Help understanding VVIS

[Eric Crowder]

[FONT=&quot][FONT=&quot]I am looking for help understanding how the NSX VVIS works. From what I understand, at low and medium RPM the VVIS butterflies close, thus reducing the intake air volume. At above 4500 (ish) RPM the butterflies open, thus increasing the air volume inside the intake plenum.[/FONT][/FONT]
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[FONT=&quot][FONT=&quot]When vacuum is applied to the VVIS actuator diaphragm, it forces the butterflies to close. When no vacuum is present in the diaphragm (atmospheric), the butterflies open. [/FONT][/FONT]
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[FONT=&quot][FONT=&quot]With the engine off, if I reach my hand and rotate the twin VVIS shafts, should they forcibly snap open using mechanical spring force, or is it normal for the shaft rotation to float between an open and closed state. If they float about, what forces the butterflies open all the way when the engine is running and above 4500 RPM? Does air velocity forces them open? I think not.[/FONT][/FONT]
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[FONT=&quot][FONT=&quot]If the butterflies are supposed to forcibly snap open with the engine off, which springs force them to do this? Rotational springs on the shafts or a coil spring inside the diaphragm, or a combination of all 3.[/FONT][/FONT]
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[FONT=&quot][FONT=&quot]My butterflies float around when I move them with the engine off so I think I have a broken spring or springs. Thanks[/FONT][/FONT]

 

[dablackgoku1234]

They are open at rest. The spring is on the outside as seen here:

 

[ralph cerbone]

this is how it works ,vacuum is sent to the diaphragm on start up to 4500 rpm , above this vacuum it cut off and the diaphragm is bled off thru thru the controller , there is a check valve in the controller that will hold vacuum after you shut it off . I played with this a few years back ,teed in a vacuum gauge and drove the car ,at 4500 ,vacuum went to zero and valves open . toyota runs a similar system , my car can sit for days and will not bleed vacuum at the diaphragm , again this is the best of my recollection . If there are more questions I can check the ser. manual

 

[Eric Crowder]

this is how it works ,vacuum is sent to the diaphragm on start up to 4500 rpm , above this vacuum it cut off and the diaphragm is bled off thru thru the controller , there is a check valve in the controller that will hold vacuum after you shut it off . I played with this a few years back ,teed in a vacuum gauge and drove the car ,at 4500 ,vacuum went to zero and valves open . toyota runs a similar system , my car can sit for days and will not bleed vacuum at the diaphragm , again this is the best of my recollection . If there are more questions I can check the ser. manual

Thanks for for the information. I believe one or both of the springs are broken on my car. If I move the actuator with my finger (engine off), the shafts rotate freely, but when I let go, they just stay put. They do not snap to the open position. I plan on checking all of the butterfly screws with an inspection device, but I don’t think that is a problem, the shafts are not binding up. It’s just that they do not forcibly snap to the open position.

 

[mwagner10702]

From the Wiki:

What is VVIS and how does it work?
[MAM] VVIS stands for "Variable Volume Induction System," and is explained in the second NSX book on pages 26-29. The VVIS optimizes the air intake for different rpm ranges. For more low- and mid-range power, these butterfly valves remain closed (they look like paddles in the intake system, one paddle per runner). The book says the VVIS is activated by manifold vacuum above 4,800 rpm. By opening the valves, the intake air has acess to a second plenum which provides more "space" for the air- sort of like the Porsche Varioram system.


[BC] A note about the NSX variable induction butterfly valves: You can make it run at max volume all the time by disconnecting the hose to the solenoid and capping it, however I didn't notice any difference in performance when I did this (supposedly I should get less low end torque). Makes you wonder if the variable induction is of any real use or if they included it as a techno-gimmick.

 

[ralph cerbone]

From the

What is VVIS and how does it work?
[MAM] VVIS stands for "Variable Volume Induction System," and is explained in the second NSX book on pages 26-29. The VVIS optimizes the air intake for different rpm ranges. For more low- and mid-range power, these butterfly valves remain closed (they look like paddles in the intake system, one paddle per runner). The book says the VVIS is activated by manifold vacuum above 4,800 rpm. By opening the valves, the intake air has acess to a second plenum which provides more "space" for the air- sort of like the Porsche Varioram system.


[BC] A note about the NSX variable induction butterfly valves: You can make it run at max volume all the time by disconnecting the hose to the solenoid and capping it, however I didn't notice any difference in performance when I did this (supposedly I should get less low end torque). Makes you wonder if the variable induction is of any real use or if they included it as a techno-gimmick.

Don't know what book you are referring to but according to my 97 service manual pg. 11-154 Intake Air ByPass (vvis is a part of system),it cleary shows that at idle vacuum it applied to close valves . At above 4800 IAB solenoid is on stopping vacuum and bleeding vacuum at diaphragm allowing the springs to open the vvis valves . The diagnostic trouble shooting section,pg. 11-155 also explains it

 

[mwagner10702]

Don't know what book you are referring to . . .

I guess you would have to ask the individual that wrote the Wiki . . .

 

[ralph cerbone]

I guess you would have to ask the individual that wrote the Wiki . . .

Is it in our nsx wiki ,what is it listed under ?

 

[mwagner10702]

Is it in our nsx wiki ,what is it listed under ?

Here is the link: https://www.nsxprime.com/wiki/VVIS

 

[ralph cerbone]

Here is the link: https://www.nsxprime.com/wiki/VVIS

Yea he's got it backwards ,if u look at the ser. man. in wiki on pg 11-119 you can clearly see the diaphragm is relaxed when open and retracted by vacuum when closed . More important are the screws that retain the throttle plates to the shaft ,they have been known
to loosen. I have posted the correct way to secure these screws . Now you get an idea how these work .