CaliBenzDriver

Our secondary chain tensioners are the low-energy type.
They use an incompressible volume of oil and a check-valve to hold a piston against the camshaft pulling the chain slack. Camshaft is forced to rotate forward when pushed by its lobes.

Tensioners are only pushing the chain guide a little to hold everything tight. The internal spring is practically weak. No need to put additional stress on the plastic guides. These last the distance well.

It's extremely important the camshaft not be allowed to jump timing at all. We're not talking jumping a gear tooth, we're talking chain slack looseness.

Timing has to remain smooth regardless of extreme forces at any RPM. When camshafts are given looseness the VVT sensor wheel gets loosened by the impact hammering of camshaft rushing forward. That repair is a brand new camshaft times x pieces.

The tensioner forward bearing is simply a hard seal. It allows to dampens vibrations while still guiding shaft loosely. Good viscosity helps counter oil losses.

The good tensioner schedule is 50 to 75kMi. They don't quit, they just gently fade away to allow more freeplay. This screws up the HPFP proportioning valve timing on direct injected engines.

The ECU is sensitive to camshaft freeplay because of CPS sensors and software exact timings computation.

Extreme looseness has a famous noise associated with it: RATTLING.
Long before this sound calls your attention, the timings are affected as mentioned earlier.
When ignored long enough, the camshaft rattling creates a CEL codes that means business.


Primary chain/tensioner:
I realized the two secondary chains are driven the primary one that's driving the oil pump.
There is a short chain complete with guides and one tensioner.
The secondary chains prevent respective camshafts from rattling primary forward.

This primarily chain/tensioner has an easy life!