RomRaider

The VE table actually represents VEm. It's the ratio of the amount of air ingested by the engine relative to the theoretical amount of air that can be ingested based upon the manifold pressure.

There will be some inaccuracies due to MAF error, logging error, etc... However, if you do enough relatively steady state runs and average them all out, you can still do a comparative analysis.

I haven't used this table. I just put it in there just in case people want to see it.

In fact, I no longer use this spreadsheet because I use knock sum these days. I have a different spreadsheet for that.

Ok...now I understand...thanks Mickey!

Is the knock sum spreadsheet available on this forum?
Would you be able to provide me with a copy?

When I try to use this spreadsheet I get a runtime error type 13 type mismatch. I don't think me rom tables are messed up like the other guy. Any suggestions? Thanks

I think your upload failed.

Huh. I'll try it again.

Did this one work?

Next time winzip your file before uploading it.

There are some errors:

1. You stopped and started your logger. This added a header in the middle of the data. You need to delete this header.
2. You overwrote the equations in the FLKC table.
3. You copied the wrong boost data over.
4. You didn't fill in learning parameters at the bottom of the rom page.

Ok thanks. For the roms I just clicked on the macro for coping the info over from airboys spreadsheet. I noticed that it copied over the WGDC in the target boost table. I wasn't sure if this was right or not at the time, but I guess it wasn't. Maybe you could fix that in the next update? Thanks again.

Oh. I didn't realize it. I don't think it's compatible with the latest version of Airboy's spreadsheet.

I haven't used this spreadsheet in a long time. I use a different knock counter one.

Mickey, I love the spreadhseet mate, but the VE values are a little off.

Following are the actual equations used to calculate VE. If you can use them instead (or add another box to display the VE with these calculations) that would be appreciated.

What logged data is required:
Engine Speed (rpm)
Mass Airflow (g/s)
Intake Temp (F)

Abbreviations :
RPM = Engine Speed (rpm)
MAFa = Mass Airflow (g/s)
IAT = Intake Temp (F)
MAFb = Mass Airflow (lbs/min)
IAD = Intake Air Density (lbs/ft3)
AVF = Actual Volumetric Flow (ft3/min)
TAF = Theoretical Airflow (ft3)
VE = Volumetric Efficiency (%)

Calulated values and excel equations:
MAFb =MAFa*0.13224
IAD =(491.67/(459.67+IAT))*0.0808
AVF =MAFb/IAD
TAF =(346*(RPM))/3456
VE =(AVF/TAF)*100


Example 1 - using the equations above:
RPM = 5446
MAFa = 285.27
IAT = 72

MAFb = MAFa*0.13224
MAFb = 285.27*0.13224
MAFb = 37.72

IAD = (491.67/(459.67+IAT))*0.0808
IAD = (491.67/(459.67+72))*0.0808
IAD = 0.0747

AVF = MAFb/IAD
AVF = 37.72/0.0747
AVF = 504.86

TAF = (346*(RPM))/3456
TAF = (346*(5446))/3456
TAF = 545.23

VE = (AVF/TAF)*100
VE = (504.86/545.23)*100
VE = 92.60


Example 2 - using Freon and TGUI's VE implementation and the same line of logged data used in the above equation:
RPM = 5446
MAF = 285.27
IAT = 72
MAP = 22.37

VE = (MAF/((2.457*MAP*RPM*0.003871098)/(IAT+273.15)))
VE = (285.27/((2.457*22.37*5446*0.003871098)/(72+273.15)))
VE = 84.97


Results:
So in the example 1, volumetric efficiency is calculated to be 92.60% at 5446rpm, while in example 2 (using Freon and TGUIs VE implementation, volumetric efficiency is calculated to be 84.97% at 5446rpm.

This doesn't seem like much, but makes things like calculating a suitable turbo compressor for your engine a little difficult.


Hope this can be implemented man.

Regards
Leslie

Okay, I'll take a look at this. However, I haven't used this spreadsheet in a long time and barely remember what I wrote in it.

The intent was never to calculate a true VEm. It was to check for relative changes.

Heya Mickey,

This is still only calculated VE, but it uses the actual equations for calculating it so it is more accurate. Since it still requires MAS g/s (as well as IAT and RPM) it will still be able to be used to measure relative VE changes for tuning/mods.

Leslie

You used the wrong units in Example 2. Freon's calculations uses mmHg for MAP and Celcius for temperature. You also used MRP instead of MAP, I think (22.37psi). Are you using the same engine displacement for both calculations?

Ok, here is my calculation using ideal gas equation for calculating the theoretical air flow of the engine as function of manifold pressure/temperature, and engine speed. Probably a lot more ways to come to similar answers.

dot means the variable in terms of rate, so Mdot is mass/s, with units of g/s in this case, Ndot is the moles/s of air, P is manifold absolute pressure in bara, Vdot is the air flow in liters/s at conditions in the intake manifold based based on the engine speed and displacement, T is the manifold temperature in K, and R is the ideal gas constant. So, rearranging the ideal gas equation for this calculation gives:

Mdot=mw*Ndot=mw*P*Vdot/(R*T)

Using an example from my STI (2.457 l):

The air flow is 350 at the MAF (g/s) @ 5700 rpm

I like metric units, so I use this ideal gas constant, R = 0.08314 (bara L/mol K)

The manifold pressure is 26 PSIG, so 40.7 PSIA which equals 2.80 bara

The manifold temperature temperature is 50 C or 323 K (note that ambient is 35 C at the MAF, so I add 15 C to get the manifold temperature - an assumption but probably ball park depending on intercooler efficiency).

The molecular weight of air is about 28.84 g/mol depending on humidity.

Vdot = 2.457 l*5700 rpm/60 s/2 rev = 116.7 (l/s)

So throwing that all into the ideal gas equation above gives an ideal flow of 351.5 g/s

VE = Vmeasured/Vtheory*100% = 99.6 (%)

I have just been following the subie newbie tuining guide which pointed me to this spreadsheet.

What do you use now?