[Diy_efi] MAP vacuum signal isolation?
wopontour at hotmail.com
Tue Jan 24 12:58:53 CST 2006
I agree with the others that have responded- that you shouldn't "T" the map
signal line with the vacuum advance. The diaphragm could certainly have a
negative damping effect on the vacuum signal.
But the next obvious question would be WHY would you desire to have a vacuum
advance at all? Given the refinement of MSnS-E there's really no reason to
limit your advance to the confines of the mechanical curves of a
distributor.So I would suggest you work towards disconnecting the vacuum
advance entirely and let the MS have full control of your timing.
----- Original Message -----
From: <pparaska at comcast.net>
To: <diy_efi at diy-efi.org>
Sent: Monday, January 23, 2006 11:35 PM
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
> 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.)?
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