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Fasteddie313 · Joined: 29 Sep 2013 Posts: 2130 Location: MI

The boost retard line is the one on the backside of the can right? Goes to the brake booster hose/manifold vacuum..
The one on the front goes to the ported vacuum on the TB right?

If so, then why does my idle change if I remove the line on the back of the can and plug it, while my idle does not change if I remove the line to the front of the can and plug it?

Confused..

I figured removing the boost retard line on the backside wouldn't change anything except for on boost, but this doesn't seem to be the case..
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80 Turbo - Slightly Modified

kondzi · Joined: 02 Jul 2018 Posts: 143 Location: MZ/Poland/EU

Not sure about 931/S1, but I’ve recently had a strong headache from 1986 930 US. This has two vacuum cans - one for boost retard, the other for vacuum advance control with additional idle advance when cold. The trick was there was US emissions system that advanced idle ignition a bit at cold engine by blocking vacuum to the idle can (letting in atmospheric air instead) When the engine warmed up, the solenoid valve opened and a fully functional vacuum advance was operational.
Maybe, but just maybe it’s similar in 931/S1?
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Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)

Fasteddie313 · Joined: 29 Sep 2013 Posts: 2130 Location: MI

Mine doesn’t have any valves in the middle of the vacuum lines..

I was just trying to figure out a way to stop it from regarding so retardedly much on boost, quick and dirty style..
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80 Turbo - Slightly Modified