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Discussion Starter #1
I've been taking notes from Honda K series kids, and they seem to go after modifying Stock Intake manifolds extensively from other K series powered cars and getting really massive gains - as much as 40whp I saw on a few. All of these intake manifolds have something in common, absolutely massive intake runners..

So getting Ideas for future projects, I was eyeballing the Kia 3.5L VICS Manifold, it is very similar to some of the Montero Manifolds but a bit more modern...

Very similar design but they have some freaking MASSIVE Intake runners on the High RPM side of their VICS Manifold, they are also fairly short.



Underside of the top half of the manifold



Bottom Half attached,,, hmmm, look at those nice Butterfly Valves just begging to have the Vacuum solenoid be replaced with a Mechanical Throttle linkage.




Handy Gasket Comparison




My Idea would be to hack off the low rpm runners, and weld the gaping holes left behind shut, ideally have some porting done to the runners before having a new plenum fabricated...

I saw this extensive port job done to a stock intake manifold on a Mild NA K-series build that porting of the intake manifold alone gained around 20whp on the Dyno...

 

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that is a massive intake! call it the "flat plane" intake for the v6. lol
 

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Discussion Starter #3
it won't be so big once I'm done with it... Mine should be here in a few days....

it won't be so massive once I lop off the long runners, and plenum

 

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the upper runners are huge... but based on the gaskets it looks like you bottleneck down to about the same size as we currently have once you hit the butterflies. Granted this would probably get you closer to the ITBs you've always dreamed of, if I understand your intentions correctly, but it seems like many of the benefits of the larger runners are going to be negated by the choke point at the lower plenum.
 

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Discussion Starter #7
the upper runners are huge... but based on the gaskets it looks like you bottleneck down to about the same size as we currently have once you hit the butterflies. Granted this would probably get you closer to the ITBs you've always dreamed of, if I understand your intentions correctly, but it seems like many of the benefits of the larger runners are going to be negated by the choke point at the lower plenum.
you are correct, The runners of the Lower Intake Manifold for the Kia 3.5L engines are considerably larger then the 3.0Ls, - the ports of the two mating surfaces between the upper and lower are definitely the bottle neck, even on the 72, but especially on the 3.5L since they are the same size as the 72... however the round ports seem to be slightly bigger - either way none of this will be relevant to how I would like to modify this manifold....

Though, when you are NA you can get by just fine with no gaskets, so you can open up those ports a lot and toss the gaskets.

ITB's aren't a priority for me anymore - it would be cool to have, but packaging just is too much of a pain, tp really benefit from ITB's for it to be worth the time and money I would need ones that come straight off the port on the head - and there just isn't enough room under the stock hood to make a setup like that correctly for the power band that would be ideal for me.

I've learned you can make about 95% of the same power with a well designed/thought out and or ported intake manifold with a considerably large Throttle body.

 

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The SR is nearly identical minus it having an egr system and not MAP sensor location like the Kia.

I’m actually running this intake on my 3.8 MIVEC truck. The stock 3.8 intake is even better but I have yet to make it fit in my truck.

 

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I don't doubt that going to big and short runners will improve your top end but it will come at the expense of your low rpm torque. Are you not concerned about hurting low end response or is the intended end result a motor you have to keep high in the revs all the time?
 

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velocity should increase with decreasing diameter runners
Velocity is good, until a little over Mach .5, then it’s time for bigger runners.

With an na engine you have an almost hard cap on maximum torque, because ve can only get so high. The only way to make lots of power is holding as much of that torque as you can to really high rpms. This takes large runners, and really big cams, much larger than the typical turbo cam upgrades.
 

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Discussion Starter #11
I don't doubt that going to big and short runners will improve your top end but it will come at the expense of your low rpm torque. Are you not concerned about hurting low end response or is the intended end result a motor you have to keep high in the revs all the time?
I'm not concerned about it, even on my 3.0L which made peak Horsepower at 7500rpm, and peak torque at 6500RPM, still maintained a pretty flat torque curve from 4,000RPM onward with around only about 20wtq difference across a 3000RPM stretch. As someone who daily drives a 9500RPM Rotary, I'm in the habit of winding the gears out to 3000-4000RPM under light load when causally street anyways.

I have an extra 0.8L of displacement to play with now and most of it is Stroke, so that will do alot for torque, and mid range power.

Velocity is good, until a little over Mach .5, then it’s time for bigger runners.

With an na engine you have an almost hard cap on maximum torque, because ve can only get so high. The only way to make lots of power is holding as much of that torque as you can to really high rpms. This takes large runners, and really big cams, much larger than the typical turbo cam upgrades.
Nailed it.
 
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The SR is nearly identical minus it having an egr system and not MAP sensor location like the Kia.

I’m actually running this intake on my 3.8 MIVEC truck. The stock 3.8 intake is even better but I have yet to make it fit in my truck.

That really just looks sooo clean!
 

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I'm not concerned about it even on my 3.0L which made peak Horsepower at 7500rpm, and peak torque at 6500RPM, still maintained a pretty flat torque curve from 4,000RPM onward with around only about 20wtq difference across a 3000RPM stretch. As someone who daily drives a 9500RPM Rotary, I'm in the habit of winding the gears out to 3000-4000RPM under light load when causally street anyways.

I have an extra 0.8L of displacement to play with now and most of it is Stroke, so that will do alot for torque, and mid range power.
Nice. I am interested to see how the torque curve changes, so hopefully you are able to grab some before and after plots. That would provide some nice insight on the actual impact of reduce runner length versus the perceived impact of reduced runner length.
 

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I don't doubt that going to big and short runners will improve your top end but it will come at the expense of your low rpm torque. Are you not concerned about hurting low end response or is the intended end result a motor you have to keep high in the revs all the time?
thats the second best reason to run HUGE cams
 

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it won't be so big once I'm done with it... Mine should be here in a few days....

it won't be so massive once I lop off the long runners, and plenum

First thing first: will it fit under the hood with a 3.5L+? Second, did you kept the 75 Mivec intake plenum? I believe it will look and fit nicely.
 

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Discussion Starter #17 (Edited)
First thing first: will it fit under the hood with a 3.5L+? Second, did you kept the 75 Mivec intake plenum? I believe it will look and fit nicely.
Unlike the Full 6G75, I had no problem fitting a 3.8L DOHC Setup under the stock hood, so shouldn't be a problem...

the 3.8L The runners while large, and in nice shape - were tad on the long side, I really want to mess around with shorter fat runners however, and I'd have to get the flange adapted to the lower intake manifold which would be a waste since the ports are so small, and the big ports from the 3.8L MIVEC Manifold don't quite line up, so it would be a bit of a mess once finished...

I received my Intake bits while I was out of town for a meeting in STL, and got back last night to finally look everything over, from what I can tell this is going to go very well... I'll try go get some photos today, but there is very little porting to be done inside the plenum to much sup4ise, the runners are indeed massive. The butterfly's are larger then I expected, however I think it would be too much of a hastle to make them into a ITB stup at this time - they do not seal the runners very tightly which would cause various drivability issues, and probably a 5000RPM Idle, lol... That being said, that doesn't mean I couldn't have the center piece of the manifold bored out, and some properly fitted CNC'd butterflys put in their place at some point...

The Bottle neck where the upper, lower (and in this manifolds case, middle) meet, have significantly larger ports then the standard 72, or my 74 manifold I had previously fitted.

I'll try post some pics this afternoon as I am cutting it apart.

Someday I'll have enough money to blow, to have the Engine bay Scanned, a Upper and Lower plenum designed in CAD, and cut via CNC.
 

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Discussion Starter #19
Waiting till I get this thing trimmed up and hacked apart how I want before I spend the time taking pictures.

but the Round ports for the lower intake manifold are significantly bigger then the square ports of the 3.0L and 3.5L Intake Manifolds,

However I see this intake manifold REALLY Tall when fully assembled, and not even close to shutting the hood - So I think I'm going to hack off the flange of the Lower Intake Manifold, and the upper flange of the Middle Intake Manifold, then just remove that hole center section and bolt it all together that way - should work nicely, just will be a bit costly - but it will give me absolute massive ports, since the rectangle ports of the upper half are even bigger then the round ports on the bottom about 50mm X 60mm..

Round ports are 48mm all the way around

the Square Ports depending on which way you measure are everywhere from 43-47mm - I understand their shape is important, but I'm not sure they are beneficial over the Pure difference in size for a build like mine..
 

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This setup will be sick with a 76mm turbo.
 
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