The Volvo S60 2.0T along with others in Volvo's range, benefit from Variable Valve Timing (VVT). Prior to VVT, you could either have an engine that was responsive at low RPM or produced good high RPM power. VVT enables the engine manufacturer (and the driver) to have the best of both worlds.
It should be noted that the air (and exhaust gasses) inside an engine can only more so fast. That fact dictates how an engine 'breathes'.
If you have 'aggressive' camshaft timing, at low engine speeds (RPM), the inlet charge can escape into the still open exhaust port and reduce the amount to be burnt, lowering the power output and raising fuel consumption.
Conversely, if you have 'sedate' camshaft timing, it cannot breathe efficiently at high engine speed as the exhaust gasses just cannot get out of the cylinder, nor can the fresh intake charge get in completely.
By varying the timing, you get the best of both worlds. Assuming it is working.
Note: The following is an extract from the Wikipedia entry for 'Powerband' and I am indebted to User:TomTheHand for his graph.
The "torquey" engine, illustrated by the blue lines, makes greater levels of peak torque. The "peaky" engine, illustrated by the red lines, produces less peak torque, and significantly less torque at the lowest RPMs, but produces adequate torque at much higher RPMs; as a result, it produces more peak power.
The "torquey" engine, by virtue of its higher torque at low RPMs, may be easier to drive in day-to-day use. The "peaky" engine, with its higher power, may be faster when driven aggressively, keeping RPMs high.
This graphic is essentially made from my understanding of the topic and needs to be revised as more hard information is incorporated.
Variable Valve Timing allows you (in theory) to have the blue lines to the left of the graph, and the red lines to the right. Getting the best of both worlds.
It makes sense that a failure will result in either poor low RPM tractability (red lines), or poor high RPM performance (blue lines).
In my case, the car performed like a peaky two-stroke motorcycle of the nineteen-eighties. Nothing, nothing, nothing - waaaah!
In the image above, dead centre of the image is the number 1 cylinder 'coil over plug'. Above that are the leads to the two solenoids, Exhaust at the top (rear of engine), inlet at the bottom (front of engine). Note that these are 'handed'. They are different part numbers.
The obvious response to an issue with the VVT system is to check that the two solenoids (or actuators if you prefer) are still working.
It was when I removed both solenoids that I noticed an issue. The filter screens were partly block or lacquered over. This would no doubt have reduced oil flow, that would have in turn reduced the effectiveness of the system.
Note: The solenoids are 'handed'. i.e. they are not interchangeable. Make sure you order the right one!
Given how easy it is to replace the gaskets, it would be sensible to replace them BEFORE they block and cause a driveability issue, such as I had.
It is also considerably cheaper than replacing the solenoids.
Last updated: 28/06/2020
All pages created with Notepad++ unless otherwise stated.