# Two-stage intake manifold, when does it switch over?



## wmorrison65 (Sep 7, 2014)

There is a mechanism in the intake manifold that changes the length of the runners. If you look under the spark plug wires top front of the engine, you can see the actuator. It turns a cylinder that extends through the intake manifold, that has holes placed to change runner length when the cylinder is rotated.

Anybody know what conditions trigger the actuator?

I don't have a problem with it, I'm just curious. I would assume this switches over at higher RPM but really have no idea, and am wondering if anybody knows.


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## 01greengti (Jun 28, 2019)

wmorrison65 said:


> There is a mechanism in the intake manifold that changes the length of the runners. If you look under the spark plug wires top front of the engine, you can see the actuator. It turns a cylinder that extends through the intake manifold, that has holes placed to change runner length when the cylinder is rotated.
> 
> Anybody know what conditions trigger the actuator?
> 
> I don't have a problem with it, I'm just curious. I would assume this switches over at higher RPM but really have no idea, and am wondering if anybody knows.


You don't mention which engine, but I'm presuming you have a VR6 which has the intake shift rod in the intake manifold that's rotated by the vacuum actuator on the driver's side end. It moves mainly with rpm and adjusts the airflow and air intake chamber characteristics. 

They're notorious for bushing failure as the material doesn't last with age and motor conditions, and they shrink causing a loud ticking noise from the rod slapping around, often mistaken for valve/lifter noise. It's easy to get to and remove for inspection, but the small arm with ball joint on the end that the actuator rotates can break easily (don't ask how I know) and you have to buy the whole (v. expensive) assembly to replace that little crucial part. I ended up 3D printing one that got the job done, but I'm not confident it will take years of engine compartment heat. 

You can buy the bushings separately. You can also remove the slotted rod and cap off the chamber. The difference is not huge but you do lose a little pep and performance (but it does cure the infernal ticking).


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## gettajetta13 (Jun 22, 2008)

This is in fact for the V6. Its located on the front of the intake mani, under the coilpack and is vacuum driven meaning it switches once vac increases with FPR. I dont have detail about when the variable intake shifts positioning though.


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