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Saikou Michi did not have a S2000 specific application, so we contacted them to design one together. We came up with a very simple bolt-in design that did not require any modifications at all. The S2000 design uses 2″ diameter cans as opposed to Saikou Michi’s more typical 2.5″ can size. The reduced diameter was so that it could fit in the space between the battery and A/C line. A new battery tie-down bar replaces the factory piece and serves as the mounting bracket for the dual OCC resulting in a very clean setup.
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| The can with the 1/2″ tubes goes to the front breather on the valve cover. The can with the 3/8″ tubes is for the PCV system. The threaded bung with allen head screw is used to attach the dual OCC to the battery tie down bar. |
Why the dual OCC setup as opposed to a single can? To explain the need for two, we need to look at how the stock valve cover venting system works. The vent on the rear of the valve cover has the PCV valve and connects to the intake manifold. The vent on the front of the valve cover goes to the intake tube before the throttle body. At part throttle, there is a lot of vacuum in the intake manifold which creates a strong suction force. In this situation, a lot of vapor can be sucked out of the rear vent. When the car is at WOT, ideally the pressure in the intake manifold is nearly ambient. On a boosted car, the pressure is obviously positive and the PCV valve shuts to keep from pressurizing the valve cover.
The front valve cover vent is connected to the intake tube before the throttle body. This location in the intake tube will always have a little bit of vacuum and never go positive. Therefore, it will always help pull vapor and pressure from the valve cover even when the car is at WOT.
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| The front breather tube had to be bent a little bit in order for the tubes to clear each other and also to allow the hood to properly close. Be careful in bending the tube! I reused the original hose clamps on this end. For the PCV connections, I had to use clamps larger than the OEM ones. |
What happens if you connect the two vents together? Well, if you connect both to the intake manifold and the car is at WOT, then there will be nothing to pull pressure from the valve cover. An even worse situation would be on a boosted car where the intake manifold is at positive pressure; the front vent doesn’t have a PCV valve so now the valve cover would actually be positively pressurized! That’s not a good thing. The other alternative is connecting both tubes together and attaching them to the intake tube. This results in much less vacuum whenever the car is at partial throttle. There is no good situation in trying to connect both vents together and only use one OCC, so we’re using a dual setup.
