HP Tuners Tutorials

[Gregski]

Key On - Vehicle Not Running - Systems Check

for the Engine RPM we just expect to see a value of 0 to prove the tach signal is coming through

[Gregski]

Key On - Vehicle Not Running - Systems Check

same goes for the Timing Advance channel we don't expect to see anything above 0 with just the key on and the engine not running, but seeing a zero is a good sign means we picked the right PID (Parameter ID) and there is a signal on the line

[Gregski]

Key On - Vehicle Not Running - Systems Check

and both O2 Voltage sensors are perfectly in the middle of .100 and .900 volts with the key on, and the vehicle not running

[Gregski]

Key On - Vehicle Not Running - Systems Check

now I would be lying if I told you I wasn't genuinely concerned about the low Control Module Voltage even if this is key on engine not running, something may be draining my battery here and low battery voltage can brick your PCM when you are flashing it

[Gregski]

OK, let's use our Basic Channel config to evaluate the second of the three vehicle conditions:

1. Key on - vehicle not running

2. Vehicle Running - Open Loop

3. Vehicle Running - Closed Loop

[Gregski]

Vehicle Running Open Loop - Systems Check

So now that the truck is running we see the presence of Manifold Vacuum, we observe that our value is now well above 0

We see a similar result for the Mass Airflow Sensor

Obviously Engine RPM has climbed as well, though we don't know if it's where it should be yet, but that's ok for now, we are learning

likewise we have a Timing Advance that is greater than zero

[Gregski]

Vehicle Running Open Loop - Systems Check

now we see an interesting condition regarding our two O2 Sensors Voltage, it appears it went from middle of the road around .450 with the key on to above .900 with the truck running and warming up, later we will learn that this reflects a rich condition, but since the rig is warming up this is acceptable (think choke on)

[Gregski]

Vehicle Running Open Loop - Systems Check

and finally the Control Module Voltage looks much better, with the engine running, it is above 14 volts

[Gregski]

Lastly, let's use our Basic Channel config to point out the channel value differences in the final of the three vehicle conditions:

1. Key on - vehicle not running

2. Vehicle Running - Open Loop

3. Vehicle Running - Closed Loop

[Gregski]

Vehicle Running - Closed Loop

I hope you stuck it out this far, as things began to get interesting. I pointed out earlier the importance of the Engine Coolant Temp and here is the first example of its cause and effect.

When the temperature reaches 131*F notice what happens in the Fuel System #1 Status channel below it?

The status changes from OL - Not Ready to CL - Normal CL meaning Closed Loop now.

[Gregski]

Vehicle Running - Closed Loop

lets take a deeper dive and see what exactly caused that switch from Open Loop to Closed Loop

We know all of our configuration settings come from the VCM Editor so we fire it up and go to Engine \ Fuel \ Oxygen Sensors and look under the Closed Loop Enable heading where we find the ECT vs. IAT table (highlighted in pink for easier spotability that's all)

We put our mouse over it, and glance at the bottom of the screen where we find the Context Clues, which read: This table sets the coolant temperature required to enable Closed Loop in relation to inlet air temperature (IAT).

We open up that little guy, and it's not really a table as it is a list, but so be it. We quickly and easily see that once the ECT (Engine Coolant Temp) hits 131 (the big green bar) and our Intake Air Temp is above at least 50* we will turn on Closed Loop. Cool beans, so things are working as they should and now we know why.

Don't take this for granted, someday you may be troubleshooting an issue caused by your PCM never entering Closed Loop mode, so just keep that in mind please.

[Gregski]

Vehicle Running - Closed Loop

further down the list allow me to point out another cause and effect of you guessed it the Engine Coolant Temp

The engine is a little warmer now, it has reached 154* F, it's time to cause another thing to happen...

Note the drop in Engine RPM to approximately 550

[Gregski]

Vehicle Running - Closed Loop

once again lets take a deeper dive and see what exactly caused the RPM to settle in at 550

so back to the VCM Editor we go (you will find this is the common Tango you will be performing whilst dueling HP Tuners ie. going to and fro from VCM Scanner to VCM Editor and back)

Engine \ Idle \ RPM is where we find the Base Setpoint heading and the Base table lurks under it

with our mouse hovering over it, we glance below to see: This table controls the desired idle RPM vs. Engine Coolant Temperature.

This being an actual table and not a simple list, allow me to explain how I read it.

There are four conditions:

• In Gear AC off (as in stopped at a stop sign or a red light)
• In Gear AC on (as in stopped at a stop sign or a red light)
• P/N AC off (in Park or in Neutral AC off)
• P/N AC on (in Park or in Neutral AC on)

So in our case in Park with the Air Conditioning off (deleted actually) and with the Engine Coolant Temp at 154* F we should be idling at 550, and we are. High fives all the way around!

[Gregski]

This concludes Chapter 1 - Logging

I hope I whetted your appetite for doing some tuning on your own or at least exploring the VCM Scanner.

If you have some channels you like to use to do your initial system checks that I have omitted please let us know, we're all here to learn.

[PGSigns]

I have been following along the entire time and have learned a lot. Thanks again for doing this.
Jimmy

[Gregski]

Long Term Fuel Trims and Short Term Fuel Trims, yeah we all heard the terms or the four letter acronyms LTFTs and STFTs, but what are they really?

A long time ago a teacher I had would tell us to substitute a word for a term we did not know instead of defining it for us, and it worked, so let's try this, any time you see the word Trims substitute it with the word "Changes"

So Long Term Fuel Trims become Long Term Fuel Changes and Short Term Fuel Trims become Short Term Fuel Changes

You could also use the word Adjustments or modifications, or what ever you come up with that works for you.

Now some may find the following analogy or example silly, but I think it works as we all can relate to it, plus everyone enjoys a good short story.

So it's the first day of Winter and you have to get dressed for school. So you put on the usual a T shirt and some jeans (socks, shoes and underwear is assumed) so in other words your VE outfit your Volumetric Efficiency or standard outfit.

On Monday you step outside and start walking to school, soon you find it's colder than you expected but you press on.

Tuesday same thing you throw on a different T shirt but still just a T shirt and a pair of jeans and you head out, freezing your butt off all the way there.

On Wednesday you step outside in your T shirt and a pair of jeans and you say screw this I am making an adjustment and you grab a jacket and put it on and zip it up to the top (there you just made a Long Term Fuel Trim) from here on out you will bring a jacket until the weather will get too hot again. You walk to school wearing that jacket but once you get to class you are sweating, you think nothing of it.

Thursday you head outside in a T shirt, jeans, and jacket of course, but half way there you think I'm getting hot, I should unzip my jacket (A Short Term Fuel Trim change) you get to school and you are no longer sweaty like the day before, you think I think I got this

Friday morning you put on your T shirt, jeans, and a jacket but you don't zip it up today, nope the Short Term Fuel Trim has now become part of the Long Term Fuel Trim baseline if you will

now if you start walking to school and it gets too cold, starts raining or snowing, by all means you have the freedom to zip up your jacket again, making yet another Short Term Fuel Trim adjustment/change

[Gregski]

Just wanted to clarify something that had me tripped up for a while and may help you. The objective is to get us thinking, in a non biased way as realists.

Do you need a Wideband Oxygen Sensor AFR Gauge to tune?

The short answer is no. The better answer is, it depends.

I bring this up for two reasons:

1. We need to understand what is controlling what as the vehicle goes through it's operational phases in order to determine for ourselves which tuning method to use and why.

2. There are many articles written on how to tune and especially many YouTube videos out there as well that do not clearly state in their title / subject which method they are using, and a beginner can spend a lot of time pulling their hair out trying to figure out why the methods differ.

Let me preface what I am about to say and tell you that I am not anti Wideband gauges I use them I run them in my vehicles, however there are Pros and Cons to using both methods.

Tuning Using the Stock Narrow Band Oxygen Sensors

PROS

• no additional costs, you already own these sensors
• in the end the PCM relies on and uses these sensors to operate, not the Wideband (think about that for a minute) this argument gets lost quite often in the debate

CONS

• can't tune Open Loop state with them such as WOT
• can't see actual ratio values in quantitative terms, ie 12.5 AFR or 15.9 AFR

You can tune 90% of your naturally aspirated engine using the narrow band method. The only thing you can't tune using the Narrow Band O2s is Wide Open Throttle aka WOT. Why did I say 90% because when it comes to street cars, our daily drivers think about it, how much time do you spend flooring it? Be honest with yourself, you probably rarely gun it with the pedal to the floor, right?

Think of the engine operation as an Oreo Cookie, the black parts being something called Open Loop and the white middle being Closed Loop. When you first start your car it is running in Open Loop, then once it warms up it enters Closed Loop (idle & cruise), then when you floor the gas pedal aka WOT you are once again in Open Loop (the other side of the cookie). In Open Loop the PCM is not relying on the stock narrow band O2 sensors, it is simply not listening to them. That is why you can not tune WOT with narrow band oxygen sensors.

Tuning Using Wideband Oxygen Sensor(s) AFR Gauge

PROS

• able to tune entire operation spectrum (idle, cruising, WOT, etc.)
• read actual ratio values in quantitative terms, ie 12.5 AFR or 15.9 AFR

CONS

• additional costs (parts and installation, bung welding, etc.)
• vehicle does not operate using Wideband sensors for input, calibration differences could impact final results
• often times Wideband is a temporary install and not permanent
• Wideband placement during tuning
• technically you are always tuning in Open Loop

It is no secret that the placement of the oxygen sensor can yeild different readings. Put it too close to the collector you get one value, put it too far past the collector you may get a different value, hewk just shove it in the tailpipe you can get yet a different reading. A lot of tuners will remove a narrow band sensor and screw in a wideband in it's place, the problem with that is, it is temporary and only tells you what you got while you are on the dyno during that hour session.

I used to play Water Polo, and our team was pretty darn good. Most of our time was spent in the pool playing [ahem] Water Polo. Folks would often times wonder what made our team so good or what was the secret that our coach had, and it was that we did not do drills, we did not lift weights, we did not run laps or stairs, we just played Water Polo. We played a lot of gosh darn Water Polo, ha ha.

I like to street tune my vehicles, because I drive them on the street and not on the dyno, ha ha. When I log my data I like to log it while driving to work or log it while driving back from work, more than taking the vehicle for a random test run down roads I will seldom or never take. In other words tune for the conditions you will face not well you get the idea...

Don't get me wrong there are good dyno tuners out there, but I hope I am getting the concept through. Getting your vehicle tuned for two hours on a sunny day on Saturday morning in a guys shop with a huge fan blowing on the front grill to keep it cool with a Wideband AFR gauge shoved into the tailpipe on a two foot long stick may not exactly precisely represent the driving conditions you face on a daily basis (cold mornings, scorching hot afternoons, rain/humidity), are there any hill climbs, how about descents, etc. How about bumper to bumper rush hour traffic?

... and please don't get me started on Mail Order PCM tunes!!! hee hee

RECOMMENDATION: In the end I like to use both methods, aka the belt and suspenders solution, that way you can cross check your results and perhaps account for any discrepencies.

[DWilbur]

I just received my HP tuner equipment in the mail last night. I will go back review the thread & make wire harness to power up my ECM so I can work on it on the bench while it’s raining. Until I get my engine harness reworked and my truck is ready.

[Gregski]

Originally Posted by DWilbur

I just received my HP tuner equipment in the mail last night. I will go back review the thread & make wire harness to power up my ECM so I can work on it on the bench while it’s raining. Until I get my engine harness reworked and my truck is ready.

Is this for "Snow White" yer '71 4x4 2004 5.3L?

[DWilbur]

Yes it is

[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