If any of you have had experience with the removal - or just close observation - of this intake manifold, you probably noticed the bolted-on bottom plate. It seals the bottom of the plenum, but aside from that obvious necessity I see no reason why it should be detachable.

Anyone have any insight on this? I'm curious because it seems like a lot of extra machine work at the factory for not a whole lot of function.

 

my dad (who works in automobile service) remarked on this when he saw my Type-R manifold before I installed it; he guessed it might be an access cover to allow cleaning of the runners and removal of any oil coming from the PCV valve that collects in the bottom of the plenum (although no such procedure is discussed in the FSM).

I'm guessing it might also have to do with the manufacturing process and the way the IM is cast. take a look in there and examine the shape of the plenum and the horn-shaped openings to the runners.

btw some may recall in the early days of the RSX, talk of a "mystery mod" that would replace this cover and change the shape/volume of the plenum for more power. no such mod ever materialized.

 

that mystery mod indeed was just a spacer kit that included longer bolts. seemed as if the idea died down after a short period of time.

the reason for the plenum plate is so that the runners can be cleaned up after casting. if you look closely into the plenum with the plate off you'll notice grinding marks from where its been smoothed out on the inside. it also enables oil cleanup.