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Discussion Starter #1
Didnt quite know how to word the title. But basically can someone explain how the vacuum setup works on the airbox/exhaust.

I thought it would simply open them both up when sport is on or maybe automatically do it at some some rpm point.
Zero vacuum they are both open, pull vacuum to go quiet.

I can hear things opening and closing by itself all the time. Usually if im going slow or just letting out the clutch etc.

The sound is like solenoid clicks and whooshes of air.

Or is it just idle control.
 

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..............

I thought it would simply open them both up when sport is on or maybe automatically do it at some some rpm point.
Zero vacuum they are both open, pull vacuum to go quiet.

.............
Yep. That's how it works.

Normally, the valve will be closed until 4700 rpm unless you use the Sport button which keeps it open all the time. The valve is set up with a spring so that if there is a loss of vacuum, it will be open to protect the engine from too much back pressure at higher RPM (they call it the EP or engine protection valve). The vacuum reservoir in the intake stores vacuum for when the valve needs it.
 

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Discussion Starter #3
So what are the noises I hear when im starting to move? Its intake sounds. Its almost like its giving me throttle when im not. Is it trying to stop me from stalling?

Thats another question. Why do we have a clutch position sensor? If it was for cruise control then wouldnt a switch like the brake be good enough?
 

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So what are the noises I hear when im starting to move? Its intake sounds. Its almost like its giving me throttle when im not. Is it trying to stop me from stalling?

Thats another question. Why do we have a clutch position sensor? If it was for cruise control then wouldnt a switch like the brake be good enough?
I believe the airbox flap was to reduce noise. The clutch position sensor is used by cruise control and engine management. See below:

1258220
 

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I'm not sure what you are hearing. I've never heard anything opening and closing as I start to move.

On your other question.....the clutch position sensor is definitely tied to cruise control:

"Data on clutch pedal position is used by the engine management
system for:
  • Cruise Control operation
  • Gearchange fuel cut off (To assist rapid smooth
gearchanges
- Start inhibit function on Canadian market vehicles."
 

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I'm not sure what you are hearing. I've never heard anything opening and closing as I start to move.

On your other question.....the clutch position sensor is definitely tied to cruise control:

"Data on clutch pedal position is used by the engine management
system for:
  • Cruise Control operation
  • Gearchange fuel cut off (To assist rapid smooth
gearchanges
- Start inhibit function on Canadian market vehicles."
Is there any way to enable the start inhibit feature on US models?
 

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I was surprised our cars didn't come with it. I thought all modern manual vehicles had that provision. But, since ours do not have it from the factory, I would guess that it (minimally) has to be programed into the ECU.

Of course, you could probably wire in a separate switch to obtain the same function, but you would have to tap into the harness to make it work.
 

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Discussion Starter #8
I'm not sure what you are hearing. I've never heard anything opening and closing as I start to move.

On your other question.....the clutch position sensor is definitely tied to cruise control:

"Data on clutch pedal position is used by the engine management
system for:
  • Cruise Control operation
  • Gearchange fuel cut off (To assist rapid smooth
gearchanges
- Start inhibit function on Canadian market vehicles."
"Fuel cut during gear changes"

On the manual?

I still have engine control when im double de clutching or rev matching though? So is it only cutting on upchange for a short time?
Ive noticed when rev matching that the number of revs I get isnt consistent. Sometimes I get almost nothing and other times I get too many. (is that throttle cut?)
 

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I was surprised our cars didn't come with it. I thought all modern manual vehicles had that provision. But, since ours do not have it from the factory, I would guess that it (minimally) has to be programed into the ECU.

Of course, you could probably wire in a separate switch to obtain the same function, but you would have to tap into the harness to make it work.
Probably editable in the ECU, but would require using BOE as they are only ones to have gotten that far into the code.
I was surprised that my 2012 didn't have it as I though it was a Federal regulation. But my 2017 S 410 does have the clutch - start inhibit.
 
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