# SCR calculations



## x47544F (Apr 11, 2012)

For my fellow ls enthusiasts. The below is wxMaxima code. (wxMaxima is freeware btw) I didn’t simplify it because it makes it easier to interpret.

SCR Calculations for stock LS2

1 cc = 0.0610237441 cubic inches

function_BDC_V(BORE,STROKE,GASKET_THICKNESS,COMBUSTION_CHAMBER,PISTON_DISH) := pi*(BORE/2)^2*STROKE+%pi*(BORE/2)^2*GASKET_THICKNESS+COMBUSTION_CHAMBER*0.0610237441+PISTON_DISH*0.0610237441;


function_TDC_V(BORE,STROKE,GASKET_THICKNESS,COMBUSTION_CHAMBER,PISTON_DISH) := %pi*(BORE/2)^2*GASKET_THICKNESS+COMBUSTION_CHAMBER*0.0610237441+PISTON_DISH*0.0610237441;


Internet said it. So it must be right.
{
Stock LS2

Bore = 4.00-in
Stroke = 3.62-in
Gasket thickness = 0.054-in
Production LS2 head combustion chamber = 64.5cc
Piston = 0cc dish
}

float(function_BDC_V(4.00,3.62,0.054,64.5,0)/function_TDC_V(4.00,3.62,0.054,64.5,0));

I get SCR 10.86:1 totally stock LS2.


So if one is looking at the AFR 225cc mongoose heads and trying to decided on combustion chamber size then the graph attached is for you. I did the graph for all 3 combustion chamber sizes… If you are looking at different heads then just manipulate the code...

Here is the code for maxima. Once again it isn’t simplified on purpose…
plot2d([float(function_BDC_V(4.00,3.62,GS,62,0)/function_TDC_V(4.00,3.62,GS,62,0)),float(function_BDC_V(4.00,3.62,GS,65,0)/function_TDC_V(4.00,3.62,GS,65,0)),float(function_BDC_V(4.00,3.62,GS,72,0)/function_TDC_V(4.00,3.62,GS,72,0)),10.9],[GS,0.010,0.080],[y,9.0,13.0],[xlabel, "Head Gasket Size (in)"],[ylabel, "SCR"]);

Also, I did the graph for a budget LQ9 408 build not attached. Conclusion is you need dished pistons if you are going FI.

NOTE: I check all my work but that doesn't mean there might be a mistake in it. So check it if you are going to use it.


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