intake manifold

[midnightsliding]

has anybody ever looked inside of their in take manifold ( i got a 91 240sx KA24DE) it has these triangle butterfly things in it, I do not know what their called, but it looks like it would restrick air folw un till a certian RPM, i was wondering what would happen if i took it out? do any of u know what it is and if it would affect perfomance? thankswes

[mattlord42]

Will the removal of secondary butterfly increase power?

Solution:

You can feel the power from 4000 rpm on. The idle is a little bumpy, However there is at least 6 hourse power gain you can feel!

MohammedEmail: [email protected]

How to:

Kevin Akita wrote:

> Hey all,>> I've been reading the list for a while and finally decided to de-lurk with> a couple of questions: Forgive my ignorance, but I've seen a couple of> references to removing the secondary butterfly and I was wondering how one> goes about doing this? The FAQ suggests that it gives a slight hp boost,> but what exactly does removing the butterfly do?>> Kevin> 92 240SX SE Coupe

hehehehe, guess I'll get this one guys, as I removed mine on my intake last night !!(aren't you guys just so lucky ?.....)

Anway, in order to do this, you have to remove the intake tract, or at least the upper section (our intake has 2 parts to it....an upper and a lower. Mine is completely off on my project motor, but I still removed it in 2 pieces for simplicity of removal.)

The butterfly on the twin cam motors, is basically a long machined shaft that has flat sections machined out in the ports, which have flat plates screwed into. This mechanism is controlled by engine vacuum by a small port like canister bolted onto the firewall side of the intake, and controls the amount the butterfly opens or closes due to engine vacuum. (stomp on it, vacuum goes down, butterfly's open up or go horizontal, to allow full air flow.) At idle, and part throttle, itcloses up the intake, to keep velocity higher (smaller area) to keep the torque factor high.

REMOVAL:

First you have to remove the injector rail, and all the other top end attachments....throttle cable etc.... and remove the upper intake tract. NOTE: you will need a new intake gasket kit...so be warned.

Once you get your upper intake tract off, you have to remove the c-clip that retains the entire assembly on....and then remove the vacuum actuator. Next, in the middle of number 2 and 3 cylinder, there's a set-scew that keep the entire tract in position. Remove this phillips screw.

Next, you have to use a fine phillips screwdriver, and lightly "tap" the end with as mall mallet to break free the loctite type material on the tiny little butterfly screws...and remove each one. (2 per butterfly.) Next is the difficult part...as I found it somewhat tuff to remove. I lubed it well, and sanded the shaft....but it took some grunt, and tiny grinding of the shaft to physically pull it out.(I bent it a little as I tapped to get the screws out....it's pretty easy to bend this long shaft.)

The shaft pulled out in one long (about 14" long) piece. It's hooped after you remove it...so don't be planning to reuse it.

NOTE: Since there's a horizontally bored hole from cylinder to cylinder, you might have to reseal up the holes with either welding or epoxy.

IS IT WORTH IT ? I don't know....... but for my application (turbo) I don't want it there.

good luck......don

[mattlord42]

That was taken from the 240sx.org FAQ on butterfly removal.

Matt

[midnightsliding]

thanks for that info i wasnt sure and i wanted to take it off, but i wanted to check befor i did it, thankswes

[midnightsliding]

Hey im putting the intake manifold on soon and i was wondering about the runner for the secondary butterfly plates, now that i took the runners out do i have to seal up the hole through each port? or could i leave it?thanks

[midnightsliding]

i silled up the one that slides out to the side of the manifold, but what about the ones in the iner ports? i dunno if that helps or not, thats the best way i can explane it........thanks