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Originally Posted by nandalora
Ok, and what do you think VVT was invented for???
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Improved emissions on ULEV cars. And if used for performance to broaden the usable power band. SAME THING IMRC is used for but one doesn't replace the other. They can BOTH be used on top of each other for even more improved performance at the expense of increased motor complexity, and design costs. Some of the engines that use exhaust cam VVT for emissions and torque also use variations of IMRC systems on the intake.
So I guess I'm saying one is not mutually exclusive of the other.
IMRC is a benefit unless it malfunctions. It has a purpose.
One reason I don't buy the whole "no secondaries increases the high rpm horsepower..." thing is this:
If the engineers calculated that their 2.5L engine needed intake runners with a total cross sectional area of a^2 for optimum performance, then they would not have just thrown IMRC on top of that and reduced cross sectional area and maybe airflow. The logical thing they would have done was calculated the cross-sectional area lost by the IMRC plates&shafts and then just added that to the total calculation to account for it; for example A^2+S.
I mean come on, that is an easy calculation considering some of the math that goes into engine design right? You really think they shot themselves in the foot with IMRC or that they designed the manfold to work well with it?
Now granted, if you changed the whole characteristic of the engine, displacement, rpm operational range, cams, etc. then you may want to remove it. For all other engines excluding forced induction, you could conceivably make improvements to the system and retaining the IMRC system that would outperform a car that did not have it.