http://www.efilive.com/forum/viewtopic.php?t=455

Here you go

 

That thread implies the 103.58% is a fix to an internal algorithm in the EFILive code. How do I know if this needs to happen with other scanners? Or am I mis-interpreting the thread?

 

If I am not mistaken ChrisB's formula assumes 30 as the scaler (we entered it when first using his software) to arrive at the PCM VE(same as Efilive,that is why i referenced the thread) when in actuality its 28.96. max ve is 2349
Which equals a correction factor of 103.58% for EfiLive and ChrisB's Log analyser(assuming you calculated yor original table using a scaler of 30). In edit we scale the whole table by 103.58% since that is the only way to scale the table by 3.58%


Hope that cleared it up

 

Use ChrisB's LFA and change the scalar to 30. ChrisB initially thought it was 25 (i.e. the magic number) but in the "Fuel Trim - VE" ( or one of the other threads I cited to Jim) thread he states to change it to 30. It has worked well for me.
Max VE should be 3000*103.58 - I believe. It never has been settled, vs another #,
that I know of.
Anyhow, NoGo said to scale previous VE #s by 103.58 as a correction factor. It just so happens EFILive was using the equation ChrisB and NoGo ironed out.

This is my take on it.

joel

 

The scalar in my version of the LFA defaults to 2500. I changed it to 2900 to create the data I put in Main VE. So you're saying to change the scalar to 3000, copy the resultant values into Main VE, then re-scale the modified Main VE cells by 103.58?

Should I be waiting to modify the Main VE until I have literally all the cells mapped? I have 133/380 mapped now. How am I supposed to get the 400/800 & 7200+ entries when my idle is above that? Just interpolate and try to make the curve smooth with the rest of the entries?

 

Yes to all. That's exactly what I did.
joel

 

Yup you wont be touching anything above 7200 anyways. When I log I dont hit all the cells that is why i was asking how to hand smooth this thing to make any transitions easy

 

Whatever the maximim Edit VE value (2900 or 3000) is it the same for every displacement or not?
If the displacement is already included in VE values I would expect the maximum possible value (for 100%) would be higher, but how to figure the number?
Thanks

 

Let me ask a simple question or 3 amid all this
high-falutin' theoretical stuff.

Is 0.773 g/cyl still believed to be the 100% VE,
100kPa-ambient "right value"? And is the dynamic
cylinder air PID we get out of (say) HPTuners, a
MAF-only derived result (that is, not colored by
any VE / SD-related calcs)? And if these are both
true, and we believe our MAF data, then could /
should a shade-tree laptop tuner use that
PID/0.773 value to check and/or massage VE
tables to try and true things up, pointwise?

 

hey jimmyblue, I tried to get the PCM gurus to address this earlier in the thread. But, since most of you guys are focused only on 5.7L LS1 engines, nobody really responded to my thoughts on determining the correct value for "100% VE" in the Main VE table.
I appreciate all the help and useful information from everyone. I agree that you can't just "calculate a VE table" to improve your car's performance. However, I would like to see someone other than myself address the issue of the differences in MainVE tables between engines of different displacement.
From looking at truck PCM calibrations, the maximum value in the main VE table varies quite drastically based on engine displacement. I believe gameover about the cylinder displacement being included in the Main VE table, it makes perfect sense when you look at calibrations for 4.8L engine versus 6.0L engine. Max EditVE for a 4.8L is 2093, and for a 6.0L its 2679. There is no way these calibrations are on the same scale... (i.e. if 100%VE = 2900 for all engines, then the 6.0L engine would be so much more efficient that everyone would have one.)

On your question, I think the correct 100% VE value for a 5.7L engine has been determined by several methods (both from mathematical analysis and from logged data) to be around 2896 to 2902 in Edit units. Translating this to g/cyl.... uhhh, assuming the max value for a 5.7L is 2349, that makes 81%VE. So divide your max value (g/cyl) by 0.81 to get 100%VE value.

 

I'm sad now that I'm at the end of this thread.

 

My head hurts

 

The thing to realise is the VE table is not a VE table in the traditional sense it is a cylinder airmass table.

The units of the table are: grams.Kelvin/kPa ie. at a given temp and pressure it will give you the cylinder airmass.

For example: a 5.7L engine has a cylinder volume of 0.708L, and at 101kPa and 20degC (293K) you get an airmass of 0.85 grams at 100% VE (ie. 0.708L of air at 20degC, atmospheric).

the table value is: V(L).(M/R).5120 g.K/kPa

V(L) is the effective volume, M=28.98, R=8.3144 and the 5120 is the internal scalar (internal binary-decimal storage).

To express this as a VE% you can just normalise to the cylinder volume. you'll see that M/R = 3.485 and (3.485).5120 is 17833, the factor i mentioned a few posts back.

Important thing to remember, you need to multiply by the MAP and divide by the AirTemp (in kelvin) to get the actual g/cyl value.

For those running HPTuners s/w to get g/cyl from the VE table multiply your VE% by 178.33, and then your cylinder volume (5.7L = 0.708). Then multiply by the MAP and then divide by AirTemp and the internal factor.

eg. if your VE is 100% at 20degC, 101kPa then:

100 . (178.33) . (0.708) . 101 / (293) . 5120 = 0.85 g/cyl

 

So Ve= g/cy * ((IAT+273)*5120)/MAP(kpa)/cyl colume/178

How come rpm isnt taken into account here

 

RPM is taken into account, it's one of the axes of the VE table.

There is a VE PID that is equal to Calulated Airmass / Ideal Airmass. Where Ideal Airmass is how much air that would be in the full cylinder volume, current temp and Baro pressure. It's limited to a max of 100%.

In the VCM Scanner under Engine -> Airflow

If you want to estimate VE from other sources such as the MAF then yes you need to take into account RPM, the numer of cylinders etc. I'm talking only about the VE table here.

 

My reference to rpm was asking about the formula. I undertand the ve table is scaled by rpm. If i wanted to use this formula for calculating a new ve table I only have one axis to go by.

Am I looking at this the wrong way?

 

rpm isn't taken account in your formula because you used grams per cylinder. If you had used grams per second, you would need rpm in your formula also. Is that what you meant?

 

i guess only because iam intrested in building a new ve table and rpm is one of the table scalers

 

HumpinSS - We developed new VEs from classic values using NoGo's and ChrisB's method. GM did this and then modified it to their intended use -> PCM. You can still use Nogo's Formula and adjust from there. Get a wideband O2 ( I've been looking for a used one). This is how I see it anyway.
joel

 

I have been using Chris's/NoGo's methods. With the new formula i wanted to compare the data between new and old. So I put the new formula in a pid in EFIlive but couldnt get it to work (Blacky is looking at that for me) to make my comaprisons