Turbo boost versus compression ratio ?

[Mike from West Australia]

Hi all,

General query so I can get my syntax/semantics straight,

Theres an email list I'm on <nissans13 at egroups.com> re Jap 200SX
and Silvia cars etc. twin cam 4 cyl turbos etc

Anyway, one of the guys (I get the impression) relates turbo boost
to compression ratio by a more or less intuitive relation. There's
been comments some months ago and its been troubling me ever since.

ie. He sounds like a very practical guy but is apt to say boost is
a substitute for low compresson and things such as 'why lower the
compression ratio when you only need to add an intercooler or something
else instead of touching the CR at all !

In other words I get the impression he's suggesting there's a
proportional factor of boost to compression ratio.

Now I'm not so sure and can't quite articulate a rationale as to
why I would happily lower the CR and up the boost for a particular
engine whereas he might admonish me for lowering the CR when all
I have to do is add an intercooler to reduce charge temp and
therefore not take the trouble to reduce CR. Somehow I know
the relationship is more complex, is there a way to explain
this issue clearly enough for the layperson,

tah and Rgds

Mike

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