converting VE% to engineering units

[MICK]

Hi,

Does anybody know a formular for converting VE% into engineering units.


cheers

mick

[Alvin]

Hi,

Does anybody know a formular for converting VE% into engineering units.


cheers

mick

Effeciency will not have a unit.

[redhardsupra]

yea except that our VE isn't a real volumetric efficiency, there's like temperature in there and some other things that don't quite cancel out.

[MICK]

yea except that our VE isn't a real volumetric efficiency, there's like temperature in there and some other things that don't quite cancel out.

Thanks for your reply. I have been checking out a few other excell spreadsheets that you have put together. Their pretty cool.

I can look at the relationship of a pre set figure and compair the differences (VE % TO Engineering Units) and form a table but its not quite as good as crunching the numbers in a formular ( if one was available).

So my question is. If I were to built a crossover table it would only be as good as the detail I put into it. Could I use this in a spread sheet that I have made and use it to convert VE% to Engineering Units....?


Really like the work you have done redhardsupra. Do you have any thoughts here.

cheers

mick

[redhardsupra]

yes, that's why i'm so anal about keeping things as constant as possible. i've seen changes based on fuel temperature, cooling capacity, variances in battery voltage, and other things that noone usually monitors, yet introducing 'noise' that we cannot account for emprically. having solid hardware really cleans up your signal and limits variation in your data, yielding better, more consistant results quicker.

if you wanna see the formula involved in getting the VE numbers read the 've table cracked' sticky in the pcm section on ls1tech.
i've been thinking of building a probabilistic model just to see where the biggest variances are, so we could locate the biggest sources of noise.

[joecar]

If you're reading the VE table from flash, you can select it's data units to be g.K/kPa.

From the units you can see that it's not really VE, but rather airmass scaled for absolute temp and pressure.

[superls1]

There are 4 views of which can be selected when viewing the VE table in EFILive:
<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>

g*K/MAP
% of Theoretical Maximum
g/cylinder
g/second<o:p></o:p>
The last two options, g/cylinder and g/second, allow an additional attribute to be considered which is Temperature. The default value appears to be 21* C.
<o:p></o:p>
EFILive indicates the formula for g/cylinder to be:
<o:p></o:p>
g/cyl = VE * MAP / charge temp
<o:p></o:p>
VE is in g*K/MAP
MAP is in kPa
Charge Temp is in kPa
<o:p></o:p>
So in units,
<o:p></o:p>
g/cyl = g*K/kPa * kPa / K
<o:p></o:p>
g/cyl = g
<o:p></o:p>
EFILive indicates that charge temp is calculated as:
<o:p></o:p>
273.15+IAT+((ECT-IAT)*factor)
<o:p></o:p>
Where IAT and ECT are in C
<o:p></o:p>
Factor is a value that can be modified through EFILive. They indicate a range of 0 – 2 in which a value close to 0 will favor/bias IAT.
<o:p></o:p>
<o:p></o:p>
My problem with the VE Table Cracked Thread (http://http://www.ls1tech.com/forums/showthread.php?t=149741&page=1&pp=20) is that nothing was ever resolved in that discussion. Here are some of the formulas posted in that thread:
<o:p></o:p>
Posted by NoGo


VE = ((massflow * IAT / (MAP * RPM * Displacement))

Massflow: grams/sec
IAT: Degrees Kelvin
MAP: Bar
RPM: Duh!
Displacement: Cubic Meters<o:p></o:p>
<o:p></o:p>
Posted by gameover
The PCM g/cyl calc for the VE table is:

g/cyl x 8192 = VEvalue * MAP * 51.2 / (IAT * 32)<o:p></o:p>
<o:p></o:p>
Posted by HumpinSS


Nogo'sve% = MAF.gp/s*(IAC+273)/((346*RPM)*MAP)*212544

gameover's = Ve= g/cy * ((IAT+273)*5120)/MAP(kpa)/cyl colume/178 derived from original formula of

ve . (178.33) . (0.708 . map / (iat+273) . 5120 = 0.85 g/cyl<o:p></o:p>
Posted by DVCrazyCamTAWS6


this is the expression i'm using to crack the VE in EFILIVE
({SAE.J1979.MAF} * {SAE.J1979.IAT} / ({SAE.J1979.MAP} * {SAE.J1979.RPM} * 0.0059))

0.0059 = 364ci 6.0L
0.0056 = 346ci 5.7L

Must Set PIDs to : (or will not work)

MAF = UNITS- Grams/Sec, FACTOR - 0.010000, OFFSET - 0 (limits = 0 to 530)
IAT = UNITS- Kelvin, FACTOR - 1, OFFSET - 233.15 (limits = 0 to 500)
MAP = UNITS- BAR, Factor - 0.010000, OFFSET - 0 (limits = 0 to 1.0500)

Expression : (MAF x IAT x / (MAP x RPM x DISPLACEMENT))<o:p></o:p>
<o:p></o:p>
And there were a couple references to this VE calculation (http://www.installuniversity.com/install_university/installu_articles/volumetric_efficiency/ve_computation_9.012000.htm)

[blandmiller]

So, if I am reading this right:

The first view is actual flow
The second is true volumetric efficiency
The third is volumetric flowrate
And the last is mass flowrate

How do you change between the various views?

[superls1]

I don't think any of them are 'truly' VE. They all have mass in them. GM's model is more 'mass-centric' as opposed to 'volume-centric'.

The good thing is that a percentage is a percentage no matter what. So, no matter your view if the PCM needs to add 10% more fuel to achieve a desired AFR you simply need to add 10% to the number in the table. The frustrating part is that if you are someone that wants to know 'how' it all actually works it is fairly complicated, and in reality you need some engineering background in: computational methods (regression, dimensional analysis, etc), thermodynamics, compressible flow, etc.

To change display units, Menu Edit->Properites (shortcut is Alt+Enter)

[blandmiller]

I have the Engineering background covered. I have just never calculated VE with any mass associated. VE has always been a percentage of theoretical maximum.

[joecar]

It is callled the "VE table", but it really is the "cylinder airmass table". ;);)

[Blacky]

As has been said by a number of posters, the "VE table" in the LS1 PCM is not a true VE table. It is a "massometric" table. It defines the predicted mass of air in a cylinder at any given MAP/RPM combination. The table predicts the *real* mass of air in grams so it is easier for the PCM to calculate the correct mass of fuel via the IFR table(s) required to achieve the commanded AFR.

EFILive has just been in CA, working very closely with EFI University to make sure the EFILive Training course that will soon be available is 100% accurate. Ben from EFI University grilled us unmercifully for two days about the "hows" and "whys" of GM's version of the "VE table". Over the course of 2 days, I think I lost 4 out of 4 "wagers" with Ben, he is too clever and has too much experience.:master:

Anyway a number of interesting things were tested that really puts the whole "VE table" in perspective. I won't try and explain what was figured out during our time with Ben, that research was conducted by EFI University and I am not at liberty to post their results on a public forum.

I highly recommend getting along to the EFILive 101 course when it is available. There will be some pretty eye-opening revelations and a sprinkling of "internet mythbusting".

Regards
Paul

[blandmiller]

Blacky, how did you lose a wager to a 'Base Efficiency Numerator'? Just kidding, I couldn't resist.

I guess we will wait for the EFI University course to get an explaination of GM's 'black art' VE tables.

[GMPX]

Blacky, how did you lose a wager to a 'Base Efficiency Numerator'? Just kidding, I couldn't resist.

Blacky said 4.........I was there, I know the real number :muahaha:
Your LL8 is a little better, it was designed to be a stand alone S.D system, not like the LS1, the S.D mode on the LS1 has always been a backup mode for a MAF faliure, we just exploit it!.

Cheers,
Ross

[caver]

I highly recommend getting along to the EFILive 101 course when it is available. There will be some pretty eye-opening revelations and a sprinkling of "internet mythbusting".

That,the advanced course and the certified course are my 1st priorities besides a roof and a job when I get to Ozz

[EFIGUY]

Guys,
Here is a look at the course outline for the EFILive training course.

While a lot of it is a basic look at how to operate the software, some time will also be spent on general tuning theory like: how to choose an A/F ratio, how to properly tune the ignition timing, why road tuning cannot match the performance of dyno tuning, etc.

We will look briefly at how some of the tables work, like the "VE" table, but the course is ABSOLUTELY NOT an engineering look at how the inner workings of a GM PCM work.

This is not an advanced level workshop for guys who have been long-time users of EFILive and are looking for engineering level answers to problems.

If you want to know how and why an engine works, and how to tune it, (using EFILive) then the course is for you.

We plan to release a schedule with various dates around the USA in the next week or so.



I. Introduction to EFILive FlashScan
a) What is it<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
b) What can it do<o:p></o:p>

II. Installing the software<o:p></o:p>

III. Scan Tool<o:p></o:p>

IV. Connecting to the vehicle<o:p></o:p>

V. Selecting PIDs<o:p></o:p>

VI. Configuring the dashboard, and charts<o:p></o:p>

VII. Creating MAPS for data collection<o:p></o:p>
a) Selecting data<o:p></o:p>
b) Setting up axis’<o:p></o:p>
c) Setting filters<o:p></o:p>

VIII. Collecting the data during operation<o:p></o:p>
a) On the street<o:p></o:p>
b) On the dyno<o:p></o:p>
c) Black-Box logging<o:p></o:p>
1) Set up<o:p></o:p>
2) Collecting<o:p></o:p>
3) Extracting data from Black Box<o:p></o:p>

IX. Bi-Directional Controls<o:p></o:p>
a) Control panel<o:p></o:p>
b) Idle Air Control<o:p></o:p>
c) Cylinder Balance Test<o:p></o:p>
d) CKP Learn<o:p></o:p>
e) Changing VIN’s<o:p></o:p>


X. Tuning Tool<o:p></o:p>

XI. Reading the calibration from the ECU<o:p></o:p>

XII. Saving to a file or folder<o:p></o:p>

XIII. Table definitions
a) Fuel tables<o:p></o:p>
1) Main VE Table<o:p></o:p>
2) PE Modifiers / EQ Ratios<o:p></o:p>
3) Closed Loop<o:p></o:p>
b) Ignition Tables<o:p></o:p>
1) High Octane<o:p></o:p>
2) Low Octane<o:p></o:p>
3) Using Spark to Control Idle<o:p></o:p>
c) Idle control Tables<o:p></o:p>
d) MAF Tables<o:p></o:p>
e) Rev Limiters<o:p></o:p>

XIV. Making Changes to Calibrations<o:p></o:p>
a) Entering changes manually<o:p></o:p>
b) Using the %, +/-, and # tools<o:p></o:p>
c) Smoothing cells<o:p></o:p>
d) Filling cells with linear data<o:p></o:p>
e) Moving forwards and backwards in calibrations<o:p></o:p>
f) Saving current file<o:p></o:p>
g) Saving new file<o:p></o:p>
h) Sending to the PCM<o:p></o:p>

XV. Using data from the Scan Tool<o:p></o:p>
a) Copy special<o:p></o:p>
b) Paste special<o:p></o:p>
c) BEN Factor <o:p></o:p>

XVI. Miscellaneous Functions<o:p></o:p>
a) Speedometer Calibration<o:p></o:p>
b) Tire size calculator<o:p></o:p>
c) Configuring display units<o:p></o:p>
d) File compare functions<o:p></o:p>
e) Modification summary<o:p></o:p>
f) Table Search function<o:p></o:p>


XVII. Installing a Custom Operating system<o:p></o:p>
a) Which version is right for you?<o:p></o:p>
b) Step by Step<o:p></o:p>
c) Things to watch our<o:p></o:p>

XVIII. Understanding Fuel and ignition requirements<o:p></o:p>
a) Selecting the proper A/F ratios<o:p></o:p>
1) Idle<o:p></o:p>
2) Cruise<o:p></o:p>
3) Power<o:p></o:p>
b) Getting the correct timing<o:p></o:p>
1) Knock Retard Count<o:p></o:p>
2) Knock retard Amount<o:p></o:p>
3) Proper Dyno Calibration<o:p></o:p>

XIX. Proper Dyno Tuning Procedures<o:p></o:p>
a) Strapping<o:p></o:p>
b) Driving safety<o:p></o:p>
1) Vehicle control<o:p></o:p>
2) Using the Brakes<o:p></o:p>
3) Using the clutch to prevent over-running the engine<o:p></o:p>
4) Circle of Awareness<o:p></o:p>
c) Thought process for tuning from beginning to end


-Ben<o:p></o:p>
<o:p></o:p>

[MICK]

yes, that's why i'm so anal about keeping things as constant as possible. i've seen changes based on fuel temperature, cooling capacity, variances in battery voltage, and other things that noone usually monitors, yet introducing 'noise' that we cannot account for emprically. having solid hardware really cleans up your signal and limits variation in your data, yielding better, more consistant results quicker.

if you wanna see the formula involved in getting the VE numbers read the 've table cracked' sticky in the pcm section on ls1tech.
i've been thinking of building a probabilistic model just to see where the biggest variances are, so we could locate the biggest sources of noise.


Funny you should say noise. I found some converting back to VE when referencing the same preset figure at a different map table location. Was very noticeable in the area just off idle, very interesting?

Thanks mick

[redhardsupra]

sure, just off idle is usually transitory, how many times do you actually cruise at 6mph? however the values corresponding to cruising at 35, 55, 75mph (usual speeds in city/hiway) are usually pretty dead on. i bet you they're directly proportional to the number of samples gathered.

[MICK]

sure, just off idle is usually transitory, how many times do you actually cruise at 6mph? however the values corresponding to cruising at 35, 55, 75mph (usual speeds in city/hiway) are usually pretty dead on. i bet you they're directly proportional to the number of samples gathered.

No Not Really. I am not gathering my info from Scaned Data. I am using two different softwares to look at the VE table of the same tune cal in bin format. (Cats OBD2 Engineering Units and EFI live VE). Then I compair a preset figure at different map table location and this is where I am finding differences in the VE % table compaired to the Engineering Units. It almost looks like temp and pe might have a play in the VE table where Engineering units table is raw code data converted without any extras. Not sure?

cheers

mick