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Active valve control system
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<h2 id="avcs">AVCS</h2> <p>The implementation of AVCS is quite different from <a href="/facts/Active_valve_lift_system/Vc7hG7at">AVLS</a>. The latter only changes the cam profile that's operating the two valves. </p><p>In AVCS, the engine computer (ECU) can command a solenoid which advances or retards the camshaft rotation by up to 35 degrees. </p><p>By retarding the cams at idle or very low engine loads, a smoother, easier idle can be achieved. From idle through medium engine loads, AVCS advances the intake valves to begin opening during the last part of the exhaust stroke, when the exhaust valves are still slightly open. Some of the pressure created during the exhaust stroke flows into the intake manifold, having the effect of <a href="/facts/Exhaust_gas_recirculation/W1T5eJbU">exhaust gas recirculation</a> (EGR). The intake valves also close earlier during the intake stroke. This helps with engine efficiency and fuel economy. </p><p>At very high engine loads, AVCS advances the intake valves further to open even sooner during the exhaust stroke. This produces a scavenging effect – that is, intake airflow helps clear the cylinder of exhaust gas. It also closes the intake valves sooner on the compression stroke. This results in improved volumetric efficiency, increased dynamic compression, and helps to generate higher power output. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Active_valve_lift_system/Vc7hG7at">AVLS</a></li></ul> <h2 id="external-links">External links</h2> <ul><li>Subaru Drive Magazine articles: <a href="https://web.archive.org/web/20110820065012/http://drive2.subaru.com/Win05_WhatsInside.htm">AVCS</a>, <a href="https://web.archive.org/web/20120624171722/http://drive2.subaru.com/Spring07_whatmakes.htm">i-AVLS</a></li> <li><a href="http://www.comeanddriveit.com/engine/subaru-avcs-explained">Subaru AVCS Explained</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"Subaru AVCS Explained". Retrieved 2017-12-06. <a href="http://www.comeanddriveit.com/engine/subaru-avcs-explained" target="_blank">http://www.comeanddriveit.com/engine/subaru-avcs-explained</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"Subaru AVCS Explained". Retrieved 2017-12-06. <a href="http://www.comeanddriveit.com/engine/subaru-avcs-explained" target="_blank">http://www.comeanddriveit.com/engine/subaru-avcs-explained</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> </ol>