Concept Generation:

With the design parameters defined, the design team generated a series of possible configurations for the system.  Presented are the four main concepts, which were developed in adherence to spatial constraints of the vehicle.  Advantages and disadvantages of each are also noted.  All four concepts are assumed to employ pre-bent exhaust pipe for the pipe sections, and formed steel sheet for other components.   Alternatively, plastic such as PVC might be employed since the system is not subjected to elevated temperatures under normal conditions.  The use of plastic would reduce weight and eliminate corrosion, and might reduce difficulty of fabrication since it could be glued rather than welded.

Concept 1: Single-Stage Ram Manifold

The first design concept is shown below. It employs primary pipes of tuned length attached directly to the carburetors via flexible couplings. The pipes are angled out through the side-covers of the motorcycle at 45° to avoid interference with internal components. Each pipe would then be fitted with a separate high-flow air filter. Since the stock manifold also supported the weight of the carburetors, some provision would have to be made to attach this design to the frame, such as a mounting flange.

Design concept 1

This design is the simplest possible, and would be the easiest to install since the four pipes are initially separate. It would require no modification of other motorcycle components, and would be easy to fabricate.  This design provides the straightest flow path possible given the spatial constraints, and the use of separate air filters would ensure the minimum filter restriction possible. Unfortunately, boost is limited to the primary point (7000 RPM) due to the absence of a resonating plenum.  The angle of the pipes places them relatively close to the rider’s legs, limiting his seating options.  In addition, the use of four separate filters would greatly increase the expense of such a design.

Concept 2: Dual-Stage 4-into-1 Manifold

The second concept generated can be seen below. It consists of four primary pipes which are bent at 45° to avoid frame members and exit through the right side-cover. They are joined at a cylindrical plenum which is partially contained in the internal frame cavity. From the plenum, a secondary pipe of tuned length undergoes another 45° bend and points toward the rear of the motorcycle. A single high-flow air filter is attached to this pipe. Support for the system would be provided by attaching it to one of several existing frame hardpoints which supported the original system.

Design concept 2

Among the advantages of this design is the fact that it will provide a boost at two different engine speeds, due to the presence of the resonating plenum and secondary pipe. It would be unobtrusive, as it exits toward the rear of the vehicle and points away from the rider’s body. Only one filter is required, and all components are simple cylinders. Disadvantages include an unevenness of flow across the different pipes due to their offset at the open ends within the plenum.  Asymmetrical synchronization of the carburetors would thus be necessary. The design is relatively difficult to fabricate, and may be difficult to install since it would most likely need to be inserted into the frame cavity as a unit from the right side.

Concept 3: Dual-Stage 4-into-2

The image below shows the third design concept. As in Concept 1, the primary ram pipes diverge toward both sides, but here they enter a cylindrical adjoining plenum located horizontally in the frame cavity. Secondary pipes continue outwards from the plenum, and each is fitted with an air filter. Like Concept 2, this design would be bolted to the frame, probably at a bracket attached to the center of the cylindrical plenum.

Design concept 3

Like the previous concept, this design would allow a dual-stage boost, and additional airflow may be induced by the blowdown effect of the onrushing wind. However, air will require a longer flowpath to reach the inner cylinders, resulting in uneven charging. The secondary pipes will protrude a significant distance from the vehicle, which may interfere with the rider. In addition, the location of the plenum will require removal of both side-covers, and may require relocation of some internal electrical components. This design would have the advantage of being easily fabricated, although installation would be difficult.

 
Concept 4: Dual-Stage Twin Plenum

The fourth design concept consists of primary pipes similar to those in Concept 1. However, the diverging pipes would then enter a separate plenum to the left and right, located outside the vehicle frame.  The rectangular-section plenums would be joined to tuned secondary pipes which undergo another 45° bend and point toward the rear of the motorcycle.  Each secondary pipe is fitted with a high-flow filter.

Design concept 4

This design would again provide a boost at two different engine speeds, selected by the component dimensions. It would be easy to fabricate and install, and would be supported by a separate mounting flange of simple configuration which would attach to existing frame hardpoints. Airflow will be relatively straight, for low loss of fluid momentum, and the multiple filters also aid airflow. Its rearward-facing geometry would be non-disruptive of the rider and allow the vehicle to maintain a slim profile. Minimal modifications would be necessary, including the cutting of holes in both side-covers to allow the exit of the primary pipes.

Based on the relative merits of all four designs, Concept 4 was chosen for further development.