finishing RB25 intake manifold, what do you think?

[thomasK(austin)]

So i bought this almost done intake manifold for the RB25. what do you think i should do, re-fab the coolant inlet and put a TB plate on straight like it is now OR keep the location of the coolant inlet and get the TB off to the side more so it will all clear?let me know what you guys think?

[thomasK(austin)]

pics

[cdlong]

i'm no intake manifold designer but that plenum looks too small. it's supposed to be a reservoir of air, not an extension of the runners. i think that one will make cylinder #1 run lean and #6 run rich. it will also act like really long runners, good low end torque but terrible top end.

you could cut the top section off and add an inch wide strip of aluminum around the horns and weld the cover back on. that would give you room to move the TB out away from the water neck.

if you don't do that, i would rework the water neck so the TB has a straight shot into the plenum.

do you have a picture of the whole thing? that will give us a better idea of the size and taper at the back end.

[AmoebAssassin]

A good way to start is to set your plenum volume to two times the engine volume. Meaning your plenum should, when completed (minus the runners) be able to hold 5L of water. Since you are clearly making a front throttle body design, you should have a good amount of taper towards the last runner, so as to slow down the air for the first runner and speed up the air for the last runner (conservation of volumetric flow and mass flow). It's good that you used trumpets, but you really should research resonance and anti-resonance frequencies before deciding on a runner length.

[shockload]

it should work, ive seen many that were a lot worse. using a smaller common chamber shoul theoretically have better response but the onlt mistake i see is the common chamber does not choke down which can be properly equated but i dont know how exactly off the top of my head.