Mr. Gasket 8703 Hot Rod Calculator - Manual (Page 51)

U
ser
'
s
G
Uide — 49
ComPRessIon RAtIo And mIll Amount
Compression Ratio is the relationship between cylinder volume
with the piston at bottom dead center (BDC) and cylinder volume
with the piston at top dead center (TDC).
BDC TDC
There are several Compression Ratio effects to consider when
determining the appropriate ratio for your application:
• The greater the Compression Ratio, the greater the amount of
air/fuel mix will be compressed.
• The greater amount of air/fuel mix that is compressed, the
greater the combustion power will be.
• The greater the combustion power is, the hotter the combustion
is, which can lead to detonation.
• Detonation (pinging and knocking) can be resolved by using
higher octane fuel (at a higher cost, of course) and/or a change
in ignition timing curve.
So, to get big power, you need big Compression Ratios to get
more powerful combustion, which requires higher octane fuels.
your Hot Rod Calc needs several inputs to calculate a Com-
pression Ratio, which you may need to track down and in some
cases, measure manually:
(cont'd)
UG8703E-B-inside.indd 49 3/3/2010 3:04:00 PM