Anyone considered a Miller cycle?
- Thread starter darkscout
- Start date
Ol'Rattler
Top Post Dawg
Sounds like you would have to have a supercharger or low end performance would suffer. Also, you might have issues with valve to piston collision with the changes in intake valve timing.
http://en.wikipedia.org/wiki/Miller_cycle
http://en.wikipedia.org/wiki/Miller_cycle
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Or you size your sequential turbos so that it is pushing boost at idle.
How would you have that? The piston is still near BDC. It's not like you're cracking the intake valve at TDC. You leave the intake valve open for a small portion of the compression stroke. You do all the 'compression' in the turbos that way you can extract the heat from it. (Unlike doing it in-cylinder)
GoFaster
Moderator at Large
It certainly won't be a "performance" mod. It will reduce torque below standard at lower revs.
The other thing with making the effective expansion stroke longer than the effective compression stroke (that's what happens with late intake valve closing), is that there will be less energy left in the exhaust gases to spool the turbo up.
There's a reason Mazda did this in conjunction with a supercharger rather than a turbo (on a gasoline engine). There's also a reason that they don't do it that way any more.
The non-forced-induction Atkinson cycle has the same effect; lots of hybrid cars use it; quite a number of gas engine cars with VVT use it to emulate the Atkinson cycle when running at part load. The hybrids use the electric powertrain to fill in the missing low-end torque.
diesel + atkinson/miller + turbocharging => probably not very happy.
The other thing with making the effective expansion stroke longer than the effective compression stroke (that's what happens with late intake valve closing), is that there will be less energy left in the exhaust gases to spool the turbo up.
There's a reason Mazda did this in conjunction with a supercharger rather than a turbo (on a gasoline engine). There's also a reason that they don't do it that way any more.
The non-forced-induction Atkinson cycle has the same effect; lots of hybrid cars use it; quite a number of gas engine cars with VVT use it to emulate the Atkinson cycle when running at part load. The hybrids use the electric powertrain to fill in the missing low-end torque.
diesel + atkinson/miller + turbocharging => probably not very happy.
TDIMeister
Phd of TDIClub Enthusiast, Moderator at Large
Done yes.