K04 vs k03 spool up

[Hedge]

At a constant cruise @ 70 both engines will be pulling a vacuum.

Sorry what does pulling a vacuum mean?

....In broad terms, vacuum relates to turbo pressure. The vacuum causes the turbo actuator to close and hence the turbo to work and give extra power. That's the simple explanation.

I don't get that. To me you are either on or off boost. At 70mph both turbos will be on boost.

Vacuum indicates a lack of pressure but if you do VCDS logs you see greater than atmospheric pressure when on boost. 

[alackofspeed]

At a constant cruise @ 70 both engines will be pulling a vacuum.

Sorry what does pulling a vacuum mean?

....In broad terms, vacuum relates to turbo pressure. The vacuum causes the turbo actuator to close and hence the turbo to work and give extra power. That's the simple explanation.

I don't get that. To me you are either on or off boost. At 70mph both turbos will be on boost.

Vacuum indicates a lack of pressure but if you do VCDS logs you see greater than atmospheric pressure when on boost. 

To clarify what I meant. When you're at low load on the motorway at a constant 70 (and low rates of accel) the engine is barely working (30-40 bhp maybe?); the throttle is only cracked open slightly, the inlet manifold is at less than atmospheric pressure and the turbo re-circ valve will be recirculating. There will be no boost as such.



 

[RedRobin]

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Pulling a vacuum can also mean this:

[rich83]

At a constant cruise @ 70 both engines will be pulling a vacuum.

Sorry what does pulling a vacuum mean?

....In broad terms, vacuum relates to turbo pressure. The vacuum causes the turbo actuator to close and hence the turbo to work and give extra power. That's the simple explanation.

Not exactly.

Vacuum.
Pulling a vacuum basically means that the engines pistons are pulling or 'requesting' a greater volume of air than the turbo charger is giving. Thus resulting in negative pressure (vacuum) in the intake manifold.

Boost.
When to turbo spools and produces pressure in the intake system that is greater than the vacuum which the engines pistons are trying to make.... Then we have boost.... And smiles :-)