LS2 VE Table values???

[Acer]

Have just started adjusting the tune in my HSV VZ GTO (E40 ECM) using Flashscan V2 & noticed some strange values in the VE table. The values range from under 17% to ~ 59% which are much lower than what I would have expected. By comparison the LS1's typically have a range of over 40% to near 100%.

At first I thought there may have been an error in the units displayed via EFI Tune 7.3.3 (Build 520) but when I select other units in the properties such as gm*K/kPa (default) it still shows the table as a percentage. Did the same test after extracting the tune file using V2 on our LS1 VX SS & it works correctly, i.e, I can change the units & ranges are as expected.

Is this a bug, misnomer or different application by GM of the VE table?

In the mean time I suggest everyone be careful about SD tuning.

Cheers,

Michael

[GMPX]

Try not to compare them to the LS1, in reality they are just numbers 0 - 4096 which in my mind (and suggested by others) is not very friendly to work with, so we chose to scale that to 0 - 100%.

Cheers,
Ross

[Acer]

Ross,

I understand that they are ultimately just numbers but it is always I good idea to understand the logic behind it if you want to calculate the values instead of just guessing them. Also, you talk of 0 - 4096 yet I can only get % out of Flashscan V7.3.3 irrespective of the units I select. Suggest you check this table again as other programs are showing the usual range of VE values for LS2s.

Thanks,

Michael

[GMPX]

Well, I guess the question should be, how would you prefer to see the VE numbers represented?

All we are doing right now is scaling 0 - 4096 into 0 - 100%, it's not really an indication of anything, but for most, 0 - 100% makes more sense. You cannot change the units to display something else because we have not implemented any others.
I guess what you are used to seeing is 100% on an LS1 is probably going to be at the upper end of the table given all other factors are correctly adjusted (Injector table etc). Yet, we do allow up to 500% to be entered in there because that is what mathematically it will calculate out to.

We are open to suggestions on what you feel comfortable with, if we were to simply show values 0 - 4096 then we would have it correct because that is how it is treated in the ECM, if tuner 'A' wants to show it as scaled to 0 - 100% then that is not wrong, if tuner 'B' wants to show it scaled to 0 to 7000 hogs breaths that is also not wrong, they are just a different representations of 0 - 4096. Though, I don't think that is an industry accepted measurement yet :-)

Cheers,
Ross

[Redline Motorsports]

I see both sides but the reality is that the number doesn't really mean anything until you can relate it back to fueling. At that point its all relative. Bigger number more fuel and vice versa. It will be a bit tough for many moving into the LS2 as we so geared for the LS1. It might not be a bad idea to post a quick comparison of differences we should be looking for. This is apparently one of them!

Ross, if the stock PCM resolution goes to 4096 and you condensed it into 100%, then seeing percentages in the mid 300's in going to be normal...correct?

Howard

[Acer]

Hi Ross,

It is not the end of the world but irrespective of what we are used to on the LS1, volumetric efficiency is a standard measure of an engine's efficiency & that is how many will interpret the current table. In fact what it is from your explanations is just a % scaling of the range of numbers that GM will allow in the table.

Personally I would much rather see the raw numbers in their units (say gm*K/kPa or however GM have done it this time) as then I can actually comprehend what they mean & compare with calculations.

I have had excellent results with SD tuning by using EFILive with the MAF connected to log data on the road & convert using a custom formula (similar to the methods described on this forum before but a slightly different equation) to convert to VE values in gm*K/kPa for the different map/rpm zones. Every time I have done this with enough logged data the LTFTs have been exactly where we wanted them (0 or slightly negative) when running in SD (without MAF) & the cars idle & run smoothly throughout the RPM range.

There are probably almost as many views as people here but from my perspective I would certainly appreciate going back to units or at least offer both display options as per the LS1s .

Many thanks,

Michael

[redhardsupra]

i made a LS2 VE spreadsheet a while back, it works in both LS2 VE units, as well as the 'theoretical VE' so you work with it any way you'd like.

http://www.ls1gto.com/forums/showthread.php?t=106410

[Acer]

Marcin,

Thanks very much for the links to your articles & tools. You have done an excellent job & generously share your insights with the rest of the tuning community . I have generally stayed away from just relying on the LTFTs to empically tweak the VE tables, as the way you drive seems to have an impact, but it should work if you do it in sufficient steps & are consistent in the way you drive the car during each attempt.

Cheers,

Michael

[redhardsupra]

it works with AFR%error too, or any other proportional error measure really.
it really doesn't matter whether you do ti in 'GMVE' as i call it, or the 0-100% 'theoretical VE', they're both directly proportional. however, the 0-100 is easier to remember and easier to understand, so i figured i'd give you a tool to do so

[joecar]

The VE table is not really a volumetric efficiency table, but rather an airmass table.