Cylinder Volume - used for SD calculations?

They go by many names, P01, P59, VPW, '0411 etc. Also covering E38 and newer here.
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NSFW
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Re: Cylinder Volume - used for SD calculations?

Post by NSFW »

I suspect that the displacement value was factored into the value that you see in the VE table.

The classic SD math, if I remember right, looks like: "load = VE * displacement * temperature"
So if displacement isn't multiplied in separately, then each cell in the VE table probably contains (VE * displacement).

It makes sense from the standpoint of limited CPU power - there's really no need to do that multiplication at run-time, since you can do it at compile time instead, and get the same results either way.
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waz
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Re: Cylinder Volume - used for SD calculations?

Post by waz »

Not sure if this is any help to you.

Changing the displacement in hptuners adjusts VE% on the VE table.
turbo_bu
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Re: Cylinder Volume - used for SD calculations?

Post by turbo_bu »

Think I might have found an answer for the VE / displacement questions. I went back and looked at the disassembly and noticed a couple of things. The first thing I saw was under the SD air flow calculation where it talks about and shows looking up the composite VE values. If you go up to the engine calibration section it labels the VE table as composite VE. The note that goes along with it says displacement x VE. It sounds like GM "normalized" the VE table so that it already has displacement built into the values. Also, thus, why the description is labeled composite VE.

NSFW - you were correct in your theory!

For those following along at home, I am using dimented24x7's marked up disassembly of a 12202088 OS. I am not sure whatever happened to him, but am truly grateful that he posted this wonderful resource for us to use.
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Gampy
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Re: Cylinder Volume - used for SD calculations?

Post by Gampy »

turbo_bu wrote:For those following along at home, I am using dimented24x7's marked up disassembly of a 12202088 OS. I am not sure whatever happened to him, but am truly grateful that he posted this wonderful resource for us to use.
Hear, hear ... I'll second that!
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ejukated
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Re: Cylinder Volume - used for SD calculations?

Post by ejukated »

From the LS1 PCM onwards, VE had the cyl displacement factored in. The actual number in the table is not % however HPT and EFILive give an option for it to be back calculated into VE for display. They use the displacement stored in the cal to calculate it.
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