plug readings vs electronics

[Greg Hermann]

At 11:46 AM 10/11/01, Ron Schroeder wrote:
>At 12:10 AM 10/11/01 -0700, you wrote:
>>Jason Mauldin <jmauld at yahoo.com> wrote:
>>
>>>ummm, why would gases cool off while they're still
>>>being compressed?

Well-- if you add heat to a supersonic flow, its temperature will drop,
remove heat and its temperature will increase, but I suspect this one's
beyond the intended level of this discussion, but if you really get into
it, there ARE Fanno and Raleigh line shock conditions existing in the gas
flow in an exhaust port/manifold under some operating conditions ! :-)
>>
>>Here, here.  According to boule's law of gases, it should heat up by
>increasing
>>the pressure.  But I'm over-simplifying on speculation.
>>--
>>David Gravereaux

Sort of true but backwards. Compression will inevitably increase the
temperature of a gas under adiabatic conditions. How MUCH the temp must
increase with compression (or decrease with expansion) varies inversely
with the molecular weight of the gas involved. (Adiabatic means no addition
or removal of heat from the system.)
>
>And of course the reverse, exhaust gasses will cool as they expand going
>thru the  turbo even if ther is no heat loss.

Absolutely true  ! (See above though!) :-)

Greg
>
>Ron Schroeder


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