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Big Kid
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Discussion Starter #1
this issue was just brought up again and made me wonder if a intake plenum shaped like a box on top of the intake manifold would yield more power. It could be made very easily and at nominal cost with a intake port for the TB. has anyone thought about this before and taken any action on it?

I dont know about youbut I hate the fact that you have to remover the intake plenum just to get at the plugs.
 

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Badassical Baddage
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6,535 Posts
I'm not an engineer, but I beleive this design helped with muscle cars (like in your previous mention of the Hemi's rat nest) because the carbs were mounted above the chamber. Like the tunnel rams and such you'd buy, you'd mount the carbs on top of that....

maybe we could make a 3.0-6pack :D

It'd probably be easier and cheap just to dump a 440 and built trans in the car...gut out the engine bay, push back the firewall a bit in some places, open up the tranny tunnel and you'd be set! :D
 

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Big Kid
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Discussion Starter #3
Now thats an Idea!!!:D But I was thinking more along the lines of sticking with the stock engine. But a SIXPACK setup would be interesting. Anyone want to plotoshop one on our engine?
 

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Registered
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I am not an engineer(yet), but I think having bigger surge tank would help.

My friend just bought an intake with bigger surge tank on his Skyline. He paid like 2000 dollars though. I am sure we can make it for 100 bucks or so with material and welding.

Now we are really making our car into the next stage!! cool. I hope many people will follow..
 

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Badassical Baddage
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ajimbo said:
I am not an engineer(yet), but I think having bigger surge tank would help.

My friend just bought an intake with bigger surge tank on his Skyline. He paid like 2000 dollars though. I am sure we can make it for 100 bucks or so with material and welding.

Now we are really making our car into the next stage!! cool. I hope many people will follow..
Mitsubishi already did this, if you look int he other thread about the intake that brainfood started I mention Mitsubishi's "other" plenumb that they designed, I've seen it and the tank is in fact quite a bit bigger and different shaped! It also has some 'experimental" things on the inside I don't quite remember...
 

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Big Kid
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Discussion Starter #6
anyone have a pic of that experimental plenum?
 
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i believe that we have the longer runners on there because it will produce more torque when you're not on boost. eliminating these will make your turbo lag seem horrible. sucks that they're there, but they gotta be.
 

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vehicular thaumaturgist
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8,289 Posts
Well I'm an engineer(ing student) and I don't have the information to figure out if that is ideal. I do know that shortening the intake runners should optimize cylinder-filling for high-rpm operation. Problem is, if you remove the entire upper plenum, that optimum may come at an rpm higher then redline. I don't know if this is true, one way or another.

I believe the volume of the intake plenum is a critical value, as are the length and diameters of the intake runners. It also matters how much and how quickly they are reduced in area as they near the cylinders (increasing the velocity of the intake air). I think that last is taken care of by the lower plenum.

If someone DID make a new chamber, complete with velocity stacks and some kind of performance benefit, that also fits under the stock hood (or provides me with a cheap CF hood with an increased power dome to accomodate it ;) ), I'd buy it! I have an IC idea that I may be doing in another year, and a plenum in that configuration would make my job much easier.

-Chris Wood
 

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Big Kid
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Discussion Starter #9
I dont understand why the runner length should matter becsuse the fuel is delivered at the bottom of the intake not before the runners. The old intakes where you had a carb abover the runners would be effected by the length and the design of the intake runners. But we are only pumping air in an open plenum then down into the chanmbers. I would think that a open plenum design would benefit our cars under boost.
 
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mjb, you must know something about carb spacers, right :D the more distance the air has to travel, the more the air speed increases. it's almost like a ram air system. this is why the non turbos have a variable intake path which varies the length of the intake runners according to RPM. long runners under 3500 and then the short runners slowly open up at 3500+ RPM.
 

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Badassical Baddage
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Multiades said:
If someone DID make a new chamber, complete with velocity stacks and some kind of performance benefit, that also fits under the stock hood -Chris Wood
Call up Brian at GT Pro and he'll have an answer for ya...that was the one and only time I saw it, he said it took months to find from Japan
 

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vehicular thaumaturgist
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8,289 Posts
I dont understand why the runner length should matter becsuse the fuel is delivered at the bottom of the intake not before the runners.
There is a resonance effect with the incoming air. It is done so that there is a pressure wave that hits the intake valves as they are closing, at a ceartain optimum RPM. There are ways to calculate runner length based on ceartain valve opening/closing characteristics at various RPM.

Ideally one would have a continuously variable intake runner length. The four-rotor 720hp Wankel rotary that Mazda used at LeMans had four sliding tubes to vary runner length. Complicated system, but it makes a difference.

I made a quick sketch of a variable plenum, check it out...

-Chris Wood

P.S. Wish we had one of these custom-made up for the turbo 6G72. There is a 2-stage system on the non-turbo 6G72.
 

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The Wizard Of Aaahhhhh's
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There was a thread going on here not too long ago about a 6 pack setup for our cars. I can't find the link to the company, but I remember I saved the pic, and I did find it.



If I remember correctly, that intake is for a 3.0 Mitsu engine. I guess the 6G72 was the only 3.0 liter they made???

Looks cool, but I don't know how practical it would be for us turbo guys. It would definatly rock the NA's though! :eek:

Chris
 
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