User Guide

36—Dyno2000 Advanced Engine Simulation
available from the gasket manufacturer. When the thickness is entered, the Head
Gasket Volume is calculated.
For flattop pistons, the next data entry field is (4) Piston Down Bore @ TDC that
allows you to enter how far down the bore the piston is positioned at TDC. Enter a
positive number for “down-the-bore” distances and a negative number if the piston
protrudes above the deck surface (see photo, above). A typical value might be
+0.040, indicating that the piston comes to a rest 0.040-inch below the deck surface
at TDC. As soon as this last value is entered, both the Deck Volume @ TDC and
the Compression Ratio are calculated.
Note: A positive Deck Volume @ TDC indicates the piston is positioned below the
deck surface and this volume adds to the combustion space at TDC; a negative
number indicates the piston protrudes above the deck surface at TDC and subtracts
from the combustion space.
At this point, you can move to any of the previous fields (by clicking in them or
using the Tab and/or the SHIFT-Tab keys) and modify any values to determine their
effect on compression ratio. At any time, you can click on the Apply button to load
the new calculated compression ratio into the Component Screen and save all en-
tered values with the simulated engine. Alternately, you can press the Cancel button
to discard all entries and leave any previously entered compression ratio specifica-
tions intact.
Using The Calculator With Domed/Dished Pistons
Or Pistons With Valve Reliefs
Pistons with domes, dishes, pockets, or valve reliefs complicate the compression
ratio issue. Each of these volumes must be accurately determined so that the net
effect of all “positive” (domes) and “negative” (pockets, reliefs) can be calculated.
Start off by verifying that the calculator is in the Domed Mode by checking the
lower radio button Piston—Has Dome, Dish or Valve Reliefs . Enter the combustion
chamber volume (in cubic centimeters—cc’s) in the first (1) Head Chamber Volume
data box. As described earlier, combustion chamber volume is typically measured
Compression-Ratio Math Calculator
Measuring Deck Height
Use a dial indicator and stand to measure
how far down the bore the piston is posi-
tioned at TDC. Enter a positive number for
“down-the-bore” distances and a negative
number if the piston protrudes above the
deck surface. A typical value might be
+0.040, indicating that the piston comes to a
rest at TDC 0.040-inch
below the deck
surface.