Interesting P&H Driver Link and a MAP Question

[Ken Bauman]

OK, I once thought I had it understood, but know I guess I don't. I'm concerned
that a system be able to easily handle altitude changes such as the example of
going up the mountain.

So am I to understand the systems that only use 1 pressure sensor (typical GM
MAP) won't have good compensation for altitude changes? One of these mfg's told
me their system reads map referenced to absolute pressure so it is not an
issue.

So Bruce can a system use only one sensor if it has more resolution? I'm
missing something, and now feel like I'm back in EFI 101. Would it be too much
to ask for a good explanation of the meaning and relationship of MAP and BARO
to EFI? Please explain.

The way I had it understood was that once the engine was pulling a vacuum there
was no way to know what the outside pressure was. That was the reason for the
second baro sensor. But obviously there is a direct connection to the outside
(the butterfly) a person recently told me that the outside pressure effects the
amount of vacuum pulled so a second sensor was not needed. So is it that we
need the second sensor because we don't have enough resolution to adequately
measure the effect outside pressure has on the vacuum? Or…???

Ken Bauman

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