electric 6 port conversion
ON nonturbo 13b engines after 84, mazda designed a variable intake system
using 4 constant intake ports and 2 auxiliary ports (6th ports) which
are supposed to open around 3500-4000rpm for better midrange and top end
power. The ports themselves are 2 hollow cylindrical sleeves inserted
into the ports in the block, each connected to a rod that runs out the
lower intake manifold and rotated by an actuator. There is a port cut
out in the side of each sleeve, and when rotated by the actuator and rod,
the hole in the sleeve aligns with the hole in the engine block’s
port, and opens the way for airflow. Between 3-6psi of airpressure is
needed to operate these actuators.
ON 84-88 cars, this air pressure came from exhaust backpressure, from
stock catalytic convertors and mufflers. A tube runs from the main cat
back to the engine, and from that pipe a small vacuum hose runs to the
lower intake manifold, which applied pressure to the actuators. This is
not a great way to accomplish port actuation. After all these years, most
exhausts either leak or have been modified, reducing backpressure and
possibly making ports operate poorly or not at all. Even when new, the
system wasn’t the best. ON a turbo car, boost is usually higher
in the higher gears, because there is more load on the engine, and it
moves more air, driving the turbo harder. Though a nonturbo engine doesn’t
have a turbo to amplify this effect, it still occurs…the engine
will move different amounts of air depending on the weather and the load.
Since the port actuators require a fixed air pressure to open, it stands
to reason that they would actually open at different times.
ON 89-91 cars, the system was set up much better. Pressure from the air
pump on the engine was routed through the emissions rack to vacuum solenoids
which the ecu switched at the proper time to actuate the ports. Though
this is a nearly bulletproof system, sometimes it must be re-engineered,
specifically if the user removes the emissions rack and/or air pump. Note
that it’s generally best to leave the stock system intact on the
89-91 engine, IMO.
This writeup is focused on the 89-91 engine, because this was the first
opportunity I had to photo document the general process. The same ideas
apply to the 84-88 cars, with 2 major differences. First, there is no
method to control the electric air pump on the older cars…there
is no ecu trigger, or other trigger that can be used. So, these owners
must set up their own trigger system. The most popular way is to get an
MSD rpm switch, and a 4000 rpm pill, and this generates an rpm sensitive
electrical trigger signal that can be used to switch the air pump off
and on. Second, the 89-91 setup in this writeup also uses a VDI intake
valve on the middle intake. Owners of older cars need not worry about
integrating this valve and solenoid into their electronic setup.
TO do this conversion, you’ll need some 5/32” vacuum hose,
some tees, a 12vdc automotive relay, 16 gauge wire, wire terminals, one
or 2 of the stock vacuum solenoids found on the engines, and a 12vdc air
pump. IF you rarely push your car hard for long periods of time (more
than 5 minutes) you can use something like an air horn motor. For extended
periods of use, you;ll want something stronger, like a small tire air
pump. I use a 12vdc air pump available for $15 from walmart.
Take the plastic case apart and remove the actual pump. You’ll cut
off the factory wires, you;ll also want to keep one of the rubber vibration
You’ll have to modify this particular air pump to work properly…as
it is, it generates too much pressure and could even damage the actuators.
Remember, you only need a max of 10psi to open these actuators, actually
5 is sufficient.
I removed the “head” from this unit, and found 2 valves, an
intake and exhaust.
I used a small screwdriver to turn the spring loaded exhaust valve so
it was constantly open..this would allow some of the generated pressure
to be vented back into the cylinder, reducing overall efficiency of the
pump and safeguarding the actuators.
I then reassemble the motor, and mount it to the fender well being sure
that the rotating fan cannot interfere with any wiring or anything else.
I use 2 long sheetmetal screws or wood screws, with a pilot hole being
drilled for each. I use the rubber vibration damper to prevent excess
ON the 89-91 NA, find the white and brown solenoid plugs, and reuse those
stock solenoids. These plugs are the ecu signal to actuate the ports,
and will both open the vacuum solenoids and trigger the motor to turn
on. ON older models, your custom rpm trigger will be used in place of
them, but you’ll still need a solenoid. To wire up the relay, s5
owners will use both wires from the brown solenoid for a trigger…I
use coax speaker wire for this. IF setting up an older car, your trigger
wires will come from the rpm trigger, and you’ll also need to run
these wires to your solenoid as well. Don’t try to pull power for
the motor directly from these triggers, they are not meant to carry amperage…this
is why the relay is used.
Run these trigger wires to the fender well area where the relay will be
mounted. Use the 2 right hand terminals for trigger (unless your relay
diagram shows differently).
Ground the motor to the chassis…
Run the power input to the motor, to the relay…either terminal is
Then, pull battery power from either the main fusebox, or the battery
terminal, and run it (a fused wire is necessary here) to the remaining
relay terminal. Now, run the hose from the motor to the solenoid(s). For
89-91’s, you’ll split this hose, using a tee, into both the
6 port (brown) and vdi (white) solenoids. For older models, the hose can
go directly into the solenoid you’re using. The input of these solenoids
is the top port..the lower ports are output and vent to atmosphere and
are connected when the solenoid is off.
Run the hoses from each solenoid to the appropriate accessory (6 ports
and vdi) actuator (s5 owners will use a tee to feed both 6port actuators,
84-88 owners don’t need a tee).
Even though the solenoids switch and vent to atmosphere when they’re
turned off, sometimes the ports still close a bit slowly.Because of this,
I sometimes remove the air filter from the solenoid (the atmosphere vent)
and install a vacuum hose, which I run to manifold vacuum…this helps
pull the pressure out of the ports once the solenoids close, helping close
the ports and make them respond quicker.