So, in the first post of this series I talked about the “secondary butterfly control system” used by the factory JDM CA18DET. I won’t rehash all of it, but basically the JDM CA18DET has an 8-port head and the intake manifold is equipped with butterfly valves in 4 of the ports. These ports are closed at lower RPM and then are opened at ~ 3,800rpm allowing full flow. Think of it like a spool valve you see on 2JZ builds with big turbos that need help spooling up.

The system is supposed to increase response and low end torque, and all evidence suggests it does. There is a mix of information on there, but the claims have been backed up with dyno sheets. The big issue though is many CA18 owners are either not running the system at all, or not running it in the factory configuration, which limits it’s benefits.

The factory setup is fairly complex and, if your CA is a swap it’s likely you didn’t get anything, but the intake manifold with the actuator bolted to it. My own S13 is a factory CA18, but it was swapped to an SR20 while it was in Japan. When I imported it into the US I decided to go back to the CA18. As a result, I didn’t have any of the power valve components I needed to get them working correctly. As you can see in the diagram below, it’s quite a few parts.

I spent a good amount of time figuring out how it worked and what pieces I would need, and then I discovered people were opting to replace the factory setup with electronic vacuum pump setups from Volvo. It was a much simpler option. Only a single electric vacuum pump, two vacuum lines and three wires were required. I was on-board immediately and had it working on the bench. I go in-depth in the process in the first post if you want to take a look.

It worked, it was simple, and I was excited at first. But, after a bit of time I started questioning whether it was as good as the factory setup. My first concern was with how loud the electric pump was. It has to run constantly as it’s creating “vacuum” on the fly and you can hear it in the cabin. The second was how slowly the butterflies actually opened. However, I didn’t know if the factory setup was any faster. I ended up “bench testing” the butterflies with my 4Runner and a “hacked” together factory setup, and it turns out they closed a hell of a lot faster.

At this point I wasn’t sure what I was going to do. The noise from the electric pump would annoy me, and the “slow-close” of the butterflies might be detrimental. So, I decided that maybe the Nissan engineers were smarter than me and to just go back to working on a factory setup. The diagram below is what I came up with.

Everything needed to run the butterflies in the factory configuration is included and it’s all fairly inexpensive. The factory part numbers are included for everything but the vacuum tank. For that, I ended up getting a newer tank/accumulator from a 2019 Pathfinder since it looks nicer and comes with a perfect bracket. That part number is 22370-7Y00A.

I have all the parts, but I haven’t had a chance to get everything mounted in the bay. I wasn’t actually planning on making this post yet, but I’ve gotten a bunch of emails asking about the power valves, and thought it was best to go ahead and get this one up. Installing everything is going to be the easy part though. The factory ECU has a table that references load and alters when the valves actually open. I’m using a Link and one of the outputs to trigger the solenoid to open the valves at a certain RPM. It’s going to take some work and time on the dyno to determine when to open the vales and under what load. It will definitely be interesting to see what happens though.