Subaru AVCS

[Ross]

Does anyone have any links explaining how this works in a technical way. Im
curious as to what it does. My STi Type UK engine does something at about
4000-4500rpm which cases the engine note to harden significally i was
wondering if this was due to the AVCS kicking in like hondas VTEC.

R

 

[Patrick Fisher]

Does anyone have any links explaining how this works in a technical way. Im
curious as to what it does. My STi Type UK engine does something at about
4000-4500rpm which cases the engine note to harden significally i was
wondering if this was due to the AVCS kicking in like hondas VTEC.

R

It's somewhat similar to VTEC. AVCS varies (on the US Spec model at least)
the Intake cam timing using a hydraulic system to "rotate" the cam lobes
with respect to the shaft (which is statically driven by the timing belt).
This allows it to run more advanced cam timing at higher RPM, allowing good
torque down low, without the typical drop in power up high. Lift is not
affected, nor is the exhaust cam timing (again, on the US spec model. I
believe either the global STi engine varies both, or the next version will
vary both, but I can't remember which).

VTEC varies both cam timing and lift, with alternate lobes, and I believe it
operates on both intake and exhaust cams.