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Discussion Starter #1
I remember reading a post a while back that said it is similar to VTEC, but I don't even know what that means. Why does the 3.5 get an added boost at 4000 RPM? I'm always telling people how cool it is, but they always ask what causes it, and I feel like a dumbass. Please help undumbassimafy me.
 

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Sounds like you're referring to wide open throttle? I think the 3.5 cams / setup are set to produce the full horsepower rating starts right about there. But I'm just guessing.
 

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Discussion Starter #3
Well, it's normally at half-open throttle and higher. And it's not just hitting peak HP. There is a noticable jump. I know I read another post that even compared it to having a turbo, or at least the sensation you get. I searched, but I couldn't find anything.
 

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Shift_lefty
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The altima brochure talks about a bypass air path that corresponds with the variable valves allowing the engine to "breath" better. Then again I listened to my service manager on the exhaust bypass:smack:
 

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Discussion Starter #6
I'm still confused, is the short intake runner only on the 4 cyl.? I've got V6 and I can feel the kick at 4000 RPM, not 5000. What's the deal?
 

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Yea, it's definately at 4000, not 5000.
 

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Discussion Starter #9
yeah, my pulse goes up a bit when I hit it. I've been trying to perfect my shift points to always hit the sweet spot. From my experience I go to 2nd at 6000, 3rd at about 5700, and 4th at 5700. What have you guys found?
 

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Discussion Starter #11
I'm talking about when I'm gunning it. Daily driving, I'd say I shift around 2500! 1500 if there's snow! Damn tires.
 

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djliquidice said:
At 4000RPM, i start shitting myself.

LOL :lol: Altima owns joo! :eek:wned:
 

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Variable intake system!!!

I think what you guys are feeling is the variable intake system opening the shorter air path. There is a longer air path at low RPM's which is better for tourqe, then when the RPM's reach about 4400 the shorter air path opens also which alows more air into the manifold. That is why you feel a surge at around 4000 RPM. This should answer your ?'s
 

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Re: Variable intake system!!!

jamiek said:
I think what you guys are feeling is the variable intake system opening the shorter air path. There is a longer air path at low RPM's which is better for tourqe, then when the RPM's reach about 4400 the shorter air path opens also which alows more air into the manifold. That is why you feel a surge at around 4000 RPM. This should answer your ?'s
Agreed, thats y u hear a change in the way the motor sounds...
Some vtec honda motors have the same thing happen, but theirs is due to the Vtec cam lobe comin online.
Our V6 cars don't have a preset lobe engagement like a older style Vtec system..we just a Variable cam timing, which is different..

The motor sure sounds sweet after 4 grand
 

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There is no variable intake system on the V6. What you are referring to is the variable cam timing system.

However, at 4000 RPM the butterflies for the secondary (short) intake manifold runners open up to feed more air (and consequently more fuel) to the engine via the "other" intake valve. The most similar analogy would be the secondaries on a four-barrel carburetor.

The variable cam timing our engines enjoy, alters the timing of the camshafts to different degree settings (retarding and advancing and NOT to be confused with ignition timing) to take better advantage of fuel/air delivery into and exhaust out of the engine under varying conditions, such as throttle opening and RPMs of operation.
 

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Incidently, my comment about "no variable intake system on the V6" refers to the concept one might have of confusing a VTEC setup with an intake system. Granted the whole thing works in concert, but they are different parts which, together, create the complete package.
 

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Discussion Starter #17
I'm starting to understand, but some visuals would help. I've got the service manual, is there a good schematic in there that would help?
 

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stlb5,

Check out nissan motors.com <--thats together. They have some type of visual.
 

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Discussion Starter #19
Yep, just saw it. Much more sense. They show both the 3.5 and 2.5 models. Anyone else who wants to take a look, it's just Nissan's US website. Go to the Altima vehicle page and they are on the right side of the screen.
 

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djliquidice said:
At 4000RPM, i start shitting myself.
In the background you hear "break now Jester" as the car veers violently to the right and the world gets blurry. Ah yes, the joys of the alti.

Yes you are granny shifting but I can't blame you with the way gas prices are these days. Besides the car moves pretty well even under 3500. The guy at the dealership gave me a hard time when I told him I consistantly get 26-27 mpg on my fillups, (real mileage not the computer) says I don't drive the car hard enough!!
 
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