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Miller timing vs F-timing on diesel engine

Miller timing vs F-timing on diesel engine

thread71-351425: Miller timing vs F timing

Good morning
A few months back, I posted a question about the F-timing vs miller timing for diesel engine.
I final got the answer.

Miller timing- Is when the intake valve close a few degree before bottom dead centre,on the intake stroke.
F-timing - is the same principle as miller timing but the intake valve is close a bit early.This timing is unique to an engine manufacturer.

RE: Miller timing vs F-timing on diesel engine


Miller timing- Is when the intake valve close a few degree before bottom dead centre,on the intake stroke.
If you talking about Miller cycle, i think intake valve should close not before, but after bottom dead centre, it's very similar to Atkinson cycle :)

RE: Miller timing vs F-timing on diesel engine

Your description is two ways of saying the same thing.

Normal timing (on any piston engine) is for the intake valve to close some time after bottom dead center, chosen for maximum volumetric efficiency in some RPM range.

Atkinson timing (as implemented by Toyota, Ford, Honda, and others) uses late intake valve closure, intentionally pushing some of the intake charge back out, intentionally reducing volumetric efficiency, such that the effective expansion ratio will be greater than the effective compression ratio.

Miller is the same thing but with forced induction to allow the reduced VE to be compensated for when the engine is running under heavier load.

I've never seen it done with early intake valve closure except how BMW Valvetronic and Fiat Multiair (variable valve timing and lift) implement it. When combined with reasonable intake valve opening timing, this would shorten the duration of the cam lobe. With most practical cam geometries, this would severely restrict effective valve lift. Valvetronic and Multiair can get away with this because (through various means) at part load they essentially don't use all of the cam lobe. (Not quite that simple but it will do for purpose of illustration)

Never heard of F-timing, and if you have a web link to an explanation, please supply it!

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