Cal

iTrader: (1)

I second this! This subject keeps coming up over and over! It is a strange LS1 quirk, and the real guru's have gotten tired of the same questions and stopped responding.

Bink

Thank you.
joel

Scott Turvey

I third or whatever the sticky suggestion.

Shinobi'sZ

So what is the VE at WOT? I am trying to calculate Boost Compression Ratio and it is asking for VE.

Bink

You need WOT : MAP -kPa (100 -101 kPa)
RPM
IAT *C
MAF gms/sec
Displacement - Cubic Inches (CI)


VE = [ MAF x (IAT *C + 273.15) x 212544 ] / [ RPM x MAP x CI ]


good luck. joel

boblk

Soooooo..., anyone want to speculate what the Secondary VE table is used for?

Bob

gameover

thought THIS might be of interest...

Still some work to be done but gives you an idea of my current understanding of this stuff and may help explain the things you are seeing.

Bink

Hey, Welcome to the Forum up here gameover. ^^^Explains some fueling issues I had. Pretty complicated - it will take some time to digest!! Thank you.
joel

Bink

gameover A few questions - please.

Calculate MAFAirmass/SDAirmass ratio -

Is -> MAFAirmass - the output of the MAF Sensor, grams/sec?

-> SDAirmass - calculated from the standard VE equation using the VE table value (at a given load site) divided by 30?? So, solving for MAF Airflow, MAF = VE * MAP * RPM * CI / {(IAT +273.15C) * 212544}? This would give us The Predicted MAF Airflow?

If (SteadyMAP) then
- Correction Airmass = MAF Airmass (filtered) -

-> Is this as long as MAP has less than a 0.8kPa delta?
-> Correction Airmass = MAF Airmass (filtered) - which/what filter?

Correction Airmass = SD Airmass x MAF/SD Airmass Ratio (calculated during Steady MAP conditions) -

-> is this is when MAP deltas exceed 0.8kPa (UnSteady MAP)?
-> Final Airmass being a function of MAF Airflow, previous MAF
Airflow, prev 3 MAP readings, prev 3 TPS readings and
Transient Corrected Airmass - Are the 9 coefficients weighted equally in the filter equation??? It doesn't seem like the SD airmass is weighted very heavily???

Thank you for posting this.
joel

gameover

Yes but convertered to g/cyl.

SDAirmass is the result of the VE table calculation, again in g/cyl. The VE table is not actually a VE table in the traditional sense, but it's close. It's just your normal PV=nRT style equation... the VE table values are more like the V in this equation...

yes, and the filter is just a simple lag filter.

no the 9 coeffs are not weighted evenly they favor the previous value (obviously) and the two MAF related terms, the SD airmass doesn't seem to be weighted too heavily compared to these terms and also take into account it is already scaled and filtered by the correction Airmass calc and the MAF/SD ratio... it is not trivial to work this out in your head unfortunately.

NoGo

iTrader: (2)

Thanks for the info!

I tried using PV = nRT 10 ways from Tuesday. I couldn't get it to work out.

Do you know what value of R (universal gas constant) they are using. That would pretty much nail down the units that they are using, and make it easier to figure out this jumbolia.

I agree with it being the V in the ideal gas law, but it is being incorporated differently than just standing for 'V'.

Any other hints?

gameover

are you using real VE table numbers from a hex editor?

NoGo

iTrader: (2)

I am using the values from LS1 Edit.

That would REALLY suck if they weren't correctly extracted.


Attached a pic of the VE values that I am using for the back-calculating.


Edit: ARRRRRGH, it's not letting me upload the file for some reason.

gameover

here's an example 105kPa MAP row as a guide (in hex)...

$1FED,$2400,$2580,$2600,$2580,$2680,$2700,$2B9F,$2 E2B,$2F8E,$30F0,$3253,$33B6,$33B6,$33B6,$33B6,$33B 6,$33B6,$33B6,$33B6

Bink

I'm not a Coder- looks like Enron accounting to me.

gameover is your PM activated??

Here's what I think the VE table represents -> Classical VE * Grams per cylinder at standard conditions, which is about 0.92 grams/cyl (This gives us the number of moles of O2 = n, sum of partial pressures etc.). So Table VE is actually n=moles in the PV=nRT ( Boyles Gas Laws) equation. Where P = MAP, T=*K IAT and V would be cylinder volume.

Since cyl. vol. is constant and n1=Table VE we have, from gas laws, n2*R*T2/P2 = n1*R*T1/P1. Where T1 and P1 are Standard Temp(*K) and Standard Pressure (kPa) and would be constant also. T2 and P2 are the MAP and IAT inputs. So we have n2 (moles or grams) = VE * R*MAP/IAT.

From gameovers above info it appears a multiple of 3 is used . And to create whole numbers multiply VE*10. 3*10 = 30. VE * grams/cyl* 30 = Edit Table values.
This would result in a reduction of VE by the Grams/cyl (0.92) which is approximately 8% across the board. Easily compensated for by IFR adjustments.

Any thoughts or corrections, flames etc.? Please, Have at it.

joel

Looks like NoGo, He Is The Man had it Right all along.

NoGo

iTrader: (2)

Gameover, thanks for the tip. The g/cyl was the problem that I was having. I kept trying to solve for massflow. Everything plunked into place when I solved for g/cyl.

Thanks,
Kevin

https://ls1tech.com/forums/pcm-diagnostics-tuning/149741-ve-table-cracked.html

Bink

OKAY, So I tried..................

87_ta

I'm Sorry,
After asking this question here several times now - now one can give me an answer!
I have yet to use LS1 edit for my self but will be soon for brother in law, as he bought but is puter illiterate. How is everyone here make fuel adjustment not knowing what to change? or is everybody settling for close enough by using INJ. constants table?
If you have it, try it! its not that hard, make a VE change in an area you know you need attention and see if it works.
Also just my 2 cents , I would never scale the whole VE table in all KPA/ Load ranges.
I would only do so from 85/90 kpa and below. Anything above I would be sure is being used for WOT operation, especially if you all agree that VE is used duing closed loop.
I have much experience tuning my current SD setup and previous MAF setup in my 87. I usualy make most of my WOT fueling changes in the 90 - 100 KPA range of the VE and zero out most of the PE enrichment for 2 reasons. 1 being I never want to be @ wot and be @ 14.7 - which in theory is where VE should be not given any PE influence. 2 because its easier for me to see the Fuel curve by looking at the MAP and being able to keep my self richer at peak torque (which is where your highest VE point should be) Because thats where your engine is @ peak Volumetric Effeciency.

I would be willing to bet that as Kevin stated that VE is always referenced, but as he said try it! You guys have the tools right there in front of you....

So with that said can anyone answer the question yet?

Bink

I'm sorry, you obviously don't understand the functioning of the LS1 PCMs. They are much different than your 1987 PCM.

87_ta

Your right Binky,Thats why I'm asking questions There was no need for that comment.
You obviously don't understand because you can't answer the question..
Can you?
please stop replying to my post if you cannot give an answer.
Ohh yeah, 87 has an ECM, not a PCM.

I have read these stickies and it still seems to be in question for some.
But I am going with what NOGO has said unless you can prove it wrong.
Joel has posted some great info as well, and I now see that there is no VE influence on PE, But you still do not want to scale the high KPA/LOAD ranges of the VE down being that it is used for back up! Do you binky?
I would'nt.
You have someone in who has scaled their whole VE by 50% and then someone tellling him thats too much to use 60%-80%.. Based on what?
Without seeing this guys BLM/FT where would anybody come up with that.

Putting in a healthy cam with some decent overlap can wreck havoc on a VE table, While the MAF should still read fairly close while still having a little trouble at idle sometimes due to reversion in the intake tract.

I asked these questions because I don't understand the code yet before I go hacking.
Yet you get mad when I tell you that using the IFR table is not the right fix and its like changing jets. In a sense you are right.
So if you holley is idleing rich, do you jet down the primaries if WOT is good?
I would not!
But after reading what Gameover has posted I understand alot more, Thanks to him.
Sorry I missed that the first time.

So reading what I wrote, what is it I do not understand? Thats why I am here to learn..