[Diy_efi] MAP vacuum signal isolation?

[Geddes, Brian J]

I think the answer is "yes", but I'll be curious to hear some opinions.


But, I'd like to expand on the question a bit.  Where is the ideal spot
to source the MAP signal from?  On my V6 setup, I am sourcing my MAP
signal from what used to be a crankcase ventilation passage, which
connects to all 6 intake runners about an inch upstream of the intake
valves.  Would it be better to source from further up in the plenum,
like just after the throttle?  Or does it matter?

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]
On Behalf Of pparaska at comcast.net
Sent: Monday, January 23, 2006 10:35 PM
To: diy_efi at diy-efi.org
Subject: [Diy_efi] MAP vacuum signal isolation?

I'm running a Megasquirt-I with a Holley Pro-Jection 4bbl TBI.

I've been grabbng the vacuum signal off of a line from a full
time vacuum source on the front bottom of the TBI (below the
throttle plates.  I share that source with a vacuum advance can
on the HEI distributor, through a T in the hose coming from the
port on the TBI that splits off to the MegaSquirt's MAP sensor
and also to the HEI vacuum advance can.

Is there a problem with this kind of setup?  Could I be
getting strange signals to the MAP sensor while the
vacuum advance can is changing it's volume (diaphram
moving)?

In general, is it better to feed the MAP a signal straight
from a manifold plenum that is removed in distance from
the power brake booster and other vacuum ports (Vac
advance, etc.)?

TIA,
Pete
http://AlteredZ.com
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