update - individual throttle body manifold for subarus

I explored making the manifold and throttle bodies as a whole system as opposed to an adapter for pre-made ITBs.

The manifold for this system would use a separate throttle plate assembly for each cylinder, with the injector ports on the manifold.

Multiple vacuum ports on the manifold would be plumbed to provide vacuum measurements in addition to IAC Valve use.

Designing a whole system instead of just a manifold would reduce the cost of the system overall. The cost of the manifold itself would not change, as adding ports does not add much in terms of manufacturing. Instead, the savings would come from the throttle plates. They are simpler to manufacture and are cheaper than purchased ITBs. The challenge with this, however, is my lack of knowledge in ITB systems.

individual throttle body manifold subarus

I have thought for the longest time that it would be interesting to put individual throttle bodies (ITB) on my Subaru Impreza. With the introduction of the Subaru BRZ/Scion FRS/Toyota GT86, I felt that there might be a market for a custom ITB intake manifold.

The first design I came up with was for a vertical mounted IDA carburetor style ITB.

IDA vertical ITB intake manifold.

The benefits of the vertical mount include a much straighter path for the air into the intake port of the head as well as a less cluttered appearance in the engine bay.

Top view. The port changes from the round opening of the ITBs to an oval opening on the Subaru heads.

This IDA style intake manifold could also be used in air cooled Volkswagens with Subaru engine swaps to maintain the appearance of a modified Volkswagen engine.

I also designed a horizontal layout manifold for use with SU side draft carburetor style ITBs.

SU side draft style ITB intake manifold.

The side draft style has the benefit of allowing a place for the stock fuel injectors, which are mounted on the angled flats near the bottom flange. The horizontal layout also points the air inlets (or the two heads on a flat 4 engine) towards the center, which would make it possible to have a single plenum and/or use the hood scoop present on Subarus to feed the inlets.

Bottom View.

These manifolds were designed around carburetor style ITBs so that it would also be possible to convert to standard carburetors. This may be desirable for a Volkswagen with a Subaru engine swap to maintain simplicity of the fueling system or to just be different on a Subaru.

I will be taking some measurements of the engine and further refining these designs.