HP Tuners Tutorials

[clay68c10]

Nice description of fuel trims! I wish I would have had someone put it in those terms before I started playing around with tuner pro and TBI.
Also a great way of summarizing the use of NB vs WB. I did my initial TBI tunes on the Caddy in open loop with the wideband, and now do my small tweaks off BLM (fuel trim) values, with the wideband just as a verification since it does respond faster. It is helpful for quicker throttle transitions, maybe the LS pcm reads/responds fast enough. TBI sure doesn’t.

[Gregski]

Originally Posted by clay68c10

Nice description of fuel trims! I wish I would have had someone put it in those terms before I started playing around with tuner pro and TBI. Also a great way of summarizing the use of NB vs WB.

Thank you I appreciate that.

Originally Posted by clay68c10

I did my initial TBI tunes on the Caddy in open loop with the wideband, and now do my small tweaks off BLM (fuel trim) values, with the wideband just as a verification since it does respond faster. It is helpful for quicker throttle transitions, maybe the LS pcm reads/responds fast enough. TBI sure doesn’t.

Nice, you are a braver man than I, ha ha.

[Gregski]

MAF Scaling - Calibration

Arguably the Mass Air Flow sensor aka the MAF is the most important sensor on our Gen 3 engines (when it comes to fueling, the Temp Sensor is King overall, ha ha). We all have heard that the engine is nothing more than a sophisticated air pump. Buying into that analogy we begin to understand how the magic of mixing the the right amount of air and fuel at the right amount of (spark) time happens.

Fuel injected engines can rely on one of two air delivery methods, using the MAF sensor or using the MAP sensor (pronounced: Speed Density). To make things even more complicated, GM decided to use both, yes at the same time. Before we get to that, let's highlight the differences.

The MAF method ~MEASURES~ the actual amount of air going into the engine at that given moment in time. Now it seems perfect and makes you wonder why the MAF sometimes gets a bad rap, I mean who wouldn't want to know exactly precisely how much air is entering the system, right? Well the MAF has a few drawbacks, first, it don't know if the air is coming or going, so it measures air in either direction as it passes through it's super duper uber sensitive wire sensor that measures air mass based on how hot or cold that wire needs to be (blah blah blah). So if for some reason a wild cam pushes some back pressure air backwards in the intake manifold guess what? the MAF measures that as if it was going in. The second issue the MAF has is with TRANSIENT (pronounced quick) throttle changes, so you slam on the gas pedal, the MAF goes WTF, same goes for when you let off the throttle pedal right quick, the MAF can't exactly keep up. Thirdly, the MAF lives about a foot and a half away from the throttle body on a cold air intake housing or some sort of plastic tube, well that's where it measure the air, so what if there is a tiny hole or leak in that housing after the MAF, ie past it, the MAF don't know anything about it, so who or what accounts for that additional air, (pronounced: vacuum leak, ha ha)

Enter the MAP. If the MAF is the Accountant in the bunch, the Manifold Absolute Pressure sensor is the Mathematician if you will. Instead of measuring the air, the MAP ~CALCULATES~ it. Well technically the PCM does the heavy lifting but the MAP feeds some crucial information into that super duper complicated formula to come up with something called Cylinder Airmass. (Google: Ideal Gas Law, or don't ha ha). Cylinder Airmass as the name implies is the calculated amount of air that arrives at each individual cylinder, not the total eight cylinders at the same time. This use of the MAP is called Speed Density, you may have heard of guys running only in Speed Density mode, and that's a topic for an entire separate discussion, it just means they disabled their MAF and don't rely on it at all (not smart for daily drivers as it castrates what makes the LSx engines such good engines). The MAP / Speed Density which uses the Volumetric Efficiency aka VE table method also has its pros and cons, such as factoring in air temp, humidity, etc. all which effects the final computation, that's why GM decided to use both.

So majority of the time our Gen 3 engines are relying on the MAF, but when we transition too abruptly with the gas pedal either on or off the PCM takes a peak at the VE table ie Speed Density to keep the MAF honest. Also according to the factory settings, above 4,000 RPM we only rely on the MAF sensor and no longer use both methods (take that Speed Density only guys, joking) as the air rushing in is more stable at that point and the readings are more accurate.

Now we are gathered here today because we most likely done did an LS Swap, in which case we altered the intake track (ditched the fugly OE air box, changed the air filter, changed to a cold air intake, changed the location of the MAF, etc.) The precise calibration that the GM engineers/technicians have done at the factory has gone out the window. This is why we start by tuning\calibrating the MAF. It sounds intimidating at first, but don't be skierd.

[Gregski]

MAF Scaling - Calibration

In order to tune or calibrate the MAF sensor the first thing we want to do is take our last tune file I think we left off on a file called 14 - Turn Off Cat Protection.hpt open it in VCM Editor and turn right around and save it as something called 00 - MAF Calibration - Initial.hpt yes this file will contain exactly precisely what the 14 - Turn Off Cat Protection.hpt file has in it, but it will be our fall back with a clear name of what it is.

As you will see below in the second screen shot, I actually geek out and create a separate directory for each component that I am going to tune, you can see below I created a Folder structure for MAF Calibration containing its own logs, channels, graphs, tunes, etc., but hey, you do you

[Gregski]

MAF Scaling - Calibration

ok, now without making any changes in the VCM Editor, simply save this file again, yet with another name, call it something like 01 - MAF Calibration - Setup.hpt and bear with me, this naming renaming files thing may seem a bit odd, but once you rinse, lather, and repeat this process a few times it will begin to sink in, it's basically that an ounce of prevention is worth a pound of cure mentality

so now in my MAF Calibration folder I show two files, the first is what I will fall back to if I jack things up too much, and the second file is where i will make my special changes to in order to setup the PCM for MAF calibration, this configuration is temporary and only for the time spent calibrating the MAF, you do not want to drive around for days, weeks, months in this temporary condition

[Gregski]

MAF Scaling - Calibration

You can calibrate the MAF in two ways, using either the stock narrow band oxygen sensors or using an aftermarket wideband oxygen sensor ie AFR gauge.

Option 1. Factory Narrowband Oxygen Sensor Method

To make things even more complicated, in this method you have three further choices:

1. Tune using only the Long Term Fuel Trims
2. Tune only using the Short Term Fuel Trims
3. Tune using both the Long and Short Term Fuel Trims simultaneously

PROS for all three choices above: you already own the narrow band oxygen sensors, you also have two of them, one in each exhaust pipe so you are monitoring both banks ie both the left and right cylinder heads, all the computations have already been programmed into HP Tuners by their programmers, and after tuning the PCM will use these stock narrow band sensors to operate anyway, not the wideband, etc.

CONS for all three choices above: you can not tune Wide Open Throttle (WOT) condition with this mthod, you are limited to only tuning Idle and Cruise modes aka the Closed Loop.

Option 2. Aftermarket Wideband Oxygen Sensor Method

PROS you can tune the entire operational spectrum with this method, Idle, Cruise, and Wide Open Throttle (WOT) so both the Closed and Open Loop.

CONS you have to buy (expensive) and install the wideband oxygen sensor, also if you only buy one you can only monitor one side of the engine, and anyone who's spent any time with engines knows often times both banks ie both cylinder heads do not run equally hot or efficient, (let's not fight, ha ha) and after tuning the PCM will use the the stock narrow band sensors to operate anyway, not the wideband, this is important to acknowledge because it takes under consideration how the stock OEM narrow band sensors have aged and degraded, etc.

Because this is a basic tutorial intended to wet your appetite for tuning we will be using the factory narrow band Option 1 above relying on both the LTFT+STFT special math function for the win! Nothing stops you from going at it a second time once you have a Wideband and confirming this tune and building upon it by also tuning WOT.

[Gregski]

MAF Scaling - Calibration

We can take a look at the current existing MAF Calibration under Engine \ Airflow \ General tab \ MAF Calibration section in the Airflow vs. Frequency table

[Gregski]

MAF Scaling - Calibration

Using the Horizontal Split menu item (red arrow below) I strongly recommend you simply take a look at what the initial exponential(?) graph looks like first, if you have a virgin factory configuration it should look like a nice quarter pipe for those of you who were skaters, ha ha, no spikes, peaks, divots, valleys, just nice smooth transition

[Gregski]

MAF Scaling - Calibration

if someone already took liberties with your configuration and mocked it all up, here you can see before you even go making any changes yourself how bad the graph really looks

you are hoping that when you are done, yours will not look like this, ha ha, if it does, you did something wrong, or more likely you got some bad data

[Gregski]

MAF Scaling - Calibration

With a mental picture of our current MAF graph we are ready to put our PCM in MAF Calibration mode. In order to do that we must disable Speed Density, in other words we don't want the MAP sensor and the VE table assisting or correcting how much air is flowing into the engine, we want to solely rely on the MAF so that we can calibrate it.

To achieve this isolation we go to Engine \ Airflow \ Dynamic tab \ Dynamic Airflow section \ and set the High RPM Disable to 200 rpm

now if we glance on the help section below we can read a rather confusing description:

"[ECM] 3003 - Dynamic Airflow High RPM Disable: Above this RPM use filtered MAF airmass for airmass prediction calculations."

yet watch what happens when I only add one word:

"[ECM] 3003 - Dynamic Airflow High RPM Disable:

Above this RPM use only filtered MAF airmass for airmass prediction calculations."

[Gregski]

MAF Scaling - Calibration

That's it, that's all you have to do in the VCM Editor to start calibrating your MAF, the rest of the magic happens in the VCM Scanner.

What about Power Enrichment won't that skew our data? Technically we have not enabled Power Enrichment yet, as it comes crippled from the factory on these trucks, for example mine would not kick in until I was above 5,500 RPM (ridiculous I know) on some 6.0L it takes that plus being above 5,500 RPM for like 30 or 60 seconds.

If you enabled your Power Enrichment like I have you can avoid it interfering in other ways, for example, don't go above 5,500 RPM while calibrating your MAF, ha ha, or stay below what ever RPM and or throttle position you set the Power Enrichment to kick in at, so you can take care of it by the way you drive (FYI factory wants you to be above 90% throttle for Power Enrichment to kick in), you can also filter out Power Enrichment mode in the VCM Scanner when you are logging the data, we will be taking this approach. Also technically WOT puts you in Open Loop and we can't tune that with the narrowband O2 sensors anyway, it's just that slight early transition from the end of cruise and into the early start of Power Enrichment that gets skewed.

Another obstacle for us can be DFCO aka Deceleration Fuel Cutoff, this is a feature where when you are cruising and you let off the gas pedal really quickly, the computer shuts off fuel delivery to the engine (why waste fuel right) well this makes the O2 sensors read super lean for a split second and those readings can jack up our MAF calibration, again you can avoid this by not lifting completely off the throttle during MAF calibration, and this too can be filtered out in the VCM Scanner during data logging.

I like the belt and suspenders method, where we try to do both, drive accordingly (no sudden throttle changes, just smooth cruising through as much of the RPM range and load as we can get) during MAF calibration driving and also I like to rely on the filters.

[Gregski]

MAF Scaling - Calibration

After we made that one simple change in the VCM Editor to disable Speed Density for the duration of our MAF calibration, now we need to add some Channels in the VCM Scanner.

First I would like to show you the bare minimum of channels that it takes, we basically need two things:

1. the Mass Airflow Sensor frequency

2. the Short and Long Term Fuel trims (all four of these channels)

that's it with these five channels we can tune the MAF, however later I will tell you why you may want to add some more channels just so you have some perspective as in how fast were you going at the time, what was the engine RPM, what was your intake manifold pressure like, what position your throttle was at, were you in Open or Closed loop, etc. just some nice to haves.

[Gregski]

MAF Scaling - Calibration

after we have our Channels now comes the scary part now we need to setup something called a Histogram (pronounced: "graph")

we also do this in the VCM Scanner, and it will look like this (right side of the screen)

[Gregski]

MAF Scaling - Calibration

and here's how you build that graph

Label: you can call it what ever you want "MAF Tuning" or "LTFT+STFT MAF" whatever

Parameter: this is key and you want to select the LTFT + STFT [Math] function

View: make sure it's set to Average

Decimals: set it to 2

Function: we will talk about this later, this is a bit advanced

Cell Hits Required: make it 20 or 50 as long as it is more than 1

Shading
High Value: 20 or 25 red usually to show lean
Low Value: -20 or -25 green usually to show rich

Column Axis
Parameter: select the Mass Airflow Frequency [Sensor]

Values: cut and paste these from the MAF Calibration section Airflow vs Frequency table in the VCM Editor by right clicking anywhere in that table and choosing Column Axis / Copy Labels

[Gregski]

MAF Scaling - Calibration

Once we have the Channels and the Graph in the VCM Scanner configured we need to go back to the VCM Editor and write the 01 - MAF Calibration - Setup.hpt file to the PCM. We should all be familiar with how the write aka Flashing works by now.

Then once the truck is warmed up, I like to switch to the VCM Scanner on my laptop and drive out to a place with no oncoming traffic and no stop lights, and start my calibration drive. I start driving and then press the start recording on my laptop. Then I just drive around without going into WOT. You do not need to stare at your laptop while driving. When done maybe 10 or 20 minutes later, stop the scan before you stop the drive, then come to a complete stop somewhere safe and save your log so that your laptop battery does not die.

Top Tip: if you start seeing numbers in the double digits like 13.60, 14.50, or 15.30 then you can increase your MAF calibration by something like 10%. You would do this by going to the MAF Calibration table in the VCM Editor selecting the entire table and then type 1.10 in the box on the menu and hit X to multiply. I make this suggestion right off the bat because it is dangerous to be that lean. Remember it is better to be a little rich like -2% than lean, and double digits lean is bad. So don't over think it, if your numbers are 17.20, 18.90, or 19.20 then increase your fueling by 15% so multiply the entire table by 1.15, kapish, get out of the red zone ASAP.

[Gregski]

MAF Scaling - Calibration

When you get back home, you can replay the log you recorded and analyze the data. You are looking for trends. Some guys like to use the Paste Special - Multiply by % - Half feature to make gradual changes, you are welcome to experiment with it.

[Gregski]

MAF Scaling - Calibration

I prefer to do things manually. For example in the sample data log below I would multiply manually by 1.05 since I see a bunch of 5.xx numbers in that data sample. It is a bit of an art and a bit of science.

[Gregski]

MAF Scaling - Calibration

If you find yourself running too rich and what is too rich or too lean? Anything in the double digits so more than 10 or -10 I would tune. If you are a total newb but are in single digits like 8 or -7 that's OK you can leave it alone. Anything 4 or -4 is a good tune already. I shoot for 2 or -2 but that's because I have nothing better to do. ha ha.

You will not get it perfect to 0 or -1 so don't kill yourself trying, the conditions change too much to try for that; weather, humidity, rain, snow, wind, elevation, load (are you towing something?) things outside of your control.

So if you see negative numbers that means you are running too rich, in the example below I would eye ball that and multiple by .97 since I want to take away 3 percent

Again it's better to be a little on the rich side, ie looking green with small negative numbers, -1, -2, up to maybe -4

[Gregski]

MAF Scaling - Calibration

here's a sample of a nice tune, all green numbers -2 or less

[Gregski]

MAF Scaling - Calibration

When your numbers look good, don't forget to take a look at your new graph.

[Gregski]

MAF Scaling - Calibration

Once you have a good tune, it is time to write it back to the PCM. First in the VCM Editor go back to Engine \ Airflow \ Dynamic tab \ Dynamic Airflow section \ and set the High RPM Disable back to 4000 rpm this will re enable Speed Density to assist the MAF sensor in metering air

then save the file with a new name something like 02 - MAF Calibration - Tuned.hpt

[First c10]

This is great! I really want to tune my MAF as soon as I get another HPtuners setup since my shop got broke into and it was taken.

[Gregski]

Originally Posted by First c10

This is great! I really want to tune my MAF as soon as I get another HPtuners setup since my shop got broke into and it was taken.

Thanks, man that sucks, and sorry it took so long.

[Gregski]

SAE Default Channels

Just wanted to do a quick write up on the SAE Default Channels and why its better to roll your own.

First note that out of the 29 listed not all will read / record data from your PCM, in my case based on my vehicle I guess and this being an LS Swap (meaning we did not bring over the BCM - Body Control Module and a slew of other sensros) only half (15) will show values.

Also as HP Tuners themselves will tell you their software is designed to work with many different animals and not just GMs.

So don't panic, it's working as designed.

[Gregski]

Vehicle Default Channels

If you are firing up your rig for the first time after the swap, or just getting started with HP Tuners, then the Vehicle Default Channels are more better.

Here you can quickly keep an eye on Engine Coolant Temp, both Short and Long Fuel Trims (aka quick changes/corrections to the air/fuel mixture) and of course Knock Retard to combat the enemy of all engines.

Of course you can add your own channels (such as Cylinder Airmass and Mass Airflow Sensor Frequency) to these to build your own list that works for you. Keep in mind you have to stop logging in order to add or remove channels to the list.

Also on an LS Swap some of these may not report proper values, such as the Fuel Tank Level in my case.