Quote:
Originally Posted by beatr911
So to bringing this back from the dead, been doing more perusing.
Seems the modern "Atkinson" engines all use variable valve timing and even the "Mild Atkinson" engines too.
So, with the Prius retarding only the intake 33* during atkinson mode, I should be able to achieve a mild effect by retarding my cam one tooth which is 14.4*. If there is no piston contact, try for 28.8* and see what happens.
Also I found out that internal egr can occur if the exhaust is retarded as well, pulling exhaust back in during the intake stroke. Retarding up to 60* may be possible, however in a fixed cam engine idle egr can become excessive rather easily making idle quality really horrible. Hey, maybe try retarding both cams as as part of a second experiment.
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Actually, I found out the prius inlet cam valve closure can be retarded as much as 95° after TDC.
33° does sound like a normal timing to me.
Also, newer motorbikes engine have a huge CR to make up for the overlap. The huge CR is mandatory in Atkinson engines.
This high CR, added to the reversion pulse in the inlet track wich I believe rules out the use of carburettors, asks for newer generation engines.
A few days ago, I had the opportunity to have a glance at a cam phaser from a car. Those are quite compact and I now believe they can be adapted to bike engines as long as the timing chain is on the side (not Suzuki's air/oil range)