Turbo boost questions

Robert Deis rdeis@io.com
Tue, 20 May 2003 17:43:53 -0500 (CDT)


On Tue, 20 May 2003, Benjamin Weste Pearre wrote:
>
> I assume that an ECU upgrade would make matters worse (if they're bad
> to begin with)?  How about just a stiffer WG spring?  Are there any
> tuners whose chips are particularly [un]suited to high altitude?

Boost levels in my 86 and 87 are set to some absolute pressure- that means
the "boost" level is actually higher up here (Colo Spgs for me) than at
sea level becasue we start at a lower ambient pressure.

It doesn't matter what form of boost control you use, the turbo will
always work harder to make 1.4 (or whatever) here than it would at sea
level.

As to how much is too much- I'm not really sure, but the thing to do would
be to set the boost control to get the same pressure ratio as people use
in the lowlands.

Example:  Lots of people seem to have had good results running 1.8 bar,
that's a pressure ratio of 1:1.8.  At this altitude that translates to
~1.4 bar.

Incidentally, if you are overspinning the turbo it will be in a very
inefficient part of its operating range, which means lots of excess heat
in the intake stream, which often means knock. However, I don't know
enough about the Kxx turbos to say for sure "if it's not knocking you're not
overspeeding."

--
------------------------------------------------------------------------------
  Rob Deis                  "Let the people know beforehand what the law
  MiB3347                      is and what they are to expect."
  rdeis@io.com                              -- 18th Congress, Rec. 75