924Board.org

[Fasteddie313]

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]

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]

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

[anthonimartini]

way late to the game here but the reason why it changes so much at idle is because the vacuum signal from the throttle body to advance side is ported. meaning it is only exposed to vacuum when the throttle plate is off idle. this allows the distributor to pull retard at idle which cleans up tailpipe emissions and stabilizes idle. under cruising vacuum the advance comes into play until the turbo creates positive pressure on both sides of the distributor which will net more timing retard keeping timing in a safe range for a the larger volume forced into the combustion chamber.
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ive saved alot of 924's
current:
79 MochaSchwartz 931
83 944
87 924S
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formerly known as turbellion, lost password.