Big Cube VE tables

[superls1]

Are the VE #'s really meant to represent actual efficiency or are they just a number that I increase to add fuel and decrease to remove fuel?

Anybody want to post up some tuned VE table values for larger displacement motors? Cam specs would be nice too. Thanks.

[Dirk Diggler]

Make sure your ifr table is represented correctly or you will get crazy looking ve values (too high or too low)

[Blacky]

Are the VE #'s really meant to represent actual efficiency or are they just a number that I increase to add fuel and decrease to remove fuel?

Anybody want to post up some tuned VE table values for larger displacement motors? Cam specs would be nice too. Thanks.

Yes the VE is the actual efficiency of the engine's ability to fill the cylinders with air.
i.e. 100% means the cylinder is full of air
80% means the cylinder is 80% full of air
etc

Based on the cylinder volume, manifold pressure and air temperature, the theoretical maximum mass of air that will fit into a cylinder can be calculated. What the VE table does is tell the PCM how close to 100% of that theoretical mass of air is "predicted" to fill the cylinder at any given MAP/RPM point.

Regards
Paul

[daveb]

I am planning to stroke my engine to 383ci, if I change the displacement in the vehicle info section will it scale the VE table accordingly or will they always remain for a 350ci, meaning I will have larger numbers in the VE?

[Dirk Diggler]

I am planning to stroke my engine to 383ci, if I change the displacement in the vehicle info section will it scale the VE table accordingly or will they always remain for a 350ci, meaning I will have larger numbers in the VE?

You need to scale (B0104} that also since it is used in a few calculations like dynamic_airflow

[joecar]

Paul,

Can I calculate VE as follows...?

1. For various RPMs use the formulas to calculate theoretical volume sucked in by engine in 1 rev; convert volume to mass using density of air.

2. At the same RPMs, take MAF readings; calculate how much time 1 rev takes, and multiply MAF readings by this to get mass.

3. Divide mass from step by mass from step 1; this is VE.

(...assuming the MAF table is correct and the MAF is working correctly...)
(...implies you first have to get your MAF calibration measured...)

Is there a simpler way to do this...?

[Dirk Diggler]

Tune it in SD first and then use the dynamic_cylinder_air values converted to gm/sec and rebuild the maf table...

[Blacky]

I am planning to stroke my engine to 383ci, if I change the displacement in the vehicle info section will it scale the VE table accordingly or will they always remain for a 350ci, meaning I will have larger numbers in the VE?

If you change the displacement, say from 346 to 383, then that's a percentage change of ((383-346)/346)*100=10.7%. So you need to add 10.7% to all cells in the VE tables - after you change the cylinder volume.

Follow these steps:
1. Open your *.tun file.
2. Change {B0104} to 47.875 CI
3. Save the file.
4. Close the file.
5. Reopen the file (notice the VE cells* are now 10.7% lower)
6. Select all cells in the VE table(s)
7. Enter 10.7 in the Adjust box on the toolbar
8. Click the [%] toolbar button.

* if the VE table is displayed as a % you will see lower values. If the VE table is displaed as the "standard" PCM units of Grams*Kelvin/kPa then the values will not be different (because those units do not include any cylinder volume information). Regardless of the display units, you must always add in the % change that you made to the engine displacement.

You will probably need to retune the VE table anyway because the VE characteristics will most likely change with the new crank. But the % change will get you back close to where it should be.

Paul

[Blacky]

Paul,

Can I calculate VE as follows...?

1. For various RPMs use the formulas to calculate theoretical volume sucked in by engine in 1 rev; convert volume to mass using density of air.

2. At the same RPMs, take MAF readings; calculate how much time 1 rev takes, and multiply MAF readings by this to get mass.

3. Divide mass from step by mass from step 1; this is VE.

(...assuming the MAF table is correct and the MAF is working correctly...)
(...implies you first have to get your MAF calibration measured...)

Is there a simpler way to do this...?

Step 1 - I presume you mean theoretical maximum mass of air at a given temp/pressure. If I recall correctly, it's about 0.8 grams of air per cylinder at STP for a 5.7 LS1.

Might as well calculate it out using PV=nRT (or n=PV/RT)
where:
n = m/M (m=mass of air in grams,M=molar mass of air=28.96)
mass of air = PVM/RT
P = pressure 101.3kPa
V = 0.70874 liters per cylinder (5.669 liter engine)
R = 8.314 (gas constant)
T = 294.15Kelvin (21 degrees C = room temperature)
so
m = (101.3*0.70874*28.96)/(8.314*294.15)
m = 2079.19/2445.56
m = 0.85 grams of air per cylinder. But remember that is only accurate at 21DegC and 101.3kPa. It will be different at different temps/pressures.

Step 2 - is already done for you by EFILive - the PID you want to use is grams/cylinder = {SAE.MAF.gps}*15/{SAE.RPM}

Step 3 - I proposed this same method, taking into account the different temps/pressures (back before we did the VE tuning using the BEN factor) and got shot down in flames - but I can't remember why.
It may have been simply that the MAF wouldn't flow high enough values to allow us to use that method to tune 2 and 3 bar VE tables.

There is another way, just use a wideband and EFILive's BEN factor/auto-VE tuning, the combustion process does not lie - unless there is an air leak somehwhere :)

Regards
Paul

[superls1]

Great info guys.

However, I would still like to see some VE tables for larger cubed motors.


If you change the displacement, say from 346 to 383, then that's a percentage change of ((383-346)/346)*100=10.7%. So you need to add 10.7% to all cells in the VE tables - after you change the cylinder volume.
Paul

I thought the VE changed automatically after changing cylinder volume?
From the VE table info:

EFILive uses the cylinder volume to calculate the VE as a percentage.
Changing the cylinder volume will change the VE percentages displayed in this table.

I am sure that I just need to play more, but I am a newbie and learning so please forgive. Are you saying that if cell says 50 when CI=346, when changing cylinder volume to equate to 383CI it will then read ~45. Therefore, I must increase it by 10.7% to get it back to 50? Would this then be my base for starting my VE tune?

[superls1]

Never mind, I re-read your post and I get it now. Thanks for the info.

[joecar]

Paul,

Can I calculate VE as follows...?

1. For various RPMs use the formulas to calculate theoretical volume sucked in by engine in 1 rev; convert volume to mass using density of air.

2. At the same RPMs, take MAF readings; calculate how much time 1 rev takes, and multiply MAF readings by this to get mass.

3. Divide mass from step by mass from step 1; this is VE.

(...assuming the MAF table is correct and the MAF is working correctly...)
(...implies you first have to get your MAF calibration measured...)

Is there a simpler way to do this...?

Step 1 - I presume you mean theoretical maximum mass of air at a given temp/pressure. If I recall correctly, it's about 0.8 grams of air per cylinder at STP for a 5.7 LS1.

Might as well calculate it out using PV=nRT (or n=PV/RT)
where:
n = m/M (m=mass of air in grams,M=molar mass of air=28.96)
mass of air = PVM/RT
P = pressure 101.3kPa
V = 0.70874 liters per cylinder (5.669 liter engine)
R = 8.314 (gas constant)
T = 294.15Kelvin (21 degrees C = room temperature)
so
m = (101.3*0.70874*28.96)/(8.314*294.15)
m = 2079.19/2445.56
m = 0.85 grams of air per cylinder. But remember that is only accurate at 21DegC and 101.3kPa. It will be different at different temps/pressures.

Step 2 - is already done for you by EFILive - the PID you want to use is grams/cylinder = {SAE.MAF.gps}*15/{SAE.RPM}

Step 3 - I proposed this same method, taking into account the different temps/pressures (back before we did the VE tuning using the BEN factor) and got shot down in flames - but I can't remember why.
It may have been simply that the MAF wouldn't flow high enough values to allow us to use that method to tune 2 and 3 bar VE tables.

There is another way, just use a wideband and EFILive's BEN factor/auto-VE tuning, the combustion process does not lie - unless there is an air leak somehwhere :)

Regards
Paul

Oh yes, the gas equation does come in handy (after so many years). :D :lol:

What is the "BEN factor"...? :?:

[Blacky]

Oh yes, the gas equation does come in handy (after so many years). :D :lol:

Yeah, back in high school, who'da thought chemistry 101 was ever going to be needed in the "real world".


What is the "BEN factor"...? :?:
BEN stands for "Base Efficiency Numerator". (And may also have something to do with the name of the person that explained how to implement it correctly).
Its a calcualted PID that computes the correction factor that needs to be applied to the VE table based on the difference between the commanded AFR and the actual/measured AFR (requires a wide band O2 sensor).

Look for the BEN PIDs in the calculated PIDs section.
Also serch the forum for BEN factor - there have been a few discussions about it.

There is also a BEN filter that can be applied (prior to using the data to update the VE table) to remove data frames where the throttle is changing rapidly (more than 5% in 100ms).

Paul

[bink]

There is also a BEN filter that can be applied (prior to using the data to update the VE table) to remove data frames where the throttle is changing rapidly (more than 5% in 100ms).


Where can we find the BEN data filter??? :?
TIA. :D


Cheers,
joel

[Blacky]

You can custom define any data filters you like...

[bink]

:shock: .....speechless!


That is too slick!! :mrgreen:

Thanks for the quick reply. You guys are amazing at your customer support. A big thumbs up.

Cheers,
joel

[hpcubed]

I am planning to stroke my engine to 383ci, if I change the displacement in the vehicle info section will it scale the VE table accordingly or will they always remain for a 350ci, meaning I will have larger numbers in the VE?

If you change the displacement, say from 346 to 383, then that's a percentage change of ((383-346)/346)*100=10.7%. So you need to add 10.7% to all cells in the VE tables - after you change the cylinder volume.

Follow these steps:
1. Open your *.tun file.
2. Change {B0104} to 47.875 CI
3. Save the file.
4. Close the file.
5. Reopen the file (notice the VE cells* are now 10.7% lower)
6. Select all cells in the VE table(s)
7. Enter 10.7 in the Adjust box on the toolbar
8. Click the [%] toolbar button.

* if the VE table is displayed as a % you will see lower values. If the VE table is displaed as the "standard" PCM units of Grams*Kelvin/kPa then the values will not be different (because those units do not include any cylinder volume information). Regardless of the display units, you must always add in the % change that you made to the engine displacement.

You will probably need to retune the VE table anyway because the VE characteristics will most likely change with the new crank. But the % change will get you back close to where it should be.

Paul

If the VE is displayed as a percentage, the percentage is a ratio of the volumetric efficiency of the engine to the theoretical max volumetric efficiency for the engines displacement. Also check out this link for more info
http://www.installuniversity.com/install_university/installu_articles/volumetric_efficiency/ve_computation_9.012000.htm

[superls1]

If the VE is displayed as a percentage, the percentage is a ratio of the volumetric efficiency of the engine to the theoretical max volumetric efficiency for the engines displacement. Also check out this link for more info
http://www.installuniversity.com/install_university/installu_articles/volumetric_efficiency/ve_computation_9.012000.htm

Has anyone ever tried this? I tried setting up a spreadsheet to perform the equations based on scan data. However, I seemed to get VE %'s that were significantly different than the actual table. Is this because the VE table uses "perfect" values/conditions like mentioned by Blacky?

I seemed to have more consistent results with this methodolgy (http://67.43.173.134/StupidWidebandTricks.htm).

[superls1]

So, why no VE table values posted yet? It seems this whole SD tune is the current fad, and with tools like autotune why not. However, I still don't see much data. I saw a few graphs posted on ls1tech. Anybody want to at least share their differences from stock to a tuned VE?

[superls1]

Is VE affected by RPM? If so, why do I get the same value ~2.468 when backing into "max" air by using/comparing VE table in both numerical units and percentage. For example

@ 400 RPM and 15kPa I see 1.029883 g*K/kPa or 41.72228% which indicates a "max" of 2.46825

@ 8000 RPM and 15kPa I see 1.268945 g*K/kPa or 51.4071% which indicates a "max" of 2.46824

Wouldn't the "max" increase as RPM increased? I took chemistry, but it was a long time ago. So, I probably just don't get it.

[joecar]

Is VE affected by RPM? If so, why do I get the same value ~2.468 when backing into "max" air by using/comparing VE table in both numerical units and percentage. For example

@ 400 RPM and 15kPa I see 1.029883 g*K/kPa or 41.72228% which indicates a "max" of 2.46825

@ 8000 RPM and 15kPa I see 1.268945 g*K/kPa or 51.4071% which indicates a "max" of 2.46824

Wouldn't the "max" increase as RPM increased? I took chemistry, but it was a long time ago. So, I probably just don't get it.

Isn't "max" your theoretical 100% volume (which shouldn't change with RPM)....? :?:

[superls1]

Is VE affected by RPM? If so, why do I get the same value ~2.468 when backing into "max" air by using/comparing VE table in both numerical units and percentage. For example

@ 400 RPM and 15kPa I see 1.029883 g*K/kPa or 41.72228% which indicates a "max" of 2.46825

@ 8000 RPM and 15kPa I see 1.268945 g*K/kPa or 51.4071% which indicates a "max" of 2.46824

Wouldn't the "max" increase as RPM increased? I took chemistry, but it was a long time ago. So, I probably just don't get it.

Isn't "max" your theoretical 100% volume (which shouldn't change with RPM)....? :?:

I guess I should say per unit of time. The engine definitely moves more air at 8000 RPM's than it does at 400 RPM's. No? So, my assumption was that if the VE table was used in a fueling equation that the values in the table might increase as RPM increased.

It is probably just a lack of understanding of the units on my part. I guess I was thinking that the table represented actual air moving through the motor. The units do not indicate that, but the algorithm could by accounting for RPM.

[Ira]

I guess I was thinking that the table represented actual air moving through the motor. The units do not indicate that, but the algorithm could by accounting for RPM.

The table refers to the amount of air going into each cylinder on each intake stroke. It usually has the biggest numbers at the torque peak.

Ira

[Blacky]

It is probably just a lack of understanding of the units on my part. I guess I was thinking that the table represented actual air moving through the motor. The units do not indicate that, but the algorithm could by accounting for RPM.

The VE table does not show actual air mass (or even air flow), but percentage of theoretical maximum air mass. The maximum won't change*, that's a fixed number: 8.5 grams per cylinder in a 5.7 liter LS1.
But as MAP and RPM change so does the mass of air that enters the engine. The VE table is just a prediction of what percentage of that 8.5 grams of air is expected to enter each cylider at various rpm/map combinations.

* except for temperature and barometric changes, but the PCM compensates for those (sometimes not very well).

If the VE table reads 50% then 4.25 grams of air is expected to be in that cylinder. That is how the PCM "knows" how much air is in the cylinder and therefor how much fuel to add to achieve the current "desired" AFR.

The whole point of a MAF sensor is to calculate the mass of air entering the engine - that is why when you have a MAF sensor you don't need a VE table. Except for transient throttle conditions and MAF failure conditions.

Paul

[superls1]

It is probably just a lack of understanding of the units on my part. I guess I was thinking that the table represented actual air moving through the motor. The units do not indicate that, but the algorithm could by accounting for RPM.

The VE table does not show actual air mass (or even air flow), but percentage of theoretical maximum air mass. The maximum won't change*, that's a fixed number: 8.5 grams per cylinder in a 5.7 liter LS1.
But as MAP and RPM change so does the mass of air that enters the engine. The VE table is just a prediction of what percentage of that 8.5 grams of air is expected to enter each cylider at various rpm/map combinations.

* except for temperature and barometric changes, but the PCM compensates for those (sometimes not very well).

If the VE table reads 50% then 4.25 grams of air is expected to be in that cylinder. That is how the PCM "knows" how much air is in the cylinder and therefor how much fuel to add to achieve the current "desired" AFR.

The whole point of a MAF sensor is to calculate the mass of air entering the engine - that is why when you have a MAF sensor you don't need a VE table. Except for transient throttle conditions and MAF failure conditions.

Paul

Thanks. Great info. :)

I was just thinking about it in terms of expected air flow through the engine for each RPM and MAP intersection as oppsed to maximum air mass.

[superls1]

I would still like to see some tuned VE tables then. Forget the big cube request. There just don't seem to be very many posted. Why? I haven't tried doing mine yet. I guess I just want to know everything before jumping in including "what" it might look like.

[superls1]

I do have one more question: How does SD account for humidity? Humid air is less dense. So, if I tune my car when humidity avg's 50%, but in the summer it averages 80% what will happen? Just run pig rich for a while until LTFT's go really negative?

[GMPX]

I would still like to see some tuned VE tables then. Forget the big cube request. There just don't seem to be very many posted. Why? I haven't tried doing mine yet. I guess I just want to know everything before jumping in including "what" it might look like.

Try one of the web sites to download bin / tun files, there is sure to be an 8.1L file on one of them.

Cheers,
Ross

[GMPX]

I do have one more question: How does SD account for humidity? Humid air is less dense. So, if I tune my car when humidity avg's 50%, but in the summer it averages 80% what will happen? Just run pig rich for a while until LTFT's go really negative?

SD compensates for humidity just like a MAF does...it err, doesn't!!!.
No humidity sensor in a MAF.
We have similar weather here in Aus up in north Queensland, PLENTY of MAFless cars up there.

Cheers,
Ross

[Ira]

I do have one more question: How does SD account for humidity? Humid air is less dense. So, if I tune my car when humidity avg's 50%, but in the summer it averages 80% what will happen? Just run pig rich for a while until LTFT's go really negative?

The change in humiditY from 50% to 80% doesn't affect the % of oxygen in the air to a significant amount. It runs a tiny bit leaner and the extra water makes it less likely to detonate so I think in the end it's basically a toss. You've never heard anyone with a carb complain about humidity messing up the mixture.

Ira

[bink]

You've never heard anyone with a carb complain about humidity messing up the mixture.

Ira

Good point!

[superls1]

I do have one more question: How does SD account for humidity? Humid air is less dense. So, if I tune my car when humidity avg's 50%, but in the summer it averages 80% what will happen? Just run pig rich for a while until LTFT's go really negative?

The change in humiditY from 50% to 80% doesn't affect the % of oxygen in the air to a significant amount. It runs a tiny bit leaner and the extra water makes it less likely to detonate so I think in the end it's basically a toss. You've never heard anyone with a carb complain about humidity messing up the mixture.

Ira

Wouldn't it run richer if fuel stays the same but oxygen decreases?

With respect to the carb statement: 1) Your statement assumes that the carb setup is tuned properly and running efficiently or producing peak power (i.e. A/F is good). How do they know? 2) I see plenty of index guys at the track with weather stations computing DA and making fueling adjustments based on that. Isn't vapor pressure/humidity a primary component of computing DA?

Give me some slack. I am learning.

One of my mistakes was misunderstanding that LTFT's can still be active while in SD. (I hope that is correct). Even with LTFT's, if the VE table is tuned when the DA is 600', and then the car is operated when DA is 5000' due to heat and humidity, won't the VE table be overly rich?

Just trying to get it all straight. Thanks for the info.