape in, and press Play, hewk on some machines it starts playing automatically. So for the time being just trust that the GM engineers knew what they were doing when they tuned our two knock sensors at the factory, remember this tutorial is for a stock(ish) LS engine swaps, not extreme builds. So for now we leave this tab alone, but this is where you would adjust knock sensor sensitivity.

Re: HP Tuners Tutorials
 

Yes after i have looked thru your post I am finding myself referring back to it as well.
I got a new daily driver a newer GMC Sierra that has the gen 5. Since I have HP tuners I decided I cant leave well enough alone so I am just sticking my toe into this. It is complex but something to look into and I am sure you understand that.
I do like the gen 3 motors they are great and have tons of potential. they will be around a long time and we will all continue to enjoy them.
Dave

Re: HP Tuners Tutorials - Timing
 

Timing - Knock Retard Amount

Here we take a look at the total Knock Retard Amount table found under:

Engine \ Spark \ Retard tab \ Knock Retard section \ Amount table

the PCM is willing to yank out up to 35 degrees of timing in my case, however this is as good of a time as any to mention the additional Multiplier tables, which take a complex system and make it even more complicated, ha ha

Engine \ Spark \ Retard tab \ Knock Retard section \ ECT Mult table

Directly to the right of this table is the ECT Mult table think of this table as that annoying friend that always chimes in when you try to tell a good story and corrects you all the time. So for example you say man I went to the Kings basketball game last night and they killed the Clippers, and your buddy goes, actually the final score was only 88-86. You get what I'm saying!?

So the ECT Mult table watches the engine coolant temp (there it is again the importance of keeping your engine properly cooled/heated) and for example when the temp is only 68 degrees and the PCM goes I'm gonna pull out 21 degrees of timing cause according to the Amount table that's what I gotta do at 800 RPM, the ECT Mult (your annoying buddy, goes) um not so fast the coolant temp is only 68 degrees at the moment so only pull out 75% of that 21 degrees.

Got it?

Re: HP Tuners Tutorials - Timing
 

Timing - Burst Knock Retard

Burst Knock Retard (pronounced: Predictive or Preventive Knock Retard) is a means of pulling timing out before a knock even happens based on an abrupt throttle change resulting in a sudden drop in cylinder airmass.

the Burst Knock settings are found under

Engine \ Spark \ Retard tab \ Burst Knock Retard section

How big of a cylinder airmass change needs to happen before the PCM can take preventive action is defined in the Enable Delta Cyl Air table (delta meaning change or difference) if you were to upgrade to a bigger cam, you most likely would increase the numbers in this table to make it more tolerant and less reactive ie less sensitive.

So for example once the PCM sees a 0.020 grams change at say 2,000 RPM it will consult the vs. RPM table to find out how much timing to pull out, and from what we can see at 2,000 RPM it will pull out 6 degrees of timing.

So that's how that works. For beginners and stock(ish) engines we leave these tables alone. If you pinky promise to only put high octane 91+ in your tank and want to add a bit of gitty up into your truck engine you can experiment with increasing the numbers in the first table Enable Delta Cyl Air in the lower RPM range say 1200 RPM and under.

Re: HP Tuners Tutorials - Timing
 

Timing - Knock Learn Factor

Think of the Knock Learn Factor like a fuel gauge that goes from 1.0 to 0 (yes I did say it goes from 1 to 0 which is backwards, but hey GM did not reverse\fix that until Gen IVs)

So when the Learn Factor is at 1.0 we are using the High Octane table values ie aggressive timing.

When the Learn Factor is low ie 0 we are using the Low Octane table, mild timing, that's one way to remember it.

Now the PCM will skew the timing by some factor when the Learn factor falls between 1 and 0 but that's for it to figure out.

Re: HP Tuners Tutorials - Timing
 

Timing

Here's a look at not a very happy Knock Retard graph.

Alright so armed with all this knowledge how do we actually get rid of the knock if we are experiencing some?

Re: HP Tuners Tutorials - Timing
 

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.

Re: HP Tuners Tutorials - Timing
 

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.

Re: HP Tuners Tutorials - Timing
 

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.

Re: HP Tuners Tutorials
 

Re: HP Tuners Tutorials - Idle Tuning
 

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

Re: HP Tuners Tutorials - Idle Tuning
 

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.

Re: HP Tuners Tutorials
 

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.

Re: HP Tuners Tutorials - Idle Tuning
 

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.

Re: HP Tuners Tutorials - Idle Tuning
 

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

Re: HP Tuners Tutorials - Idle Tuning
 

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.

Re: HP Tuners Tutorials - Idle Tuning
 

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.

Re: HP Tuners Tutorials - Idle Tuning
 

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

Re: HP Tuners Tutorials - Idle Tuning
 

Idle Tuning

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

Re: HP Tuners Tutorials
 

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?

Re: HP Tuners Tutorials - Idle Tuning
 

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