What is a Variable intake and how dose it work?

V6 engine air intake divides into two 3cyl manifolds. Between these is a air flap which opens/closes depending on various variables. Opened flap increases a little the available air amount to one cylinder in intake -phase. This increases peak hp (maybe 10hp?) but sacrifices torque. Thus its closed on 3k or lower rpm's. See various model intakes in FSM's page EM-9, check for 'top left Favorite Links' below. The available FSM pages indicate that 2000model intake hasnt got that variable intake flap, but 2002 has, dunno.

The 3gen -93 VGE engine definitely has... see its vacuum pwred work cyl circuit pic below. The

2k2 circuit [similar to VGE] contains a ctrl valve, surge tank working as vacuum reservoir for this work cyl /flap mech. ECU controls all...

more pics at

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History of variable intakes in Maximas;

1992-94 SE, the 190 HP motor, had a variable intake. 1995-99, all Maximas of the 4th gen, the USA model, did not.* 2000-2001 Maximas have a variable intake on its 3.0 liter V6 2002+ Maximas have the bigger 3.5 liter V6 . . .also with a variable intake.

*Concerning the 4th gens (1995-1999): Nissan made a variable intake for the 95-99s but never gave it to the USA model. Users on Maxima.org discovered this and started importing them. Later on it was discovered why. The stock fixed length USA manifold, while weak at top end, had a very strong mid-range, strong enough such that the variable intake that Nissan built actually made the car's mid-range response weaker. Top end was better though. Also, the Nissan variable intake for the 95-99 was not a true dual intake as someone else posted in theat pretty graphic (which is pretty much all the other maxima dual intake systems). Put simply, the 95-99 variable intke was a compromise design that achieved most of the effects of a true dual intake manifold, but not quite.

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