Is there any difference between 13B NA and turbo rotor housings in the
years 87-93? There is a turbo one on ebay, and I need one NA.

Doc Custer
Retired Software Engineer and sometime Audiologist

I don't think so in those years. I think Mazda modified the 1993 and
up 3rd gen
housings in a mill to vent the steam pockets. Probably a good idea for
aircraft use.

Paul Lamar ...No rotor no motor.

Hi Doc,

There are differences between the generations of housings:
    http://www.rotaryresurrection.com/2ndgen/tech_housing_differs.html

NA housings have an exhaust port noise splitter/diffuser in the insert.
The insert can be replaced or the
splitter ground out (with some difficulty).  (see bottom left of photo)
Also some minor passage differences...
Series 5 and later housings have a knock sensor above the top trailing
spark plug (top right in photo)

Some people have said the spark plug timing is slightly different
between S4 and S5 and should not be mixed.
I have not bothered to measure it.  Others have mixed the housings
without ill effects...

I am not too familiar with the 93+ housings - I don't think the stock
housings have venting above the plugs.

Cheers
Cary

I forgot about the exhaust splitters. Thanks Cary.

Paul Lamar

Thanks for the info. The web site was very helpful. Thanks Cary.

The web site mentions removing the exhaust port noise splitter/diffuser. I
don't recall ever having heard about this before. Is this something we
should do?

Doc Custer
Retired Software Engineer and sometime Audiologist

Nice site. Lots of good how-to info. I will add it to the links.
He also mentions a couple of sites for used parts.

For a turbo you need to take them out. For a side port you might not
notice any difference in power and the engine will be quieter with
them in. There will probably be a slight power loss with them in for
a p-port but I don't know how much.