pros/cons of modding RB25 intake like this?

[maxgohan]

thinking of modding my stock rb25 intake to something like this,
can anyone think of a good reason not to?

will i see some advantages by reducing the FMIC piping length??

http://us1.webpublications.com.au/static/images/articles/i19/1920_5mg.jpg

[dreadedfist]

Some say it leans out #6. I've never seen evidence either way. If you want a front entry manifold, I'd get one that's designed for it. The OEM setup can make boat loads of power.

[raz0rbladez909]

I'd honestly stick with the oem setup, it promotes more even air distribution to all cylinders vs creating a greater length to get to cylinders 5 and 6

[maxgohan]

i did think of the even distribution thing,

how do the greddy/freddy type manifolds overcome this problem? or is it just overlooked?

[PoorMans180SX]

i did think of the even distribution thing,

how do the greddy/freddy type manifolds overcome this problem? or is it just overlooked?

Bigger plenum and tapering to the 6th cylinder is how they fix the problem.

[conrad_s13.5]

^this,....stock or f/greddy

[OBEEWON]

I've heard that even the Greddy's lean out #6.

A friend of mine rebuilt his motor and #6 was all toasty and things.

[dftsilvia]

i have noticed over the years of watching D1 option videos that most the guys over there run the stock I/M. seems to work really well. its ugly, but it works!

[!Zar!]

If cyl #6 is running lean, why not increase fuel to that injector?

[maxgohan]

i guess stock it is!!

thanks for the help anyways guys....

[IIIXziuR]

I know it is more efficient but, man, does it look goofy.
I've always hated the way the manifold went over the V/C on the 20/25s

[OBEEWON]

Its like having only one titty in a bra.

[cdlong]

If cyl #6 is running lean, why not increase fuel to that injector?

You can't increase fuel to one injector, but you can get your injectors flow tested and put the highest flowing injector on #6.

[silver04rsx]

You want to decrease your intercooler length with the stock manifold, purchase a vertical flow intercooler with the inlets/outlets on the same side.

[pacotaco345]

If anything it would make #6 rich.. Lean = too much air and not enough fuel, #6 would be starving for air at the end of the intake leaving too little air and too much fuel ie rich... If any cylinder would be made lean from this setup it would be #1

[vas570sx]

i'm kind of curious as to why some of you are saying that it cant distribute air evenly to cylinders 5 and 6, then in the same breathe, you say that it will lean out cylinders 5 and 6...

i also do not see this causing an issue to the back cylinders as each runner is pulling from a common plenum at different times.

If the RB is under boost, there is always a positive pressure in the plenum, so air starvation should never happen.

[atom]

Air flows to the rear of the manifold first, thats why the rearmost cylinder is always the first to go lean. A manifold doesn't pressurize instantaneously.

[!Zar!]

You can't increase fuel to one injector, but you can get your injectors flow tested and put the highest flowing injector on #6.

I was thinking something along the lines of this

BT Writeups: Tuning Reliability & Repeatability: An Example of Individual Cylinder Fuel Trims (http://btwriteups.blogspot.com/2011/06/tuning-reliability-repeatability.html)

[PoorMans180SX]

You want to decrease your intercooler length with the stock manifold, purchase a vertical flow intercooler with the inlets/outlets on the same side.

This is by far the best way to do it. An intercooler with shorter tubes generally has less pressure drop and better flow anyway.

[cdlong]

If anything it would make #6 rich.. Lean = too much air and not enough fuel, #6 would be starving for air at the end of the intake leaving too little air and too much fuel ie rich... If any cylinder would be made lean from this setup it would be #1

Air that flows into cylinders 1-4 has to make a turn into the runner based on vacuum alone. Inertia of the air flow takes air to the back of the plenum where it's turned by the wall of the plenum into #6 (and 5 to an extent). This is in addition to the vacuum that 1-4 have.

[fliprayzin240sx]

I'm seen enough folks do this in Japan. When I asked why this is done, the answer is almost always because it's simplier for FMIC routing. That and a damn aftermarket intake manifold cost over $1k.

[dftsilvia]

You want to decrease your intercooler length with the stock manifold, purchase a vertical flow intercooler with the inlets/outlets on the same side.


this is what i did, bought a cx racing one for a buick grand national, works awesome and i dont have the piping running inbetween my rad and engine

[nathanong87]

junyan , the exciting car company , is coming out with a fully CAST manifold. will also come in a coupe color choices!