Toyota's new low-friction Rav4/Venza engines 1AR-FE & 2AR-FE

[taco]

my guess is secondary runners that open at load?

my wifes old 2000 v6 cougar had that, but at 30k on the clock they woud get stuck and the car would hesitate like something awful. actully the car was awful, great areo, decent(ok knda low) power for a v6 (170hp), relaibily sucked warped flex plate was awful on everyone of those cars.

[Daox]

Yeah, thats pretty much it Taco. Here is a pic of a Toyota ACIS manifold off an older engine. In the second picture you can see they use a vacuum actuator to open the butterflies on the secondary runners. When vacuum is low in the intake manifold plenum, the actuator opens up and opens up the secondary runners. To prevent this from happening at too low an rpm (not enough airflow to make the secondary runners worth opening), they use a vacuum solenoid valve. Below X rpm the solenoid stays shut and the actuator can never see low vacuum pressure. Its actually a pretty simple setup.