MAP Question

Phil Lamovie phil at injec.com
Fri Apr 6 13:31:56 GMT 2001


While it is true that you cannot measure the back pressure drop
( and thus the change in VE ) associated with high altitude operation,

the divergence from target AFR's is not impossible to correct for.

It is always possible to correlate a previously known manifold
vacuum vs throttle position and thus infer barometric activity.

As the only way to produce the same results at sea level would be
to drop the exhaust or at least some portion of the restriction would
need to be removed.

This " operation " is conducted by mainly untrained personnel
and seems to be the most popular " engine mod " performed.

It appears that the ECU's with only a single absolute sensor are
able to maintain 51 state emission compliance without any extra
adjustment.

It would also follow  that 8 bit resolution of the MAP input is indeed

sufficiently fine for the the job. (approx 85 kPa ((-80 to +5 ))
resolved to
255 steps of approx 0.33 kPa.

HTH

Phil

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