Ok, I've noticed that when I hit 3500 RPMs the engine gets a kick and I accelerate faster. It is similiar to what happens in my dad's Taurus SHO. A second throtle body opens up at 4000 RPM and you can feel it. It was a nice feature as he get 32mpg if he takes it easy but once you get the RPMs up, it takes off. Does anyone know if the same thing is happening in the X's engine? I do not have the service manual and am curious if anyone else has read about it.
Kurt

I would assume you are feeling the cams profile. It was designed to have that "burst of acceleration" around that rpm. I have a Jetta 24V VR6 that does the same thing and I can change where the power is delivered by changing cams. Of course it is expensive!

It is similar to the situation on the SHO, which has a Yamaha designed and built engine. Nissan calls it "variable intake system": "Variable Intake... variable air in take system features an in take manifold that "breathes" differently at high and low rpm. You get rich torque off the line; then, as speeds rise, a shorter air flow path opens to unleash deep reserves of passing power."

The engine also has variable valve timing "....extremely advanced Continuously Variable Valve Timing Control System makes constant, precise adjustments to the opening and closing of the valves based on rpm and throttle position. Which ultimately delivers optimum power and emissions."

The Maxima page has a couple of animations POWER

That's exactly what you're feeling. A solenoid (controlled by the ECU) opens up a throttle blade that's internal to the intake manifold, causing a shorter path for the air charge to follow. Higher rpm's demand quick air (just get it in there, NOW!) for power. Lower r's demand speedy air (which is what the longer intake runners provide, velocity into the combustion chamber).

The variable timing is always adjusting, so it's not something that you'll feel 'kick in'. But the computer controls the timing through the individual coils, the mixture through the injectors, and now even the air that's introduced into the engine (not to mention cam timing!).

Sure beats the ol' days of the Chevy V8 with 1 cam and 2 barrels, huh?

I still love the feeling of an old Chevy V8 when the Holly FOUR barrels kick in. If you ever watch the carb when the 4 barrels open up, it's like two garden hoses flowing gas down the chamber. Simply awesome for a smash of power, but man does it hurt the wallet.

I trully enjoy when the xterra hits those rpm especially having a K&N air intake the sound and the force is pretty awesome. I always look forward to a yellow light so i have an excuse to waste some gas and floor my gas pedal.......
anyone else with the K&N air intake????

i love that little kick, especially when following someone doing 10 under the speed limit and you just want to go flying by them. always learning something new about my X is always cool too. im also planning on getting the K&N as soon as i get some extra money.

All of you that are using or interested in K&N's REALLY need to look at this > Filters I have used K&N's for years and have switched.

Thanks for the reply. I've been wondering that for a while. The SHO's version almost feels like a turbo kicking in. The X's is a little more subtle but still quite affective. Now I know I'm not nuts and will keep it in mind next time I'm looking for a quick boost of power.
Kurt