S-AFC/S4 GXL: What's the best way to hook it up?
I wish I was driving!
Joined: Dec 2001
Posts: 5,241
Likes: 84
From: BC, Canada
Originally Posted by 89GTUs Lady
I don't disagree with you here. The NA Boost sensor output is not the problem. The problem is that the car is always in vacuum, so the output from the sensor is always the same.
In a TII the pressure sensor sees boost and vacuum, so the output varries. the S-AFC can be set to use the High map when in boost and the low lap when in vacuum. On an NA, you'll only ever get one map.
In a TII the pressure sensor sees boost and vacuum, so the output varries. the S-AFC can be set to use the High map when in boost and the low lap when in vacuum. On an NA, you'll only ever get one map.
On a vacuum signal taken between the engine and the throttle plates, as the stock pressure sensor does, varying throttle loads and positions will give vauum read-outs between almost zero inches of mercury and 26 inches of mercury.
Typical idle readings are around 16-18 inches, 26 under full decel, and 0 inches under WOT.
Vacuum is created by removing air from a closed volume... so when the throttle plates are closed, you are creating a vacuum by pumping air out of the intake manifolds... when you go to WOT, you remove this closed volume, and the only remaining, minute vacuum is caused by frictional losses of the intake runners.
Just because the engine is sucking in air does not mean there is measured vacuum...
I wish I was driving!
Joined: Dec 2001
Posts: 5,241
Likes: 84
From: BC, Canada
Originally Posted by 89GTUs Lady
It sounds great in theory, but does not work in practice. The output of the NA boost sensor (while in vacuum) is in such a narrow range that the S-AFC sees the signal as 0% thottle at all times.
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