89-91 Non Turbo Intake on an 86-88 Block

Installation difficulty? Hard - Fabrication Required

Total time: ~20-30 hours - depending on the amount of cleaning you do

***** APPLICATIONS:  86-88 Non-Turbo Cars ONLY!!!! *****

Vocabulary:  "S4" refers to 86-88 model vehicles, "S5" refers to 89-91 model vehicles.

BEFORE SWAP:

AFTER SWAP:

DISCUSSION:

I guess I should explain why one would want to do this.  The one and only reason would be approximately a 10-12 HP gain.  The 89-91 non-turbo intakes had a VDI system that utilizes the pulses generated by the intake charge.  The VDI works by opening a port in the middle of the intake path that allows the intake charge pressure waves to bounce into the opposite rotor housing.  The VDI valve is closed at lower RPM's to give better torque, and opens via pressure from the air pump at higher RPM's.  

A pictorial explanation:

So that gives a brief explanation why someone would want to do this, but there is a lot more to this job than just a simple swap if the intakes.  There are several subtle differences between the 86 and 89 engines that make this job challenging but very rewarding.  For example, during the process of this job I learned the true status of my engine. 

IE:  I found the screw from my pulsation dampener had fallen out (The leading cause of rotary fires).  Also during this job I was able to verify the operation of my oil injectors and clean my 6-port actuators to ensure 100% operation.  Over all, I basically gave my engine the biggest tune-up possible without actually tearing the engine down.

Project Goals:

I'm trying to gain all of the benifits of the S5 engine without replacing my S4 engine block.  My number one goal for this project was to install an 89 intake on the engine block while retaining AS MUCH OF the emissions apparatus as possible.  This included retaining the ACV, BAC, The Air-Pump, and the switching solenoids located on the drivers side of the engine. Other goals included: 

1)    Reusing the '86 throttle body

2)    Maintaining proper operation of the '86 mechanical oil metering system

3)    Operation of the 6-port actuators by utilizing the back pressure of the exhaust (stock system)

4)    Operation of the VDI from the air pump (using an RPM switch to open the port at 5000 rpm)

5)    Reuse all of my fuel injectors

Project Hurdles:

1)    The EGR Valve must be removed and blocked off.

2)    The middle section of the intake rubs on the 86 engine block, metal must be removed prior to fit.

3)    The 86-88 throttle body has a 'nipple' on the bottom that must be removed

4)    The location of the vacuum hoses are very different

5)    The rod that attaches the throttle body to the oil metering pump must be modified / bent

6)    The BAC plug need to be moved to the passenger side of the engine.

Project Supplies:

At a minimum, You will need:

1)    The TWO sections of the 89 intake.  (The Dynamic Chamber and Upper VDI intake)

2)    The 6-port actuators and lower intake from the 86 lower intake manifold

3)    The VDI actuator

4)    UPPER AND LOWER fuel rails from the S5

5)    The mounting bracket that holds the dynamic chamber up

6)    New manifold gaskets (throttle body to dynamic chamber (DC), DC to upper manifold,

        upper to lower manifold, and finally lower manifold to engine block.

7)    An 89 BAC valve, but you will also need the electrical connector to use this piece. 

8)    A lot of carburetor cleaner!  

9)    New injector o-rings, upper grommets, and lower grommets

10)  Other things that I purchased: new vacuum hose, some JB weld, and some new fuel line.

MY RESULTS!

I now know why Mazda raised the redline to 8000 in the 89-91 cars...  The VDI rocks, but it sucks that I can only feel it from 5000 to 7000 RPM.  

Overall, I'm very pleased with the results of this swap.  The "Seat of my Pants" can really tell when the VDI kicks in.  (Especially in 2nd and 3rd gear.)  The RPM's will be climbing steadily, and then all of a sudden at 5000 RPM, you feel it the port open up and a second latter the "over-rev" warning buzzer starts screaming at you to shift! 

For anyone who is considering performing this modification:  If you feel mechanically up to the task, GO FOR IT!  I'd recommend it.  It took a lot of work, but nothing that was very hard, just time consuming.  I spent about 30 hours performing this swap, but 80% of that was spent on cleaning and polishing.

Procedures...

Ok, so your ready to jump in with both feet!  Lets get started:

Disassembly    Modifications    Re-Assembly    Tuning    Counter-Points