ducetius

What is the hole between the Seconday Throttle valves for?

See picture

NZConvertible

If feeds air to the nipples on each side of the plenum chamber that go to the oil nozzles, injector bleeds and purge valve.

ducetius

Is there anywhere you can get a diagram of the internal routing?

NZConvertible

I doubt you'd ever find a diagram if the internal stuff unless someone made one.

It's not too difficult to follow if it's all apart, but if you study the FSM vacuum routing diagram you can figure out the external stuff.

For your S5 turbo, the nipples on the plenum are:

Front (top to bottom): relief valve (after throttle), purge valve (after throttle), purge valve (before throttle)

Back (top to bottom): secondary injector air bleed, primary injector air bleed, oil nozzle air bleed spider (all before throttle)

ducetius

Thank you very much

From the FSM that I have (90) it looks more like this to me, I'm assuming I am wrong and just can't follow the lines very well.

Front (top to bottom): swtich valve (after throttle), purge valve (after throttle), purge valve (before throttle)

Back (top to bottom): secondary injector air bleed, oil nozzle air bleed spider, primary injector air bleed (all before throttle), seconday throttle valve actuator (after throttle)

So regardless this passage feeds both sides, front side at bottom (one nipple), back side at top (three nipples).

NZConvertible

You're right, it's the switching solenoid, not relief. My 89 FSM doesn't show the seconday throttle valve actuator on the vac diagram. I wondered where that connected to. Yep.