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Engine & Performance Modifications Discuss Engine and performance modifications from intake to suspension to rotors to etc. :)

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Old 01-18-03, 02:57 AM   #1 (permalink)
Dv8
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Intake Manifolds opened to reveal VIS

Well its time to do some machine work and what a better time to do it than on my spare engine.

Here i have a TYPE II manifold i just removed from my spare engine. I opened it up to see what if any Port and polish was needed. I had a vuage idea of what the vis system was like, but i had no idea i would find three big flaps all controlled by the air butterflies. (thats why it sounds like a CROSSOVER when i pass 4000RPM one if not all of these flaps open up.

I now have a clearer picture of what LEGENDTYPERKON removed from his....idiot.

Now wait, is he really that moronic or did he actually screw up his idle but eventually for the real race car driver gain more raw hp?

how about removing one plate? i know your ide ,gass etc will goto ****, but im solemly talking performance.

just curious.

what im really curious about, is the seqence of these flaps. when do them open and which ones. Dave you there?

Like DAVE C said the top portion of the 3 peice manifold is very rough, mine had a lot of carbon deposits and some oil in it!?

hoever the other 2 plates are flawlessly smooth with noneed for anything.

please input i want to know how they work and when they do.










~Hybrid
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Old 01-18-03, 07:22 AM   #2 (permalink)
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Like I said. Extrudehone and port match the upper plenum. You can match the lower plenum and butterfly plate but gains would be very small.

Butterfly actuation is clearly described in the service manual.

IMO removing any butterflys will impair engine operation. Remember they are RPM controlled.
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Old 01-18-03, 10:11 AM   #3 (permalink)
 
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I was thinking the same thing. I was on the NSX forums a while back or something and remember reading that one of them removed and polished the manifold and actually had some decent gains. I will try to find it.
I was looking at mine the other day too, and was wondering the same thing DV8.
Ill look into it.
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R
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Old 01-19-03, 01:00 AM   #4 (permalink)
 
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thanks for the pic, i always wonder how the vis function look like
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Old 01-19-03, 01:12 AM   #5 (permalink)
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As I understand it, the butterfly valves are for torque control to maintain torque at low and high RPMs.

Of the three valves, I believe that the first is open pretty much all the time. The second (or Low Intake Air Bypass) opens above 3,400 RPM, and the third or High Intake Air Bypass valve opens at 4,300 RPM. These are Type II specs. The Type one opens the low at 3,300 RPM, and the high at 4,000 RPM.
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Old 01-19-03, 03:51 AM   #6 (permalink)
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Quote:
Originally posted by LegendGS
As I understand it, the butterfly valves are for torque control to maintain torque at low and high RPMs.

Of the three valves, I believe that the first is open pretty much all the time. The second (or Low Intake Air Bypass) opens above 3,400 RPM, and the third or High Intake Air Bypass valve opens at 4,300 RPM. These are Type II specs. The Type one opens the low at 3,300 RPM, and the high at 4,000 RPM.
these are type II 's

bothe right and left flaps are controlled by the same butterfly so if one opens the other does too.

middle on is controlled on its own.

i think that they are all closed to start off with and gradually the middle opens as do the left and right a 4300 rpm.

Pics? Anytime.

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Old 01-19-03, 04:00 AM   #7 (permalink)
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OK. I took a closer look at the diagram.

The left and right valves are the low (3,400 RPM), and the middle is the high which kicks in at 4,300 RPM.

I don't think that there is gradual opening. I believe that the valves are either opened or closed.
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Old 01-19-03, 12:49 PM   #8 (permalink)
 
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Basically is changes the resonnant frequency of the incoming air so that it about matches the speed that the intake valves are opening up. That way it lets the engine "breath" a little easier.
By changing the area of the intake manifold, it changes that frequency to match higher RPM's.

I dont think it makes a HUGE difference, but my main questions is once you are pulling in as much power as DV8, for example, so much more air is coming in that it may be starving the engine at lower RPMs until the other butterflys open. So it may benifit to remove it and polish the entire manifold, on the other hand it may always still match the RPM's/Frequency since when you are making that much more power you rev quicker so it still may be in tune.

Theres only one way to find out. Any other input is welcome. I have my intake manifold sitting here as well and I was trying to figure out if that would be better or what.

This is from an NSX page-
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.

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.
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Old 01-19-03, 01:00 PM   #9 (permalink)
 
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Also now that I am thinking about it, that is all tuned for the pressure waves of an NA engine. If you are going to supercharge it, it may be in your interest to remove then since the length of each chanber would need to be changed and tuned for a different pressure level when under boost. So when you are under boost I dont think it will do anything but restrict the ariflow since it is out of tune with the pressure waves. Otherwise if you are staying NA I'd prolly leave it there.
Just my thoughts.
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Old 01-20-03, 02:16 AM   #10 (permalink)
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Well i guess a simple answer to all this is, get my downpipes and you'll see what i mean.

above 4k with the downpipe in place the engine get a big boost of power( a veryvery audible roar of air, very much like VTEC. Something the little paddle coulnt do.) which makes me think the two side flaps open up. If your around N. CA and want to see and hear it for yourself contact me.

once i get everything back up and running i will disconnect the small paddle and surpress the hose so that it remains open, we'll see what happens at the track.


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Old 01-20-03, 01:29 PM   #11 (permalink)
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the stages are


1st stage: all butterflies are closed and the air takes the TEDIOUSLY long route around the back edge of the manifold then around, then back up fron to the runners. thorugh 1500rpm i think, this long tedious tract is optimal for most lowend torque.

2nd stage: the outer flaps open and air flows freely upwards to longer of the runners...

3rd stage THE MOVIE( inside joke): the middle flap opens to expose a direct run to the intake runners and act as a single plenum instead of a bunch of runners.


sorry i dont know if anyone answered this yet but i saw Dv8 wondering something....that doesn't happen often


i dont have my book with me here, i wish i could scan it...it has the diagram of the stages.

Last edited by B+O; 01-20-03 at 01:39 PM.
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Old 01-20-03, 06:21 PM   #12 (permalink)
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i would say take the 2 out that are clean and leave the dirty one but clean it. But i dono
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Old 01-20-03, 06:30 PM   #13 (permalink)
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Quote:
Originally posted by 92coupeon18s
i would say take the 2 out that are clean and leave the dirty one but clean it. But i dono

AWESOME TECHNICAL INSIGHT!!!!





j/k


maybe...i might have stage 2 and 3 backwards...dammit i cannot remember the DIAGRAM....
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Old 01-20-03, 08:36 PM   #14 (permalink)
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Quote:
Originally posted by Bang&Olufsen DK
maybe...i might have stage 2 and 3 backwards...dammit i cannot remember the DIAGRAM....
Nope. You got it right.
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Old 01-21-03, 02:27 AM   #15 (permalink)
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if its all ture then that little flap carries quite a load.


~Hybrid
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