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Manifold vac pressure? 

 

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 Post subject: Manifold vac pressure?
Posted: Wed Jun 22, 2005 7:26 pm 
Getting Side Ways
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Power: 315 rwkw

Location: Under the flight path of incoming packpackers
NSW, Australia

What is the vacume pressure spose to sit at on idle? Mine is -75kpa in P and about 61kpa in gear... does this sound correct?
Also a slight vacume leak will raise or lower the idle? I ask this as today I was tidying up the Wolfs wiring and tightned a few clamps on the vac hose that runs off the fuel reg to the boost guage and ecu. When I started it up it now idles at 1400 rpm in P... what have I done here?
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Posted: Wed Jun 22, 2005 7:46 pm 
Getting Side Ways
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Haha - metric boy!! Mine idles between 21inches mercury to 19inches mercury of vacuum.... should be similar for all engines. See link:

http://www.engineeringtoolbox.com/press ... 2_825.html

Where 6.9kpa = 2.03 inches/hg

Therefore 69kpa = 20.3 inches/hg

So i'd say 75kpa roughly 21inches.... seems like yours is all good...

Vac leak should raise idle... example being the idle speed controller - this is simply a computer controlled vac leak to increase idle.

Maybe your inital tune was done using incorrect manif vac at idle?!?

 

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Posted: Wed Jun 22, 2005 7:49 pm 
Getting Side Ways
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Power: 315 rwkw

Location: Under the flight path of incoming packpackers
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Hmmm, maybe, I'll have to see how it drives then.

Initial tune? hehe, its an ongoing tune... I fiddle with the pulse widths ever time I drive it.

Thanks for that
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Posted: Thu Jun 23, 2005 6:31 pm 
Fordmods Junkie
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I thought if you had a small vaccum leak around the map it would increase idle due to the ecu dumping more fuel in. Less vaccum usually means more fuel, which would raise idle a bit.
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