How To Test The 5th and 6th Ports

ll naturally aspirated second generation RX-7s have a 6 port induction system. The 5th and 6th ports stay closed until approximately 3800 RPM, at which time they open. This is similar to the VTec cam in a Honda engine. The resulting port allows the intake to form a natural supercharging effect, and changes port timing slightly. This results in more high end horsepower. Because keeping these ports open at low RPMs degrades performance, they are only open when required.

Unfortunately, these ports have a tendency to stick and freeze up if not used (and shame on you for not using them). A surprising amount of RX-7s are running around with non-working ports, which will result in a loss of about 25HP above 4000 RPM. There is a simple you can do to test your own ports. If you find them inoperable, the actuators will have to be removed and cleaned.


Instructions


Step 1 - Start the car and let it warm up
Start the car and let it warm up. While it is warming up, you can locate the ports and actuators. Looking at the image below, you will find that they are on the passenger side of the engine right above the exhaust manifold.



Now, put a dab of grease onto each actuator rod.


Step 2 - Drive the car
Go for a spirited drive. Be sure to redline the car a few times, and vary the RPMs so the tach spends some time above 4000.


Step 3 - Check the grease
Park the car and check the grease on the rods. If it has moved or been smeared, then the actuators are working properly. Clean the grease off or it will accumulate dirt and cause them to start sticking. If the grease has not changed, then the actuators are not working and they will need to be fixed.