MAP sensing for IR systems

[Bernd Felsche]

mike mager writes:

>What are the practicalities of MAP sensing for an IR (Independent Runner) 
>intake system?  'Theoretically', with symmetrical intake and exhaust, each 
>cylinder has the same MAP, and needs the same fueling and advance, but what 
>happens in the real world?  My books fail to address this obscure issue.

Flow dynamics is what happens. That means you need to filter the
readings to determine the average pressure - but that probably won't
do you as much good because the average pressure doesn't tell you
the amount of flow - not directly. You'd need to do quite a deal of
testing to  determine the mass of air drawn into the cylinder for
the average pressure.

OTOH, if you measured the pressure just above the intake valve(s)
from just before opening, until just after closing, you'd get a
reasonable picture of cylinder filling. Note that this could be
affected by excessive exhaust backpressure!

Another option might be to measure the pressure difference along the
runner which also tells you the flow direction - and depending on
the length of the runner, will not be as susceptible as a
single-point pressure measurement. It would still be smart to
measure the pressure difference during intake. An integration of
that signal over time is closely related to the amount of air drawn
in. You still need to know an absolute pressure, which to save on
pressure transducers, could be from a common "collector".


-- 
Real Name: Bernd Felsche
    Email: nospam.bernie at perth.DIALix.com.au
     http://www.perth.dialix.com.au/~bernie - Private HP
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