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Old 02-06-2013, 09:47 AM   #28 (permalink)
mechman600
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Quote:
Originally Posted by renault_megane_dci View Post
Let's not forget we want to increase static compression ratio to match the previous dynamic compression ratio to get the most out of this mod.
Yes - I don't think 12.5:1 (static) mentioned above is nearly enough to make the Atkinson cycle "profitable". 12.5:1 is already the realm of many motorcycle engines. I am thinking that 14-16:1 is more like it.

Since DIY cam grinding is a daunting task (at least for me), I wonder if a partial cylinder fill could be achieved by a second throttle valve that restricts intake to achieve a certain vacuum at all times. It would have to be self adjusting with a manifold absolute pressure sensor and control system of some sort...or with the use of a vacuum gauge and a very careful throttle hand.

I realize this would cause more pumping losses compared to an actual Atkinson cycle, but I wonder if these losses would be more than offset by a very high compression ratio.
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