It is my understanding that the 5.5gen intake manifold secondary runner is closed between 1800-3500 rpm. While it makes sense that the secondary runner opens past 3500 rpm, could someone please explain the purpose of it being open prior to 1800 rpm? I would think keeping the IM closed by default would benefit low rpm response...

 

Maxima's variable air intake system features an intake 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.

video of how it works http://www.nissanusa.com/maxima/gall...ke_System.html

 

There are no secondary runners.

I've dynoed open and closed and have other dynos that show the way it is from the factory, is the ebst for torque

That video is invalid because the 2k2+ Im is far different.

 

thats a vid from a 3.5 IM (according to nissan)

 

I understand what you are saying but the diagram is actually incorrect: Until ~1800rpm both runners remain open. I question the reasoning behind this, as it seems counterintuitive, no?

EDIT:

Technically there are no secondary runners, but the intake manifold is variable. Does it not restrict airflow between 1800-3500 rpm?

 

soonerfan: Yep, but unfortunately, it's inaccurate.


Others:
There are no second runners people, can you not read?

Click on the FWD version and then click the IM, theres a cutaway view for the IM

http://www.nissanusa.com/stories/?Cu...e:::MDLMAXHome

 

the im is different from 02 to 03 wtf

 

Who the hell said that?

 

cool...i trust you over anyone else

 

no one i made it up. im going crazy i thought you said 2k2 was different for some reason

 

It's a strange IM .
My guess is that it was made to compensate for lack of VTC tq the G/Z gets, and was given that weird design. But this also makes high rpm power suffer.

Here a an **** load more pics
http://www.cardomain.com/ride/301377/9

 

So...what function does that vacuum operated actuator mounted to the passenger side of the intake manifold perform by changing position first at 1800rpm and then again at 3500rpm?

 

Sucks the butterfly shut.

It's actually 3600 RPM (FSM)

2k2/3 phsycially the same, 2k4+, EGR stuff added but functionally the same.



http://forums.maxima.org/showpost.ph...3&postcount=14

 

That animation is of a QR25DE IM.

 

yup.. I have the old SCC mag with the introduction of the QR. Stricking resemblence.

 

i remember looking up 03 in the manual and it said it opens at 5500

 

You were corrected in another thread by Puppetmaster and me about this same exact thing. Per the FSM, it is closed from 1800-3600 RPM and open otherwise.

 

Which manual is this and where in the manual does it say that? I'm curious to know.

 

We really have to stop meeting like this...

 

But why is it open at < 1800 ?? It seems counterintuitive and does not seem helpful in terms of off idle engine response...that's been my question all along

 

 

He's asking why it's OPEN below 1800? and it is true...from idle (650rpm) all the way to around 2k, i notice it stays open...thats according to me watching the actuator, with someone revving the engine

this is why i got confused at first...cuz originally, i came from a 4th gen maxima...we had MEVI and 00VI's....their designs had butterfly valve in each runner...and they stay CLOSED until a certain RPM....where as the 2k2 IM, they stay OPEN....then CLOSES...then OPENS again...pretty strange i know....thats why i THOUGHT that zip tying the actuator on the 2k2 IM would keep it stuck open....when in fact, it's keeping it stuck shut...

 

I honestly don't have a good answer as to why its open below 1800, but does it really matter? When are you ever driving at < 1800 rpms? If you're worried about low end torque at 1800 rpms, then you should just downshift.

 

The motives for my inquiry were much less complex: I simply found the IM operation design somewhat bizzare, thought it warranted a question and that perhaps someone had an answer. Now we officially know otherwise

 

Well, just wasn't sure of your motives that's all. I'm sure we can speculate on the reason, but I still think its just an idiosyncratic design that has no significant impact on performance. Of course, that's just me. I'm sure someone out there knows.

 

I just find it weird how Nissan had other VIAS such as 00vi and MEVI...that is closed during default, and opened at a certain RPM...then when they designed the 2k2 VI, its default is OPEN....then it closes, then opens again...I mean, why couldn't they just stay with the same setup? it just seems logical to keep it shut for idle to 3800 performance...

 

Relax guys i said i remember.
In our dealership we use original Nissan ESMs.
I never had to look that up for any issues but i remember reading about it while i was just browsing.
I will look it up tomorrow again if i remember...
If you are so positive i am sure you are right. Like i said not much experience with that.

 

Judging from the dynos, it (opening @ 5500) must hurt HP, because that's where the OEM IM starts dropping off in power