I have two 13B housings that have 2 coolant passages on the intake side and do not have a hole for the knock sensor above the spark plugs. When I line them up to FD housings, the top plugs line up perfectly but the lower plugs on the other housings are higher than the FD ones. It looks as though they run a closer split from the factory. I assume these are 87/88 Turbo housings but just want to be sure.

Also, How can you tell the difference between the 89/91 turbo housings from the FD ones? Are they identical?

I also have one rotor that has machined ridges on the faces. This rotor came out of a mazda reman but the other rotor has smooth faces and a dull copper look to it. The one with the machined faces was a more silver. I can take pics if necessary.
Are both of these FD rotors?

I searched the forums and mazdatrix website but was unable to locate this info, if anyone has any links that can ans the questions, please let me know.

Thanks,

Anthony

 

Hi Anthony,

Let's start with the rotor housings:

87-88 turboII housings have NO knock sensor hole and Leading spark plug openings are a bit higher, closer to trailing plug opening. Don't get confused with physical location and ignition timing. Therefore those 2 housings are most likely TurboII housings.

89-later rotor housings are pretty much identical. The main difference is that the FD housings are cast with cooling mods around the spark plug area. Material is removed from behind the Leading plug opening to maximize cooling.

Now the rotors.

87-88 turbo II are 8.5:1 compression and 10.04 lbs each and are completely cast with slight machining to the "bathtub" area.

89-91 turbo II are 9.0:1 compression and 9.54 lbs each. "
Bathtub" areas are competely CNC machined. CNC ridges noticeable.

93-95 FDs are also 9.0:1 compression and 9.54 lbs each.
A majority of the FD rotors I have seen have the complete compression faces CNC machined including the "bathtub" areas making all faces and rotors identical.
CNC ridges will be noticed on all compression rotor faces.

I have also noticed on FD engines (maybe reman) to have one fully CNC machined rotor and one where only the "bathtub" area is CNC machined.

Hope this helps.
JD

 

John,

Thanks for the response. It clears up a lot of questions.

Anthony