Anyway to tell the difference by looking?

 

The pic below shows the biggest difference. Both motors had S5 rotor housing. The only difference I could find was the casting around the dowel pin area on the rear plate. S4 and S5 ports in side the motor are the same. The ports going in to the motor is bigger on the S5 plates. Have 2 S4 and 3 S5 motors and only one S5 motor had the bigger casting around the rear dowel pin area. But all the S5 motors had the bigger ports going in to the motor. These are Jpec motor if that matters. Thought I would post this if anyone was thinking of buying a Jpec S5 motor for the better rear end plate. all of them do not come with the better end plate..??.. Could be wrong, Just my observation.

chuck

 

i just had both an s4 and s5 rear plate together and the only difference i can find is the water temp sensor thread is different for s5

 

Sleeper7 you are the man.

 

Sleeper is right on the money. I've torn down a bunch of motors within those years and I've come to the conclusion that Mazda did alot of experimentation and changing interim during those years ('88 to '90 roughly). That's why you'll see some motors with larger dowel pin land, etc over others.



B

 

so is this difference only on the rear plate? meaning, if you put together the first 4 housings together that were s4 and then threw on an s5 rear plate would it still have the hp rating of a whole s5 core?

 

BigTurbo

No you can not use S4 and S5 end plates in the same motor. The ports that go in to the motor is different. Now if you are going to port them to be equal then I don't think there would be a problem.

chuck

 

Front iron has the stepped o-ring groove for the front oil cover.

Center iron has SMALLER ports (on the combustion chamber side) for the primary ports - they open 10-degrees later.

The side housings ports on the secondaries ports are wider on the manifold side, by about 1/8".







-Ted