Intake Manifold Goodness!

[r34 gtr]

Today I went and removed all traces of the terrible butterfly valve system in my lower intake manifold. Sure they may be good for low end torque and whatnot, but this is a 1.8l so to hell with low end grunt. I wanted as little stuff in the way of my intake air flow as possible, and even when completely open these valves create quite an obstruction. Now, I took out the valves themselves a long time ago, but the bar was still in there because well, I was lazy. This afternoon I went and removed this bar, and here is what I did.

First off, you have to remove your intake manifold. This may seem like a terrible job but it really only takes an hour or two if you work at it. I believe all you need are 10, 12, and 14mm sockets and box end wrenches. I dont really want to get into this in detail - you can look it up yourself, but its pretty straight forward. Just make sure you remove the upper manifold first, and then the lower manifold. I have not tried removing it as one, but it didnt look worth the effort.

With the lower half of the manifold removed, you need to remove the actuator deal from the rod. I removed this when I removed the butterflies so I didnt have to do this; you may not have to either. whatev.

Then come the butterflies. These are each held to the rod with two small brass screws. They are going to strip when you put a screwdriver on them, so just drill them out. It takes way less effort.

Next you need to separate the two halves of the lower intake manifold. There should be one brass looking tab with a phillips head screw on each end on the underside of the manifold. They probably will just strip if you put a screwdriver on them, so i got mine out with some large vise grips which will just fit over the screw on the rear half and still give you some leverage.

Once the two halves are apart, the rod can be pulled out. The little wierd deal in between the two manifold halves will lie flat so it fits through the holes the rod went through. Just grab it with some pliers or something and yank, it wont put up a fight. Heres a picture of mine with the rod removed:



And here is a picture of the hole the rod went through:



Now we need to plug the holes in the manifold we just created when we removed the rod. For this I used a 3/8in-24 tap and some allen head plugs. You will need three of these: one 1/2in long, and two 3/8in long. Pull out the rubber plugs and tap the holes. You may not want to tap them all the way, because then you can just crank the plugs in there and they will stay much better. I found that they were a little loose in there still, so i wrapped the plugs with a good bit of teflon tape so they would sit more snugly. The long one goes in the back of the rear half of the manifold, and the two short ones go where the two halves come together, respectively.

Here is a picture of one of the little plugs I got from Ace Hardware (aka the bomb):



Heres a picture from the top of the plug going into the front half of the lower manifold:



And here is a shot from the inside of the runner. Please excuse my camera phone at 215am with incandescent lighting.



Thats about all there is to it. This isnt a particularly hard thing to do, but it will probably take you a whole day if you dont haul through it. You can put the intake manifold back on yourself. Its a dirty job but someone has to do it.

This does not stop there though. I went through and performed some liposuction on the lower manifold while I was at it. Now, I just had my upper intake manifold done up nasty by Southern Cylinder Heads so I needed the lower manifold to breathe equally well.

I used a dremel xpr 400 and various round files. This took me about three hours and made my arms very tired. They are used to that particular motion though, so I expect a full recovery by tomorrow morning. The ports on the right have been opened up, whereas the ones on the left have had only a light pass on one side.



Here is a closeup of the more or less unmolested runners. Notice how the divider piece is very fat, and there are ridges where the runner straightens out and the butterfly valves once were.



And here is a closeup of the runners I went to town on. I actually did a good bit more work after this, but it gives you a good idea.



I now have the divider down to a knife edge and all the ridges are totally smoothed over. Its pretty damn nice as far as stock manifolds go. I even port matched the two halves, which by the way dont line up all that precisely, and the throttle body to the upper manifold. All of this ran me about five hours. I may have done a little more work but dinner rolled around and I called it quits.

[jdm_master_X]

excellent write up. im assuming this would also apply to a s13 KA intake manifold. definitely a good chunk of info.

[NUT-CSE]

I did the exact same think on my manifold but instead of the allen key bolts i just got the holes welded up. (Didnt think of the allen bolt idea)

I also ported the divider par of the lower manifold but i used a bastard file as it is round and was perfect fit and i took out quite abit of metal and it looks like it will flow a whole lot more.

I wish i took photos of it tho as i just rebuilt my motor so i havent had a chance to see the results.

[float_6969]

It looks good Tim, nice work!

[r34 gtr]

I am currently waiting on my intake manifold gaskets to arrive in the mail, and while it is all off I am considering doing more smoothing work. The new head is on the car, and the engine bay was wiped down a little, so it doesnt look too shabby. I'll get some pics of that here in a few if anyone cares.

I am using a copper treated stock gasket so we will see how she holds up. As soon as my gaskets and lifters get here I can start wiring up the megasquirt.

[DjLiquid]

Since this has been done, how's the performance aspect of it or is the engine not back in the car yet?

I wanna hear a testimonial

[r34 gtr]

the engine is technically in the car, but it wont be running for another week. I am still waiting on some parts, and thinking about replacing others while its apart.

[r34 gtr]

Ok boys, you ready? I picked up over 100cfm as a result of all my hard work. Sounds like the butterfly valves really do suck after all. Ill post the numbers when I get around to it, but it was something like 300cfm before and 410cfm after. In any rate, totally worth the trouble. More updates as I get more stuff in.

[sjbsuperman1425]

Ok boys, you ready? I picked up over 100cfm as a result of all my hard work. Sounds like the butterfly valves really do suck after all. Ill post the numbers when I get around to it, but it was something like 300cfm before and 410cfm after. In any rate, totally worth the trouble. More updates as I get more stuff in.

you know, its been like 8 months...i was thinking maybe you'd like to post your numbers and/or updates you have? lol

[r34 gtr]

Bwahaha numbers. My car never runs well enough for that. I usually just get it running well enough to drive around, then do donuts and pendulum turns until it breaks or I buy new stuff for it.

[sjbsuperman1425]

oh lol well thats reasonable!

in your write-up, you said you needed one 1/2" long and two 3/8" long 3/8"-24 allen head plugs correct? so i take it there are only 3 holes that would leak in the manifold correct? im probably going to do this when i do the KA TB this March.

[r34 gtr]

Yeah you only need three, because the shaft for the butterfly valves only goes all the way through one of the two halves of the lower manifold .

[sjbsuperman1425]

Yeah you only need three, because the shaft for the butterfly valves only goes all the way through one of the two halves of the lower manifold .

sweetness, now i can't wait to do this to my shiz.

(btw, great write-up)

[jrsink]

so you removed the butterflys awile ago. the nu finally wen t back just to take the bar out. do you really think that little thing would restrict muc tho? i figure the butterfly were the main restriction, not a 1/4" thick bar...just wondering

[bentvalves]

its deff disrupting flow, and slowing it down as a result if your going to remove the butterflies removing the bar alltogether is the way to go.

The bar and 2 other tabs hold the sub plenum together though (its split, 2 pieces) so care has to be taken to properly align it afterwards. The built motor I purchased last year had the shaft removed from the sub plenum and it was aligned horribly to the head, and the holes from runner to runner weren't sealed. If you dont have access to a TIG welder, fill them with epoxy or jb weld etc.

[Logan76]

Just a bit of info to help this nice writeup along, NPT thread is always tapered, you never run an NPT tap the whole way down, you only tap to about 4-5 threads from the top of the tap, that way theres a taper to hold in your plug, if not your hole will be too large and your plug will not get tight.

[sjbsuperman1425]

so you removed the butterflys awile ago. the nu finally wen t back just to take the bar out. do you really think that little thing would restrict muc tho? i figure the butterfly were the main restriction, not a 1/4" thick bar...just wondering

no i never removed my stuff..im going to remove the butterfly system while im doing the KA TB.

also, regarding position the lower runners and upper manifold..is there anyway to hold the two lower halves together, or is it just all about eyeballing and test fitting?

[r34 gtr]

Ive taken my lower manifold off many times, and Ive never had a problem with it not aligning properly. The studs on the head seem to keep the halves where they need to be.

Just use a lot of care when re-installing and you won't run into any problems.

I went back in and removed the bar because the thing was a mess. I couldn't undo some of the screws holding the butterflies on, and had to drill a couple out, so the bar was really chewed up. I just wanted it gone before bits flew off and went into the engine.

And listen to Logan76, don't tap the whole way through. Its bad, M'kay?

[The_Chosen_One]

powder coat it while its off.

[DALAZ_68]

bringing this back from the dead...

so my motor is finally getting some work done (been mainly fixated on chassis upgrades...lol)

and im gonna get the upper intake removed to do TB upgrade and also Inj and FPR install, so ive been debating removing the butterflies to make things look nicer...

since i know nothing of porting...should i even attempt doing it, or was that just a little icing on the cake for you...?

im getting the work done by my buddy who does swaps and junk all day, so im pretty sure he knows wat to do...but im pretty sure this is the first CA he's getting his hands dirty with...

[mbmbmb23]

since i know nothing of porting...should i even attempt doing it, or was that just a little icing on the cake for you...?

Butterfly removal mod is easy, remove valve flaps, remove rod, dremel out the inside with a wire wheel brush to remove carbon, fill holes with JB weld....smooth out JB weld in the holes.....let dry.

[DALAZ_68]

since i know nothing of porting...should i even attempt doing it, or was that just a little icing on the cake for you...?

Butterfly removal mod is easy, remove valve flaps, remove rod, dremel out the inside with a wire wheel brush to remove carbon, fill holes with JB weld....smooth out JB weld in the holes.....let dry.

actually, he has a welder...so i was just gonna ask him to do something a bit more permanent...

as far as the porting, ill let him decide...

[mikk]

sorry to dig this up again, but before anyone read this thread and considers going to the extended trouble of taking out the butterflies because it "looks nicer" or "don't want it restrictiung high end power" and other such reasons, take a look at some dyno graphs of what it actually does to low end power and high end power.

here are the facts:
-about 40% of the engine's torque is lost low in the rev range if the butterfly valve system isremoved or not working
-the butterflies have almost no effect on high end power until the engine is making over 400hp.

[themadscientist]

I would be interested in any dyno graphs you have. Nissan seems to think the butterfly system needed the boot.

[TheMAN]

when bean counters are the ones that give the approval stamp, engineers don't have much to say

[themadscientist]

While there is some truth to that it does not account for a significant part of Nissan's move away from these sorts of designs.

[TheMAN]

well remember the 80s was a time of over complication and over engineering... then the bubble economy burst

[Seishuku]

Nissan stopped using those valves because of VVT, VVL, and CVVT.

[D_Stirls]

Here's a thread that contains my graphs related to the powervalves also there is a link of that thread that contains Meminto's flow bench charts. There's no doubt that the provide a lot more low down and transition power as well as bringing turbo on earlier, the only question is how much do they cost you when you start making decent numbers (ie 450-500hp).


http://www.nissansilvia.com/forums/inde ... pic=365186