Cylinder volume ls2 gto

[Pabs1]

So I am having some issues tuning my car. I just noticed right now that my cylinder volume on the general engine tab is 0.75000 which equals to 6.0 Liters. I pulled up several stock ls2 gto repository tunes and they all have 0.70819 which equals to 5.66552 Liters. When i looked up other LS2 equipped vehicles like the 2006 corvette it was 0.75000; Trailblazer 0.75000.

I am at a loss for words here... Can someone explain? If my cylinder value is incorrect what would be the tell tale signs? Why do all the 2006 GTO stock tunes have a different value cylinder volume when compared to other same engine models

Kytune is my personal GTO
bengto was provided to me by a forum member
1190253517 is a stock 2006 corvette from the repository
84701868 is a stock trailblazer

[2xLS1]

Australian math?

[Pabs1]

So which do I go with? Is there any risk in trying the different value?

[MikeOD]

Cylinder volume affects the speed density side of calculations...if you're tuning the VE table, I would advise you to make it correct.

[Pabs1]

But what is correct, of the stock ls2 gto files that I have are like this...

[2xLS1]

What MikeOD is referring to is on the older PCMs when you changed the Cyl Vol number it would physically change the numbers populating the VE table. I just changed the value to .75 in a 06 GTO E40 and it had absolutely no effect on the numbers in the VE Table. So since all the 05 and 06 GTO files I've looked at have the Cyl Vol set at .70819 I would guess it doesn't have the same effect as it does in the older PCM/OS vehicles. Sort of like changing the Engine Size Type doesn't seem to do anything on the older PCMs.

Interesting note, on the older PCMs when you do change the Vol parameter and it populates the VE table with different numbers, when looking at the table values with the compare function on, the differences in the values will display, but the color of the VE Table button does not change colors like there is a difference and using the View Comparison Log feature, it doesn't show as being changed. Would be nice if a HP Tuners rep could explain what is happening.

[Road]

I would like a good explanation on it too. Doesn't seem to change any thing noticeable with HP Tuners but maybe it will with other tuning software?

[mowton]

I would like a good explanation on it too. Doesn't seem to change any thing noticeable with HP Tuners but maybe it will with other tuning software?

Greg Banish gives a great explanation in his 2nd video. Essentially starting in 2005 (Gen IV) and the E40, GM began using GMVE instead of the standard VE% tables. This new approach is an equation based system instead of a lookup table used in the Gen III's. To this, the cylinder volumn is "baked into" the equation embedded in the PCM which is why changing the value in Gen IV's doesnt give you the same results. FOr Gen III's you can easily scale the tune by copy/save orifginal VE values, scale the cylinder volume to your requirement, save the file, open it and replace the VE table with your original. In Gen IV you scale the entire VE table which you need to develop using the BlueCat VE tool.

As far as the other SW, EFI works the same way but doesnt alter the original VE table when you educe the cylinder volume in your scaling process.

Ed M

[Road]

Greg Banish gives a great explanation in his 2nd video. Essentially starting in 2005 (Gen IV) and the E40, GM began using GMVE instead of the standard VE% tables. This new approach is an equation based system instead of a lookup table used in the Gen III's. To this, the cylinder volumn is "baked into" the equation embedded in the PCM which is why changing the value in Gen IV's doesnt give you the same results. FOr Gen III's you can easily scale the tune by copy/save orifginal VE values, scale the cylinder volume to your requirement, save the file, open it and replace the VE table with your original. In Gen IV you scale the entire VE table which you need to develop using the BlueCat VE tool.

As far as the other SW, EFI works the same way but doesnt alter the original VE table when you educe the cylinder volume in your scaling process.

Ed M

Thanks for the info. So on gen 3 changing the cylinder vol does populate different values in the ve table. Lowering cylinder vol increases ve values how would the effect the tune? Thanks for your wisdom and knowledge

[mowton]

Thanks for the info. So on gen 3 changing the cylinder vol does populate different values in the ve table. Lowering cylinder vol increases ve values how would the effect the tune? Thanks for your wisdom and knowledge

HPTuners will "believe" the scaled cylinder volume is correct and automatically reduce the VE to maintain the same cylinder fill charge relationship. Again this is only in the Gen III setups.

Ed M

[MikeOD]

Yes sorry, I forgot that the GMVE cars work differently. On cars that use %VE, the cylinder volume matters.

[MikeOD]

What MikeOD is referring to is on the older PCMs when you changed the Cyl Vol number it would physically change the numbers populating the VE table.

That's actually not the PCM changing anything, it's the tuning software. It wasn't really what I was referring to. Basically, on the %VE cars, they have to calculate out the GMVE number, and the cylinder volume is part of that equation, when I was replying, I read "VE table" and forgot that E40 cars have a VE table, but use GMVE numbers, unlike the previous PCM's. The cars that use GMVE in the VE table (or in the parametric VE equations) have one less step to calculate the final result.

[2xLS1]

That's actually not the PCM changing anything, it's the tuning software.

Really. So PCMs can't change the data in their tables on their own? Thanks for letting me know that.

[Road]

Still trying to understand thanks for the patience. So on gen 3 the ve coefficient is cylinder volume multiplied by the ve efficiency and on gen 4 they eliminated that equation and jumped straight to the ve coefficient? thanks

[schpenxel]

Still trying to understand thanks for the patience. So on gen 3 the ve coefficient is cylinder volume multiplied by the ve efficiency and on gen 4 they eliminated that equation and jumped straight to the ve coefficient? thanks

Basically gen 4's have the cylinder volume baked into the values in the "VE" table (most call it "GMVE"). This simplifies the math the computer has to do. Instead of having to multiple the VE table by the cylinder volume over and over and over and over, GM baked that into the gen 4 "VE" table. I can't remember the exact translation from VE to GMVE, but I'm sure someone else here does.

So, changing just the cylinder volume doesn't do anything in and of itself. It's already baked into the GMVE table.

HOWEVER. I have read that HP Tuners tries to automatically adjust the GMVE table if you make changes to the engine volume.. so keep an eye out for that. That may only be on gen 3, I'm not sure.

My 2005 corvette's original stock tune had the same cylinder volume as the OP posted about.. around 0.7 liters. It's actually 0.75 liters. Doesn't matter.

[Road]

Thanks