HP Tuners Tutorials

[Gregski]

Volumetric Efficiency VE Table Calibration

So now that you have calibrated your MAF it is time to calibrate something called a VE table. Now for the record it really does not matter which you calibrate first, we can arm wrestle over it, but it don't matter.

Top Tip before we dive in. When tuning remember these simple marching orders: Same or better!

That's it, simple as that, we make changes hoping to make things better, they don't have to be perfect, just better. For example if your MAF was 15% out of whack on the lean side ie reading red or pink in the histogram graph, and you bumped it up so now it is only 10% lean, great job, you did it, that's an improvement. You can drive around for a week like that and regroup next weekend and bump it up another 5% if you like. That's what i mean by same or better, as long as you did not screw up and make it run 20% lean, you are following the same or better mantra.

OK, so Volumetric Efficiency table (pronounced: how well your engine breathes) is a table that shows in percentages how full your cylinders can get at certain RPM / engine loads.

It is important to dial this in because if you remember our GM engines rely on both the MAF and the VE table to calculate how much fuel to spray at any given time based on how much air is entering the engine. And the VE table corrects the MAF when need be so it ought to be accurate.

Time for another terrible analogy, ha ha.

It's January / February so new years resolutions are still in effect (let's hope). So you head off to the gym to meet with your personal trainer, aka the MAF sensor, ha ha. Tucked in under your arm is a clip board with today's exercises, aka the VE Table.

You approach the squat rack (it's always available as 99% of peeps there are there to do upper body or play with their iphones, sorry couldn't resist a gym joke)

You look at your trainer (MAF) and ask: "What are we doing today?" to which he (MAF) replies: "Three sets of 15 or as many as you can, I'll count the exact reps" [that's the MAF in action it will "measure" aka count the exact reps, just as the MAF measures the exact amount of air going in]

You following the trust but verify mentality embedded in you via this very Tutorial [ha ha] glance quickly at your clip board (ie VE Table) and go hmmm it says here:

Set 1: 135 lbs - 15 reps
Set 2: 185 lbs - 12 reps
Set 3: 205 lbs - 10 reps

and there you have it, that's sorta how the MAF and the VE table work together in conjuction, the MAF measures in real time, the VE Table holds a chart ie table of hard coded information.

[Gregski]

Volumetric Efficiency VE Table Calibration

So we start by setting up our file structure in File Explorer.

So under the default directories of HP Tuners \ Logs and Tunes I like to create a folder called VE Calibration and under that I will create a sub directory for:

Channels
Graphs
Logs
Tunes

each of these sub folders above will hold the specific Channels, Graphs, Logs or Tunes only and directly related to VE Calibration

then under the Tunes directory I create a folder for each attempt at tuning like so:

First Attempt
Second Attempt

... again don't mean to micro manage you at all, you do what makes sense to you, but this is sort of to show you how the rinse, lather, repeat process is going to work, it may seem like overkill at first but it sure will help when you go back to review your steps 6 months later, trust me

[Gregski]

Volumetric Efficiency VE Table Calibration

With the folder structure for VE Calibration set up, (a process that you only have to do once and you're done) we then create our files.

We start with the last tune we wrote, in our case it may have been 02 - MAF Calibration - Tuned.hpt if you forgot what it was, that's ok, just read your PCM and save that tune file, so either rename the last file to 00 - VE Calibration - Initial, or save your newly read file as that.

This is our safety net, this is the tune we will write if things go south on us, that's all.

[Gregski]

Volumetric Efficiency VE Table Calibration

Next we open the 00 - VE Calibration - Initial file right away in VCM Editor and do a Save As 01 - VE Calibration - Setup

This is where we will make all of our changes to trick the PCM into thinking that the MAF has failed so that it only relies on the VE Table to calculate airmass so that we can calibrate it.

[Gregski]

Volumetric Efficiency VE Table Calibration

Now in VCM Editor we need to trick the PCM into thinking the MAF has failed in order to do that we go to Engine Diag \ Airflow tab \ Mass Airflow Sensor section and set the MAF Frequency Fail High to some low value such as 100 Hz

Note: back in the day and especially on Camaros or Corvettes people used to just unplug the MAF sensor however we can't do that on the truck engines since that will also unplug the Intake Air Temp sensor as it lives in the same housing as the MAF sensor.

[Gregski]

Volumetric Efficiency VE Table Calibration

So now the MAF has failed, but the PCM won't start solely using the VE Table until a failure code is written to the log. So in order to do that we need to go to Engine Diag \ DTCs tab and change the Error Mode on P0103 Mass or Volume Air Flow A Circuit High to MIL on First Error.

This way as soon as the PCM sees the MAF has exceed 100 Hz it will write a P0103 code to the log and acknowledge the MAF has failed and only use the VE Table for airmass calculations.

If we were to leave the Error Mode on MIL on Second Error, we would need to start the truck run it, then turn it off, and start it a second time and hope the code was thrown on the second start.

Now as far as the SES Service Engine Soon light, you can leave that on or you can leave that off it does not effect functionality, it just lights up the check engine light. I prefer not to turn it on because I expect this error, but I may want to see others so I don't want it coming on and me thinking it's just this MAF failure and ignore it.

also very important, in Speed Density mode your PCM only relies on the Low Octane table so you must copy the values from the High Octane table to the Low Octane table while calibrating the VE Table

GM considers 93 Octane high octane (if all you can find is 91 Octane in your neck of the woods, then be sure to run that) hey if you are taking the time to tune your engine, then I assume you are feeding it the good stuff

the High and Low Octane tables can be found under the Engine \ Spark \ Advance section

during the calibration process both tables need to match, afterwards you can change the Low Octane table back to Low Octane values or leave it set same as the High Octane if you promise to always fill your tank with High Octane fuel (once we get to tuning Timing Advance we will check for knock and may reduce the Low Octane table manually by 2 or 4 degrees)

[Gregski]

Volumetric Efficiency VE Table Calibration

and that's all there's to it to disable the MAF and run in what the cool kids call Speed Density mode (pronounced: only using the VE Table)

at this point just save your file (you don't have to do Save As) since we want these changes in our 01 - VE Calibration - Setup file

then write / Flash these changes to the PCM

and just as with the MAF we don't want to stay in this tune for days, weeks, months, this is just for like a 20 or 30 minute drive with controlled throttle changes and staying out of WOT

[Gregski]

Volumetric Efficiency VE Table Calibration

Now we turn our attention to the VCM Scanner where we have to setup some channels to capture the data and create a histogram aka a fancy graph to mimic the VE Table in order to plot the percent errors.

Just as with the MAF you can calibrate the VE Table 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 mehod, 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]

Volumetric Efficiency VE Table Calibration

We only need three sets of Channels to calibrate the VE Table.

Engine RPM
Manifold Absolute Pressure
Fuel Trims

How do you know what Channels you need?

Well you look at the table you are going to tune and make sure you can build a Histogram (graph) to match.

For example, we look at our VE Table and see that the X axis is made up of Engine Speed (rpm) so we know we have to add the Engine RPM (SAE) channel, the names don't match exactly but that's just how HP Tuners does it, you get the idea though, it's basically RPM.

Same goes for the Y axis, the VE Table in the VCM Editor has Manifold Absolute Pressure (kPa) as the Y axis, so we add the Intake Manifold Absolute Pressure (SAE) channel in the VCM Scanner.

And the values in the table come from the Short Term Fuel Trims and the Long Term Fuel Trims because we are using them to calibrate in Closed Loop as opposed to using a Wideband, that's a decision we made ahead of time.

The SAE is the default flavor of the channels that's all, some folks grab them first some grab the ones without the SAE suffix.

Once you added your channels I suggest you save them for future use.

[Gregski]

Volumetric Efficiency VE Table Calibration

next we will add a Histograph aka Graph to our Channels, remember you can only build the graph out of the Channels you have previously added, if it aint in the list of channels you can't add that parameter to the graph. The graph is in the right pane in the screen shot below, and looks exactly like the VE Table except right now it is blank.

[Gregski]

Volumetric Efficiency VE Table Calibration

If we unpin the Channels on the left by clicking on that little thumb tack in the Channels upper right corner, that entire Channels pane will shift out of the way and to the left, so that we can appreciate the Graph in all it's glory. I wanted to just show you how the columns match the RPM break points in the VE Table column for column all the way from 400 to 8000 that's very important, as is matching the Y axis from 15 to 105 kPa or what ever values your VE Table has.

[Gregski]

Volumetric Efficiency VE Table Calibration

and here are the detailed properties of that graph

Label: call it what ever you want "VE Tune" or "LTFTSTFT VE" what ever fits in that little box

Parameter: LTFT + STFT [Math] this is a special computation provided to us by HP Tuners

Cell Hits Required: the more the better I think I usually set this to 20

High Value: 20 make it show lean in Red

Low Value: -20 make it show rich condition in Green

Column Axis
Parameter: and here's our X axis aka Engine Speed [Sensor] aka RPM

Note: to make RPMs look like RPMs set the Header Cell Factor to 1 otherwise they will look like decimals such as 1.2 or 1.6 instead of 1200 and 1600

Values: cut and paste these from the VE table in the VCM Editor by right clicking anywhere in that table and choosing Column Axis / Copy Labels

Row Axis
Parameter: and this is our Y axis aka Manifold Absolute Pressure [Sensor] so kPa

Values: cut and paste these from the VE table in the VCM Editor by right clicking anywhere in that table and choosing Row Axis / Copy Labels

[Gregski]

Volumetric Efficiency VE Table Calibration

Once you created your graph I suggest you save it for future use.

[Gregski]

Volumetric Efficiency VE Table Calibration

alright with the changes in the VCM Editor written to the PCM, and our Channels and a Graph setup in VCM Scanner we are ready to do some driving around and logging, but first make sure you warm up your truck

How do we ensure our rigs are properly warmed up? Take it for a spin around the block, it's honestly the best way to bring it up to operating temp - think 194* F.

Now all you are going to do is log the data as you drive around. No one says you have to use this information to do anything, you can just look at it. I say this to relax you, so that if you forgot to do something - missed a step, if your laptop dies half way through the drive, so what, no big deal, no problem, no worries.

Gentlemen, and ladies, we are learning here, so please give yourself the permission to fail, it's ok, that's how we learn.

[Gregski]

Volumetric Efficiency VE Table Calibration

after your first test drive is over save the log file with a name that means something to you, 01 Test Drive Around the block.hpl I like to make my first test drive nice and short just around the block to catch any huge anomalies such as you running way too lean, or the engine running way too hot, or crazy knock etc

I also create a folder under my VE Calibration called Logs and under that create sub folders called First Attempt and Second Attempt and save all my logs there like so

again this isn't so much for now ie today, it is for looking back at it six months from now... think long term historical data

[Gregski]

Volumetric Efficiency VE Table Calibration

So now that we've recorded our short (5 mins) test drive around the block lets take a peek at the results, so open the log file in VCM Scanner.

It may look something like this, pink!

[Gregski]

Volumetric Efficiency VE Table Calibration

Let's just zoom in on that graph aka the right side of the previous screen shot.

This is pretty typical of what you may see, when doing this for the first time on your stock(ish) engine.

The factory likes to run these engines hot and lean do to fuel economy and emissions constraints.

We will take some liberties with these settings and tune for Power and Performance.

As with the MAF based on this data we could just go into the VCM Editor and bump the entire VE Table by 10% so multiply it by 1.10

again going from lean (pink) to rich (green) in such a big jump fashion is acceptable as you are not going to hurt anything by going fat and happy

[Gregski]

Volumetric Efficiency VE Table Calibration

As with the MAF, before we go making any changes to the VE Table don't forget to take a look at the graph. We do so by clicking the Horizontal Split icon on the top menu bar (red arrow) or which ever split you prefer.

Unlike the two dimensional MAF graph the VE graph is three dimensional, and you can rotate it aka spin it around to see it from all the different angles, simply right click it with your mouse and have at it.

[Gregski]

Volumetric Efficiency VE Table Calibration

So this is a close up of the stock factory VE Table graph, notice how it's pretty good but still has some sharp peaks and valleys, that's ok, when you create your own don't get too carried away with smoothing it out, you don't want crazy random spikes in it, but also you don't want to smooth it out so much that you smooth out majority of your changes.

[Gregski]

Volumetric Efficiency VE Table Calibration

Alright so based on your first test drive you may determine that you are 5% lean or 10% lean or 15% lean, etc. At this point you can increase your VE Table 10% for example and lift the entire graph up to get yourself out of the Danger Zone.

There are some tuners who will bump the VE Table up 15% before even going for the first test drive if they are tuning an engine with a bigger cam for example.

PROS of bumping the entire graph by a fixed amount include:
1. Easy and quick to do, you select all the cell and then just type 1.10 in the box on the menu bar and click X
2. You maintain the natural shape of the graph, same peaks same valleys, you're essentially just raising the entire thing by 10%

CONS of bumping the entire graph by a fixed amount:
1. Not all cells may need to be richened up like that, it's not a precise calibration

However keep in mind, this is just the first step, the first attempt, nothing saying you can't go for a second drive, then adjust the graph some more, then go for a third drive and adjust it even further.

[Gregski]

Volumetric Efficiency VE Table Calibration

We are going to take the more precise approach for demonstration purposes.

In the VCM Scanner select all the data in the Histogram (graph) by clicking in the upper most left hand cell (just like you would in Excel) then right click and click on Copy, we want to copy all the cells, one's with and without values, doing so will ensure that when we go to paste these correction in the VE Table their position will be relative, ie they will only change the exact cells that have these corrections.

[Gregski]

Volumetric Efficiency VE Table Calibration

Now you go to the VCM Editor you pull up the VE Table and you select all the cells and right click and do Paste Special \ Multiply by %

This is a special feature of HP Tuners that makes our lives easier, no longer do you need to remember if you need to multiply by a number greater than 1 such as 1.10 to richen things up when your graph in VCM Scanner show pink values, or multiply by a number less than 1 such as .90 to lean things out if your scanner shows green values that are too rich.

Also on the first calibration attempt it is ok to multiply by percent afterwards on your second and third test drives you can Multiply by % - Half to make more incremental changes, but as always you do you!

[Gregski]

Volumetric Efficiency VE Table Calibration

and here's the result of that Paste Special - Multiply by %

notice how only the cells with values in our VCM Scanner graph have been altered here and the rest were un affected, that's how that works

OK so save this file with a new name, something like 02 - VE Calibration - Multiply By Percent.hpt and write / Flash the changes to the PCM

[Gregski]

Volumetric Efficiency VE Table Calibration

OK, now it is time to go for a second drive and test our changes. So just as before go around the block again, replicate the same first drive with no sudden throttle changes and record / log the data.

Save your file as something like 02 Secont Test Drive Around the block.hpl

[Gregski]

Volumetric Efficiency VE Table Calibration

lets compare the results of our second test drive, looks like the numbers went down, we are less pink, we are moving in the right direction but still no green cells