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Re: S.P.E.A.R.C.O.intercooler guys??

Huw Powell <human@nh.ultranet.com> wrote:

>> I guess humidity would lower the oxygen density

> But not there. - I think.  The water just adds to the mix, making it
> heavier and .... wet.  Sorry if I'm wrong.

Water does dilute the oxygen.  Total pressure is constant, partial
pressure of water is variable up to saturation point, and the N2, O2,
etc. make up the rest.   "Bone-dry air" is 20.95 % O2,  while air
saturated w/ water at 60 F is 20.58 % O2.  Boost has no effect on this
dilution, because the composition is fixed upstream of the turbo.

> I think the key measurements would be ambient temp and pressure vs.
> resulting inlet temp and pressure.  Which is what Ross is measuring,
> right?

The engine computer gets air flow/ mass flow/ whatever at approx ambient
conditions.  It may correct for pressure and temp (already in mass
flow).  Closed loop O2 control compensates for other things incl
humidity, but not at WOT.  So a question is, what does the lambda vs.
torque response of the engine look like at WOT?  Probst says a small
change in lambda around 0.86 has little effect on engine power output,
but doesn't address varying RPM or ignition timing.

Dave Weiss
'91 V8 5-spd
'91 90 CS UnQ