not really EFI-related, regarding compression

[Raymond C Drouillard]

The thickness of the gasket is included in with the V (Volume of
combustion chamber) in the formulas below.  The combustion chamber is
everything between the piston and the head when the piston is at top dead
center.  It is affected by such things as the shape of the face of the
piston, the deck height, the thickness of the gasket, and the shape of
the head.

In a practical sense, you can look in the specs of your engine (if it is
unmodified in that area) for the compression ratio, and use that to
calculate the combustion chamber volume.  Sometimes, the combustion
chamber volume is included in the specs.

If you, for instance, use a thicker gasket, add the change in size.

If your old gasket thickness is .030, and you change it to .039, you
calculate the volume of a cylinder with the same bore as your cylinder,
and a length of .009 (.039 - .030).

Added volume = (new thickness - old thickness) * bore * bore * Pi / 4

CR = D / V + 1 = D / (origional volume + added volume) + 1


Ray Drouillard



On Sat, 27 Jun 1998 11:23:25 -0400 Barrett Flowers <vette at disknet.com>
writes:
>That will come in handy, thanks. Just one question about it though,
>where/how do you plug in the cylinder head gasket thickness, such as
>.039 in my case? Add it to the stroke?
>Thanks.
>
>> D  = Displacement of cylinder = stroke * bore * bore * Pi / 4 = 
>total
>> displacement of engine / number of cylinders
>> 
>> Pi = 3.1415926536 (approximately)
>> 
>> V  = Volume of combustion chamber
>> 
>> CR = Compression Ratio
>> 
>> CR = (D + V) / V = D / V + 1
>> 
>> If you don't know the combustion chamber volume, but you know the
>> compression ration and displacement rearrange the above equation to 
>yield
>> the following:
>> 
>> V = D / (CR - 1)
>
>     -Barrett                                          
>vette at disknet.com
>     1989 Carroll/S.C.A.R. Performance Corvette
>     Paxton S/C, Borla, FX-3/z51/HD Springs, Exorbitant engine mods.
>     PBM Racing heads, PBM custom cam, valves, springs, retainers, 
>etc.
>     1984 S.C.A.R. Performance Corvette- Mod Engine, leather, TCI 
>700-R4
>     ICQ contact # 6317092   Owner: SCAR PERFORMANCE
>     WebPage: http://members.tripod.com/~Barrett_VETTE/index.html
>     Don't Forget To WAVE! I am.....
>     Southern Indiana, near Louisville, KY
>     Member: Ohio Valley Vette Assoc. New Albany, IN
>
>
>

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