2.5i and the VVL system explained
Posted: Thu Jun 13, 2013 5:24 pmSo I had a few questions lately about how the VVL system(aka AVLS) in the 2.5i works and have devised a brief summary based on the email replies that should cover the blanket response 
The EJ25 AVLS is not for 'performance' the VVL system is there for fuel economy, with the concept actually stolen from Honda with their VTEC-E Engines... that is VTEC - E with the E for Economy and is one reason why the USA has the 2.5i listed as a PZEV. Here is an article on the VTEC-E engine
http://www.b18c5eg.com/VTEC/sohcvtece.html
which further explains how fuel economy is achieved by only having one inlet valve open below 3000rpm and the factory tune running fully in closed loop with 14.7:1 AFR's for fuel economy and lower emissions. Above 3000rpm, the factory tune actually richens up by 7% to account for the sudden rush of airflow generated by the second cam lobe activating
As you can see, only 1 inlet valve opens with the second yellow pin activating the second inlet valve when required
Once exhaust mods or intake mods are done, the added engine flow dictates that the AVLS RPM point should be lowered to eliminate the single inlet valve as being a restriction but if you want to keep fuel economy, it can still be achieved with stock AVLS rpm by tweaking the AVLS airflow value so once airflow goes past a predetermined value that is considered a restriction, the AVLS activates, even if engine rpm is not high enough, just need to set the fuel table to add fuel above this value
The EJ25 AVLS is not for 'performance' the VVL system is there for fuel economy, with the concept actually stolen from Honda with their VTEC-E Engines... that is VTEC - E with the E for Economy and is one reason why the USA has the 2.5i listed as a PZEV. Here is an article on the VTEC-E engine
http://www.b18c5eg.com/VTEC/sohcvtece.html
which further explains how fuel economy is achieved by only having one inlet valve open below 3000rpm and the factory tune running fully in closed loop with 14.7:1 AFR's for fuel economy and lower emissions. Above 3000rpm, the factory tune actually richens up by 7% to account for the sudden rush of airflow generated by the second cam lobe activating
As you can see, only 1 inlet valve opens with the second yellow pin activating the second inlet valve when required
Once exhaust mods or intake mods are done, the added engine flow dictates that the AVLS RPM point should be lowered to eliminate the single inlet valve as being a restriction but if you want to keep fuel economy, it can still be achieved with stock AVLS rpm by tweaking the AVLS airflow value so once airflow goes past a predetermined value that is considered a restriction, the AVLS activates, even if engine rpm is not high enough, just need to set the fuel table to add fuel above this value
