2.5i and the VVL system explained

Posts specific to the 2.5 litre NA engine

2.5i and the VVL system explained

Postby KiDo_Tuning » Thu Jun 13, 2013 5:24 pm

So 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 :)

Image
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 :)
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Re: 2.5i and the VVL system explained

Postby turner_822 » Thu Jun 13, 2013 5:49 pm

Great post! Good for anyone looking to tune/boost/modify their engine.

It would have made things a lot easier for me when I did stage II cams, instead I was groping around in the dark. I ended up removing the mechanism altogether as I had the engine out...felt like playing :lol:
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VVL in the 2.5i. See the split rocker arms on the intake valves (top).
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Re: 2.5i and the VVL system explained

Postby Tradewind » Mon Jul 22, 2013 4:34 pm

Probably one of the best posts about this motor and its mechanisms on any forum anywhere around the world at a guess - excellent.

No one has really bothered with it much but with an SC and tuning available - its output is very respectable
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Re: 2.5i and the VVL system explained

Postby lump_a_charcoal » Mon Jul 22, 2013 9:12 pm

Subscribed!
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