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Message
On a 60 F day, the OAT at 16k ft is
about 22 F; on an 80 F day, the OAT is maybe 42 F. These temps would tend
to reduce intercool requirements and cool the turbine which I assume (key word
here) is the reason for limiting boost to 8 psi.
8 psi is a rough figure that I came up with after searching
through some RX-7 forum info. This seems like a reasonable value that
folks are running on the street. Since that's already more than I need, I
didn't look further to see why they don't go higher. It may not be a
turbo limit, so much as a limit to the engine computer, or fuel injectors.
For example, on the 3rd gen engine, you can run aftermarket exhaust and
intake with the stock 10 psi boost level using the stock computer. If you
want more boost, you have to install an aftermarket computer. This will
get you to about 13 psi, then you run out of fuel injector
capacity. Next you run out of fuel pump capacity,
etc. The stock twin turbos can be run to about 17 psi, but this
is way above their efficient range, which means they're heating the air
much more than a larger turbo would do at that same pressure. In that
respect, running higher than normal boost for a given turbo will increase
the need for
intercooling.
Rusty
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