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Location:
Newcastle
Registered:
September 2002
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 What compression is safe for boost??
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Mon, 20 January 2003 12:30
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About how many PSI cylinder pressure should you have for boost?
eg. is 180-200psi to much?
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Location:
Rocky Mountains, Canada
Registered:
May 2002
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Re: What compression is safe for boost??
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Mon, 20 January 2003 13:15
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Yeh, that will be too much for any medium amount of boost.
180psi is over 10:1 compression.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: What compression is safe for boost??
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Mon, 20 January 2003 14:26
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good luck trying to link cranking cyl pressure to static compression ratio. the cam timing and duration etc will totally screw any figure you want to pull out of your ass.
for info on dynamic comp ratio with boost, check out:
http://www.goodvibesracing.com/Compression%20Ratio .htm
but youll need to know your static compression ratio first, not your cranking pressure.
ed
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Location:
Brisbane
Registered:
May 2002
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Re: What compression is safe for boost??
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Tue, 21 January 2003 01:06
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There are many factors which influence the maximum "safe" compression ratio for use with forced induction. The combustion chamber design, the material used to construct the cylinder head, even the position of the spark plug can have an influence. In other words, there is no magic formula you can apply to determine the best compression ratio; it varies for every type of engine.
People in the US are running small amounts of boost through Honda S2000 engines (with a static CR of over 11:1), while on the other end of the scale a Holden 202 probably wouldn't cope with any more than 8:1 compression for even moderate amounts of boost.
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Location:
Newcastle
Registered:
September 2002
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Re: What compression is safe for boost??
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Tue, 21 January 2003 09:31
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The motor i have in mind is my 2TG-EU it also has a set of mild cams About 260deg and high lift  . is there a way that i can figer out the compression ratio? eg, by knowing the stroke and bore size?
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Location:
Brisbane
Registered:
May 2002
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Re: What compression is safe for boost??
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Wed, 22 January 2003 01:33
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You can calculate the CR if you know the combustion chamber volume and the swept volume of each cylinder. If the engine is assembled you can roughly measure the CC volume by pouring oil into the spark plug hole when the piston is at TDC; the volume of oil required to fill the cylinder to the top should be approximately equal to the volume of the combusion chamber.
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